# 28 Weeks Later



## Patrick Bateman

I traded in my sedan on a CUV about 28 weeks ago, so it's time to install a stereo.

This thread will document the install.

This project will be quite a bit different than my other cars; Gary and Jon's cars have turned me into a real DSP nut, so this one will have quite a bit of processing.

I believe it will also have the most unorthodox tweeters you've ever seen 

Stay tuned...


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## Patrick Bateman

The title of the thread is a 'tip of the cap' to my install for my Mazda 6 
28 Days Later - diyAudio


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## Patrick Bateman

The front stage is going to be a combination of three different projects:

1) Gary's Mercedes:


















My Honda Accord from '05
























Documented here : http://www.diymobileaudio.com/forum...ussion/60146-creating-perfect-soundstage.html

And a third project, documented here, which I'll keep under wraps. (It's the strangest aspect of this install.)


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## SkizeR

sub'd for probably the most bizarre, unorthodox install this place has seen


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## Patrick Bateman

I came close to copying the midrange setup that Gary has. I like the fact that he's using direct radiators, but it's almost as loud as a horn car. The reason it gets so loud is Hoffman's Iron Law; Gary is using a midrange with an F3 that's much higher than you typically see in that type of setup. Most people with midranges on the dash have an F3 around 100hz. Gary's mids only play down to 500hz or so, but they're much, much louder than a 3" woofer.

At the last minute I switched to horns. Couldn't resist 









I'm making my own compression drivers for the project. My compression drivers are based on the Altec compression drivers that Richard Clark used to run. (Richard also sold Mark Eldridge his Altecs.)










































The Altecs feature a patented phase plug that's rather complex. I'm copying it because I'm going to try and squeeze all the bandwidth I possibly can out of my DIY compression drivers. I'm hoping I can get them to play smoothly up to five or even ten khz.

The pics above show how the phase plug is designed in 3D. It took me a while to figure out the process, so if anyone has a 3D printer and wants a description of how it's done, LMK.

The key to the phase plug, as always, is to get the wavefront in-sync at the exit. If you used something simply, like a cylinder, the sound from the edge of the cone would be out-of-sync with the middle by about .4"

Four tenths of an inch doesn't sound like much, but at 13,500hz that's four tenths of a wavelength, and that's enough to screw up your high frequencies. So we need a phase plug.


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## damonryoung

I'll ride along...


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## jb4674

SkizeR said:


> sub'd for probably the most bizarre, unorthodox install this place has seen


You forgot ghetto looking... 

OP, what were you thinking when you did that to your accord???


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## HiloDB1

jb4674 said:


> You forgot ghetto looking...
> 
> OP, what were you thinking when you did that to your accord???


You obviously dont know the OP...


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## Patrick Bateman

jb4674 said:


> You forgot ghetto looking...
> 
> OP, what were you thinking when you did that to your accord???


Did I ever tell you guys about the time I was on a date, and I accidentally electrocuted her?

Her teeth were chattering and everything, it was terrible.

Luckily she married me, but we still laugh about it.

TLDR: The reason I finish projects so fast is because I'm sloppy


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## SkizeR

Patrick Bateman said:


> Did I ever tell you guys about the time I was on a date, and I accidentally electrocuted her?
> 
> Her teeth were chattering and everything, it was terrible.
> 
> Luckily she married me, but we still laugh about it.
> 
> TLDR: The reason I finish projects so fast is because I'm sloppy


please go more into depth about that.. sounds hilarious


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## Patrick Bateman

SkizeR said:


> please go more into depth about that.. sounds hilarious


My car stereo was a mess, as usual.

I hadn't bothered to solder or even insulate any of my connections.

This girl I had the hots for was in the passenger seat, having a conversation, when suddenly her teeth start chattering and I realize she's getting electrocuted 


It worked out fine, she's alive and we're married


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## thehatedguy

I knew the thread title looked familiar.


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## sirbOOm

Wrong forum section, just sayin'


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## SkizeR

Patrick Bateman said:


> My car stereo was a mess, as usual.
> 
> I hadn't bothered to solder or even insulate any of my connections.
> 
> This girl I had the hots for was in the passenger seat, having a conversation, when suddenly her teeth start chattering and I realize she's getting electrocuted
> 
> 
> It worked out fine, she's alive and we're married


yeah you should probably not do that this time around, for the sake of not burning the car down


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## cajunner

stupid question:

would the tangerine itself, be useful as a sort of waveguide, even if there is no horn attached?

I realize it will create compression but I was thinking of what would happen if you simply moved the vertical axis, oh... say about 30 degrees?

that would be radical huh?

the off-center tangerine, used like Kef's tweeter pod in their uni-q, over an inverted dome but capable of "throwing sound" to the side?


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## Patrick Bateman

cajunner said:


> stupid question:
> 
> would the tangerine itself, be useful as a sort of waveguide, even if there is no horn attached?
> 
> I realize it will create compression but I was thinking of what would happen if you simply moved the vertical axis, oh... say about 30 degrees?
> 
> that would be radical huh?
> 
> the off-center tangerine, used like Kef's tweeter pod in their uni-q, over an inverted dome but capable of "throwing sound" to the side?


It's not a stupid question at all, I've been toiling for ten years to try and do that  Probably the prettiest waveguide I ever built was designed to do that, but it didn't work. It looked similar to a PVC 90 degree bend, but it expanded.

The reason it won't work is that you have to keep the pathlengths absolutely equidistant if you want to reach 20khz. *Even an error of 0.25" will cause issues, because 20khz is 3/4" long.* Due to the very short wavelengths, you'd have to limit your error to 3/16" of an inch(!) for everything to work. (That's because 3/16" is one quarter of 3/4")









If you look at the phase plug, that's the reason that the dome is inverted. If it wasn't inverted it wouldn't work.

My drivers aren't inverted, but hopefully they'll make it to 5khz, which is all I need from them.

An obvious question is "why don't conventional tweeters need phase plugs?" And the answer is basically because they're so small to begin with. Since the edge of the dome is only 1/2" away, it works out. And if you look at the frequency response of 1" domes, you'll notice that the top octave is starting to droop a little bit; that's partially because of this geometry problem.

None of this is set in stone btw; if my waveguide doesn't work, I'll just use a 2" dome, like Gary did.


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## Orion525iT

jb4674 said:


> You forgot ghetto looking...
> 
> OP, what were you thinking when you did that to your accord???


Oh, he has done much worse . But why does it matter? I am pretty sure you don't understand, and the reasons are lost on you. I will admit that if I saw a truck with the words "Bateman Construction", I would be worried. But we are not making buildings or bridges here. The aesthetic is not a consideration with his experiments, they only serve to explore hypothesis. 

I can tell you a have learned very valuable things from some very ugly sources.

Looking forward to seeing were this round of "ghetto" ends up.


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## Dodslobber

I'm in on this one!


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## Patrick Bateman

waveguide on the passenger side









waveguide on the driver's side









this was my ****ty attempt to make pods like Gary's

















the waveguide is *tiny*. Here's the size compared to my cruddy stereo remote


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## subterFUSE

Sub'd.

This is either going to be an amazing success, or a barrel of laughs. I don't want to miss out either way.


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## 1996blackmax

Subscribed


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## funkalicious

I am so in on this. I run Great Plains Audio 909s (based on the Altec 909 series) and am very intrigued to see how your reverse engineering and audio mad scientist inclinations resolve themselves .


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## SkizeR

my man.. you gotta at least put down painters tape :laugh:


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## brett

SkizeR said:


> my man.. you gotta at least put down painters tape :laugh:



dude, right?

that foam aint no joke. it's hard as **** to get out of carpet, but he should be able to scrape that off with a razor.


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## SkizeR

if the only surface that itll completely come off of is the glass and maybe plastic. dont ruin a new car just to experiment. do it at least halfway decent


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## therapture

jb4674 said:


> You forgot ghetto looking...
> 
> OP, what were you thinking when you did that to your accord???


Oh man...if you only knew.


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## thehatedguy

And it's the wrong kind of foam too.

That looks like Great Stuff out of a can. It's not quite the same as a 2 part foam...especially when it is laid on thick. The Great Stuff will take forever to harden when it is thick like that...learned that lesson the hard way.

The easier and less messy way to do something like you want to do is to use green floral foam. Cut it and sand it. Then you can either lay the glass on top of it, or put some aluminum foil over it, spray some wax on the foil, and once it's cured pop the piece off and glass that piece back on to the baffle(s).


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## Theslaking

Orion525iT said:


> I am pretty sure you don't understand, and the reasons are lost on you.
> 
> I will admit that if I saw a truck with the words "Bateman Construction", I would be worried.


Now both of those statements are quite amusing. I really did lol.


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## Patrick Bateman

https://www.youtube.com/watch?v=8jJZUKxjdWA

_Six o'clock
This is Playboy News
We gonna interview today Patrick Bateman
He is from straight from the jungle
Patrick, let me ask you this thing
What you think about the situation in car audio today?
*Er, si, I'm Patrick Bateman
And I think that car audio today is a little bit boring*
A little bit boring?
*Yes, a little bit boring*
So why is that Patrick?
*Ah, gimme a break, Playboy*
Break?
*I want something to bang my head on
Bang my head on [x2]
Do you understand what I'm saying?*
Yeah, I understand what you're saying
You want something rough
*Yes*
You want something very loud
*Yes*
You want something to bang your head on
*Yes*
Ah, you mean probably something like this"_

OK, that's not entirely true, but I *was* looking at my waveguide and thinking I could do a little better. I think I could make the following improvements:

1) Use a spline to join the throat to the mouth, to reduce diffraction a la Geddes
2) Make the array of drivers symmetrical to improve polar response and frequency response
3) Make the mouth triangular so it fits better in my car









Something like this


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## Patrick Bateman

The M2 is an evolution of the constant directivity horns from the 80s, designed by Don Keele. IIRC, JBL hired Don from Electrovoice, and this design was an attempt to achieve what Don did at EV, without violating their patents. The horns in car audio in the 90s were (somewhat) similar to the EV.









The Focal Audiom tweeters from the 90s copy the JBL curve, but there's a mistake there. (I'll get to what the mistake is shortly.)









To make the waveguide, we start with a sphere. I'm too lazy to look it up, but IIRC the EV design used a cylinder instead of a sphere. So a small difference really.

Note that these aren't horns, these are waveguides. We're not using horn theory here, we're simply trying to get a decent wavefront at the exit.









To start our waveguide, we slice off a chunk of that sphere.

The tricky part, that Focal didn't know about, is that the exit angle of the radiator should match the *entrance* angle of the waveguide.

For instance, if you had a compression driver, the waveguide would be *deeper*, because the exit angle is narrower.

I used a 45 degree exit angle because the exit angle of a direct radiator will vary with frequency. My 2" speaker will "beam" beginning at 6,250 hz so I used 45 degrees. If I had a lower xover point I might consider a shallower waveguide.


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## Patrick Bateman

In post #30, I thought the M2 waveguide was created by arranging four spheres around the throat.

After looking at it for a bit, I think that's incorrect; it uses cylinders.









Here's another attempt to make it. We start with an arc, which we'll extrude to create four cylinders. (Instead of four spheres.)









Here's our four cylinders.









This is fairly close to the waveguide in the old JBL HLS series.









One nice thing about this setup is that I made the back side flat, which will be ideal to do something that looks like this:


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## subterFUSE

Last picture looks like Synergy horns?


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## slade1274

Is there a difference between unity horns and synergy horns?


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## thehatedguy

The key difference between the Unity and Synergy horns is the crossover. A Synergy horn has flat phase response, or as near flat as possible so it acts even more as a single speaker than the Unity horn.


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## thehatedguy

They are. Those are from Paul Spencer's Red Spade Audio page.

Red Spade Audio: DIY point source horn



subterFUSE said:


> Last picture looks like Synergy horns?


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## Patrick Bateman

thehatedguy said:


> And it's the wrong kind of foam too.
> 
> That looks like Great Stuff out of a can. It's not quite the same as a 2 part foam...especially when it is laid on thick.  The Great Stuff will take forever to harden when it is thick like that...learned that lesson the hard way.
> 
> The easier and less messy way to do something like you want to do is to use green floral foam. Cut it and sand it. Then you can either lay the glass on top of it, or put some aluminum foil over it, spray some wax on the foil, and once it's cured pop the piece off and glass that piece back on to the baffle(s).


Even worse, it was an old can that wasn't working too well, so the foam had the consistency of pudding. Basically too much foam in the can and not enough air.

I wish the Home Depot sold big sheets of Foamular, I love that stuff.

The sub box is going to be foam and wood CLD, so I better figure this out soon.


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## thehatedguy

I need to keep an eye out here and read that thread on DIYA...think I am going to be needing a way to widen the dispersion of my midranges so they'll have a better polar response to my tweeters.

That is if I can't get the domes in the doors.


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## Elgrosso

Patrick Bateman said:


> In post #30, I thought the M2 waveguide was created by arranging four spheres around the throat.
> 
> After looking at it for a bit, I think that's incorrect; it uses cylinders.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's another attempt to make it. We start with an arc, which we'll extrude to create four cylinders. (Instead of four spheres.)
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's our four cylinders.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This is fairly close to the waveguide in the old JBL HLS series.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> One nice thing about this setup is that I made the back side flat, which will be ideal to do something that looks like this:


Patrick, why not using one of these?










Sizewise it should be useable in a car, if someone want to crack open cut and re-use the waveguide I'm sure it can only be you!


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## Patrick Bateman

Elgrosso said:


> Patrick, why not using one of these?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Sizewise it should be useable in a car, if someone want to crack open cut and re-use the waveguide I'm sure it can only be you!


20khz is 0.675" long.









When you have your tweeters a couple inches from the glass, the sound 'wraps around' and you get a reflection off the windshield.









When you do what Gary did - and push them all the way into the corner - you eliminate that early reflection.

So basically there's two ways to mount a tweeter up high:

1) Push it so far back that you eliminate the first reflection. That's what Gary did with his Mercedes.


2) Put it significantly closer than the windshield, so the first reflection happens a millisecond or later. (Read up on 'the precedence effect.)


I did the same thing that Gary did, in my 2009 project that's linked on the first page of this thread. But I scrapped it quickly, because I didn't like the 'giant headphone' effect.

But after having synergy horns in my home for a while, I grew to like the effect.

That's one thing that's a bit of a bummer about this project. It will probably sound strange to the average listener, because it takes a while to acclimate to this kind of presentation. I noticed the same thing when Earl Geddes was demo-ing his speakers at the Rocky Mountain Audio Fest. 80% of the attendees walked in, hung out for less than five minutes, and bailed. Constant directivity speakers sound "rolled off" at first. After you get used to the sound, conventional domes sound bright and unnatural.



TLDR: I am not using a commercial waveguide because the entire windshield is the waveguide. In order to pull off this trick you have to use small drivers that allow you to push the waveguide all the way back into the corner. I am literally shaving fractions of an inch off the waveguide to make it fit.

This isn't the only solution to the problem. Andy W recommends another solution which is viable, but different than mine.


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## cajunner

I would like to see a sausalito lens attached to the windshield, using it as the top plate and underneath, another plate that sits on the compression driver's face. 

my understanding of why there are complex radial curves built into the Sausalito is that a dome transmits waves at variable times depending on where you take the time/FR measurement in relation to the dome surface.

but supposedly, you can take the phase plug built into a compression driver at it's word, and everything coming out of that opening just above the CD back plate, is time-coherent.

supposedly, it takes a rocket scientist to develop the amount of expansion vs. dome radii, to keep the sound waves traveling at basically a unified front, once they reach the end of the tunnel that we would screw a horn on to.


so what I was thinking is it would be great to mini-le'Cleach, and just put a shaved donut on the CD driver facing up on a dash, but then I realized the Sausalito is more of a forward shooter, and if you used the windshield you could lift a soundstage to possibly near the sun visor's down position, or basically higher than you ever heard a soundstage image, in a car...

that's what I'd like, I picked up a pair of Radian CD drivers, and I'm going to add a spacer and see how low they can go, and put them into some sort of foamed up contraption that looks like a Sausalito if you knew a Sausalito before the CD conversion, but different...

then I might take some advice on getting the first bounce, without a Sausalito in place, might work...

but obviously, trying to go with a bounce seems beneficial, since you can aim your virtual driver to the eyeballs, just by looking at the reflection in the glass.

The mylar surrounds on the Radian are supposed to give a little, so I might be able to take a 450 dome down to 750 hz, at some power level, which may be all that, and a bag of chips.


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## tulse

Patrick Bateman said:


> When you have your tweeters a couple inches from the glass, the sound 'wraps around' and you get a reflection off the windshield.
> 
> When you do what Gary did - and push them all the way into the corner - you eliminate that early reflection.
> 
> So basically there's two ways to mount a tweeter up high:
> 
> 1) Push it so far back that you eliminate the first reflection. That's what Gary did with his Mercedes.
> 
> 2) Put it significantly closer than the windshield, so the first reflection happens a millisecond or later. (Read up on 'the precedence effect.)


You wrote about that issue in older thread here in post #41 where you gave this nifty equation: 

(13500 / distance / 4)

Can you go into more of where that comes from? Is that a dumbed down form that originally takes the angle of the windshield into account?


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## Patrick Bateman

tulse said:


> You wrote about that issue in older thread here in post #41 where you gave this nifty equation:
> 
> (13500 / distance / 4)
> 
> Can you go into more of where that comes from? Is that a dumbed down form that originally takes the angle of the windshield into account?


It's really simple, here's how it works:

1) The sound radiates from the speaker
2) The sound hits something
3) The sound radiates back










Here's an example:

1) Sound travels 13.5" in one millisecond
2) 1khz is 13.5" long. (because it's 1/1000th of a second)
3) If you have a 3.375" gap between the tweeter and the windshield, then the sound that's reflected back to your driver is going to be 180 degrees out of phase. (Because it's traveled one half of a wavelength.)

It gets tricky because it's in three dimensions. The easiest way to visualize this, by far, is the ripple tank simulator in hornresp. It's a lot easier to understand what's happening if you can see it happen.


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## Patrick Bateman

Here's some pictures of the waveguide coming together. This is an extension of the WG from post 38.

It's basically four cylinders joined at 90 degree angles.

The 'shuriken' looking thing isn't just there for looks. Basically the M2 waveguide has two different curves. There's progressive transition waveguide on the X and the Y axis. But on the orthogonal axis you have a conventional conical waveguide.

This does something interesting, it basically gives you the high gain of a PT waveguide, with the beamwidth of a conical waveguide. It's clever, back in the 80s and 90s there were a lot of attempts to bolt a horn to a waveguide but this is completely different.

Having said all that, I am scrapping this waveguide and I'm trying it again. If you look at the throat the drivers are too close together and the walls of the wave are too thick.









Here's the M2 for comparison.


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## Bmxnick101

More interesting reading!!! 

Thank you sir.


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## Elgrosso

Ok I get it about the kind of natural waveguide of windshield/dash now, but still don't get it about the giant headphone effect (still reading gedlee's paper about that).

Just one last, why do you start with a square shape on your 3d if you want to throw it in the corner triangle at the end?


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## Patrick Bateman

Elgrosso said:


> Ok I get it about the kind of natural waveguide of windshield/dash now, but still don't get it about the giant headphone effect (still reading gedlee's paper about that).


The 'giant headphone effect' is what you get when you (mostly) eliminate the room signature. Forum founder npdang talked about this as a goal, but the problem with it is that it sounds a bit weird (at first.)

It sounds like you have headphones on, but you don't. You get that solid center, left and right, but virtually no ambience.

At first, I didn't like the effect, but I grew to like it.

Bose 901s do the exact opposite, and I think they can sound pleasant too, particularly if you're off axis. The 901s are ultra spacious.

The latter effect might be preferable by some; heck I might try it again at some point. In a listening test of a 901 clone versus a Linkwitz Orion, the 901 won.

The 901 gets that "ultra spacious" effect by firing most of it's output into the back wall. So it's actually exacerbating the room sound, not minimizing it.



Elgrosso said:


> Just one last, why do you start with a square shape on your 3d if you want to throw it in the corner triangle at the end?


Great question!









The 2009 project (http://www.diymobileaudio.com/forum...ussion/60146-creating-perfect-soundstage.html), which was fairly successful, re-used a mold that I built for my 2006 project. (Twelve Inch Woofers In My Dash - CARSOUND.COM Forum)


















































After I scrapped the 2009 project, one of the first things I wanted to do was build a mold which was an *exact* replica of the corner of the car. So I carefully designed a waveguide which morphed a circular throat into a triangular mouth.

This was before we had 3D printers, so I had to literally draw layer by layer, and manually "morph" a triangle into a circle, then print each layer on wood.

And you know what? *It didn't work.* The polars were ****ty and so was the frequency response.

It's funny, when I look at that waveguide a few years down the road, it really looks nice. Compared to most of my work, I really took my time with this one. I don't recall how long that mold took, but I *do* recall that the waveguide mold that I made for the 2006 project took an entire week to finish. Easily forty hours.








_JBL PT Waveguide, circa 2009ish?_








_My elliptical oblate spheroidal waveguide, circa 2006. The 2009 project used the same mold._

One of the reasons that I constantly recommend the $14 JBL clone at Parts Express is because it's virtually identical to my waveguide from '06. We arrived at the same solution independently, which is usually a sign that it's a good solution. The JBL has a little less gain because it's rectangular, but the horizontal and vertical directivity is identical.

This triangular waveguide is one of a kind, and it didn't work


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## Patrick Bateman

Here's a 3D rendering of the yet-to-be-printed waveguide

Basically I'm going to take a triangular "slice" out of the rectangular waveguide.
I can't remove much, because nearly every square inch of the waveguide is covered with drivers. That's five woofers, on a waveguide that's about 1/4 the volume of the 2006 waveguide! *Don't try this at home kids, this cannot be done without 3D and a printer.* We're talking about millimeter tolerances here.









Here's the not-so-successful waveguide from five years back or so


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## Patrick Bateman

The drivers are packed so tightly, there are very small holes in the throat. This was unavoidable; if I spaced them out further the waveguide wouldn't fit on my 3D printer.

So I'll have to let the very edge of the frame poke through the walls of the throat, then cover it up with clay.

We're talking about a couple millimeters here; if it screws up the polars I'll file down the edge of the woofer frames.

But it's an illustration of how silly you can get with the tolerances when you do it in 3D.

I have no use for it, but I keep thinking it would be fun to horn load a driver intended for cel phones, just to see how that would work :O


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## Patrick Bateman

I really hate to throw in the towel at the finish line, but those holes in the throat of the waveguide from the last post are going to be a problem.

I've made enough waveguides to know that discontinuities at the mouth aren't a huge problem, but at the throat they're a deal-breaker.

So I've started from square one again, but this time I've added a very short diffraction slot, identical to what JBL has in the M2. (The waveguide from the last post omitted the diffraction slot.)


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## Patrick Bateman

As noted in post 49, I started over again from scratch.

I made some improvements this time around:

1) Earlier in the thread, I talked about how the ideal phase plug is the tangerine phase plug. I wasn't able to use that in the first or second waveguide, because it was difficult to "weld" the phase plug in 3D. This time around, I figured out how to do that. *The trick is that you design one wall of the waveguide at a time.* IE, instead of building a waveguide with four walls, *You make one wall of the waveguide first.* Once you have one wall finished, you copy the first wall to the other three sides. Besides making it possible to use the ideal phase plug, it also saves time. Because I spent a heck of a lot of time "drilling" twenty holes into the waveguide for the bolts that fasten the five drivers.
2) When you're printing in 3D, it's not possible to drill the holes for the drivers. This is because the drill bit heats up the plastic. So you have to "drill" the holes in 3D. If you do one wall at a time, then duplicate it three times, you save yourself a lot of hassle.
3) As noted in post 49, there's a very short diffraction slot which will raise the efficiency.


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## Patrick Bateman

Here's some pics of that wall mirrored in on the X axis, and then both the X and the Y axis.

You can see why me and JBL like rectangular waveguides; it's a heck of a lot easier to build in 3D.


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## Elgrosso

hoho more and more crazy!
For the m2 it almost look like they worked with fabric, like pinched into the tweeter on a structural frame.
Could be a way to smooth out everything?

About that


Patrick Bateman said:


> The 'giant headphone effect' is what you get when you (mostly) eliminate the room signature. Forum founder npdang talked about this as a goal, but the problem with it is that it sounds a bit weird (at first.)...


Ok I see, never experienced it.
So in a car, with very directive speakers, over 500Hz, we could get closed to this effect?




Patrick Bateman said:


> ...This triangular waveguide is one of a kind, and it didn't work


Is it more related to our ear system than to your solution?
(like our ears optimized to work with two axis H&V, not three)


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## Patrick Bateman

Elgrosso said:


> hoho more and more crazy!
> For the m2 it almost look like they worked with fabric, like pinched into the tweeter on a structural frame.
> Could be a way to smooth out everything?


The M2 waveguide is basically JBL's attempt to "have your cake and eat it too."

I think that one of the reasons that Gary's car sounds so darn good is that his day job involves mastering audio for movies in front of a set of these:










Let's be honest here, I'm fairly decent at 3D modeling and writing software. But Gary's job literally involves listening to music and dialog, thousands of hours per year. *And he's listening to JBL and B&W.*

The reference speakers up there at Skywalker Ranch use the familiar "progressive transition" curve that's been the norm for JBL for about a decade now. As demonstrated in this thread, it's four cylinders.









The M2 waveguide is identical on the X and the Y axis, but on the orthgonal axis, *it's a plain ol' conical waveguide.*

















Geddes uses a variation of conical called "oblate spheroidal" and Danley uses plain ol' conical.

So the M2 is a real strange design, conical on the orthogonals and PT on the rest. Ideally the best of both worlds; the high gain of the former with the smooth response of the latter.
About that



Elgrosso said:


> Ok I see, never experienced it.
> So in a car, with very directive speakers, over 500Hz, we could get closed to this effect?


A windshield is quite large, so the effect basically goes all the way down to subwoofer territory. It sounds like headphones.



Elgrosso said:


> Is it more related to our ear system than to your solution?
> (like our ears optimized to work with two axis H&V, not three)


The reason that the triangular waveguide doesn't work is fairly complex.

This will be hard to describe without diagrams, but I'll take a stab at it:









With a flat baffle, your driver is radiating into 180 degrees.









With a ninety degree waveguide, your driver is radiating into 90 degrees.

*As the angle gets lower, the output goes UP.* Technically, it's not that the speaker is more efficient. It's just "focusing" the output into a narrower angle.


So far, so good right? Narrow that angle, *and more energy is focused on axis.*










I think the problem with that ill-fated triangular waveguide is that the angle changes depending on where you are. IE, if it was rectangular the vertical angle would be constant. But with a triangular shape, the further off-axis you are, the higher the output gets. (Because it gets narrower and narrower as you go off axis.)


----------



## Patrick Bateman

Here's the third waveguide, about to get the 'Shuriken Treatment'









This is a shuriken, for you young'uns that never played Shinobi









Here's the second (aborted) waveguide. Note that the gap between the throat and the mouth is smaller, which is what led to the holes in the waveguide. There was literally no way to fit the midranges without buying a larger printer.


----------



## Elgrosso

Patrick Bateman said:


> I think the problem with that ill-fated triangular waveguide is that the angle changes depending on where you are. IE, if it was rectangular the vertical angle would be constant. But with a triangular shape, the further off-axis you are, the higher the output gets. (Because it gets narrower and narrower as you go off axis.)


Yeah I think I see!
To stay on-axis while walking back of this, you'd have stay on a virtual line, almost a log arc in 3 dimensions in the air (far from a straight flat line.)
Thank you for your answers!


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## Patrick Bateman

some pics of the printed waveguide

one down, one to go...


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## rton20s

Surprised I hadn't seen this soon. I'm in for this wild ride as well.


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## mosconiac

Patrick Bateman said:


> I think the problem with that ill-fated triangular waveguide is that the angle changes depending on where you are. IE, if it was rectangular the vertical angle would be constant. But with a triangular shape, the further off-axis you are, the higher the output gets. (Because it gets narrower and narrower as you go off axis.)


Shouldn't the diminishing angle *help* from the perspective of focusing the energy transmitted to the far-side seat...therefore maintaining inter-channel volume? It wouldn't help path-length issues, but would help mask amplitude issues.


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## Butt Hz

PB is building his own Langolier


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## Patrick Bateman

mosconiac said:


> Shouldn't the diminishing angle *help* from the perspective of focusing the energy transmitted to the far-side seat...therefore maintaining inter-channel volume? It wouldn't help path-length issues, but would help mask amplitude issues.


That occurred to me too.

Basically, the on-axis SPL will vary with the beamwidth.

The smaller the beamwidth, the higher the on-axis SPL.










If you want to see an example of this in action, check out the Danley SH-25. As far as Synergy horns go, it's fairly conventional, but due to it's narrow beamwidth, *it's one of the loudest speakers in the world.*









By comparison's sake, the Danley JH 90 is the size of a golf cart, and it's efficiency level isn't much higher.


TLDR : there's a definite correlation between SPL and beamwidth; the lower the beamwidth, the more the SPL




Unfortunately, there's another variable in the equation, and that's frequency response. Basically, *wide beamwidth has smooth response and narrow beamwidth has lumpy response.*

Danley sells a ton of Jericho horns, but I've never seen anyone use a SH25. If I had to speculate, I'd guess that the wide beamwidth Jericho horns are smoother.

At some point, I posted data comparing the frequency response, and IIRC, the SH25 was kinda rough.



TLDR: A triangular waveguide will have frequency response that varies depending on whether you're on-axis or off-axis. Definitely NOT a good thing; we want the response shape to be consistent.


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## mosconiac

Always a compromise, huh? Just couldn't be that simple...just couldn't be! LOL


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## Patrick Bateman

mosconiac said:


> Always a compromise, huh? Just couldn't be that simple...just couldn't be! LOL


Here's where experience comes in handy:

Above 1khz, our hearing mechanism is particularly sensitive to frequency response.
Below 1khz, our hearing mechanism is particularly sensitive to phase.

The ideal wavefront is spherical, not triangular.

Therefore, a triangular waveguide is particularly bad if you're using it above 1khz. Below 1khz? Not so much.









Which is why my waveguide shape doesn't shift until the waveguide is 6" in diameter. Six inches is 2250hz.

Ideally, I'd maintain that shape until the waveguide is 13.5" or larger, but that would make the car undrivable.

TLDR: The ideal wavefront is spherical. If you can't maintain that down to 1khz, maintain it for as long as possible.


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## Patrick Bateman

I lost enthusiasm for the waveguide solution.

The reason is because it was starting to get very large.

My woofers are only 2" in diameter, *but the DEPTH of the woofers was becoming a problem.*

At this point, I think I'll use a single 4" woofer instead of four 2" woofers. Output should be fairly comparable.

The advantage of a waveguide loaded with 2" drivers is that you can maintain directivity control, possibly as high as 10khz. This is important in a car, because we're listening to the speakers off-axis.

A 4" woofer will only maintain directivity to 3375hz, but I was aiming for an xover of 5khz, so that should be alright.

You wouldn't want anything larger than 4", and I'd use a 3" if there was one that could get really loud. (I have some Faital 3FE20s on hand, but I think the Peerless 2" and the JBL 4" both sound and measure better.)




























Here's a picture comparing the sizes of the waveguide I built two weeks ago, versus the JBL 400GTI.









Here's a picture comparing the depths of four 2" woofers on a waveguide, versus a single 4". This cross-section is idealized; basically I was trying to figure out how small I could make that waveguide. The 4" design is fairly straightforward, just a woofer in a sphere.

















The JBL is a unique woofer. Most 4" woofers have a voice coil of 1", maybe 1.5". Because of that, they can play to 10khz, maybe 20khz. The JBL has a 2" voice coil, which is about as big as you'd use on an 8" woofer, maybe a 12" woofer. My 10" subs don't have a 2" voice coil, but this JBL does.

But that big voice coil comes with a penalty, which is that the inductance lowers the high frequencies. JBL doesn't publish a response curve for the 400GTI, so I did some quick measurements. I posted two, because I had to use a short gate to remove the reflections in my living room. But we can see that it reaches 4khz.


















Here's some pics of the new enclosure coming together.


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## seafish

How large are those spheres in terms of diameter and volume??

They look only a little larger then the Harman/Apple pods that I am modifying to slip some AP-NZ3 into deep on my dash. The cool things about the sphere, at least the way I plan to inset and mount mine, is that they will be ENTIRELY adjustable in terms of aiming AFTER installation.

Here are some mock-up pics in my truck--

The larger midrange pods will be set into the stock dash location but amiable in ANY direction...but know that the smaller tweeter pods will be set further into the dash/a pillar/windshield corner by removing some of the a pillar plastic trim that is no holding them out at least 2" or more then they could be, but they will still be rotatable (is that word?? lol) after install

The reason I am asking about the sphere volume of your design is that I recently came to understand from Papasin that the NZ3 I will be using in the pods would probably like a larger enclosure then what I am using, so I may well have to figure how to turn the pods into an AP enclosure instead of sealed.


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## garysummers

I think if you both made your 4 inch drivers point source speakers I think you would have better results. If you can get from 200 Hz to 20 kHz in phase and in time, it's amazing what happens to the sonic image. I have been experimenting with point source speakers, listening in my living room using my home system. I'm talking about four and 5 inch point source drivers. If you mount the drivers back in the far corners of the dash as deep as possible and the windshield and the dashboard form the horn, I belive the results would be good. You will no doubt have to do major reconstruction of your dashboard to make it symmetrical and to create the proper waveguide, but I still believe it would be worth it.


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## Orion525iT

garysummers said:


> I think if you both made your 4 inch drivers point source speakers I think you would have better results. If you can get from 200 Hz to 20 kHz in phase and in time, it's amazing what happens to the sonic image. I have been experimenting with point source speakers, listening in my living room using my home system. I'm talking about four and 5 inch point source drivers. If you mount the drivers back in the far corners of the dash as deep as possible and the windshield and the dashboard form the horn, I belive the results would be good. You will no doubt have to do major reconstruction of your dashboard to make it symmetrical and to create the proper waveguide, but I still believe it would be worth it.


Well that's an f'ed up thing to say. Why would you plant that in our fragile little brains? You know we are already dealing with addiction.


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## truckerfte

Orion525iT said:


> Well that's an f'ed up thing to say. Why would you plant that in our fragile little brains? You know we are already dealing with addiction.


Cause he's mean? He makes me think though. My ion has a center stack, so symetrical sides, an upper dash panel that is easy to remove. A pillars that are pretty deep at the dash. So I could really cram em in deep and wide....


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## subterFUSE

truckerfte said:


> Cause he's mean? He makes me think though. My ion has a center stack, so symetrical sides, an upper dash panel that is easy to remove. A pillars that are pretty deep at the dash. So I could really cram em in deep and wide....



That's what she said.....


Sent from my iPhone using Tapatalk


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## subterFUSE

Just heard some Synergy Horns by an offshoot of Danley Sound last weekend. Impressive to hear a crowded dance club with true stereo imaging.


Sent from my iPhone using Tapatalk


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## Patrick Bateman

garysummers said:


> I think if you both made your 4 inch drivers point source speakers I think you would have better results. If you can get from 200 Hz to 20 kHz in phase and in time, it's amazing what happens to the sonic image. I have been experimenting with point source speakers, listening in my living room using my home system. I'm talking about four and 5 inch point source drivers. If you mount the drivers back in the far corners of the dash as deep as possible and the windshield and the dashboard form the horn, I belive the results would be good. You will no doubt have to do major reconstruction of your dashboard to make it symmetrical and to create the proper waveguide, but I still believe it would be worth it.


I can't believe it took two weeks for someone to bring this up lol

That's The Big Reveal here, it's why this system is different.

I've been messing around with Opsodis and I managed to come up with a set of crossover points and slopes that achieves something I've been chasing after for years:

A solid center image with width.

Here's the challenge I've been facing with my stereos:

In 2009, I really went for broke with the Synergy horns. When I finished the project, I noticed something annoying:

*Most of the music I listen to sounds mono.*

Sure, there's a handful of well-recorded tracks, but 95% of what I listen to ended up sounding like my "stereo" was playing back in mono.

This is one of the reasons I always play these really obnoxious tracks on the finest stereos in the world. I've played Excision on Jon's Magic Bus, I played some Placebo in your Mercedes, and I've done the same thing with some megabuck home stereos.

Every time I did it, the experience was the same:
*Great stereos can extract magic out of great recordings, but 95% of what I listen to is just audio garbage.*

So I spent about half a decade trying various things which would bring some "space" to bad recordings. I tried Opsodis, Ambiophonics, many variations thereof.

The reason that I've gravitated towards these solutions is because I've found that *Opsodis makes bad recordings sound better, but good recordings still sound good.*

I'm not trying to pat myself on the back here, but I think in some respects this is "the holy grail" for sound reproduction. I've been doing this for a long time, and I generally find that schemes designed to make music more exciting or enveloping sound good at first, but become fatiguing over time.

I have a hunch that JBL and Bose have likely done tons of research on this, because it's a goal that has some real marketing potential. For instance, one of the selling points of my car was that included a Lexicon (owned by Harman) sound system with some DSP features that DO make a noticeable improvement in the "soundstage."

I put "soundstage" in qoutes, because I concede that we're screwing with the recording here; we're basically doing some tricks to make a recording that *doesn't* have a soundstage sounds like it does.

On a side note, I think that the conventional stereo triangle does the same thing. IE, when you listen to a bad recording on a conventional stereo triangle, *the stereo triangle creates width that's not actually there.* The thing I don't like about conventional stereo is that you get a "hole" in the center. Opsodis solves this.

BTW, a center channel *also* solves this. But in my Lexicon stereo, I notice that going from stereo to Logic7 narrows the width. This is because the center channel is full range. In Opsodis, the center is band-limited.


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## Patrick Bateman

Back in the nineties I read a review of some hideously expensive line arrays in _The Absolute Sound._
Based on that glowing review, I built some of my own. (I'd never heard a line array in my life, I just built some based on Internet reviews.)

*I did not like the sound.* At all. I found that the sound was effortless and dynamic, but I also found that the treble was AWOL. The thing I liked the least about line arrays was that they made EVERYTHING sound humongous. Big or small, run it through a line array and it comes out sounding as large as the room.

At first, I thought it was a flaw in my design, but as I critically listened to many many line arrays, I found they all did it. Some more than others, but they all did it.

The reason that I bring this up is because the solution I'm detailing in this thread isn't going to be everyone's cup of tea. I'd actually be a little bummed if I saw everyone going the Opsodis route. It's definitely adding something that wasn't there in the original recording.

The thing is, I kinda like it. After listening to line arrays for years and years, I started to realize that one of the reasons that they were so off-putting was that I was comparing them to conventional loudspeakers. If you *like* the accurate soundstage you get when you sit equidistant between a pair of speakers in a stereo triangle, line arrays probably aren't for you, and neither is Opsodis. But if you listen to a lot of crappy recordings, like I do, line arrays and Opsodis can add some welcome "space" to what is an admittedly bad recording.










Here's the start of that Absolute Sound review, from sixteen years ago, that led me down the line array rabbit hole:









_All told, the PipeDreams are the best loudspeakers I've heard. Thanks to their superb dynamic range they have real-life presence; their redundancy of low-mass/high-energy drivers and excellent subwoofers makes them sensationally quick, powerful, and detailed from the bottom to the very top; and their soundfield must be heard to be believed. *We're not just talking about a little difference in soundstage depth or width; we're talking an entirely different gestalt–an almost surround-like presentation that wraps around speaker boundaries*, blows out walls, and so pressurizes the room that, with certain discs, the music seems to envelop you. _

read more here : PIPEDREAMS™ by Nearfield Acoustics™


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## Patrick Bateman

subterFUSE said:


> Just heard some Synergy Horns by an offshoot of Danley Sound last weekend. Impressive to hear a crowded dance club with true stereo imaging.
> 
> 
> Sent from my iPhone using Tapatalk


It's a mother ****er isn't it? Same thing happened to me listening to Nine Inch Nails last year, over an L'Acoustic line array. For me, it was one of those moments when I realized that the folks over at Stereophile and TAS are somewhat deluded. Stereo imaging isn't about owning the right amp or the right cable, or having "fast" drivers. Stereo imaging simply requires you get the sound from the loudspeaker to your ears in phase, with the left channel matching the right channel.

That's all there is to it.









The L'Acoustic arrays work because they pack all the midranges and tweeters into a space that's the width of a basketball.








By masking off the face of the midrange drivers, the Synergy horn takes even further, to an acoustic size that's about as big as a baseball.


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## Patrick Bateman

Last year I used Dayton ND91s in bandpass boxes for my Mazda6.

They were a complete and total p.i.t.a. to build, literally more work than building a sub box, and there were four of them. But they worked the way they were supposed to; by using a bandpass box you raise the efficiency and narrow the bandwidth. Basically a couple of the Dayton ND91s can put out as much as a 6" woofer in a sealed box.

If you're curious, read this: http://www.diymobileaudio.com/forum...162495-new-way-increase-soundstage-depth.html









This was the predicted response









The green line is the measured response. Note that it's smoother than predicted.









The long port was unwieldy, and the enclosure looked quite ridiculous.


















Unfortunately, the stupid box didn't work. Basically the woofers are too close together. I sawed the enclosure in half, and strongly considered using "shims" to spread the woofers apart, then decided it's just too much work.

I'll re-design it and reprint it. Sucks because I spent about six hours designing it and spent over 24 hours printing it.

One thing that I'm going to do the second time around is put a single woofer into the box. I like the distortion reduction that you get with push-pull, but you really don't need to have the woofers an inch apart. 200hz is five feet long, so as long as the boxes are within fifteen inches or so, the distortion reduction will take place. (As long as one is inverted, of course.)


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## Patrick Bateman

Here's a table comparing the published specs of the ND91, versus my measured specs. This is important with bandpass boxes, horns, vented boxes, etc. This is because a variance in the Thiele Small params will screw up the alignment. This isn't really a problem with sealed boxes.

spec / published / measured
fs / 63.4 / 85.5
qes / 0.44 / 0.6
qms / 3.06 / 6.6
qts / 0.38 / 0.55
re / 4.1 / 4.3

The specs are quite a bit off. I measured two of them, and they are consistent from unit to unit. This is something I notice with home audio and car audio drivers; they tend to exaggerate the FS and QTS values quite a bit. I can't tell if they're lying, picking a good unit out of the batch, or what. You'll see the same pattern with other people who measure drivers, so it doesn't *appear* to be my DATS that's giving bad data, it's the manufacturers.









I dunked the woofer in water to figure out the volume of the frame. It came out to 0.2 liters. I'd say it's closer to 0.15 liters, since there's some "empty" space in the frame that you won't pick up with my "wrap the woofer in cellophane and submerge in water" method.


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## Mless5

Can I have a puff of whatchoo smokin'  ?


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## Lycancatt

is that jbl 4 woofer something that's readily available? it'd solve a few problems for some stuff I'm working on ie efficiency..


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## Patrick Bateman

Mless5 said:


> Can I have a puff of whatchoo smokin'  ?


I'm not high, I'm insane, hence the "American Psycho" pseudonym


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## subterFUSE

Patrick Bateman said:


> I'm not high, I'm insane, hence the "American Psycho" pseudonym



High is more fun than insane.


Sent from my iPhone using Tapatalk


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## thehatedguy

Would the Audax HM100Z0 work? 93dB 4" midrange.



Lycancatt said:


> is that jbl 4 woofer something that's readily available? it'd solve a few problems for some stuff I'm working on ie efficiency..


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## Lycancatt

yes indeed it would! only trick is, it'd be neat to have an all jbl system and I already have 2118s and the titanium bigger tweeters something t18? no idea..just fishing for options really and learning about drivers I might never have heard of.


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## Patrick Bateman

Lycancatt said:


> yes indeed it would! only trick is, it'd be neat to have an all jbl system and I already have 2118s and the titanium bigger tweeters something t18? no idea..just fishing for options really and learning about drivers I might never have heard of.


400GTI is really hard to find. I bought them from Crutchfield fourteen years ago.

I believe it's an evolution of the venerable LE5:









LE5


















LE5 efficiency is in the mid 90s


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## Lycancatt

still regretting giving a friend a pair of le5 drivers I got from a goodwill set of diy speakers, gave them to him because he wanted to build something and I wanted him to have better sound..turns out he was a dick and I never saw them again..oh well.


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## Patrick Bateman

Lycancatt said:


> still regretting giving a friend a pair of le5 drivers I got from a goodwill set of diy speakers, gave them to him because he wanted to build something and I wanted him to have better sound..turns out he was a dick and I never saw them again..oh well.


True, but they're super easy to find. I see them at pawn shops all the time.


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## Patrick Bateman

This thread has got me seriously tempted to try HLCDs under the dash again : http://www.diymobileaudio.com/forum/2492594-post70.html

Eric Holdaway demo'd Harry Kimura's Acura for me around 1998 or so, and that really "sealed the deal" for me, as far as horns go. Up until that point I'd built a bunch of my own HLCDs based on what I'd read in magazines and the Internet, but hearing it done by Speakerworks really put it over the top for me.

It's odd that I've built so many horns for cars, because I think I've only heard two cars that use horns besides my own:

1) Harry Kimura's Acura in 1998 or so
2) Mikey7182's Toyota Tacoma

There was a horn car competing at a sound-off in Vancouver WA that I went to, but I couldn't find the owner for a demo and didn't get to hear it. I think that Gary Summers car is pretty close to a horn car; with the way that he's mounted the midrange and tweeter, he's definitely getting horn loading for the midrange and I think that's part of the reason his Mercedes has such crazy dynamics.

At the moment, this is the plan for the Mazda :

tweeters : Celestion or BMS compression drivers (3.5 octaves, 2khz - 20khz)
midranges : Gento or Peerless 2" in a Synergy Horn array (two octaves, 500hz - 2khz )
midbass: an array of four Dayton ND91s per side (1.5 octaves, 200hz - 500hz)
subwoofer1 : A TC Sounds 8" mounted in the center of the car (40hz-200hz)
subwoofer2 : An Alpine SWS-10" in the trunk (40hz- ?hz)
ULF sub : A Diyma 12" in the trunk (30hz - 100hz) 

I'm doing a lot of the filtering via bandpass enclosures. So it "looks" like a five way system, but I don't plan on using more than two or three amps.

The big question right now is where to put the midranges and tweeters. I have enough room on the dash to do a Synergy horn. But seeing how well Mic has done with his BMW, and how well the Speakerworks cars have done, I'm tempted to try speakers under the dash again.

Another advantage to speakers under the dash in my Mazda is height; there's a HUGE height disparity between the top of the Mazda's dash and the floor. IE, if I put horns under the dash, the midrange and tweeter will be closer to the midbass in the vertical plane.

















If you look at the SpeakerWorks cars, you'll notice all the drivers are on the same vertical plane. I think this *might* be important to keep the soundstage height from varying. (IE, you don't want vocals to sound like they're 6" tall while drums sound five feet tall.)









OTOH, Jon has a gap of about a foot between the midrange and midbass in his Magic Bus, and it images great.









From the top of the dash to the floor in my car is about 2'. If I used a spacing of one wavelength between the midrange and the midbass, then I'd want to have a crossover point of 563hz for the midrange to midbass transition. Which is just about right for my ND91 array.









The top of the dash *and* the bottom of the dash of the CX5 are shaped well for horn loading. Basically you want it smooth and symmetrical. One nice this about the dash of the CX5 is that you can draw a straight line from your ears to the diaphragm of the tweeter. That helps a lot with soundstage height; what you DON'T want is a situation where the tweeter is buried under the dash.









The reason that Mic can get away with having his tweeters buried so far under the dash is because BMW puts the drivers ass practically on the floor of the car. The seats are very VERY low for a sedan, the seating position is closer to a sports car than your typical sedan. And this puts your ears lower, which gives you the luxury of pushing the horns all the way back to the firewall.

I don't have that luxury; if I put horns under the dash they'll have to be right at the edge of the dash, not deep under the dash.


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## sqnut

Three subs and four mid basses per side That's a total of 15 speakers, if I'm counting right. Unless you're planning to use like 2, 8 channel processors to control response and timing from each driver, The mid bass array alone will cause phase and timing nightmares. Why not use one large midbass per side and call it a day?


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## Patrick Bateman

sqnut said:


> Three subs and four mid basses per side That's a total of 15 speakers, if I'm counting right. Unless you're planning to use like 2, 8 channel processors to control response and timing from each driver, The mid bass array alone will cause phase and timing nightmares. Why not use one large midbass per side and call it a day?


I should use this as my sig:

"that's not a defect, that's a feature!"

It's a phrase I use a lot in engineering. Basically take something which would normally be a drawback, and use it to our advantage.

For instance, the narrow bandwidth of a bandpass box is sometimes viewed as a negative. But in this install, *it's a feature.* I'm using bandpass boxes to limit the frequency response, lower distortion, increase efficiency, and increase output.

The use of bandpass boxes allows you to do some strange things. For instance, my last Synergy horn used the same amplifier for the tweeter AND the midbass. This was possible because the bandpass box keeps the highs out of the midbass, without the use of a passive or active filter. And I still had digital delay! I applied the delay to the midrange, and based the "starting point" on the midbass. IE, the midbass arrival dictated how much delay was used on the midrange. Here's the project if anyone's curious:

Black Mirror - diyAudio

The "28 Weeks Later" project features twenty one drivers:

1) tweeters (two... or maybe one.)
2) midranges (four per side, in a Synergy horn)
3) midbasses (four per side, midbass array)
4) subs (one per side)
5) ULF (one, mono)

I think that high frequency arrays are a nightmare, due to phase and timing differences. For instance, 10khz is 3.4 centimeters long. At that frequency, *if you move your head a fraction of a centimeter, the response changes.* That's why Danley doesn't sell arrays, and why they invented the layered combiner, etc. *You really don't want two sources at high frequencies*, the pathlengths are too short to pull it off. (Unless your head is literally in a vise.) At 500hz, it's a completely different story. That wavelength is seven tenths of a meter long! If you can get your midbasses within seven inches of each other, they're going to behave like a single unit. I'm using 3.5" midbasses, so that's easy to do.

I'm kinda surprised no ones asked me about using one tweeter lol. By far, that is the strangest element of this project. I'm still not 100% sure if I'll do it. I've been using a single tweeter at home to good effect for about a month now.


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## seafish

PB, I am VERY interested i n your idea of running different sized/type subwoofersi n different bandpasses in a car. As I have mentioned before in other threads, I am also interested in doing the same sort of thing and have received zero positive feedback about the idea. My idea is to use a pair of ID XS69 midwoofers mounted thigh level in the doors actively band passed from 125-350, a pair of IDQ10v2 subs up firing under each side of the rear seat of my truck operating stereophonically (not monaurally) from 75 to 125 hz and then also use a single SI BMmkIV mounted down firing in the front seat center console for 20 to 74 hz. The Single SI sub will likely be isolated from the truck chassis using wire rope isolators. Between the DRZ9255 HU and an Alpine H800, I DO have enough DSP to do this. Obviously, I will pay detailed attention to the actual speaker install and enclosure volumes, as well as speaker aiming, and while I expect it to be complicated tuning, I think that it could work REALLY well to complement the front stage mounted deep and wide in the corners of the dash/windshield/apillar. One of my concerns is all that the bass overwhelming the AP-NZ3 midrange and Illusion C8 tweets, but I figure I could just use the gains on the different subs to help achieve that balance. 

Can you please tell me what you think about the idea overall and ALSO what you think about running the two IDQ10v2 subs in stereo instead of mono ??


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## Patrick Bateman

seafish said:


> PB, I am VERY interested i n your idea of running different sized/type subwoofersi n different bandpasses in a car. As I have mentioned before in other threads, I am also interested in doing the same sort of thing and have received zero positive feedback about the idea. My idea is to use a pair of ID XS69 midwoofers mounted thigh level in the doors actively band passed from 125-350, a pair of IDQ10v2 subs up firing under each side of the rear seat of my truck operating stereophonically (not monaurally) from 75 to 125 hz and then also use a single SI BMmkIV mounted down firing in the front seat center console for 20 to 74 hz. The Single SI sub will likely be isolated from the truck chassis using wire rope isolators. Between the DRZ9255 HU and an Alpine H800, I DO have enough DSP to do this. Obviously, I will pay detailed attention to the actual speaker install and enclosure volumes, as well as speaker aiming, and while I expect it to be complicated tuning, I think that it could work REALLY well to complement the front stage mounted deep and wide in the corners of the dash/windshield/apillar. One of my concerns is all that the bass overwhelming the AP-NZ3 midrange and Illusion C8 tweets, but I figure I could just use the gains on the different subs to help achieve that balance.
> 
> Can you please tell me what you think about the idea overall and ALSO what you think about running the two IDQ10v2 subs in stereo instead of mono ??


I've built a bunch of horn loaded subs for the car. Everything from an Alpine SWS-10 in a front loaded horn to a 12" prosound woofer in a tapped horn to an array of 8" drivers in a TH.

There was an SPL competition in Vancouver WA that I attended, and I saw a dude with a CRX and an 8" Sundown *crushing* people who showed up with SUVs and way, WAY more woofers than that dude.

The light bulb went off over my head and I realized that if you move your subwoofer *dramatically* you can turn the whole damn interior into a horn basically.

What that dude was doing with his CRX, accidentally, was horn loading the eight.










Here's a visual example. Imagine if the green line is the sound generated by Mr CRX's Sundown 8. The blue line is the reflection off of the car boundaries. The red line is the combination of the initial wave and the reflection.

Get the distance and the timing right and you get a ridiculous bump in output, like six decibels, which is more than enough to win a SPL event where the difference between the winners and the losers is usually a few dB.

So now we just have to figure out what the right distance is:

With a cabin depth of about 8', we wind up with a resonance at 70hz:
speed of sound / distance / 4 =
13500" per second / 48" / 4 =
*70hz.*

So that's the reasoning behind my unorthodox subwoofer setup. I have a Diyma12" for ULF in the trunk, where the 'trick' above does not work. But I also have a TC Sounds 8 which will end up in the *center* of the vehicle, where it (theoretically) should see a 'bump' in output that's enough to get it to produce as much output as a 16" woofer. (To raise the efficiency by six decibels you need to quadruple the cone area, hence a horn loaded 8 performs fairly similar to a sealed 15.)

BTW I'm not using multiple subs to improve the imaging really, I'm mostly using multiple subs to raise the output level. I'm kinda eager to see how much output I can squeeze from a high excursion 8" in the middle of the car, like that CRX dude did. But I can also see that the 8" won't provide much output below 50hz, which is why the Diyma12" is in the mix too.


If anyone wants to try the "put the sub in the middle of the car trick", here's an idea: 
Mr CRX was running a ported box. A ported box will widen your bandwidth, but you get a 180 degree polarity flip (all vented boxes do this.) If you REALLY wanted to squeeze every last decibel out of the enclousre, you might consider a bandpass box. With a bandpass box you can narrow the bandwidth, and when you narrow the bandwidth, you get a bump in efficiency. IE, a horn-loaded 8" woofer can compete with a conventional 15" woofer. But if you put that eight in bandpass, you might be able to generate as much output as TWO fifteens. And it might actually sound MORE musical than the vented box, because bandpass boxes don't have that polarity flip (because all of the output is coming from one side of the cone, whereas a vented box has output from the front THEN the back.)


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## seafish

So you are saying to choose the XO point on a center mounted sub to reinforce the first reflection of said output ?? 

Sorry for the confusion.

Also, still wondering what you think about dual subs running two channel rather then mono??


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## Patrick Bateman

seafish said:


> So you are saying to choose the XO point on a center mounted sub to reinforce the first reflection of said output ??
> 
> Sorry for the confusion.
> 
> Also, still wondering what you think about dual subs running two channel rather then mono??


No. I'm moving the subwoofer to a location where the reflected energy will come back and reinforce the subwoofers output.

Take a look at the sine wave above; see how the *reflection* increases the output of the original wave? Same idea.









*If you know the distance of the reflection, you can calculate the frequency.* And we know the distance, because the reflection is coming off of the ceiling, the floor, the doors, the windshield, etc. What we're aiming for is a big strong reflection off of the front and the back of the car.

The reason we put the sub in the middle is because it gets the front and back reflection to happen at the same time.

As for stereo subs? Yeah I don't subscribe to the concept of stereo bass. You might be able to pick out the left and right channel at 200 or 300hz, but by 100hz it's just pressure changes, there's no stereo information there.


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## Patrick Bateman

In post 74, I described how my last Mazda had Dayton ND91s in a push-pull bandpass.









Here's a pic of the enclosure from the last car

















Here's a pic of the enclosure for my CX5.

The volumes and the tuning are basically the same. The big difference this time around is that I 3D printed it. Also, as noted in post 74, I had some issues trying to cram two woofers into one box. (Couldn't fit them.)

So this time around, it's a single woofer.

One of my criterias was to make it as short as possible; if you look at the height of the box you can see there's a fraction of an inch of clearance above the woofer. The ports for the bandpass exit out the side.










































Here's some measurements of the midbass enclosure that I did this afternoon. Over the years, I've learned that many enclosure types are INSANELY sensitive to air leaks. I think these measurements are an excellent example of this.

The blue line in the measurement is the bandpass response; the green line is the sealed response. I was able to get measurements of both because I left one wall off of the enclosure. IE, I could change it from "sealed" to "bandpass" by closing off the wall. Every one of these measurements shows the progress as I worked to seal the enclosure more and more.

If you review these measurements, you'll notice a few things:

1) The F3 of the enclosure dropped an entire octave. AN OCTAVE. That is huge; that's literally the difference between a 6" woofer and a 12" woofer. And I didn't do anything but seal the enclosure better. In the first measurement the F3 of the midbass is 300hz and by the time I finished it had dropped an octave, down to 150hz(!!!)
2) The frequency response had a series of peaks and dips which mostly disappeared by the time I finished sealing it off.

If anyone is curious how I fixed it, I basically sealed off the interior and the exterior of the enclosure with Loctite PL 400. My hypothesis was that the Dayton woofers were pushing air right through the enclosure walls. This is because I 3D printed the enclosure. Since the enclosure is built up, layer by layer, my hunch was that there's a "gap" between each layer that's a fraction of a millimeter. The enclosure is even watertight, but air has a way of squeezing through gaps in way that water doesn't. I progressively sealed the enclosure more and more, by slathering the inside with Loctite, and then the outside.


















The green line in the top graph shows the response of the bandpass box from my old Mazda.
The blue line in the bottom graph shows the response of the bandpass box from my new Mazda.
The green line in the bottom graph shows the response of the bandpass box from my new Mazda if you "omit" the front chamber, basically turning it into a plain ol' sealed box.

The reason that the rolloff on the two graphs looks so different is that the second graph shows 7.5 octaves while the first graph only shows five octaves.


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## Patrick Bateman

Oh, one more comment:

STOP MOUNTING MIDBASSES IN YOUR DOORS.

It's just a terrible idea. Look at these graphs - the tiniest of leaks will screw up your frequency response, increase distortion, and raise your F3. Doors are leaky as ****. You can put 10,000 pounds of Dynamat in your door and it still won't stop it from leaking. If you absolutely must put a midbass in your door, build a dedicated sealed enclosure like all the pros do. (Gary Summers, all the SpeakerWorks cars, Jon Whitledge, etc.)


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## claydo

Ok.....tried to resist.....but **** it.....sub'd. I guess I'm in for the epicness, be it fail, or success.....

21 drivers.......phew, my 8 give me more headaches than I can handle.....lol.


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## Patrick Bateman

In post 91 I demonstrated how sealing the box made a tremendous difference in the smoothness and the output level - as much as TEN DECIBELS at low frequency.


















Here's a before and after of the enclosure. Notice how you can almost see the gap between the layers? It's probably a fraction of a millimeter, literally microns, but it counts. Air is rather amazing in it's ability to "find a way" out of box. You can have a box that's literally watertight, but air will still escape.

Of course this box is anything but, which is why a liberal application of loctite made a tremendous difference.

Unfortunately this also puts some of my other measurements in doubt, particularly my 3D printed paraline! It appears that a layer of Loctite is basically a requirement if you're going to 3D print something. Paint might do the trick too, but I like Loctite because you can physically 'rub it in' to the surface. (The surface of a 3D printed object is noticeably rough, due to the hundreds of layers.)


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## Lanson

You may also appreciate some form of "plastidip" or something that can coat a surface. I personally like using Rubbermaid rubberized sealant, comes in big-ass cans at Sam's Club.



Patrick Bateman said:


> In post 91 I demonstrated how sealing the box made a tremendous difference in the smoothness and the output level - as much as TEN DECIBELS at low frequency.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's a before and after of the enclosure. Notice how you can almost see the gap between the layers? It's probably a fraction of a millimeter, literally microns, but it counts. Air is rather amazing in it's ability to "find a way" out of box. You can have a box that's literally watertight, but air will still escape.
> 
> Of course this box is anything but, which is why a liberal application of loctite made a tremendous difference.
> 
> Unfortunately this also puts some of my other measurements in doubt, particularly my 3D printed paraline! It appears that a layer of Loctite is basically a requirement if you're going to 3D print something. Paint might do the trick too, but I like Loctite because you can physically 'rub it in' to the surface. (The surface of a 3D printed object is noticeably rough, due to the hundreds of layers.)


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## Patrick Bateman

One thing that I've been trying to do with my 3D printer is "think outside the box" as far as box design goes. For instance, it's very difficult to do spherical enclosures with wood, but spheres are about as good as it gets. Besides reducing diffraction, they're also incredibly strong. I made some spheres for my JBL 400GTIs and the enclosure feels "un-crushable." I wouldn't be surprised if you could run it over with a car and it wouldn't crush. A wood box would break under that kind of pressure.

Home audio manufacturers have been doing this for ages, but they typically use methods that are out of reach to DIY. For instance, Kef sells egg-shaped speakers that are cast out of aluminum.

With a 3D printer, these types of designs are within reach. No need to cast aluminum or built a wooden sphere - you can print just about anything.









This is what a bandpass box looks like. Pretty simple stuff here; it's a sealed box that fires into a coupling chamber. The vent is tuned to the Fb of the sealed box. The net effect is that the vent filters out distortion and high frequencies. The increase in box size raises efficiency. You can also tune the box lower to get a lower F3 than would be normally possible with a plain ol' sealed.









Here's my 'twist' on the design. A sphere inside of a cube. This offers the following advantages:

1) I wanted to get the height of the box as low as possible.
2) A cylinder is stronger than a cube, and a sphere is stronger than a cylinder


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## mitchyz250f

Patrick why did you select the diyma12 and what kind of enclosure will you be using?

Added: Funny that you mentioned a CRX. I am currently building a CRX and am thinking about replacing the 2204s currently in the quarters of my RSX with AE TD12's and eliminate the need for a dedicated sub entirely. I am not interested in going lower than 35Hz. I would be interested in any comments you have on this substitution.


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## legend94

mitchyz250f said:


> Patrick why did you select the diyma12 and what kind of enclosure will you be using?


Because it's the best sq sub ever


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## seafish

Patrick Bateman said:


> Oh, one more comment:
> 
> STOP MOUNTING MIDBASSES IN YOUR DOORS.
> 
> It's just a terrible idea. Look at these graphs - the tiniest of leaks will screw up your frequency response, increase distortion, and raise your F3. Doors are leaky as ****. You can put 10,000 pounds of Dynamat in your door and it still won't stop it from leaking. If you absolutely must put a midbass in your door, build a dedicated sealed enclosure like all the pros do. (Gary Summers, all the SpeakerWorks cars, Jon Whitledge, etc.)


Will using an aperiodic enclosure mounted into the door work as well as a sealed enclosure??

The reason I am asking, is that an AP box can be much smaller then the properly sized sealed box and thus would be much easier to use in some doors.
Obviously, the AP vent would be on the back of the box, inside the door, and the door would still need to be sealed to the inside of the vehicle.


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## Patrick Bateman

mitchyz250f said:


> Patrick why did you select the diyma12 and what kind of enclosure will you be using?


I won it in a contest about a decade ago. npdang sent it to me and I could tell that it was a lot better than the ****ty subwoofers I was using from MCM. I bought one more, with no idea what to do with it. Eventually I wound up putting it in a tapped horn the size of a refrigerator. Nearly died trying to move it:

Night of The Living Bassheads - diyAudio



mitchyz250f said:


> Added: Funny that you mentioned a CRX. I am currently building a CRX and am thinking about replacing the 2204s currently in the quarters of my RSX with AE TD12's and eliminate the need for a dedicated sub entirely. I am not interested in going lower than 35Hz. I would be interested in any comments you have on this substitution.


Tom Danley posted a video on his facebook page, which showed that it took something like EIGHT horn-loaded eighteens to "keep up" with a single 12" midrange.

Basically, I'm on the same page as Danley. If you're using a 12" as a midrange, you should consider using EIGHT eighteen inch woofers to keep up. If you're using a 6" woofer as a midrange, consider using eight 9" woofers, or four 18" woofers.

TLDR: To generate some bass, you need a lot of displacement. Eight 18" woofers is a good start. If you can't do that, figure out what you can fit.


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## mitchyz250f

Patrick I would be using the AE TD12's as a Subwoofer/Mid-bass operating from 35 to 300Hz not as a mid. The mids, centers and rears will be will be PHL 1120s.


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## Patrick Bateman

The beauty of a bandpass box is that you can take a woofer and make it perform like a larger one. For instance, a 3.5" woofer in a bandpass box can put out as much SPL as a 5" or even a 6" driver.

In my Mazda, I'm using four per side to get something that approaches the output of a 10" or 12" woofer.

It looks good on the simulations, but here in the real world you can really see why bandpass boxes have such a ****ty reputation. It too some serious tweaking to get this to work:









This is the "final" design. Green is the sealed response. Red is the bandpass. FINALLY I have it to a point where it's doing what it's supposed to do: play lower and louder than it would if it were in a sealed box.

But that took a ton of work; the tiniest of leaks ****s the whole thing up. There's some kind of weird irony there, that a box with a giant hole in it (the port) is the box that's insanely sensitive to leaks.









Here's the response curve before I went crazy with the rope caulk and the loctitite. Note that the output of the bandpass is actually a little *less* than sealed! (Voltage levels are the same for both measurements, in all the graphs I posted.)


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## Patrick Bateman

seafish said:


> Will using an aperiodic enclosure mounted into the door work as well as a sealed enclosure??
> 
> The reason I am asking, is that an AP box can be much smaller then the properly sized sealed box and thus would be much easier to use in some doors.
> Obviously, the AP vent would be on the back of the box, inside the door, and the door would still need to be sealed to the inside of the vehicle.


IMHO, aperiodic boxes in car audio were mostly just a way to confuse the competition.










Imagine it's 1992 and everyone is running tens and twelves in giant vented boxes. And you see this dude show up with dual fifteens in a tiny box. *It looks like he has some "edge" that you don't.*

The truth is, *this is an infinite baffle design.* The airspace of the entire trunk is "in play."

The reason that it's truly infinite baffle is that it's TRIVIAL to seal off a trunk. In my Hyundai Genesis, the trunk is practically watertight. The entire trunk is walled off with steel, and even the wires going into the trunk have rubber grommets to seal off the trunk. 

Look at my measurements on this page and the one before it. An air gap the size of a thumbtack is enough to kill one or two decibels of output. I can't stress this strongly enough : *leaks cost you SPL.*

And a car door is INSANELY leaky. Dynamat is a band aid, if you want good response from a midbass in a door, *build an enclosure.*



By the way, there might be *another* reason that SpeakerWorks did the aperiodic enclosure. Have you ever considered that the fiberglass was there to filter out high frequencies coming from the trunk?

For instance, imagine that you have two big ol' woofers in the trunk. And you have a pile of gear back there too. *What if the fiberglass filters out the rattles generated by the subs?*

In my home set up, I have all of my electronics built into the midbass cabinet, and the output of the midbass *definitely* generates some buzzing of the electronics. It would look ugly to put Dynamat on your processors, but a foot of fiberglass insulation would definitely dampen those high frequency rattles.

Here's what David Navone wrote about "bass up front." If you agree that the entire trunk is the enclosure, then damping the interface between the enclosure/trunk and the car is critical:

_"There are seven basic requirements for the Bass Up Front illusion. 
#1 = As good a front soundstage as possible
#2 = A well defined psycho-acoustic image
#3 = A steep sub-woofer crossover
#4 = A low distortion sub-woofer
#5 = A quiet, sensible enclosure design
#6 = A suitable vehicle
#7 = A quiet, sub-woofer installation"_


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## thehatedguy

If you did an AP mat over the cones then it would and does clean up the HF output from the woofer. But the same doesn't happen when you have the mats on the rears of the speakers and the cones firing directly into the cabin.

But the fiberglass only acts as a barrier at higher frequencies, the lower stuff pretty much goes straight through.

An AP enclosure can flatten out the impedance curve of the speaker, reducing the resonant peak of the speaker in the enclosure.


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## Patrick Bateman

thehatedguy said:


> If you did an AP mat over the cones then it would and does clean up the HF output from the woofer. But the same doesn't happen when you have the mats on the rears of the speakers and the cones firing directly into the cabin.
> 
> But the fiberglass only acts as a barrier at higher frequencies, the lower stuff pretty much goes straight through.
> 
> An AP enclosure can flatten out the impedance curve of the speaker, reducing the resonant peak of the speaker in the enclosure.


What I'm thinking is that the fiberglass *might* be there to filter out buzzes and rattles from the trunk itself.

Here's an extreme example:

Let's say you have a pair of fifteens installed in your coupe. The trunk is 100% airtight; there ain't no air entering the cabin via the trunk.

Now generate some noise in the trunk, *and the only path into the cabin is via the cone of the woofer.* IE, we're not filtering out sound from the woofer itself, *we're filtering out rattles coming from the trunk itself.* (This is because the cone of a paper woofer is almost acoustically transparent)

You can figure out how much attenuation you'll get fairly easily. It's basically equivalent to the depth of the fiberglass. IE, 13.5" of fiberglass will nuke just about everything from 1khz and up.

But this also means that you really need a TON of fiberglass to get down to 500hz or 100hz.

And the "cutoff" of the fiberglass isn't cut and dry; 13.5" of fiberglass will definitely nuke anything above 1khz, but it will still have a significant effect at 500hz and even 250hz. But the effect at low frequency is less and less pronounced.









Of course, this is why transmission lines are so long.


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## thehatedguy

I would think the amount of fiberglass back there would be pretty insignificant compared to the foam in the rear seat the speakers are playing through.


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## Patrick Bateman

thehatedguy said:


> I would think the amount of fiberglass back there would be pretty insignificant compared to the foam in the rear seat the speakers are playing through.


It's pretty astounding how *little* attenuation you get out of foam.









In my 2014 project, I put closed cell foam *in* the port. So 100% of the woofers output is going *through* the foam.









Here's the frequency response with *and* without the closed cell foam.

The effect is subtle - about two decibels.

Reticulated foam is much more subtle than that; in my Gedlee Summas the tweeter is firing through a foot of solid reticulated foam.

Fiberglass really kills the output; the effect is far, far more pronounced than either closed or open cell foam.

I personally don't use it a lot, because it's results are so difficult to predict. IE, it's so effective, if you have a stereo pair of speakers and the fiberglass moves around a bit, or settles, you could easily wind up with two speakers that don't match.

I'm guessing this is also the reason that manufacturers use closed cell foam. It's 100% predictable.

Dave Smith from Kef/JBL/Snell/Bose etc has posted about this over on diyaudio. I was completely unaware of how ineffective foam is until he posted about it there.


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## Patrick Bateman

Two down, six to go!

















Midbasses fit under the seat rails. I could probably fit an 8" woofer under the seats fairly easily. Downside with an eight is that I can't print it. Also, my 8NDL51s are the midbasses in my home theater now. So those aren't "available" for this project.


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## Lycancatt

so going off what your saying in reguards to fiberglass thickness, I need to make a bass trap in the back right corner of my house to obsorb all the low frequencies that go over there and wash out every other part of the room..13 inches thick will do most down to 1khz, so to get to 40 hz I'd need..a whole lot more, something like 6 ft of fiberglass? then we have to find out over what area I'd need it..I've never built a bass trap before but this just doesn't seem right going off what I've read in the past.


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## Patrick Bateman

Lycancatt said:


> so going off what your saying in reguards to fiberglass thickness, I need to make a bass trap in the back right corner of my house to obsorb all the low frequencies that go over there and wash out every other part of the room..13 inches thick will do most down to 1khz, so to get to 40 hz I'd need..a whole lot more, something like 6 ft of fiberglass? then we have to find out over what area I'd need it..I've never built a bass trap before but this just doesn't seem right going off what I've read in the past.


Yes, to absorb 40hz you would need a piece of fiberglass that's a significant percentage of it's wavelength. 25% would be a good start (2.125 meters) but 100% would be a lot better.

OTOH, to absorb 1000hz you would need a piece of fiberglass that's between 4.25cm and 17cm.










Here's a graph showing the attenuation versus thickness.


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## Donanon

Would adding rockwool or OC-703 to the 'regular' pink fibreglass reduce the thickness required for lower frequency absorbtion? 

D.


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## Patrick Bateman

Donanon said:


> Would adding rockwool or OC-703 to the 'regular' pink fibreglass reduce the thickness required for lower frequency absorbtion?
> 
> D.


Poke around online, I'm not 100% sure.
I know that David Smith was advising people to use fiberglass insulation, because it's so effective. (This was in the context of a discussion of transmission lines IIRC.)

I've seen people use rockwool for cardioids: 2-way: Waveguide + Cardioid-like - diyAudio

A lot of this is academic though. The reason that the SpeakerWorks cars were running open baffle subwoofers was because amplifiers were quite inefficient in that era. Some of the most popular amps of the era were 45 watts(!) and the number of amps and processors that Clark used was considered outrageous at the time. Here in 2015, you can get that much power and processing for about 1/4 the cost, it works better, and the footprint is less than half as much also.

I'm not saying open baffle is bad ; in fact it's great! But if you're running a couple of sealed twelves and a big Class D amp, all of the aperiodic stuff might be more trouble than it's worth.

It *would* be interesting to see someone try it with a modern prosound fifteen. The excursion on those woofers from the 70s was a fraction of what you can get today. Then again, even moder prosound woofers work in smaller boxes, so using the whole trunk might be pointless.


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## Patrick Bateman

Here's some pics of my amplifier, my 12V to 24V step up converter, and my mini DSP.

That 3D printed case is a leftover from my home theater. (This amp and miniDSP was used for my last set of home synergy horns, documented here : Black Mirror - diyAudio )

Come to think of it, the step-up converter is the first thing I've had to buy for this project. The midbasses are from this project : Monster Massive - diyAudio









Here's a pic of where they came from. This project worked pretty well. Too bad I'm so ADHD about my projects.

Right now it's looking like I'll have twenty two drivers, six channels of amplification, and four channels of processing.
I'm hoping to avoid adding another four channels of amplification and DSP, but I can't rule it out.
One cool thing about the way that I'm setting it up is that I can scatter the devices across the car. For instance, I'm going to put the 12V to 24V converter behind the dash, so that I can reduce the size of the electrical wiring that I'm using. (Because 24V requires a conductor that's half the size.)

Still haven't decided if the miniDSP will wind up in the trunk or somewhere else.

The third of eight midbasses is printing right now.


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## SkizeR

sometimes i wonder how much better off you would be with a traditional pro audio set up.. like is there any reason you do all these crazy things in a car when it could be done much easier with traditional methods? like before you said you have 4 3" drivers in a bandpass box in your doors to mimic a 10".. why not just put a 10" in there or the kicks? and why these crazy horns (which i cant admit i even come close to understanding) with multiple drivers on your dash with expanding foam all over the place? why not just a traditional compression driver with a good waveguide on the under dash? im actually curious


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## Patrick Bateman

SkizeR said:


> sometimes i wonder how much better off you would be with a traditional pro audio set up.. like is there any reason you do all these crazy things in a car when it could be done much easier with traditional methods? like before you said you have 4 3" drivers in a bandpass box in your doors to mimic a 10".. why not just put a 10" in there or the kicks? and why these crazy horns (which i cant admit i even come close to understanding) with multiple drivers on your dash with expanding foam all over the place? why not just a traditional compression driver with a good waveguide on the under dash? im actually curious


My 2001 Honda Accord was basically un-sellable after I finished with it.
Sound deadening, removing body panels, opening up the doors.

After that experience, I vowed that if I wanted a quiet car, I would buy a quiet car, and if I wanted to put a stereo in it, I wouldn't touch the stock stereo. I haven't removed a door panel or cut a wire in any of my cars in ten years now.

When I tried to sell my 2001 Honda Accord I literally couldn't find anyone. I ended up giving it to a relative. When I sold my 2005 Honda Accord I got $8000 for it.

TLDR: putting stereos in a car ruins their value.

There's also some technical advantages:

1) If you build the midbass enclosure outside of the car, you can really perfect it. Check out the graphs - I increased the sensitivity of the midbass enclosure by four decibels, lowered the distortion, and lowered the F3. All from the comfort of my desk. Didn't even have to go in the garage or the car. I came close to buying a big printer, so that I could print the subwoofers! 3D printers seriously change your life if you tinker a lot with stereos. Even silly parts you would never consider - for instance I'm printing the wiring organizers, and I'm printing grommets.

2) The world reaps the benefits of this methodology. I can upload the file to Mega and you guys can print it at shapeways. By printing the loudspeakers, literally anyone with a Shapeways account can copy my stereo. Even the crossovers are an XML file. (I posted the crossover for "Monster Massive" at Diyaudio - you can cut and paste it and load the crossover yourself.)

3) Synergy Horns are just a no-brainer, they outperform a $2000 TAD compression driver and cost about $150 to build. I can't think of a single good reason to use a large format compression driver like Mark Eldridge or Richard Clark did. What they used was the best technology available in 1995, but here in 2015 we have better options. It's the same reason I don't get nostalgic about 40 watt class AB amplifiers from the 90s.


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## SkizeR

yes but were in a car.. your doing so much work to put these in a tin can, when you could probably have just as good of results (or even better due to less complications and the unpredictable tendencies of a car) with a traditional method. and most stereo installations car retain value of a car no problem.. when you go and put expanding foam in the corners of you dash without taping stuff off and covering everything else, well then you might see some value loss from the stains and ruined panels lol


----------



## Patrick Bateman

Oh, I should clarify, *this isn't a condemnation of prosound drivers.* If I had a larger 3D printer I probably would have printed an enclosure for a couple of eights. I went with an array of 3.5" drivers because I knew that four of them would offer as much output, I could print them, and they'd fit under the seat.

Another problem with an 8" driver is that you have to figure out some way to move the apparent source of the sound to the edge of the car. A "bare" eight, facing up, is going to narrow the stage because the apparent source is about 10" from the car door. With a 3.5" woofer in a bandpass I can move the apparent source of sound all the way to the edge of the car.

I could also further widen the stage with some crosstalk cancellation. That would be particularly easy in this scenario because I have multiple midbasses. (IE, I could use half of them for crosstalk cancellation, or 25% of them.)


----------



## Patrick Bateman

SkizeR said:


> yes but were in a car.. your doing so much work to put these in a tin can, when you could probably have just as good of results (or even better due to less complications and the unpredictable tendencies of a car) with a traditional method. and most stereo installations car retain value of a car no problem.. when you go and put expanding foam in the corners of you dash without taping stuff off and covering everything else, well then you might see some value loss from the stains and ruined panels lol


It's not a "tin can", it's a 3D printed bandpass enclosure.

And all the work is done in front of the computer. (ahem, do the math, I'm posting at 9:55am, guess who's at work... )

Even the printing is done from the computer.

And the great thing about this is that once you design it, you can print another one whenever you want... Anyone, anywhere in the world.

Imagine if a Mark Eldridge or a Richard Clark had a forum post which included the following:
1) what drivers to buy
2) what amps to buy
3) what crossovers to buy
4) the crossovers, that you can download and run yourself
5) the enclosures, that you can download and print

You could literally have the exact same stereo that they do. And the only cost would be the drivers($800), amps($300), processors ($100), and printing ($100).

Recreating what Eldridge spent hundreds of hours at a cost of $1300 would be neat.

Keep in mind, the real expense of this hobby is TIME. I've probably blown eighty hours on waveguides alone for this project. But once you get it right, BOOM, you can use it for years. The waveguide from my 2009 project was the exact same mold as my 2006. But now I don't bother fiberglassing, I just hit "print"


----------



## SkizeR

Patrick Bateman said:


> It's not a "tin can", it's a 3D printed bandpass enclosure.


i was referring to cars


----------



## rton20s

Patrick Bateman said:


> It's not a "tin can"...


It's aluminum...


Patrick Bateman said:


>


----------



## sqnut

Patrick Bateman said:


> Recreating what Eldridge spent hundreds of hours at a cost of $1300 would be neat.


Eldridge's car, Jims's car, the magic bus, KP's car and my buddy Aarons car sound the way they do because the owner spent thousands of hours tuning the damn thing. Equipment and install matter but only ~30%. It's a do once and forget about it thing. The secret is in the tune.


----------



## Patrick Bateman

sqnut said:


> Eldridge's car, Jims's car, the magic bus, KP's car and my buddy Aarons car sound the way they do because the owner spent thousands of hours tuning the damn thing. Equipment and install matter but only ~30%. It's a do once and forget about it thing. The secret is in the tune.


Absolutely. And that's what's so magical about the process that I am proposing.

*You would get the same tune.*

Heck, you could even have three or four "tunes" saved up.
Here's why this is:

If you print the speakers, use the same DSP and amps, and copy the crossover and EQ settings, *that's the whole thing.* There's nothing left to do.

What boxes like the MS-8 do is try and automate that tuning process. But what if you could copy the 'tune' of a Gary Summers?

I think that's one thing that's interesting about Gary's car is that Gary hired experts to do the fabrication, and Gary focused on the tuning. And since music is literally his job, he can probably tune better than 99.9% of us.

Now would it be practical to have Gary tune your car? *No, it wouldn't.* Gary's got a day job - you can enjoy the sound of his car but I don't think he's going to come to your house and tune your car.

But what if you could simply COPY every last part of it? Literally go on the Internet, get the parts on Amazon and download everything else? With 3D printing, we can do that. It also opens things up for collaborative projects. For instance, I can make a decent waveguide in 3D and print it, but my sub boxes are embarassing. What if I made the waveguide and Jason designed the subs? We can design a car stereo the same way we design software, in groups.



On a side note, if you ever go to hifi shows, you'll quickly notice that 75% of the speakers are expensive and don't sound good. And 25% of the speakers sound great, and they barely ever change. I think the reason for that is that it's mostly the tune. You can have the best amps, speakers, DSP, and fabrication, but if the tuning is crap, the end results will be forgettable. IE, even at the stereo shows, the best speakers have frequently been refined over years or even decades. (Kef's wonderful monitors are an evolution of a design that's pushing 40 years old now.)


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## SkizeR

different car = completely different tune. how many people do you know with the same cars running similar equipment? hell, i dont think ive seen many build logs of the same car another member has.


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## Patrick Bateman

SkizeR said:


> different car = completely different tune. how many people do you know with the same cars running similar equipment? hell, i dont think ive seen many build logs of the same car another member has.


Think of it this way:

If you went to a sound off, and heard someone's car, and it blew you away. And then you found out that everything you heard was available as an open source project.

*Would YOU consider buying that car?*

I would. Heck, we've seen a handful of cars trade hands in the community.

Also, though it's true that the car will make a big difference, I feel fairly certain that you could take most systems and 'forklift' them into a similar car. For instance, a system that works in a 2006 BMW 3 series will likely work in a 2015 BMW 3 series, as long as the speaker locations are the same.

IE, this type of 'open source' project would be a good route for the same type of person who wants to build a headphone amplifier or DAC, but doesn't want to spend ten years learning HOW it works. That type of person just wants it to work.


----------



## SkizeR

Patrick Bateman said:


> Think of it this way:
> 
> If you went to a sound off, and heard someone's car, and it blew you away. And then you found out that everything you heard was available as an open source project.
> 
> *Would YOU consider buying that car?*
> 
> I would. Heck, we've seen a handful of cars trade hands in the community.
> 
> Also, though it's true that the car will make a big difference, I feel fairly certain that you could take most systems and 'forklift' them into a similar car. For instance, a system that works in a 2006 BMW 3 series will likely work in a 2015 BMW 3 series, as long as the speaker locations are the same.
> 
> IE, this type of 'open source' project would be a good route for the same type of person who wants to build a headphone amplifier or DAC, but doesn't want to spend ten years learning HOW it works. That type of person just wants it to work.


no i wouldnt.. best car i heard was a kia, and i certainly dont ever plan on getting a kia lol


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## rton20s

SkizeR said:


> no i wouldnt.. best car i heard was a kia, and i certainly dont ever plan on getting a kia lol


There is a big difference between what Kia was and what Kia is.
This...









is not the same as this...


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## Patrick Bateman

I'm thinking I *might* do a Paraline for the mids and highs.

For those who haven't suffered through my threads at Diyaudio, a Paraline is a plain ol' waveguide, but it's folded in such a way that you get a wavefront that's like a ribbon tweeter. 

Paralines allow us to do something with underdash waveguides which is otherwise impossible.

This is about to get hideously technical so bear with me.









When you put a horn under the dash of a car, you end up with a speaker that is firing into your knee caps. The reason that it works surprisingly well is that only a *fraction* of the sound goes into your knee caps; the rest of it radiates into 180 degrees. In other words, *there are certain frequencies in an underdash waveguide which DO make it to your ears.* Unfortunately, it is not 100%. To be specific, *everything shorter than the height of the waveguide will not make it past your kneecaps.* (And when I say "past your kneecaps" I mean "the sound isn't radiated UP and to your ears - it goes straight forward.)

For instance, 6750 hertz is 2" long. So if you have a waveguide that's 2" tall, *everything above 6750hz is going straight into your kneecaps.

This is why you see a lot of HLCD guys ask about adding tweeters up high. The high frequencies from their compression drivers are sometimes going into their kneecaps. There's also another way to fix the problem that Eric Stevens uses.

Okay, so in picture number one, our driver has a lot of high frequencies going into the knees.

In picture number two, we've angled the waveguide UP. This fixes the problem quite nicely. Unfortunately, it makes the car undrivable. Because if you have a waveguide that's 6" deep and you tilt it up 45 degrees, you won't be able to reach the pedals.

So here's where the Paraline comes in. It is a folded horn - so you could have a waveguide that would be six inches deep if unfolded... But once you fold it it's an inch deep.









Here's a Danley Paraline. We're talking about an inch thick.









The problem I always had with any horn or waveguide that expands slowly is that they sound terrible. For instance, here's a measurement of a 'Smith Horn' I made. Waves really REALLY hate parallel surfaces, and the Paraline has a bunch of them.









Here's the response of a Danley Paraline. It is head and shoulders better than the yellow measurement above, the Smith horn I made. I haven't heard the Danley Paraline but I'm certain it sounds better than my Smith horn.









I 3D printed a Paraline. With the 3D printer, I'm getting much MUCH closer to the response of Danley's Paraline. (I believe Danley uses CNC routed aluminum.) The graph above shows the vertical response, on and *off* axis. (See how it drops off quickly? We want that, so we can "aim" it past the kneecaps.)

So I'm thinking I might be able to exceed the performance of the Danley Paraline, if I increase the expansion rate a little bit, 3D print the waveguide, and seal it up tight. (Remember from a couple of pages ago, 3D printed speakers are leaky... This Paraline that I made has not been sealed up 100%.)

*


----------



## seafish

Do not want to oversimplify things here that i do not necessarily understand, but couldn't you install/mount the paraline horn at an upwards facing angle towards the listener??


----------



## Patrick Bateman

seafish said:


> Do not want to oversimplify things here that i do not necessarily understand, but couldn't you install/mount the paraline horn at an upwards facing angle towards the listener??


That's exactly what I would do. (If it works at all.)

It's just basically a way to take a horn that's 6" deep and flatten it into 1" deep.

(When I first started doing it I tried it with horns deeper than that, and ran into issues.)


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## thehatedguy

A lot of car horn guys want or wanted tweeters because of RTA competition.

That and the HF dispersion really narrows with the horns, and the tweeters add some ambiance/sparkle/shimmer to the highs that is really missing from horn cars because of the narrow dispersion.


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## Patrick Bateman

Since I'm going all 3D and ****, I have to figure out how tall to make it.









First, we start with a radial horn, like a smith horn. The only difference here is that we're going to make it radiate in 360 degrees and we're going to make it shorter.

We need to figure out the proper height. In order to do this, I am going to simulate a waveguide that radiates in 360 degrees, then sim one that has 40 degrees of coverage. (I think 40 degrees is about as low as you want to take it, any lower and you start to get ripples in the response.)









Here's a sim of the 360° waveguide, and the 40° x 40° waveguide. *You can see the 40° x 40° is smoother.* Two decibels at 2khz isn't much, but I generally find that the ripples continue across the entire bandwidth. (Hornresp has a hard time predicting high frequencies; it's really designed to sim midranges and subs.)

















Here's the sims showing the 360° waveguide versus the 40° x 40° waveguide. The main thing to note is that the area of the 360° waveguide is a little bit too low; it needs to be increased by about 30%. That would raise the height of the Paraline from 0.2" to 0.26". (Yes, that's not a typo. About one quarter of an inch.)


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## Patrick Bateman

If anyone is interested in seeing some proof of how the expansion rate affects the response, here's a couple of real examples.

















^^ here's one with a slow expansion rate and parallel walls. Lots of peaks and dips. This is not hifi.

















Here's the awesome QSC waveguide, with a fast expansion rate, and beautiful response.

TLDR: slow expansion rates and parallel walls are a bad thing.


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## Patrick Bateman

I'm going to see if I can make something like the VDOSC waveguide from L'Acoustic. It's basically a paraline, but in 3D.

















Some pics of it coming together.


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## Elgrosso

Didn't know L-acoustic, interesting article on the Hollywood Bowl on their site... Thanks for sharing!


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## Patrick Bateman

Hopefully I should be ready to print this by this afternoon.









Here's the real deal

Patent US5163167 - Sound wave guide - Google Patents
Here's the patent. It's invented by Christian Heil. For some reason that name sounds familiar, didn't he do some home speakers too?

https://www.youtube.com/watch?v=-EHIragGFDg
Here's a video of them playing. I wish I could figure out which is which. (Video is in polish.)


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## thehatedguy

Oskar Heil created the air motion transformer.

Dr. Christian Heil was a partical physicist before starting that company.

Don't think the 2 are related.


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## Patrick Bateman

I really need to stop building VDOSCs and Paralines because they don't work so hot 

Here's a measurement of the one I built Saturday:

1) The best response graph, the green trace, is my underdash waveguide.
2) The second best response, the red trace, is the VDOSC I printed
3) The worst response, the blue line, is the Paraline I printed

The VDOSC definitely seems to work a little bit better than the Paraline, but difference is subtle. And the Paraline is significantly smaller. The waveguide is the largest but it is by far the smoothest. It also sounds better.

I feel like if I made some tweaks to the VDOSC I could probably improve, but I'm not convinced it would equal the waveguide.

It would be "neat" to have a very narrow vertical coverage angle, but if that's a requirement, it probably makes more sense to use a Sausalito Audio Works lens.

I'm not 100% ready to abandon it, but I *am* ready to fire up the printer and print a waveguide.


By the way, the Paraline and the waveguide in this measurement are loaded with a compression driver. The VDOSC is loaded with a Dayton RS28. I'm trying to use my 3D printers to print the phase plug, so we can use regular domes instead of compression drivers.


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## Patrick Bateman

Here's a couple pics of a 'proof of concept' of a RS28 waveguide, using a plain ol' waveguide.

The sphere is to see if there's enough space to squeeze some mids onto the waveguide, a la Synergy Horn. It's tricky with a dome because the exit angle of a dome tweeter is much larger than a compression driver.


----------



## Orion525iT

Would a small AMT tweeter work, or would it be too difficult to get it to play low enough? 

Maybe the fact that I just threw down three beers after a 20+ mile blitz on my single speed mountain bike has me addled, but I always feel like these things end up too big. You design a waveguide, and I notice you seem to keep drifting back to some version of a unity, then once you get it to work, you have to retroactively go back and try to cram it into a place where it will fit. Its all seems like a lot of square peg, round hole. 

So, I know I have mentioned this before, and I think your reply hinted that I was thinking backwards. But why not try to get better polars from a larger driver? You get more output, and more power handling. You can separate your drivers. You can place them in less then optimal angles and locations because your power response has improved. It just seems the options are much wider by going that way about it. I am saying throw out any idea of directivity control, the environment is too darn chaotic to begin with and there just isn't enough space.


----------



## Patrick Bateman

Orion525iT said:


> Would a small AMT tweeter work, or would it be too difficult to get it to play low enough?


Ribbons work better than domes on a waveguide. In fact, they can work better than a compression driver.

Main problem for my projects is the center-to-center spacing; if you're trying to do a Synergy horn or the like, it's hard to get the mids close enough because the diaphragm is so big.

Also, you can't get much horn loading with something like a BG NEO3 because the throat is too large.

If you're willing to sacrifice the vertical polars, a tall thin ribbon works great. Which is why Peavey uses a tall thin ribbon in their arrays.

I think a French company called "Stage Accompany" did the same thing, but they're kaput iirc



Orion525iT said:


> Maybe the fact that I just threw down three beers after a 20+ mile blitz on my single speed mountain bike has me addled, but I always feel like these things end up too big. You design a waveguide, and I notice you seem to keep drifting back to some version of a unity, then once you get it to work, you have to retroactively go back and try to cram it into a place where it will fit. Its all seems like a lot of square peg, round hole.


Nah, I tend to do variations on the same thing over and over again. Synergy horns with everything miniturized. Smaller tweeter, smaller midrange, smaller midbass than The Real Deal.

All of this works because the Synergy Horn concept scales; the same math you use to design a 100lb Synergy horn is the same math you use to design a 1000lb Jericho horn. Same idea, just bigger.



Orion525iT said:


> So, I know I have mentioned this before, and I think your reply hinted that I was thinking backwards. But why not try to get better polars from a larger driver? You get more output, and more power handling. You can separate your drivers. You can place them in less then optimal angles and locations because your power response has improved. It just seems the options are much wider by going that way about it. I am saying throw out any idea of directivity control, the environment is too darn chaotic to begin with and there just isn't enough space.


I already have a car with separate drivers. I have a Hyundai Genesis with the Lexicon system in it. Sounds nice.

I generally find that my Synergy horns have sweeter treble, better imaging, better dynamics, and better bass than my Lexicon system. But the Lexicon system is better than 85% of the aftermarket stereos I've heard.

As far as 'throwing out the idea of directivity control', well that's just silly. Most of the best car stereos have directivity control:

1) Richard Clark did it with horns
2) Gary Summers does it with a horizontal array
3) Mark Eldridge did it with horns
4) Jon Whitledge does it with a vertical array
5) Harry Kimura did it with horns
6) Gary Biggs did it with waveguides
7) Mic Wallace did it with horns

I could go on and on. In fact, I can't think of many truly good systems that didn't have some sort of directivity control, be it with waveguides, horns or arrays.


----------



## Orion525iT

Patrick Bateman said:


> Ribbons work better than domes on a waveguide. In fact, they can work better than a compression driver.
> 
> 
> Also, you can't get much horn loading with something like a BG NEO3 because the throat is too large.
> 
> If you're willing to sacrifice the
> 
> 
> 
> Nah, I tend to do variations on the same thing over and over again. Synergy horns with everything miniturized. Smaller tweeter, smaller midrange, smaller midbass than The Real Deal.
> 
> All of this works because the Synergy Horn concept scales; the same math you use to design a 100lb Synergy horn is the same math you use to design a 1000lb Jericho horn. Same idea, just bigger.
> 
> 
> 
> 
> As far as 'throwing out the idea of directivity control', well that's just silly. Most of the best car stereos have directivity control:
> 
> 1) Richard Clark did it with horns
> 2) Gary Summers does it with a horizontal array
> 3) Mark Eldridge did it with horns
> 4) Jon Whitledge does it with a vertical array
> 5) Harry Kimura did it with horns
> 6) Gary Biggs did it with waveguides
> 7) Mic Wallace did it with horns
> 
> I could go on and on. In fact, I can't think of many truly good systems that didn't have some sort of directivity control, be it with waveguides, horns or arrays.


I was kinda joking about the directivity. I am trying to load one of those little Amtpod things in the corner of the dash, and i simply don't have the room for anything else up there. So I am back to doing 2 driver horizontal arrays using whispers, mounted under the dash kinda like a horn would be.


----------



## thehatedguy

Mark's NASCAR and Ben Volmer's Acura (used to be Harry Kimura's Acura) use an array (which I think) is similar to the one Keele outlined in a patent that I have linked to about horizontal arrays in a car.

Most people say the NASCAR is better than the 4 Runner...I haven't heard it yet.

But I don't think it was done in those cars for directivity control though.

But if you are basing "good" on winning and scores, Scott Buwalda's black car is the highest scoring car in IASCA history...and it uses 8s in the kicks with a 4 and tweeter in the dash somewhere.


----------



## Patrick Bateman

thehatedguy said:


> Mark's NASCAR and Ben Volmer's Acura (used to be Harry Kimura's Acura) use an array (which I think) is similar to the one Keele outlined in a patent that I have linked to about horizontal arrays in a car.
> 
> Most people say the NASCAR is better than the 4 Runner...I haven't heard it yet.
> 
> But I don't think it was done in those cars for directivity control though.
> 
> But if you are basing "good" on winning and scores, Scott Buwalda's black car is the highest scoring car in IASCA history...and it uses 8s in the kicks with a 4 and tweeter in the dash somewhere.


Interesting, I'll have to see what I can find on that.

It would be really awesome if we could just array a bunch of small speakers across the dash, since they'd fit so easily.

But when you have pathlengths that are different, you can't get the signals in phase, and if you can't get the signals in phase, you get trashed frequency response too.

The only reason it works with Opsodis is that the filters are steep, so the xover between elements is minimal.

BUT...

You can make a bunch of horizontal speakers look like *one* driver via the use of:

a) delay

or 

b) built-in curvature

There's a follower of Keeles that make a couple of horizontal arrays like this, one using method b, then another using method a.

Might be interesting to explore if it would work.

Of course, I have no idea how to do that in stereo.


----------



## thehatedguy

Keele does do an array across the dash in that patent and explains a bit on how to process it.

Mark is using 6 or 8 (I forget which) JL C5-650s across the dash in his car with a 12W6 in each kickpanel. The only processing is the dBx unit.

Ben's car has XR5.25s across the dash (I think they are 5.25s) and a single 10 in the center. He is running a pair of dBX 482s.


----------



## thehatedguy

An amplitude based panned array would be the ticket...to steer the sound to a speaker or between speakers.


----------



## Patrick Bateman

thehatedguy said:


> Keele does do an array across the dash in that patent and explains a bit on how to process it.
> 
> Mark is using 6 or 8 (I forget which) JL C5-650s across the dash in his car with a 12W6 in each kickpanel. The only processing is the dBx unit.
> 
> Ben's car has XR5.25s across the dash (I think they are 5.25s) and a single 10 in the center. He is running a pair of dBX 482s.


Damn Jason why do you have to get me thinking about doing an array 









In my previous post, I mentioned that I couldn't see how to do it in stereo. This is because I was picturing a horizontal array like Monty Kay's CBT. The way that Monte's array works is that it behaves like a point source that's a few feet away. Basically, *a point source expands spherically, so Monte's array mimics the behavior of a point source after it's expanded into a circle.*

Of course, you'll notice that Monte's array is one-dimensional; if it was truly spherical, it would look like a sphere, not a ring. (That would get pretty expensive.)

Monty ditched this array, and replaced it with a FLAT array, where DSP is used to curve the output. IE, he still gets the circular wavefront, but the curvature is done via DSP, not via physically curving the array.

This is an attractive option for a lot of folks, because building a curved cabinet is not trivial.

You can also use DSP to make all kinds of weird wavefronts, or do it physically.









The JBL CBT array is J-Shaped. Also, does anyone "see" what happens when you go from a full-on half circle (like Monty's) to the gentle J-shaped curve of the JBL? What you end up with is a narrower vertical beamwidth. Basically a perfectly flat array would create a flat wavefront, a 45 degree array would create a 45 degree wavefront, and this gentle curve on the JBL creates something like 20 degrees of vertical coverage. (I'm too lazy to look at the PDF, I'm eyeballing it.)

I had a six hour drive to Arizona today, and it occured to me that you could get stereo by simply doing a couple of curved arrays in each corner. OR you could use a straight array, all across the dash, and do the curvature via DSP. (Like Monte did.)

I believe that the JBL is passive, hence the physical curvature. And of course you *could* do both. This is how the giant rigs at concerts work, they can 'dial in' the vertical angle via DSP. You use DSP to pick your vertical coverage angle.

Of course, all of this is academic, and I generally find arrays to sound horrendous. But if Mark's car had good reviews, I'm curious. I've heard the L'Acoustic arrays and they definitely sound head and shoulders better than any array I've heard in the last decade.


----------



## cajunner

I've read where the array sound for hi-fi, is that of an expansive, larger than life stage presentation.

some people dig that, I don't know if I'd like it as much as the clarity of a point source for vocals and stuff.

but maybe that's dependent on what you play, as much as what you play it on.

if you like big orchestral works that you can close your eyes and it sounds like you're in the venue, with big air overhead and Michelangelo's hand pointed to...

well, then you'd not be me, because I have not been able to supplant the classic rock base that is comfort food for my listening time.

I can dig some Skrillex because you know, it's like that but in the same vein, do you expect a concert sized stage in your car because you put in some arrays?


And is that the goal, then?

Anything that goes from intimate, chair height sized acoustic music, to blasting "Sprites" 40 feet from car's front end, is a win, haha...

I think I read where the stage is supposed to be about the size of a sheet of plywood floating 5 feet in front of your car's windshield, and about as thick as a sofa...


----------



## Patrick Bateman

cajunner said:


> I've read where the array sound for hi-fi, is that of an expansive, larger than life stage presentation.
> 
> some people dig that, I don't know if I'd like it as much as the clarity of a point source for vocals and stuff.
> 
> but maybe that's dependent on what you play, as much as what you play it on.
> 
> if you like big orchestral works that you can close your eyes and it sounds like you're in the venue, with big air overhead and Michelangelo's hand pointed to...
> 
> well, then you'd not be me, because I have not been able to supplant the classic rock base that is comfort food for my listening time.
> 
> I can dig some Skrillex because you know, it's like that but in the same vein, do you expect a concert sized stage in your car because you put in some arrays?
> 
> 
> And is that the goal, then?
> 
> Anything that goes from intimate, chair height sized acoustic music, to blasting "Sprites" 40 feet from car's front end, is a win, haha...
> 
> I think I read where the stage is supposed to be about the size of a sheet of plywood floating 5 feet in front of your car's windshield, and about as thick as a sofa...


For imaging, my gold standards are probably the Danley SH50 and the Quad ESL. Both work on a similar idea.









The Quad ESL has a series of concentric rings. In order to generate a spherical wavefront, Quad uses a delay network. Details here : Quad ESL News

The key thing here is that the Quad might *look* like a flat array, *but it's not.* It creates a wavefront equivalent to a point source via the use of delay. It's pretty difficult to find someone that isn't enchanted by the sound of a Quad. The only real complaint is that it won't get loud.









SH50 works the exact same way. A concentric ring of high, mid, and low. The drivers are physically located forward of the apex to compensate for the delay introduced by the passive filters. IE, if you used digital or analog delay, you could "flatten" it like the Quad.

I haven't had Quads in my house. I've had some SH50s in my house. I found that the soundstage was as big as the recording. IE, on a recording with a really large stage, the soundstage was large. And vice versa.

It really makes you appreciate the recording engineer. For instance, I was listening to "Maps" by the Yeah Yeah Yeahs, and at the beginning of the song you can hear this HUGE acoustic space. And then the space collapses. Basically what was happening was that the beginning of the song was minimally mic'd, so you got a good sense of the space. And then, when the rest of the band kicked in, all the ambience of the space disappears. (Due to the multiple mics in play.) Neat stuff - it's hard to hear a space like that without using headphones. And I hate headphones.


----------



## Jepalan

Patrick Bateman said:


> <snip>
> It really makes you appreciate the recording engineer. For instance, I was listening to "Maps" by the Yeah Yeah Yeahs, and at the beginning of the song you can hear this HUGE acoustic space. And then the space collapses. Basically what was happening was that the beginning of the song was minimally mic'd, so you got a good sense of the space. And then, when the rest of the band kicked in, all the ambience of the space disappears. (Due to the multiple mics in play.) Neat stuff - it's hard to hear a space like that without using headphones. And I hate headphones.


I'm so glad someone else actually hears these things. I do this with Yes recordings all the time - Yes Album, Fragile, Tormato, Going for the One, et al. There is so much 'recording engineer' to listen to in these recordings.


----------



## thehatedguy

I think ideally if you had the processing power, you would line a mid and tweeter (or coax) across the dash...at minimal you would want left, left-center, center, right-center, and right speakers. Anything that was left would go left and right-center would go to that speaker location. It would be an array of sorts, but one long one. It wouldn't be stereo per say, but you would have l-r separation from signal steering.

I am fairly certain that is what Mark has done in his NASCAR and what he did in Ben's/Harry's old Acura. I haven't read the patent recently in depth to see how you would pull it off in terms of processing power. If you had a carputer, and a **** load of speakers, VBAP would be the **** if you could get it to work out.

I know Mark is supposed to be pretty forth coming with the hows and whys in that car- many people have seen behind the dash covers and have talked to him about what is going on in the car. If I ever see him in person again, I will ask a few questions...as I know it is an array and it's not "stereo" as we know it to be.


----------



## thehatedguy

And I think Keele's patent mentioned putting the speakers somewhere between the windshield and dash boundaries...and he wanted them to be as fullrange as possible. I remember the drawing having a **** ton of 3s lined all the way across the front of the car.

It really is neat...you wouldn't need directivity control because the image location is where the speaker is at, splitting between pairs of speakers.

*[8] Steven W. Hutt, D. B. Keele, Jr.,**“Vehicle Loudspeaker Array,” **U. S. Patent No. 8,073,156 (Dec. 2011).*
*ABSTRACT:*
An audio processing system for a vehicle includes a plurality of loudspeakers positioned to form a single line array. The loudspeaker line array is positionable in a vehicle on a dashboard of the vehicle substantially at the convergence of the dashboard and a window of the vehicle. When the loudspeaker line array is driven by an audio signal, a vertically and horizontally focused and narrowed sound pattern is perceived by a listener in the vehicle. The sound pattern is the result of the constructive combination of the direct sound impulses and the reflected sound impulses produced by each loudspeaker in the array. Using delay, attenuation and phase adjustment of the audio signal, the sound pattern may be controlled, limited, and directed to one or more locations in the vehicle.


----------



## cajunner

thehatedguy said:


> And I think Keele's patent mentioned putting the speakers somewhere between the windshield and dash boundaries...and he wanted them to be as fullrange as possible. I remember the drawing having a **** ton of 3s lined all the way across the front of the car.
> 
> It really is neat...you wouldn't need directivity control because the image location is where the speaker is at, splitting between pairs of speakers.
> 
> *[8] Steven W. Hutt, D. B. Keele, Jr.,**“Vehicle Loudspeaker Array,” **U. S. Patent No. 8,073,156 (Dec. 2011).*
> *ABSTRACT:*
> An audio processing system for a vehicle includes a plurality of loudspeakers positioned to form a single line array. The loudspeaker line array is positionable in a vehicle on a dashboard of the vehicle substantially at the convergence of the dashboard and a window of the vehicle. When the loudspeaker line array is driven by an audio signal, a vertically and horizontally focused and narrowed sound pattern is perceived by a listener in the vehicle. The sound pattern is the result of the constructive combination of the direct sound impulses and the reflected sound impulses produced by each loudspeaker in the array. Using delay, attenuation and phase adjustment of the audio signal, the sound pattern may be controlled, limited, and directed to one or more locations in the vehicle.


with the digital manipulation, you could put a series of small radiators down the A-pillars to create the spaciousness, while the horizontal in-dash would give you that directed or steered point of attack. The fun part of digital sound domains is that if you can direct the image to a point in the car, you should also be able to recreate any listening venue or space as well. The signatures would not be restrained by factory locations for speakers.

Didn't some guy, Bongiosto or something like that, attempt to make some kind of stereo manipulation that deals with this?

Maybe had a special process, algorithm that did something, anyone remember that one?


----------



## Orion525iT

Patrick Bateman said:


> Damn Jason why do you have to get me thinking about doing an array
> 
> This is an attractive option for a lot of folks, because building a curved cabinet is not trivial.
> 
> You can also use DSP to make all kinds of weird wavefronts, or do it physically.
> 
> Of course, all of this is academic, and I generally find arrays to sound horrendous. But if Mark's car had good reviews, I'm curious. I've heard the L'Acoustic arrays and they definitely sound head and shoulders better than any array I've heard in the last decade.


Yeah, one of the first things I did when I got my 2x8 was hook 4 whispers in array, and spent some time fiddling with the delays. You could get some really weird effects. It was neat to be able to play into beaming range off axis, and then bend the wave front back towards the listening position. I think there is a limit to how far and at what frequencies you could effect. But it seemed like 60 degrees more or less in either direction. I am sure the reason is in the math. If I am thinking about this correctly, the absolute maximum angle at a particular frequency is essentially cardioid, 

You could potentially set up a system with a whole bunch of drivers in an array off axis (not just in an linear fashion, squares circles ect) play into a range where the array would normally start to beam (like a larger driver would) and then bend the wave front back towards you. 

I started to wonder what could be done with a whole crap ton of processing. You could set up a system that would track the seat position and then adjust the array dynamically to that new position. Heck, you could have a laser tracking you as you moved around in a room so that you are always in the "sweet spot".


----------



## cajunner

Orion525iT said:


> Yeah, one of the first things I did when I got my 2x8 was hook 4 whispers in array, and spent some time fiddling with the delays. You could get some really weird effects. It was neat to be able to play into beaming range off axis, and then bend the wave front back towards the listening position. I think there is a limit to how far and at what frequencies you could effect. But it seemed like 60 degrees more or less in either direction. I am sure the reason is in the math. If I am thinking about this correctly, the absolute maximum angle at a particular frequency is essentially cardioid,
> 
> You could potentially set up a system with a whole bunch of drivers in an array off axis (not just in an linear fashion, squares circles ect) play into a range where the array would normally start to beam (like a larger driver would) and then bend the wave front back towards you.
> 
> I started to wonder what could be done with a whole crap ton of processing. You could set up a system that would track the seat position and then adjust the array dynamically to that new position. Heck, you could have a laser tracking you as you moved around in a room so that you are always in the "sweet spot".


I saw that on MI:Mission Impossible.

they sprayed some radioactive dye on this guy's hair and...


haha..

nice bit about the Whisper arrays, how far apart did you have them, and did you do 4 per side or just 4 across?

the Whispers are pretty sweet when you can use a bunch of them, I think that was the Pioneer flagship plan when they put a few dozen of them in a flat panel that sat under the plasma tv...

but would it work in the car?

I mean, if you had 40 of them, how low could you comfortably go with them if they were all just loafing along?

a not-too-expensive experiment that could mimic the B&O Audi, I think it was?

The 62 speaker steered array?


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## thehatedguy

Amplifier channels would get pretty spendy...lol


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## cajunner

thehatedguy said:


> Amplifier channels would get pretty spendy...lol


in comparison to the cost of the software for the carPC, I wouldn't think it to be too bad...

I mean, I wouldn't link 5 2X8 miniDSP's together for something like this, I'd have to go all VST plug-ins and ****...

haha.. I don't have the technical savvy to know if linking the miniDSP's would be better than something more centralized, the Mac mainframe or the IBM PC stations...


but for amplification I would stumble, since I'd go 12V chip amp, and the 8 ohms per Whisper will stymie...

stymie, that's not a word you see every day.


----------



## Patrick Bateman

thehatedguy said:


> I think ideally if you had the processing power, you would line a mid and tweeter (or coax) across the dash...at minimal you would want left, left-center, center, right-center, and right speakers. Anything that was left would go left and right-center would go to that speaker location. It would be an array of sorts, but one long one. It wouldn't be stereo per say, but you would have l-r separation from signal steering.
> 
> I am fairly certain that is what Mark has done in his NASCAR and what he did in Ben's/Harry's old Acura. I haven't read the patent recently in depth to see how you would pull it off in terms of processing power. If you had a carputer, and a **** load of speakers, VBAP would be the **** if you could get it to work out.
> 
> I know Mark is supposed to be pretty forth coming with the hows and whys in that car- many people have seen behind the dash covers and have talked to him about what is going on in the car. If I ever see him in person again, I will ask a few questions...as I know it is an array and it's not "stereo" as we know it to be.


Jason,

I usually dismiss arrays because I haven't heard any that didn't sound like crap. But I think you may have found one that's special. I gave it some thought, and I think there may be a solution here.

Bear with me, this is about to get confusing.

First off, I have heard the Keele CBT, and I didn't like it. The reason that I didn't like it was because the soundstage was very diffuse. Basically, *you could walk around the room and the sound did not change, but the image never came "into focus" the way it does with a set of Dynaudio or Vandersteens.* The thing that really disappointed me about the CBT was that it was $7000 but it didn't sound much different than a Bose Wave Radio. Big, spacious, pleasant, and unfocused.

But hold that thought, I think there's a fix...









The reason that constant directivity waveguides work well in a car is because *the far speaker gets louder as you move off-axis, and the near speaker gets quieter as you move closer to it.* The graph above shows this in detail. This is a polar response of a Gedlee Abbey. Basically you can see that if you cross-fire the speaker *it's louder at the passenger seat than at the driver's seat.* This is a neat trick; it means that you can have a loudspeaker that's literally inches away from you and you can't tell that it's there if you don't see it.

My favorite example of this is when I had some Danley Synergy horns at my house. Our twelve year old daughter was sitting literally a FOOT from the loudspeaker and asked "is it on?" It was playing about 100dB! But thanks to the wonder of constant directivity, she thought that the sound was coming from the other side of the room. (Because the OTHER speaker was pointed at her, and the one near her was pointed away.)









For some nifty diagrams, check out Geddes paper here: http://www.gedlee.com/downloads/Philosophy.pdf
And my forum post here: http://www.diymobileaudio.com/forum...ussion/60146-creating-perfect-soundstage.html

















Here's some horizontal polars of the Keele CBT array. *See how they're dramatically different than the Gedlee polars?* The Gedlee speaker is "hot" on axis, but if you move off-axis, it falls off. The Keele CBT doesn't do this; if you're on axis or you're off axis, *the level is basically the same.* Except in the treble, where it's hotter on-axis.

THIS IS TERRIBLE.

We want polars that look like the Geddes speakers : similar shape on-axis as off. The CBT doesn't do that.

















Here's something interesting though. This is the VERTICAL polars of the CBT, versus the HORIZONTAL polars of the Geddes waveguide.
Check out how similar they are!

I'm going to go out on a limb here and state that *for listening at home or in the car, the CBT array works better horizontally than vertically.*









IE the optimum CBT is horizontal, like this, not vertical, like the one that Keele has published.









This begs the question:
If the CBT works better horizontally, then why did Don Keele design a vertical CBT for Parts Express?
I think the answer is very simple : the CBT array was never intended for home audio. Keele works for JBL, designed it for JBL, and it's intended for live audio. *Check out Don's measurements.* The CBT is "hot" at the center of the array. If you put a CBT into a church or into an auditorium, *the majority of the volume is directed at the back of the room.* Even better, *the "quietest" part of the beam is aimed at the front of the room.

So for a big room, the CBT is brilliant. It allows JBL to sell a speaker that gives even coverage from the front of the room to the back of the room. Point the center of the CBT at the back of the room, and it's basically going to sound the same from the front of the church to the back.

But here in car audio we don't have that problem. I'm not trying to light up the people in a car thirty feet behind me. What I want to do is give the passenger good sound from the speaker in front of me, and give ME good sound from the speaker in front of the passenger.

And to do that, you flip the CBT on it's side.




BTW, if anyone is wondering "how is this different than a line array?", the difference from a conventional line array is that a conventional line array melts your face off when you're in the front row. A traditional line array is loud at the top, loud at the center, and loud at the bottom. Due to that, a traditional line array deafens everyone in the front row but isn't loud enough for the people in the back of the venue.

*


----------



## Patrick Bateman

https://in.news.yahoo.com/creativity-psychosis-share-genetic-source-150008026.html

"Creativity and psychosis share a genetic source"

Well I coulda told 'em THAT...


----------



## sqnut

Patrick Bateman said:


> My favorite example of this is when I had some Danley Synergy horns at my house. Our twelve year old daughter was sitting literally a FOOT from the loudspeaker and asked "is it on?" It was playing about 100dB! But thanks to the wonder of constant directivity, she thought that the sound was coming from the other side of the room. (Because the OTHER speaker was pointed at her, and the one near her was pointed away.)


Assuming your daughter was sitting somewhere there, imho the levels from the two speakers are less important. The sound from the nearer speaker will kick in the precedence effect. Even if the on axis, louder speaker but further speaker is 10db louder, you will still perceive the sound coming from the near speaker. If that didn't happen, then something else is at play.


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## Patrick Bateman

sqnut said:


> Assuming your daughter was sitting somewhere there, imho the levels from the two speakers are less important. The sound from the nearer speaker will kick in the precedence effect. Even if the on axis, louder speaker but further speaker is 10db louder, you will still perceive the sound coming from the near speaker. If that didn't happen, then something else is at play.


There are two parts to the process.

The first you know well. If you reduce the volume on the loudspeaker that is closest to you, it will cause the image to shift towards the other speaker.

All of us have heard this, but we have also noticed that the effect is subtle. In particular, it does not work at midrange and midbass frequencies. This is due to phase; you can reduce the amplitude but reducing the amplitude does not change the phase response. IE, your ears still perceive that the loudspeaker is there.

In the case of the Synergy horn, the phase part is complicated by two things:

1) the Synergy horn has near-perfect phase. Due to this, it doesn't "sound" like a regular loudspeaker.

2) The more significant part of the illusion is that the apparent source of the sound in a Synergy horn varies with frequency. At high frequency the apparent source of the sound is deep in the horn. At midrange frequency, the apparent source of the sound is somewhere in the middle. And at low frequency the apparent source of the sound is at the mouth.

So we have a strange combination of attributes:
Excellent phase response, but an apparent depth that isn't at a single point in space.

Subjectively, the sound from the speaker does not seem to come from the cabinet.

My old Summas did this too, but not to such an apparent degree. The difference is because the lower midrange and midbass frequencies in the Summa all radiate from the same depth. (In the Summa, the upper frequencies radiate from different segments of the waveguide.)





By the way, your question may have solved a problem I had with the CBT design. I think that it's a bad idea to have more than one tweeter in a loudspeaker. Your question gave me an idea of how you can have a CBT with just one tweeter, that doesn't sound "weird" the way that most arrays with a single tweeter do. (Hint : there's a way to put the tweeter *behind* the CBT...)

Alright, back to work now, lunch is over...


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## Patrick Bateman

I've cycled through half a dozen different ideas for the front stage in this project.

On the drive up to Anaheim for the MECA show yesterday, I had another idea.









This is a vertical array. This is how most companies do loudspeakers. The way these work is that all the drivers are equidistant from the listener. (That's why the center drivers are further away; it's to equalize the pathlength.) In addition to get the pathlength correct, you also have to have a specific combination of vertical spacing and crossover points. Basically you can determine what the xover point from the spacing, and vice versa. The way that a lot of people do it in car audio, where they pick the xover points "willy nilly", that doesn't work. You can get the response correct at one point in space, but you can't get good polars unless you follow the rules. And the rule is that the center-to-center spacing is equivalent to the frequency. IE, if you want a xover point of 3400hz, then your center-to-center spacing needs to be 10cm. (Sound travels at 34,000cm per second.)









It took me literally *years* to figure out what's going on here. One of my big "Eureka" moments was when I realized that the low pass filter virtually "moves" each driver back by one wavelength. When you look at the layout here, it doesn't make sense how you could have the midranges nearly nine(!) inches in front of the tweeter, and the woofers about 24(!) inches in front of the tweeter. This makes no sense, until you realize that the filters create a delay, and the delay is (approximately) equal to one wavelength.

Once *that* makes sense, you'll realize that you can be in front of the speaker, or to the left, or below it, and the phase response is still correct. The delay is basically moving the midranges *backwards.*

For ages I've been trying to cram one of these into my car, but it takes up a lot of space.

As mentioned in some other posts, I've had one of these in my home, and it does something "neat" which is that it's hard to tell where the loudspeakers are. Both horizontally and also depth-wise. IE, it's difficult to tell if the soundstage is three feet deep or ten feet deep.









I was thinking about it on the drive to Anaheim, and it occurred to me that you could reduce the footprint quite a bit if you "settled" for getting everything right on one axis only.









While this wasn't intentional it winds up looking quite a bit like a Danley Genesis horn


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## thehatedguy

If you had parallel walls or near parallel and put them under the dash, you would have that little guy you made a year or two a go.


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## cajunner

traditional line arrays are more efficient, I don't know if CBT is able to do the same, but at a concert/church/traditional line array venue, the amount of drop off in sound is only half the amount of a conventional speaker.

which gives great horizontal coverage, but acts like a waveguide in that the polars won't budge in the tighter vertical coverage plotting.

basically, the line array has the ability to make the sound loud further into an audience spread, distance wise, vs. width wise.

so while this is great as a physics bump, or cheat sheet, or whatever, I am not sure if the use of line arrays in the car is capable of focused energy at deafening levels....

wait, of course I'm sure!

instead of a big happy long box, we could just bang the floor pan so it's concave instead of convex, in a narrow strip about 3 inches from the kicks. Then we'll fill that sucker with about 8 little Whispers, and make an Aperiodic cover for the back side so they are weatherized, and if we judge the angle of the curve properly we won't need anything more than the Gladen focus, all-pass filter to do single seat, or we could just go all analog anyways, since the width is there, and if we are doing it right, the vertical will miss the underdash side, and the knees and shoot sound energies right to our apex between the eye sockets, drilling down, getting happy, making the old classic ultraviolence once again, shades of pooh bear and a psilocyber escapade, drop the LCD shades and fire up the projection, we're going into the rabbit hole once again, friends...


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## Patrick Bateman

thehatedguy said:


> If you had parallel walls or near parallel and put them under the dash, you would have that little guy you made a year or two a go.


And that didn't work, so this time around there's no walls 



















Here's my thought process -

In an underdash horn, if you make it deep, you end up with all the energy firing into your kneecaps.

Typically a horn has four walls. (top, bottom, left, right)

If you remove a couple walls, you still get some loading, just not as much as if you had four walls.

So that's basically what this thing is; it's a waveguide with half the walls removed.


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## Patrick Bateman

That took a long time! Time to print it.


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## Patrick Bateman

This is the first time I've made a waveguide in two pieces. I had to do this because it's so wide. Fingers crossed that everything fits. You'll note that some of the edges are warped; this is hard to avoid with a 3D printer. I intentionally put those edges on the back side. (The other edges are fine, you only get warping on one side, the side that touches the bed of the 3D printer.)


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## Elgrosso

Wow
Too bad you had to cut in the middle of two, no big deal I guess.


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## Patrick Bateman

Elgrosso said:


> Wow
> Too bad you had to cut in the middle of two, no big deal I guess.


Yep. Maximum width that my printer can do is 15cm

It actually ended up being three pieces, because the piece 'shifted' towards the end of the print and I had to kill it. (Print time was sixteen hours.)


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## Elgrosso

Still impressive, and the lens looks very nice.

I should definitely digg into that for a future project.
(Especially with my friend's 3d scanner)


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## Patrick Bateman

Here's the on-axis, 22.5 off axis, and 45 degree off axis of the SAW lens.

What a strange device!

I don't think I've ever seen polars which look like this. Doesn't matter what angle you're at, the response is basically the same.

To put this in perspective, here's the polars for a typical 29mm tweeter:

































Oddly enough, the SAW lens combined with a waveguide, as detailed here*, performs a little bit better I think! Go figure. The waveguide project is probably a dead end, because it won't fit, but it's interesting how well it works.



* http://www.diymobileaudio.com/forum/2573257-post60.html


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## Patrick Bateman

This waveguide can go under the dash or ON the dash. I don't have it in the car yet, but I wanted to simulate both scenarios. This is the "under the dash" scenario. I basically put a barrier next to the waveguide, to simulate the effect of being butted up against the side of the car, under the dash. The effect isn't too bad; a dip in the lower treble but that's about it.









I simulated a windshield by putting a barrier on TOP of it, and angled at 45 degrees, as if it was pushed into the corners of a windshield.

YOWZA, this is terrible! No wonder so many tweeters on the dash sound atrocious. Yikes. EQ could tame this to some extent, but the interference pattern generated by the reflections is unmistakable.


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## Patrick Bateman

Here's the response on axis, and 22.5 degrees off axis VERTICALLY.

I'm surprised it's this smooth; I'd expected a sharp drop off of the high frequencies. But the response shape is surprisingly conistent.


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## Patrick Bateman

With a little bit of EQ I was able to get those measurements to look good.

Here's the results:









First off, I set a really shallow low pass at 8khz. If anyone's curious, I can explain why these devices "like" a very high electrical xover point. (Hint : they're basically constant directivity waveguides.)









Then I added a modest amount of boost at 2khz, and a TON of boost in the top octave. The former did what it was supposed to. The latter didn't; I get the impression that this big Dayton tweeter just can't get to 20khz on a CD waveguide. It basically needs more motor. I will probably put this thing under my dash and put a couple of super tweeters up high.









Here's the result:

1) The on-axis response is +/- 3dB from 2khz to 10khz. No big dips, no big peaks. *There's no smoothing whatsoever on this graph.*
2) The response at 22.5 degrees off axis is basically identical. Neat!
3) At 45 degrees off axis it's starting to droop. But I don't care all that much, I don't need 90 degrees of coverage, fifty degree or even forty degrees is fine.

Very cool.


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## Patrick Bateman

Here's the completely unfiltered response of the midrange array (in green) along with the *filtered* response of the SAW waveguide (in blue.)

This response will improve a lot; the box is still really leaky, which hurts the low frequency output and also generates a lot of high frequency "hash."

But there's a lot of good news here too. First, my midrange array is more efficient than my tweeter! That's great. It's hard to get a lot of output from a 2" driver, but it looks my array is doing what it's designed to do: raise the output, lower the distortion, raise the efficiency.

Second, my midrange array is able to play up to 2500hz. That probably doesn't sound like a big deal, but it gets tricky to get the midranges to play high enough on a Synergy horn. (And that's basically what this is, except with two walls instead of four.)


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## Patrick Bateman

The reason that the array is curved like this is that it gives me a wavefront that's forty degrees wide. (If it was flat, I'd have zero degrees, if the array was a quarter circle I'd have 90 degrees, etc.)









Here's some quick polar measurements on the midrange array. You can see that the array is doing it's job, but I may have used a beamwidth that was too narrow! The output is *really* falling off as you move off-axis. This isn't the end of the world; if it gets to be a real problem I can fix it with response shading. But I was a little startled by how directional it is.

Note that the array only controls directivity down to 1478hz. That's because the array is 23 cm wide. (speed of sound / 23cm = 1478hz)

It's interesting, because you could easily do something like this that would extend from one side of the dash to the other. And if you did that, you could control the directivity much much lower. Heck, I could've easily fit a wider array under the dash, I limited the size to 23cm because my 3D printer can't print large objects.


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## Patrick Bateman

OK, last post of the night!









As noted in post 174, this is the *filtered* response of the tweeter, along with the *unfiltered* response of the woofers.









One neat thing about Synergy horns is that if you get the geometry right, everything basically "pops" into place. *Here's the polar response of the tweeter *and* the woofers,* but with no filtering on the woofers, and a single cap to keep the tweeter from exploding. You can see that the woofer level needs to be brought down by six dB, but once I do, I'll be close to "flat" while only using a single(!) crossover component. Yowza.









Here's the phase response from that pic above. The secret sauce in the Synergy horn is the spacing and the xover; you can see that our drivers AREN'T coaxial, but you wouldn't know it from the phase response. At the xover point between midrange and tweeter, the phase response looks like one driver. (And sounds like it!)









Here's the frequency response and phase response of "the real deal." Note that the phase doesn't have any sudden jumps at the xover points. That's the goal here.


And again, *all of this is very early on.* I still have weeks of work to do. But it's good to see that I haven't run into any "deal breakers" yet.


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## Patrick Bateman

I took a look at the measurements from last night and realized this waveguide won't work.









This is the filtered response of the tweeter, along with the unfiltered response of the tweeter. You'll notice that the output from the tweeter is 10dB lower at 10khz than the output of the midranges. If I was listening on axis, this would mean that my tweeter would be "holding" back the system by about 10dB.

Unfortunately, this was going under the dash. So that means I'd lose about another 10dB since I'm listening off-axis.

Bottom line : the maximum SPL of my system would be somewhere around 100dB, due to the output limitations of the Dayton tweeter.

Sucks, because in all other respects it was looking good.

I'm going to take the exact same setup, flip it on it's side, and make it a VERTICAL array for the dash.









To start off, I have to figure out the curvature of my array. I have about 10 inches of vertical height on my dash. I'm going to make it 9", just to make sure I don't run out of space. I'm going for a 45 degree beam. (Same idea as a 45 degree waveguide, but I'm getting the beam via an array, not via a waveguide.)

I use this illustration to figure out where to put the midranges, to get my 45 degree beam.









It will wind up looking a lot like this, but vertical.


----------



## Patrick Bateman

Here's some pics of the device

Basically it will go up on the dash vertically, with the tweeters tucked into the corners


----------



## Patrick Bateman

Here's some pics of the previous array, from the last couple of pages, in the car.

You can see it's quite compact. Only reason I'm not using it is because the tweeter level isn't enough. I looked at using a compression driver instead of the dome and it wouldn't fit.


----------



## thehatedguy

What about a small compression driver like the new BMS 4526Nd?


----------



## Patrick Bateman

thehatedguy said:


> What about a small compression driver like the new BMS 4526Nd?


I had to sleep on it to figure out why the top octave on the SAW lens is just totally AWOL.

*But I believe I have it figured out.*

















Here's the polar response of a 29cm tweeter, in this case a Scan Speak.
*Notice how there's literally no output above 18khz, and how it is starting to beam at 8khz?*

OK, hold that thought.

















Here's the polar response of a 29cm tweeter, in this case a Dayton RS28. *Notice how there's literally no output above 18khz, and how it is NOT beaming?*


A lot of people assume that waveguides and horns raise the efficiency of a driver. That's only half-true; they raise the output *but only in one direction.* What a horn does is it takes the energy which would normally radiate in 360 degrees, and it focuses it into a beam.

Now if we look at the SAW lens, we see that it's taking the energy, *and it's spreading it out.* So what is happening in that top octave is that the output which normally be focused *forwards* is actually getting spread out across one hundred and eighty degrees.

So when we have a tweeter that's already beaming at 8khz, if we stick it on a SAW lens, we end up nuking the top octave. Basically the tweeter is already struggling to reach 18khz, and we took the very meager output it has and we spread it across 180 degrees. And since we're not actually raising the efficiency, we're just focusing it, we ended up turning a 90db tweeter into an 80dB tweeter!


I hope that makes sense. The key here is that we're not actually raising the output level; we're focusing it. Except in this case, we're lowering it because we focused it into a wider beam than it would normally produce.




So...

What does that have to do with the BMS?


The thing is, *I think I can get the output level back up if I focus the radiation into something *besides* 180 degrees. There's nothing from stopping you doing a 180 degree SAW lens, or a 45 degree SAW lens, or a 90degree SAW lens, etc.

Basically narrowing the angle will raise the output level.









If you look at my lens, you'll see it's nearly 270 degrees. (Due to the roundover at the edges.)









B&O is using 180

I think I'll continue to use a lens for this project, but I'm going to narrow it down to sixty degrees or so, maybe less.


*


----------



## rton20s

I'm probably way out of my depth here, but let me see if I get this. 

With the Sausalito lens you are only able to focus acoustic energy that is already present. Your taking what energy is there and focusing it. The problem comes in that your taking the chaos of beaming, bringing it back into focus, but if the tweeter is dropping off to nothing the dB drop off is just exacebated by the function of the lens? 

Would then a tweeter which played flat beyond 20 kHz, or even had a rise in frequency response prove a better candidate? 

Say a ScanSpeak R3004/6020-10 would be a better choice









than a ScanSpeak D3004/6020-00?









Or am I still missing something?


----------



## Patrick Bateman

rton20s said:


> I'm probably way out of my depth here, but let me see if I get this.
> 
> With the Sausalito lens you are only able to focus acoustic energy that is already present. Your taking what energy is there and focusing it. The problem comes in that your taking the chaos of beaming, bringing it back into focus, but if the tweeter is dropping off to nothing the dB drop off is just exacebated by the function of the lens?
> 
> Would then a tweeter which played flat beyond 20 kHz, or even had a rise in frequency response prove a better candidate?
> 
> Say a ScanSpeak R3004/6020-10 would be a better choice
> 
> 
> 
> 
> 
> 
> 
> 
> 
> than a ScanSpeak D3004/6020-00?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Or am I still missing something?


You hit it right on the head:

1) There is a point where all drivers begin to beam. That point is equal to the diameter. For instance, a 1" tweeter beams at 13,500 hz. (13,500hz is 1" long.)

2) When the driver starts to beam, *it may be flat on axis, but it won't be flat off axis.* So if you took the amount of energy on AND off axis, and you combined it, *the overall level would be lower than an octave lower.*









The lens takes that energy and focuses it into a single point, then BOOM, sprays it across the room.









That's why the on and off axis response is so freakishly identical. Believe me, you could look at a thousand spec sheets and you're never going to see a loudspeaker that measures the same ON axis as OFF axis at 15khz. 15khz is under a inch in diameter!









The Vifa ring radiators are about as close as you can get to that, due to the fact that half of the diaphragm is absent. (Due to the phase plug in the center.)









By the way, you can see the same thing in compression drivers too. Due to the fact that the exit is 1" in diameter, their beamwidth narrows dramatically at 13,500 hz. In the measurement above, you can see the beam narrows dramatically as soon as you hit that frequency.


----------



## Patrick Bateman

The array from here didn't print properly : http://www.diymobileaudio.com/forum/2599706-post178.html

I'm getting pretty good at 3D printing, but these ones were exceptionally difficult to print.

















I said "**** it" and made some simpler ones. Instead of spherical they're mostly cubical. I also moved the woofers to the side, instead of the front, to make the cabinet narrower. (At these frequencies, it doesn't matter what direction they point, all that matters is the pathlength.)


----------



## Patrick Bateman

I just bought the "2x4 advanced plugin" from miniDSP

This seems like the hot ticket. Unless I've missed it, there is no way to get a mono sub output if you don't use this plugin or the 2.1 plugin from miniDSP.

(do NOT, repeat do NOT do it with a y-cable unless you like blowing up your electronics.)

I used the "2 way advanced" for all my other projects, but I can't see any reason you'd opt for the "2 way advanced" or the "2.1 plugin" when you can get the "2x4 advanced."

Basically the "2 way advanced" can't do a mono sub at all. The "2.1 advanced" can do a mono sub, but it appears to limit you to three outputs. (Two stereo, one mono.) The "2x4 advanced" lets you do a bunch of interesting things:

2 stereo, 2 mono
2 left, one right, one mono
2 left, two right
four mono

etc

The reason that this is great is that you can do things like have two subwoofers with different xover points. This can be really handy if you have a ULF sub. IE, you might have two mono subs, but you high pass one of them to keep the 40hz-80hz octave from getting muddy

In my scenario, it's handy because I may wind up using one tweeter instead of two.


----------



## Orion525iT

I am pretty sure you can do this with the 4x10 pluggin too if you have a 2x8 or 4x10. Normally you would sum mono for the subs, but there is no reason why you can't for a tweeter. I know when tried this without a summed signal, it still worked out surprisingly well. I might try this again now that I have processing. Glad this came back up.

What frequency are you crossing the tweeter?


----------



## Patrick Bateman

Orion525iT said:


> I am pretty sure you can do this with the 4x10 pluggin too if you have a 2x8 or 4x10. Normally you would sum mono for the subs, but there is no reason why you can't for a tweeter. I know when tried this without a summed signal, it still worked out surprisingly well. I might try this again now that I have processing. Glad this came back up.
> 
> What frequency are you crossing the tweeter?


The original plan was to have something fairly similar to Gary's car, but with SAW waveguides.









If you look at the frequency response of the Dayton tweeter on the SAW waveguide, it's just completely AWOL above 8khz or so.

So I'm thinking about doing a four way instead of a three way.

If I move forward with this plan, it will look like this:

1) midbass : still the array of Dayton ND91s
2) lower midrange : array of Gento 2" drivers
3) upper midrange : Dayton RS52 on SAW waveguides
4) tweeter : maybe a BMS 4540ND? Something that has enough output to do 110dB or so at 20khz


----------



## Patrick Bateman

If you look at the best performing waveguides on the "Great Waveguide List*", most of them have a really gentle transition from one angle to another. Basically waves hate sharp edges; if you can create a gentle spline that connects one angle to another, you get smooth frequency response, low diffraction, and the sound just sounds silky smooth.

















With that in mind, and considering how well the other SAW waveguides worked, I'm really going crazy with the splines on this one for my Dayton RS52s.


----------



## Patrick Bateman

After going crazy with the splines, I wound up with something fairly similar to what B&O sells.









Here's the real deal

























Here's my RS52 waveguide coming together.


----------



## Patrick Bateman

The RS52 waveguide, from last night, looks cool.

*But it is freaken BIG.*









About this big. I went in my car to check and see if it will fit, and it will. But I'm a little leery about having tweeters that big.

Before I hit "print" on the ol' printer, I'm going to try an idea I had...


----------



## Patrick Bateman

Today's project will look vaguely like a cross between the PT waveguide on the right


Along with the older style waveguides from Image Dynamics


























All the "new-school" waveguides are all about the splines, so I'm doing likewise. There won't be a straight edge on this entire thing.


----------



## Patrick Bateman

It's starting to look like a waveguide now









Another pic of the Image Dynamics, for comparison's sake


----------



## Patrick Bateman

Try making *this* out of wood 









Here's a pic of the waveguide, along with it's inverse, to give you an idea of the what the waveguide is shaped like. Basically the whole idea is to create ultra-gentle splines from the throat to the mouth of the waveguide, to make it sound as smooth as possible.

















Finished! This is one strange looking waveguide.









Here's a pic from the inventor's latest patent. There's definitely a family resemblance here.









One thing I noticed in the patent, that's kinda interesting, is that the reflector is much shorter now. Theoretically this should cause problems. Bascially if it's too short you end up getting a waveguide that focuses all the energy at one point, like a parabolic reflector. But maybe it doesn't work like that "in the real world?"

Here's the patent : https://www.google.com/patents/US20140119588


----------



## Orion525iT

Wow, that wave guide is crazy looking. Every time I see one of those messed up print jobs, I think of Jeff Goldblum in _The Fly_... Brundleguide .

I've been looking at Gary's build a lot lately too. I have always had good results with midrange in the kick panels, but for some reason in this car, it's not working out. So I started messing with little waveguides in the corners of the dash. The one thing I can't figure out is if he has sound absorbing materials lining the waveguides. It appears there is fabric in them, but I wonder what is under it. If there is some acoustic foam or something underneath, I guess that means that only low frequencies are really benefitting. 

I also messed with around with a single tweeter using a summed signal on my 2x8. I crossed the tweeter to single (I was using 2 driver arrays before) aura whispers in each corner of the dash. I have them crossed at 7000 hz. It seems to work, but i am not sure if it technically sounds correct. The other thing I noticed is that higher order crossovers do not work at all for this.


----------



## thehatedguy

What waveguides does Gary have in his car? I didn't recall seeing any in the pictures.


----------



## Orion525iT

thehatedguy said:


> What waveguides does Gary have in his car? I didn't recall seeing any in the pictures.












Maybe I am wrong, but I don't think those pods are made like that strictly for aesthetic reasons.


----------



## thehatedguy

No, but they aren't waveguides IMO either.

They look to be made to stop an early first refection off of the glass.


----------



## Patrick Bateman

thehatedguy said:


> No, but they aren't waveguides IMO either.
> 
> They look to be made to stop an early first refection off of the glass.


My first reaction when I heard Gary's car was "that sounds like a horn car." It has the big dynamics of a prosound speaker, but without the high order modes.
I posted some thoughts on that about a year ago here. (Too lazy to look up the thread.)

Over the year that followed I posted a lot of stuff trying to figure out how to make the entire car into a horn. In particular, check this out:

http://www.diymobileaudio.com/forum/2313922-post72.html

Basically, here's what's happening in Gary's car, IMHO:

When the distance between the top and the bottom of the windshield is smaller than the wavelength, *the windshield will act as a waveguide.* For instance, Gary is using something like a 3" midrange, with a flange of about 1". *So any waves larger than 5" are going to be constrained by the windshield itself; the windshield will act as a waveguide.*

5" is 2700hz

So everything from 2700hz and down will act as if it was mounted on a waveguide (because it is.) The other benefit here is that the efficiency is going to go up, because the 3" driver is radiating into a fraction of the space that it would if it was on a flat baffle.

Put all that together, and you get these awesome dynamics. (and keep in mind, all those movies that Gary's worked on, they're all mixed on high efficiency equipment. Nobody is using low efficiency speakers to mix movies, it's all prosound gear.)



At this point, someone is going to say "everybody is putting their speakers on the dash these days."

The thing that's unique about Gary's car is that it's the only one I'm aware of where the drivers are pushed WAY back into the corner. If you pull the drivers even six inches closer to you, you widen that gap significantly. You still get the waveguide effect, but it starts at a lower frequency, and you get a dip in the response from the first reflection. (Works the same way as driving a waveguide with an offset midrange, which is something I know well from all my futzing around with tapped horns and Synergy horns.)


----------



## Orion525iT

thehatedguy said:


> No, but they aren't waveguides IMO either.
> 
> They look to be made to stop an early first refection off of the glass.


But how do they stop an "early first reflection"? Might have to define "waveguide". Are you saying that they absorb the first reflection? I can't remember if he ever mentioned xover points for the mids, but the material does not seem thick enough to absorb the lower frequencies.


----------



## Patrick Bateman

https://lh3.googleusercontent.com/-FAs2IO5hPxs/VZAzprG_rlI/AAAAAAAAK_U/8bHmNBMtgJ4/s800/opsodis118.jpg[/img]

























Came out nice!


----------



## Orion525iT

Patrick Bateman said:


> The thing that's unique about Gary's car is that it's the only one I'm aware of where the drivers are pushed WAY back into the corner. If you pull the drivers even six inches closer to you, you widen that gap significantly. You still get the waveguide effect, but it starts at a lower frequency, and you get a dip in the response from the first reflection. (Works the same way as driving a waveguide with an offset midrange, which is something I know well from all my futzing around with tapped horns and Synergy horns.)


I can't find where I read it, and I don't think Gary said it directly. But, iirc, he alluded to in another thread.

I really do think it does both. There is some horn loading. But I am still curious as to the possibility that some absorption is going on too.


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## Patrick Bateman

Orion525iT said:


> But how do they stop an "early first reflection"? Might have to define "waveguide". Are you saying that they absorb the first reflection? I can't remember if he ever mentioned xover points for the mids, but the material does not seem thick enough to absorb the lower frequencies.


Assuming that the windshield itself acts as a waveguide from 2700hz and up, you'd want some type of acoustical treatment to deal with the three octaves from 2500hz to 20khz

BUT...

A 1" dome tweeter is going to be "beam" in that last octave

So...

If you used the windshield as a waveguide, and the tweeter beams above 10khz, you only need acoustic treatment to absorb spurious radiation in the two octaves from 2500hz to 10khz

If you were clever with the crossover you could probably create some off-axis nulls at the xover point which would eliminate any real need for treatment at the xover point

Assuming a center to center spacing of about 4", that means you could put some off-axis nulls at the xover point of 3250hz




TLDR: By combining off-axis nulls at the xover point, the waveguide effect of the windshield, and the beaming of the tweeter, you could basically eliminate the need for room treatment, except in the octave of about 5000hz to 10000hz... Which isn't an octave that's very audible anyways. This is also an interesting lesson in why it's often better to use a small midrange. (A larger midrange would move the problems in the octave of 5000hz to 10000hz into the octave of 2000hz to 4000hz, where it's much more audible.)


----------



## Patrick Bateman

Orion525iT said:


> I can't find were I read it, and I don't think Gary said it directly. But, iirc, he alluded to in another thread.
> 
> I really do think it does both. There is some horn loading. But I am still curious as to the possibility that some absorption is going on too.


Oh yeah it's definitely there for a reason. I think he may have reduced the height of the instrument console also. That was a big problem for me in my '05 Accord; the instrument console was so big, it got in the way of the left speaker array.

The Honda Civics and Priuses have a really nice dash for these types of setups.


----------



## Patrick Bateman

Okay here's some measurements of the new waveguide.

[img]https://lh3.googleusercontent.com/-PWR3M_cS8xA/VYd6jiPdcwI/AAAAAAAAK2A/Yv4dfZJcCAM/s800/opsodis93.jpg








This is the OLD waveguide, from last week. I'd hoped to put this under my dash. The reason I killed it was because the top octave is AWOL, and there's a dip at 10khz. *This measurement included ten decibels of EQ in the octave of 10khz to 20khz.* As detailed on page seven and eight of this thread, I found that there's was just no way to get to 20khz, the Dayton RS28 just can't do it on this waveguide.


















Here's some quick polars of the new waveguide. *This has no EQ at all.* All I did was high-pass it, to keep the compression driver from blowing up. To me, this waveguide is a significant improvement over the last. It's smaller, it's smoother, and most importantly it reaches 20khz without breaking a sweat.

I'm going to EQ it and do some more polars, including ones a couple of feet above the waveguide, to simulate the effect of being mounted under the dash.


----------



## Patrick Bateman

As noted in post 204, this is the frequency response of the waveguide from last week. Note that the octave above 10khz is AWOL. This measurement includes 10dB of EQ in the top octave.

















Here's the polars of the NEW waveguide, with EQ. 
YOWZA! This may be the best waveguide I've ever made. I've measured my QSC waveguides, and they're better than this, but this is VERY good for it's size. *And check out the consistency above 10khz!* I've never seen a speaker that could do this, direct radiator, horn, ribbon, nothing. Except for the off-axis dip at 7khz, this waveguide measures that same on-axis as off, within about three decibels. Yowza.









Distortion looks good. You wouldn't want to run this lower than 2khz, but keep it above 2khz and the distortion is inaudible.

















Here's the EQ and the crossover. Very very simple.

I'm posting the EQ and xover because I'm going to give this waveguide away. This waveguide is screaming to have some midranges bolted to it


----------



## Patrick Bateman

Here's some measurements of the polar response, but measured 12" ABOVE the waveguide.









This is intended to simulate how they sound in a car, mounted under the dash.

Dare I say it, these look REALLY good. With a conventional waveguide, when you're above the axis, the response drops like a rock, but only in the top octave. So you end up having to put tweeters up on the dash to bring the top octave back. Which is tricky to integrate.


----------



## thehatedguy

I don't believe there is horn loading going on with direct radiators next to the glass. You might get some boundary reinforcement, but not horn loading.

But the easy way to tell would be to run an impedance sweep and see how many peaks you have in the sweep. If they are horn loading, then you'll have the trademark 3 peaks of horn loading...otherwise they are not horn loading.


----------



## Patrick Bateman

thehatedguy said:


> I don't believe there is horn loading going on with direct radiators next to the glass. You might get some boundary reinforcement, but not horn loading.
> 
> But the easy way to tell would be to run an impedance sweep and see how many peaks you have in the sweep. If they are horn loading, then you'll have the trademark 3 peaks of horn loading...otherwise they are not horn loading.


"Boundary reinforcement" and "horn loading" are the same thing.
The output gain that you get from a horn is due to the driver radiating into a narrower angle. For instance, if you have a 5" woofer on an infinite baffle, it's radiating into 180 degrees. If you reduce the beamwidth into 90x90 with a waveguide, the output level goes up by six decibels. Reduce it down to 45x45, and it goes up further.

Take a look at the spec sheets for the Danley SH25 and the Danley Jericho horn. You can see this plain as day.


















Though the Jericho horn is much MUCH larger than the SH25, the SH25 has nearly as much output, *because the angle is so narrow.*

That's all that horns and waveguides do; they simply take a given amount of energy and focus it into a beam. The difference between a horn and a waveguide is that a horn has curved walls, so the beamwidth gets wider and wider as the frequency goes lower. Conversely, horns are flat at high frequency because the beam gets narrower and narrower at high frequency. (Same amount of energy, focused into a narrower beam.)


----------



## thehatedguy

You could test it all with an impedance sweep. If there are 3 peaks and 2 nulls, then you have horn and/or dual reflex loading.

The things on Gary's dash are not waveguides and don't work that way. They are there for or to help stop reflections...just like the dash pad on his dash. IMO if they were waveguides, they would need to be much closer to the dash/glass, especially the tweeters. This is a pretty common practice in competition cars.

Some take a DATS or WT3, place the tweeter up there and do a sweep and see how the impedance curve changes.


----------



## thehatedguy

But the Allison Effect and horn loading are two different things.


----------



## Orion525iT

thehatedguy said:


> The things on Gary's dash are not waveguides and don't work that way. They are there for or to help stop reflections...just like the dash pad on his dash.


So they absorb the sound then and that's it? They look to be only 1/4" thick with structure underneath, which mean the absorbing material is even thinner. The dash mat by comparison looks thicker.

I can't think of any other way to "stop reflections". 

Might we just ask him about it?


----------



## thehatedguy

I can put a towel on my dash and hear the improvements in focus and stage height. We (Team Image Dynamics) used to put towels on our center consoles at shows for the same reason.

If you have a WT3 or DATS, go test it for yourself. I don't have either or I would. The raw speaker/sealed box will have one peak, a ported or single reflex bandpass enclosure two, and a horn or dual reflex bandpass will have 3.

Try it fullrange and then with a crossover.


----------



## thehatedguy

Let's not forget that for a waveguide or a horn to function properly, the interface between the speaker and WG is critical...they need to mate very closely so that the initial wavefront sees the WG and is controlled by the WG. Gary's pods and the hats around them do not do that- they are wings on a flat baffle. The wavefront is wide only narrowing as dispersion narrows...they would never "see" the "sides" of the supposed WG, and would not function as a WG. 

The flare is too large to contain the wavefront effectively...and it's designed all wrong to function as a WG. Just look at it. You've ever seen a WG anywhere else that is shaped remotely like that? I know that I haven't.


----------



## Patrick Bateman

In post 205, I talked about taking the very good waveguide from Sunday and adding some midranges to turn it into a Synergy Horn.

I worked a LONG time to come up with this:


















I'm not too happy with that design though. The main issue is something I figured out a few weeks ago. I've mentioned this before, about how I rented some Danley SH50s and I really liked how the soundstage was very deep. The reason that the SH50s have a deep soundstage is because the midranges, tweeter, and woofer are spaced out over a foot a and a half. Basically the midranges are about a foot closer than the tweeter. This has the net effect of giving you a deep soundstage.

With my waveguide pictured above, I'm struggling to fit three midranges onto a tiny waveguide.

I don't think I'll print this waveguide; I think that what I'll do is use a dedicated waveguide, along with an array of woofers that's about 10" ahead of the tweeter. So it will still be a Synergy horn, but the drivers won't be physically on the same waveguide. *The key is in the crossover and the spacing.*

In the case of the "real" Synergy horn, the SH50, the midranges are exactly 10.5" from the throat. Not coincidentally, that's 1285hz, which is also the xover point.


----------



## garysummers

Orion525iT said:


> So they absorb the sound then and that's it? They look to be only 1/4" thick with structure underneath, which mean the absorbing material is even thinner. The dash mat by comparison looks thicker.
> 
> I can't think of any other way to "stop reflections".
> 
> Might we just ask him about it?


The A-pillars in my car were originally constructed without the shrouds. After listening for a while, I added a mockup of the shroud and continued to listen.
With the shroud the sonic image seemed to be more coherent and more focused.
So we constructed the shroud you see now.The shroud does have some foam applied to it, approximately 1/8 of an inch, then covered in Alcantara. Was there a clear intention of creating a "waveguide" ? No.


----------



## Patrick Bateman

garysummers said:


> The A-pillars in my car were originally constructed without the shrouds. After listening for a while, I added a mockup of the shroud and continued to listen.
> With the shroud the sonic image seemed to be more coherent and more focused.
> So we constructed the shroud you see now.The shroud does have some foam applied to it, approximately 1/8 of an inch, then covered in Alcantara. Was there a clear intention of creating a "waveguide" ? No.


I've noticed that when I messed around with cardioids. The additional radiation backwards makes the stage more diffuse.


----------



## Patrick Bateman

Here's a status, as of Monday:









This waveguide from yesterday worked really well. Literally one of the best I've ever made.

I tried turning it into a Synergy horn, but wasn't happy with the results. (More comments in post 214.)

















Since the SAW reflector can successfully bend sound ninety degrees, I can do something like Mic Wallace's BMW now. (Without chopping up my firewall.) Basically stick the compression driver underneath and bend it UP to the listeners.

















Here's some Pyle PH612s, to see how much I can fit under the dash. Normally the PH612s would be tricky to use, but because you can bend sound ninety degrees, it allows me to do something like the PH612 and still push the waveguide all the way to the firewall.

This doesn't just allow for better pathlengths and a deeper soundstage, it's also a much MUCH better match to the car interior. Basically you don't want a gap between the waveguide mouth and the car if you can avoid it.


----------



## Patrick Bateman

Here's the finished waveguide. Basically the idea is that the tweeter is upside down, tucked into the corners of the dash. The sides of the waveguide are designed to create a gentle transition from the waveguide to the interior of the car itself.









Jadis Eurythmie II loudspeaker | Stereophile.com
It wasn't intentional, but it reminds me a bit of the Jadis Eurythmie


----------



## rton20s

At what point are you going to admit that you just create these threads to get people to look at your weird models of alien anus?


----------



## Patrick Bateman

Here's the 3D render of the waveguide 









Here's the 3D printed version of it









Here is the polar response. On axis, 22.5 degrees off axis, and 45 degrees off axis. The entire crossover is a single cap, 1mfd. (The 5dB peak at 1800hz is due to the cap being too small to offset the impedance peak of the compression driver; if you used an active xover or a 2nd order passive you wouldn't get this peak.)

Dare I say it, this is very nice performance.

















To put this in perspective, I'm getting polars from this waveguide that are about as good as the JBL econowave guides. Which are very good.


I'm not too big on self promotion, because a lot of my projects are experiments and wind up in the trash. But I'm going to go out on a limb and say that this might be the best measuring car audio waveguide ever. Those polars are ridiculous. There are probably a handful of soft dome waveguides that are smoother, but I guarantee you there's nothing that's this consistent, over a bandwidth of four octaves. Just insane performance.









For comparison's sake, here's a pair of underdash HLCDs that I bought about ten years back. I did this measurement on Sunday, was holding off on posting it until I was sure that I was on to something with the new design. No, these polars are not from an Image Dynamics waveguide, I don't own one.


By the way, if anyone is curious, I have figured out why the performance of the SAW lens is so redonkulous. If anyone is curious to hear a technical explanation, I can post it. (It's long-winded, and this thread is already a snoozefest, so I'll hold off on that unless anyone's curious.)


----------



## Weightless

I'm curious. Post it please!


----------



## funkalicious

A) Please post your findings on the SAW lens. 

B) Do you have the physical dimensions of your wg and can you post a pic, with say a soda can, to get some size perspective?

C) How do you explain the dip in response centered around 7.2kHz for your wg and how do you plan to address it if at all?


----------



## cajunner

it's time to run.

wipe this thread, shut down your screen name and get to a patent lawyer, then start futzing with the design using neodymium large diaphragm compression drivers, and get that sucker stable to under 700 hz.

it's the Bateman 2000, model...


----------



## truckerfte

cajunner said:


> it's time to run.
> 
> wipe this thread, shut down your screen name and get to a patent lawyer, then start futzing with the design using neodymium large diaphragm compression drivers, and get that sucker stable to under 700 hz.
> 
> it's the Bateman 2000, model...



Not yet, I've got a Saturn ion, with the symmetrical dash already hacked up. I think a set should be sent my way, for testing and all...


----------



## Patrick Bateman

funkalicious said:


> A) Please post your findings on the SAW lens.
> 
> B) Do you have the physical dimensions of your wg and can you post a pic, with say a soda can, to get some size perspective?
> 
> C) How do you explain the dip in response centered around 7.2kHz for your wg and how do you plan to address it if at all?


The waveguide is exactly 6"x6"x6". That's as big as my printrbot will print.

If you look at the measurements of the Dayton tweeter you'll see at dip at 10khz. I think it's probably related to the reflector.

I'm not too worried about it; it's hard to hear dips and peaks at high frequency, due to the fletcher munson curves.

I have a hunch that you could reduce the dip by smoothing the transition from the lens to the waveguide.


----------



## Nismo

Patrick,
I see where you have shown the model of the bandpasses, but how did you settle on the design elements? How do you affect the bandwidth? I do recall seeing that size gives us efficiency, but not how the bandwidth can be affected, or the response can be moved up/down.

If I want to go from 60ish to 300ish, how do I get that bandwidth, and how much am I sacrificing to get that?

Thanks!
Eric


----------



## funkalicious

Technical explanation of the SAW performance still forthcoming?


----------



## Patrick Bateman

Nismo said:


> Patrick,
> I see where you have shown the model of the bandpasses, but how did you settle on the design elements? How do you affect the bandwidth? I do recall seeing that size gives us efficiency, but not how the bandwidth can be affected, or the response can be moved up/down.
> 
> If I want to go from 60ish to 300ish, how do I get that bandwidth, and how much am I sacrificing to get that?
> 
> Thanks!
> Eric


First, you figure out this figure: (2 * fs / qes)

For instance, for the ND91s that I am using, that works out to 329hz. 

That math will tell you how HIGH you can "push" the driver. 329hz isn't the upper frequency limit, its how HIGH you can push the resonance of the driver. In real life, you could get the ND91 to cover about one or two octaves in the neighborhood of 329hz. 

So, you're looking at about 160hz to 640hz for the nd91. (Two octaves.)

Just do the same math with your driver options, and you'll see what you can get out of them. 

If you want to go the opposite route, and push them LOWER in frequency, that's easy. In fact, you could get 20hz out of a 3" woofer in a bandpass, if you didn't mind the hit in efficiency. 


TLDR: (2 * FS / QES) will tell you the neighborhood that your driver will play in a bandpass, if you're pushing for maximum output (which is always at the upper end of the passband)


Once you have those figures, use the bandpass calculator over at carstereo.com. I've never found anything better than that calculator, and I've been building bandpass boxes since 1991.


----------



## Patrick Bateman

funkalicious said:


> Technical explanation of the SAW performance still forthcoming?


What would you like to know?


----------



## Nismo

Patrick Bateman said:


> First, you figure out this figure: (2 * fs / qes)
> 
> For instance, for the ND91s that I am using, that works out to 329hz.
> 
> That math will tell you how HIGH you can "push" the driver. 329hz isn't the upper frequency limit, its how HIGH you can push the resonance of the driver. In real life, you could get the ND91 to cover about one or two octaves in the neighborhood of 329hz.
> 
> So, you're looking at about 160hz to 640hz for the nd91. (Two octaves.)
> 
> Just do the same math with your driver options, and you'll see what you can get out of them.
> 
> If you want to go the opposite route, and push them LOWER in frequency, that's easy. In fact, you could get 20hz out of a 3" woofer in a bandpass, if you didn't mind the hit in efficiency.
> 
> 
> TLDR: (2 * FS / QES) will tell you the neighborhood that your driver will play in a bandpass, if you're pushing for maximum output (which is always at the upper end of the passband)
> 
> 
> Once you have those figures, use the bandpass calculator over at carstereo.com. I've never found anything better than that calculator, and I've been building bandpass boxes since 1991.


This is all good to know, but that site doesn't exist any more.

Eric


----------



## Patrick Bateman

Well that sucks. 
Nearly 100% of my designs have depended on that calculator. 

Looks like it's still available from the Google cache and the way back machine. But the JavaScript doesn't work from the latter.


----------



## Patrick Bateman

Bandpass Subwoofer Box Design (Fourth-Order)

This is the URL from way back


----------



## seedlings

Patrick Bateman said:


> Here's some Pyle PH612s, to see how much I can fit under the dash. Normally the PH612s would be tricky to use, but because you can bend sound ninety degrees, it allows me to do something like the PH612 and still push the waveguide all the way to the firewall.
> 
> This doesn't just allow for better pathlengths and a deeper soundstage, it's also a much MUCH better match to the car interior. Basically you don't want a gap between the waveguide mouth and the car if you can avoid it.


Did you ever actually listen to off-the-shelf horns in this position? I was literally just wondering about this concept.

BTW, your DIY attitude and persistence is fantastic. Don't change.

CHAD


----------



## Patrick Bateman

Thanks!

I used the JBL waveguides for the original iteration of this project, titled "28 Days Later" over at diyaudio

They work well. At some point I moved them to the dash, bcuz having them in the kicks contributed to a low soundstage

Then I gave up and sold the car


----------



## seedlings

Patrick Bateman said:


> Thanks!
> 
> I used the JBL waveguides for the original iteration of this project, titled "28 Days Later" over at diyaudio
> 
> They work well. At some point I moved them to the dash, bcuz having them in the kicks contributed to a low soundstage
> 
> Then I gave up and sold the car


I see your .PDF plans for the synergy horns, and you mentioned they are scalable. Is it conceivable that the gap between 100Hz and 300Hz could be closed using a 1" horn driver and a 5.25" or 6.5" also mounted to the throat? How much would that plywood waveguide need to be extended? It would be awesome to have a single point source. Would active crossover between drivers help/hurt?

I have space under the dash, and willing to be unconventional.

CHAD


----------



## funkalicious

Patrick: Pure curiosity only. I was going off your offer in post #220 to explain the SAW's performance in technical terms.


----------



## Patrick Bateman

I'm going to take a little detour and try making an array. Jason said that Mark Eldridge's arrays sounded better than his horns, and I haven't put an array in the car for at least a decade.

Plus, the more I mess with my 3D printer, the more I realize that the Unity horn I made back in 2009 was about as small as you can make it:


















It's just really hard to cram 2-4 midranges and a tweeter in the corner of a dash. You can *easily* do it below the dash, but then you have the problem that the soundstage is at knee height. (You can raise the soundstage by using underdash HLCDs, but I have an incredibly difficult time coming up with an underdash HLCD that's small enough to fit under the dash, but large enough to play down to 500hz.)









I want 45 degrees of coverage, so my array is a 45 degree arc. Looks a bit like a slice of cheese.









Depth is about an inch and a half.









When it's done it will look a bit like the JBL CBT array, minus the tweeters.


----------



## Patrick Bateman

I need to do some work finishing the enclosure, but here's what the array looks like.
It uses four of the "m70" 2.5" drivers that are currently on sale at Parts Express.
My beloved Peerless 830970 probably works a little better, but I didn't want to invest $80 per side for drivers. (The M70s are something like $4 each.)


----------



## Focused4door

Had a chance to hear these yet?

The first time I saw the JBL CBT 100 line arrays it was one of those things that clicked and made me want to do a dash mount setup.


----------



## mitchyz250f

A couple of questions regarding Gary's installation.

Rather than using foam to reduce early reflections could a waveguide been made to transition waveguide basically blending the space from the dome to the to the windshield and dash? 

The side channels are placed directly against the windshield but the center channel appears to be a foot or so from the windshield, Why not put the center right up against the windshield to take advantage of the boundary effect?


----------



## garysummers

mitchyz250f said:


> A couple of questions regarding Gary's installation.
> 
> Rather than using foam to reduce early reflections could a waveguide been made to transition waveguide basically blending the space from the dome to the to the windshield and dash?
> 
> The side channels are placed directly against the windshield but the center channel appears to be a foot or so from the windshield, Why not put the center right up against the windshield to take advantage of the boundary effect?


The scenario you speak of is exactly my next build if I can find the funds. 
Since I do not drive the car anymore, I can take greater liberties with the build than if it were a daily driver. I would rebuild/reshape the dash to be the lower half of the waveguide, symmetrical on both side, instrument cluster moved to the center, AC/ventilation rerouted, etc. The windshield forms the upper half. The transition from driver to waveguide would be as smooth as possible. The drivers would be located as far back, and as much into the firewall as possible,center as well, aim properly. The reason this is possible now is I will ignore the airbag on the passenger side of the vehicle. I have been experimenting with various concentric point source speakers with some nice results. If this research pans out I would use this type of driver, One in each of the four corners and one center. I would try to get at least a 5 1/4" driver in each location. The supremo mid bases will pick up where the concentrics drop off.

The current center channel is touching the windshield at the back of the midrange pod.


----------



## Patrick Bateman

Your car is really dynamic; it's one of the few cars I've heard that can get LOUD while still sounding clean. When I first heard it, I was mystified by it, because most cars with direct radiators sound "polite" and "boring" to me.

If you went with a coax, I wonder if that would be a downgrade, because the tweeters in coaxial speakers tend to be kinda wimpy.

Not to dash your plans or anything 
But you have a car that's in the top 1%.

Has Andy heard it?


----------



## Patrick Bateman

A member of the 'hlcd' forum on diyma posted some cars from back in the 90s, and it got me a bit nostalgic for my 2001 Accord. While it didn't image as well as my 2005 car, it had an "x-ray" quality that I liked, and the midbasses were much better. My 2001 car used an 8" B&C midbass, which gave me a ton of headroom.

It's hard to replicate that with speakers on the dash, because of Hoffman's Iron Law. Basically I'd need three or four 3" woofers up on the dash to get that kind of output, and there's simply no room.

Looking at those pics from the 90s, it got me wondering if it would be possible to do something similar, but with the shallow waveguides that are in vogue nowadays?


















If you look at the first pic in the post, it would look a lot like those cars from the 90s. But instead of using a compression driver and a horn, it would use a dome, loaded on a waveguide, in the same position. It seems like this could deliver a compromise. It wouldn't be as efficient as the horns from the 90s, but it would have better vertical directivity. (This is due to the waveguide; deep horns have narrow directivity, shallow waveguides have broad directivity.)


----------



## seafish

Patrick Bateman said:


> Looking at those pics from the 90s, it got me wondering if it would be possible to do something similar, but with the shallow waveguides that are in vogue nowadays?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> If you look at the first pic in the post, it would look a lot like those cars from the 90s. But instead of using a compression driver and a horn, it would use a dome, loaded on a waveguide, in the same position. It seems like this could deliver a compromise. It wouldn't be as efficient as the horns from the 90s, but it would have better vertical directivity. (This is due to the waveguide; deep horns have narrow directivity, shallow waveguides have broad directivity.)
> [/font]


PB, I just bought a pair of these Dayton waveguides --

Dayton Audio H45E 4.5" x 4.5" Elliptical Waveguide 1-3/8"- 18 TPI

As you can see from the link,m they are almost identical to the tweeter waveguide pictured on the JBL spaeker in your last post.

They are relatively small and shallow and accosrind to Dayton, work well down to 3500 hz. I am hoping to either run the Auduble physics AAT in it (though that might well be redundant given the dispersion of the AP aat driver) or perhaps the Illusion C8 tweeter which would just about fit into the waveguide throat with very minimal shaving of the throat opening. These are only 3.125" deep and the 4.5" square could easily be reduced down to the 3" x 4" or even less with careful trimming. 

I plan to mount them as far forward and deep into the dash/windshield outside corners as possible…I believe that I might make it into the very sorter, with the only problem being the need to either slightly shorten the throat or perhaps even heat and curve it into a bend that will go DOWN into the dash void.

My question is this-- how much can the waveguide throat be shortened without impacting its acoustic integrity and can it be "turned or bent", as long as the internal dimensions remain the same, without impacting its acoustic integrity. 

TIA for any advice or insight!!!


----------



## Patrick Bateman

Geddes has done a lot of work to eliminate diffraction in loudspeakers.
His top-of-the-line speaker was my reference for most of the last decade.

Due to that, I'm super-sensitive to the sound of diffraction and it's really easy for me to hear it in 95% of the loudspeakers out there.

To reduce diffraction in a loudspeaker you REALLY want sloooooooow transitions from one surface to another. The Genelec pictured above is about as good as it gets. See how the transition from the surface of the tweeter, to the waveguide, to the cabinet edge flows from one curve to the other?

When you get this right, the result is really audible. The source of the sound is not as apparent, it seems like the sound isn't coming from the loudspeaker, but somewhere in the general vicinity. And you notice that when you're listening, the sound is less fatiguing.









The reason that I'm bringing all this up is that it requires a different waveguide for a dome and a compression driver. If you look at the Dayton waveguide, the angle at the entrance of the waveguide is quite narrow. Looks like about thirty degrees to me. For a dome, you'd want something in the neighborhood of 90.

*TLDR - if you use that Dayton waveguide, you'll probably want to use it with a compression driver.*

In my waveguide designs, I generally do what Genelec does. I make a curve that transitions from the EXIT angle to the baffle. IE, if the exit is 90 degrees, I make one gentle curve that goes from 90 at the entrance to 180 at the exit.

I kinda lost interest in 3D printing a B&O acoustic lens because the lens kept getting too big. But I think I could make something that would go under the dash fairly easily.

*The key to all of this is the midrange down there in the kicks.* We wouldn't be able to run the tweeter down to 1000hz like we do with compression drivers, so the midrange in the kicks would need to be able to run up to 2000hz at least.

Basically you'd be looking at a system that wouldn't be as loud as those old school prosound systems, but it wouldn't be as anemic as most car audio two ways. It would sit right in the middle of the pack. It would be a lot cheaper too. You could use a $20 tweeter and a $50 midbass easy.


----------



## garysummers

Patrick Bateman said:


> Your car is really dynamic; it's one of the few cars I've heard that can get LOUD while still sounding clean. When I first heard it, I was mystified by it, because most cars with direct radiators sound "polite" and "boring" to me.
> 
> If you went with a coax, I wonder if that would be a downgrade, because the tweeters in coaxial speakers tend to be kinda wimpy.
> 
> Not to dash your plans or anything
> But you have a car that's in the top 1%.
> 
> Has Andy heard it?


You very well could be right. I am still testing various point source speakers. When I say testing I mean listening. I don't have the know how or gear to test as detailed as others on here. But if I can't hear it then it isn't an issue, right?

Andy has an open invite for a demo!

G ?


----------



## seafish

Patrick Bateman said:


> Geddes has done a lot of work to eliminate diffraction in loudspeakers.
> His top-of-the-line speaker was my reference for most of the last decade.
> 
> Due to that, I'm super-sensitive to the sound of diffraction and it's really easy for me to hear it in 95% of the loudspeakers out there.
> 
> To reduce diffraction in a loudspeaker you REALLY want sloooooooow transitions from one surface to another. The Genelec pictured above is about as good as it gets. See how the transition from the surface of the tweeter, to the waveguide, to the cabinet edge flows from one curve to the other?
> 
> When you get this right, the result is really audible. The source of the sound is not as apparent, it seems like the sound isn't coming from the loudspeaker, but somewhere in the general vicinity. And you notice that when you're listening, the sound is less fatiguing.
> 
> 
> The reason that I'm bringing all this up is that it requires a different waveguide for a dome and a compression driver. If you look at the Dayton waveguide, the angle at the entrance of the waveguide is quite narrow. Looks like about thirty degrees to me. For a dome, you'd want something in the neighborhood of 90.
> 
> *TLDR - if you use that Dayton waveguide, you'll probably want to use it with a compression driver.*
> 
> In my waveguide designs, I generally do what Genelec does. I make a curve that transitions from the EXIT angle to the baffle. IE, if the exit is 90 degrees, I make one gentle curve that goes from 90 at the entrance to 180 at the exit.
> 
> I kinda lost interest in 3D printing a B&O acoustic lens because the lens kept getting too big. But I think I could make something that would go under the dash fairly easily.
> 
> *The key to all of this is the midrange down there in the kicks.* We wouldn't be able to run the tweeter down to 1000hz like we do with compression drivers, so the midrange in the kicks would need to be able to run up to 2000hz at least.
> 
> Basically you'd be looking at a system that wouldn't be as loud as those old school prosound systems, but it wouldn't be as anemic as most car audio two ways. It would sit right in the middle of the pack. It would be a lot cheaper too. You could use a $20 tweeter and a $50 midbass easy.


PB, thanks for your response….I was hoping to make that small Dayton waveguide work for my applcaiition, but obviously need to reconsider making my own curved waveguides using router bits and hardwood...could you please make some drawings to show HOW you are measuring the entrance and exit angles?? 

Also, do you think that the tiny Audible Physics AAT tweeter would benefit from a waveguide??


----------



## Patrick Bateman

seafish said:


> PB, thanks for your response….I was hoping to make that small Dayton waveguide work for my applcaiition, but obviously need to reconsider making my own curved waveguides using router bits and hardwood...could you please make some drawings to show HOW you are measuring the entrance and exit angles??


Figuring out the exit angle of a cone is easy; just look at the profile of the cone. TBH, I always use an exit of 90 degrees. In the real world, it's probably a bit wider than that, maybe 100 or even 120 degrees.

The main thing is that you DON'T want any sudden 'jumps' in the angle. On a woofer with a flat baffle, you have a sudden jump from the cone (about 100 degrees) to the baffle (180 degrees.) Even worse would be if you put a conventional driver in a narrow horn or waveguide, like what you have there. For instance, if you had a cone (about 100 degrees) mated to a narrow horn or waveguide (45-90 degrees.) That's a worst case scenario, because the last thing you want is a *reduction* in the angle. You want it to be expanding, or at the least, staying constant.

























This is why loudspeakers look like this now. It improves the imaging, the frequency response, and arguably it makes the loudspeaker less fatiguing. (The research on that is still evolving, but I believe it.)


seafish said:


> Also, do you think that the tiny Audible Physics AAT tweeter would benefit from a waveguide??


You absolutely MUST have a seamless match between the edge of the tweeter and the waveguide. The problem that I see with 90% of the tweeters out there is that it's difficult/impossible to mate the tweeter with the waveguide. For instance, I futzed around with the Dayton RS28 on a waveguide, then gave up. I am having good results with the SB Acoustics 19ST. At this point, I can only recommend that and the Vifa ring radiators.

These aren't expensive; about $21 each. SB, SB18ST-C000-4


----------



## Patrick Bateman

As mentioned in the 'five channel soundstage thread', I've switched this project from an Opsodis type of setup to a Dolby Prologic II setup.

I think I can probably tweak the xover settings to get some of that Opsodis goodness with the PLII setup. For instance, in an Opsodis setup you'd normally have a couple of tweeters in the center, then the midranges are located where you'd 'normally' put your midranges. (At 9 o'clock and 3 o'clock.)

To get some of this 'Opsodis' goodness in my setup, I'm not going to have tweeters for the left and the right speakers. So basically it's similar to a 'Opsodis' or mono tweeter type of setup. But instead of having a left and a right channel, I'll have a left, a center, and a right. *But only the center will have output to 20khz.* The left and the right speaker will be limited to 5khz or 10khz.





































Here's some pics of the left and the right speaker coming together. I'm using a 3" full range. I thought about doing a couple of 2" speakers, but the dual drivers would require some added complexity on the xover to eliminate interference above 1khz. So a 3" was the easiest.

The Dayton ND91 is my favorite 3" driver, but the magnet is really deep. That makes it difficult to squeeze into the corner of the dash. The Fostex FF85WK is my second favorite 3". But it's magnet is fat, which ALSO makes it difficult to squeeze into a corner. Due to this, I used the Peerless 830970.

The shape of the baffle is designed to increase output on axis a bit, and also to reduce diffraction. It is largely inspired by Genelec.


----------



## thehatedguy

It's odd you didn't have good results with the RS28 in the waveguide...the folks on the PE forum LOVE those tweeters on waveguides. They'll play to 1k on most waveguides, and are pretty flat doing so.


----------



## mitchyz250f

This is a great thread.

Patrick can you throw the waveguides into your Accord so we can get a better idea of the fitment?

Thehatedguy the RS28 waveguides are 8" in dia. I think we need something smaller. Are there any smaller waveguides for the RS28 or is the geometry easy to adapt?


----------



## Patrick Bateman




----------



## mitchyz250f

Patrick are you going to 'fill in the gaps' between the windshield/dash and waveguide? Seems like you would get a lot of diffraction as is. 

A few years ago you did something similar with a two 2" woofers in the middle of the windshield. You had blended the baffle to the windshield and dash and put PVC 1/2 tubes on the sides to prevent diffraction.


----------



## Patrick Bateman

mitchyz250f said:


> Patrick are you going to 'fill in the gaps' between the windshield/dash and waveguide? Seems like you would get a lot of diffraction as is.
> 
> A few years ago you did something similar with a two 2" woofers in the middle of the windshield. You had blended the baffle to the windshield and dash and put PVC 1/2 tubes on the sides to prevent diffraction.


Yep, I was thinking the same thing. The problem isn't necessarily diffraction, the problem is that you get an abrupt change in directivity if you can't push the speaker all of the way back into the corner. What happens is that the sound will 'wrap around' the enclosure because it's not all the way in the corner. It's not the end of the world, but it will definitely screw up the frequency response. More importantly, if you fix the frequency response problems caused by those reflections, *it will still sound weird*, because the problem is directivity. Basically you want directivity to stay constant, or a the very least, have directivity which doesn't change dramatically. (IE, the optimum would be directivity that's constant from 20hz to 20khz; but this isn't easy or possible, so the second best option is to have directivity which doesn't change abruptly, directivity which sloooowly transitions from one beamwidth to another.)









Here's the setup from a week ago








Here's the new setup. It's still not perfect, but it's a lot better.









Here's Gary's car and my old car, to show a couple of other approaches to this kind of setup. I think the waveguides in my old Accord were even a better match than these. But they were also very large. They don't look huge in this pic, but they're easily four times as large as the waveguides I built this week.


----------



## Patrick Bateman

another pic

















It's hard for me to express how tight the tolerances are. I literally made it as big as it needs to be, and not an ounce larger. The tolerances are so tight, I found that I couldn't use terminals on the driver because they wouldn't fit! (I just soldered the connections.)




































Some pics of it coming together. I wrote up how to make these waveguides here : 3D Modeling Tips and Tricks - diyAudio


----------



## craiggus365

Ummm, those are awesome!
To think I'm having enough trouble getting my PVC pods to work. I need to set up my game!


----------



## oabeieo

Sick


----------



## mitchyz250f

Patrick, It seems to me (that means I am guessing) that most waveguide are trying for a graceful transition to the baffle plane. In our example you are trying to make a graceful transition to the windshield and dash. Most of the WGs I have been looking at have an initial angle of 40 degrees and a convex in shape to gracefully match the speaker baffle. If we want to match our baffle (windshield/dash) our shape needs to be convex...possibly.

In Gary's example that is what he does as much as he can. And what he can't match he seems to solve with the foam 'eye brows" to reduce early reflections.

I don't think I am saying anything new here just restating what you have already said.


----------



## Patrick Bateman

mitchyz250f said:


> Patrick, I seem to me (that means I am guessing) that most waveguide are trying for a graceful transition to the baffle plane. In our example you are trying to make a graceful transition to the windshield and dash. Most of the WGs I have been looking at have an initial angle of 40 degrees and a convex in shape to gracefully match the speaker baffle. If we want to match our baffle (windshield/dash) our shape needs to be convex...possibly.
> 
> In Gary's example that is what he does as much as he can. And what he can't match he seems to solve with the foam 'eye brows" to reduce early reflections.
> 
> I don't think I am saying anything new here just restating what you have already said.











Ideally you'd want the same angle as the windshield. But that's not possible; to achieve that the drivers would have to be on the other side of the windshield!

The next best option is some angle that's greater than the angle of the windshield. For instance, my windshield is about forty five degrees. I used an angle of sixty degrees for my waveguide; basically the smallest angle I could get away with.

Taken a step further, you could use a flat baffle (180 degrees) or even a baffle that's more than 180 degrees. (IE, it's curved forward.)

What's going to happen when you do this is that you'll get a directivity change from one angle to the other. For instance, mine will transition from sixty degrees on the waveguide to 45 degrees on the windshield.

Whatever you do, DON'T use a concave waveguide. That will focus the sound at a single point in space. IE, if you move your head forward or backwards by even a few inches, the sound will change.

That's how satellite dishes work; the sound is focused at a single point. You can do the same thing with loudspeakers but it's pretty darn specialized. I've seen some concave waveguides used in stores, where it was designed to focux sound on a single listener. It didn't sound good


----------



## mitchyz250f

I understand what you are saying but I still don't understand the large 'reverse' radius where the window and dash meet the waveguide.


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## rton20s

Not to simplify it too much (if I even understand it correctly), but it seems like the origin opening of the waveguide at the driver should be something around 90 degrees. Whereas the windshield to dash angle is something around 45 degrees. For a smooth transition from a larger angle (waveguide origin)to a smaller angle (windshield/dash) would require a convex curve. This convex curve focuses the energy of the driver. What you are looking for in a waveguide is a concave curve to improve dispersion. 

The question remains though... What is the best way to transition a concave curve with a larger angle to the surrounding surfaces that are a smaller angle? Like Patrick said, the only way to completely eliminate the issue is to have the drivers beyond the glass/dash. I think what we see in Gary's car with the "eyebrows" is probably one of the best attempts we have seen to address the issue.


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## Patrick Bateman

mitchyz250f said:


> I understand what you are saying but I still don't understand the large 'reverse' radius where the window and dash meet the waveguide.


There's three ways to deal with shortening a waveguide:

















1) You can just chop it off abruptly. Pick an arbitrary point on the waveguide and cut it. That's what I did in the '09 project. Just cut it, added a baffle and painted it black.

2) You can do that, and add foam to treat the diffraction that results from the discontinuity. Peavey did this with their 'quadratic throat waveguides.'

3) You can use a roundover.

I went with #3 with this project. Roundovers are difficult to do without a 3D printer, but if you have one, it reduces the footprint quite a bit.


Basically you have to do *something* to transition from the edge of the waveguide to the car itself, that's the route I took.


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## Patrick Bateman

rton20s said:


> Not to simplify it too much (if I even understand it correctly), but it seems like the origin opening of the waveguide at the driver should be something around 90 degrees. Whereas the windshield to dash angle is something around 45 degrees. For a smooth transition from a larger angle (waveguide origin)to a smaller angle (windshield/dash) would require a convex curve. This convex curve focuses the energy of the driver. What you are looking for in a waveguide is a concave curve to improve dispersion.
> 
> The question remains though... What is the best way to transition a concave curve with a larger angle to the surrounding surfaces that are a smaller angle? Like Patrick said, the only way to completely eliminate the issue is to have the drivers beyond the glass/dash. I think what we see in Gary's car with the "eyebrows" is probably one of the best attempts we have seen to address the issue.


I went and measured my windshield and found that the angle was quite a bit smaller than I thought. I'd been 'eyeballing' the angle in my models, and had used a figure of 45 degrees.

It's quite a bit less - it's 31 degrees.


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## Patrick Bateman

This thread has become embarrassingly OCD. It should be obvious by now that I like building things more than I like finishing things, but I'm afraid it's taken a turn for the worse again.









If you look at one of my previous attempts, you'll notice that it simply doesn't fit all the way in the corner.









I improved on that with this speaker, but then I created a couple of new problems. The first problem is that the waveguide is about five centimeters too small. I know this is seriously nitpicking, but it was bugging me. One idea I had was to fill that gap around the edges with some felt or fiberglass. But it occurred to me that would require about four hours of work, and I could make an entire new speaker in about the same time.

*This is the main problem with 3D printers. It's almost TOO easy to try things out, it really brings out my OCD need to tinker.*

The bigger problem with this waveguide is the 2" driver. I'd intended to use the 830970 to cover about four octaves, from 250hz to 5khz. I'll post the polars later, they're amazing. The 830970 does exactly what I need it to do. *Unfortunately, it just won't get loud.* Zaph made the same complaint about all the 2" drivers, and unfortunately, he's probably right. In all of my projects I've used these tiny drivers in arrays, and I'd never noticed that a single driver really isn't capable of much output.

I don't want to slam the thing TOO bad, because it's one of the best speakers that I've 3D printed. If I wasn't such a basshead it probably would work find.

I think I'll probably post this set for sale, because I think that it's too nice of a design to just toss in the trash.

































A few weeks ago I figured out how to make nice elliptical waveguides. And then I figured out how to apply that technique to a SAW lens. So as of now, I'm leaning towards doing another Synergy horn up in the corners of the dash. This time around, it will use a dome at the apex, in a SAW lens. The pics above show the evolution of the waveguide, from a start with an elliptical shape, to the final product that's been chopped up to fit in the corners of the dash. The last image is intended to show the boundaries of the dash and the windshield; those parts won't be printed, of course. There just there to illustrate how it fits in the corner.

Having said all that, this isn't the final design. I spent a few hours trying to figure out how to mound the midranges, and I'm having a heck of a time. In a lot of ways, too much knowledge is a dangerous thing. For instance, the obvious location for the midranges is to the left or the right of the tweeter, like Gary did. But that creates a big problem for your crossover. Basically you wind up with a situation where the pathlength difference between the midrange and the tweeter varies from one side to the other. 

YES, this can be fixed with delay. But delay won't change the directivity pattern, and I really want the left and the right to match. And that means that midrange needs to be above or below the tweeter. (That's why 99% of the loudspeakers out there have the woofer and tweeter in vertical line.)

Another possibility would be to cram the midrange and tweeter so close together that the orientation doesn't matter. With a crossover of 2000hz, that would be about one quarter wavelength, or 1.6875"(!)

This might sound impossible, but I think I might be able to pull it off with the SAW lens, because you can mount the drivers face to face.









JBL did this in the M2 - the tweeter diaphragms are face to face, and they fire push-push into each other.









Tymphany did the same thing with the LAT


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## Patrick Bateman

Here's a quick illustration of what I proposed in the last post, basically putting the midrange and the tweeter face-to-face. Same idea as JBL in the M2 compression driver.

The thing that sucks is that the steep rake of the windshield forces you to push the waveguide closer and closer to the driver. To me, it looks like every inch you grow in height, you have to move it about TWO inches closer!

*This means that you want a midrange that's insanely low in depth.* Less than an inch would be ideal. I have a pile of 2" drivers that would work. But you need to use two or four of them to get any real output, and then that creates a pathlength problem 

Maybe I should try using a midrange dome. The Parts Express 3" midrange dome has an efficiency of about 91dB. To put that in perspective, an array of FOUR of the 2" mids from Peerless won't get you that much output.









Tang Band W2-852SH 2" Shielded Speaker Driver

Ironically, the woofers I used six years ago are a pretty good choice too. The TB W2-852SH has a moving mass that's over 30% lower than the Peerless. This raises the efficiency by a whopping four decibels.

Normally I don't worry too much about efficiency specs. My attitude is "if the efficiency is too low, use more drivers." But this is a special case, there's a very finite amount of room here. And it would take more than two of the Peerless woofers to equal the output of the TangBand's output in the midrange octave.


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## Orion525iT

Patrick, the whispers are about a bit over an inch deep, which is why I used them in my dash pods. I pushed them back as far as I could against the windshield. 

It seems the only way to get the space you desire is by cutting into the dash. The angle of the windshield prevents anything else. The only other thing is that trying to cover 250-5000hz will be difficult because of a lack of eq. I am covering 600-5000hz with my whispers, it there really isn't enough eq with my minidsp to get the job done. I wish I could get them lower, because my midbass response (especially on the left side) is a friggin nightmare.


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## seafish

PB, PLEASE do not take my suggestion in a bad way…I really DO like reading about all your experiments and ideas to get mo bettah sound out of smaller, less expensive drivers by using creative and unique waveguides as well as DSP meant for video games. And from a fellow OCDer, I am SERIOULSY impressed by your commitment to it.

But for the sake of simplicity AND sanity, why not try the Audible physics NZ3AlBe 3" widebanders that run flat near field from 150 to 15khz mounted in your car somewhere deep in the dash or wide in the a pillars or better yet, tucked into the dash/windshield/pillar corner like you are trying to do with these waveguides??

If 15k is not quite high enough for you FR tastes, then throw in the AP - AAT ribbon tweeter (less then 1/2" tall by 1" wide) right next to it on the speaker bevel and call it a day. I mean check out this FR plot--


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## seafish

And look at how close you can mount the tweeter to it--

http://www.diymobileaudio.com/forum/1993653-post54.html

And with some ingenuity, that distance could be reduced even more.

Furthermore, the ribbon tweeter is wired in parallel to the sideband speaker and has natural roll off above 20k…it doe not need or use a separate channel, meaning less DSP and amplification needed, OR leaving more of the above for processed rear fill. 

At least that is how I am looking at it.


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## thehatedguy

If he is going to some sort of uniform polar response...that little "tweeter" is going to be horrible. I wouldn't call it a ribbon...more like a piezo element.


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## Patrick Bateman

seafish said:


> PB, PLEASE do not take my suggestion in a bad way…I really DO like reading about all your experiments and ideas to get mo bettah sound out of smaller, less expensive drivers by using creative and unique waveguides as well as DSP meant for video games. And from a fellow OCDer, I am SERIOULSY impressed by your commitment to it.
> 
> But for the sake of simplicity AND sanity, why not try the Audible physics NZ3AlBe 3" widebanders that run flat near field from 150 to 15khz mounted in your car somewhere deep in the dash or wide in the a pillars or better yet, tucked into the dash/windshield/pillar corner like you are trying to do with these waveguides??
> 
> If 15k is not quite high enough for you FR tastes, then throw in the AP - AAT ribbon tweeter (less then 1/2" tall by 1" wide) right next to it on the speaker bevel and call it a day. I mean check out this FR plot--


I'm not familiar with any of the Audible Physics drivers.

I *do* think that widebanders are a good option, and that's exactly what I was trying to do about two weeks ago. I started with a Peerless 3" widebander, but found the enclosure was too big. I reduced the driver size to 2", and went with a Peerless 830970. That enclosure was the correct size, if anything it was a little too small. *But then I found that I couldn't get acceptable output levels below 500hz.*

I've been a big fan of the Peerless 830970 because it's one of the very few drivers that can take a lot of abuse *and* play out to 20khz. I need to post some polars; it really and truly reaches 20khz, and it will *also* play down to 500hz. There are about four or five drivers that can do that.*

The problem with the 830970 is that it wouldn't generate a lot of output. (It's sensitivity is something like 81dB)

It's definitely maddening; if you use a driver that's over 2", it's hard to get to 20khz. If you use a driver that's under 3", it's hard to generate any real output.

An array is the obvious solution, but horizontal arrays are a p.i.t.a.

There's another possibility here, which I haven't talked about much. *The Peerless may not age well.* John Hasquin over at Diyaudio mentioned this once, that he basically won't buy drivers that have a rubber surround. I bought my 830970s about five years ago, and I bought eight of them. As of 2015, over half of them are broken. The main issue that I'm seeing is that the surround cracks or it delaminates. I hand-picked the 830970s for the pods that I posted last week; I wound up skipping about four drivers that didn't look good. The 830970 also has a plastic frame that cracks easily.

It's possible that's the problem that's leading to these output issues. If there's any kind of mechanical issues with the driver it could limit the output easily.

Bill Waslo uses the $2 Gentos for his project, and I have something like fifty of those. I'm semi-tempted to give those a try, because they have a paper cone and a cloth surround. The paper cone will raise the efficiency and the output, and cloth surrounds are apparently more durable than rubber. The Gento also has a steel frame (the Peerless is plastic.) On the downside, the Peerless has a nicely damped aluminum cone and a shorting ring.

Building midranges is a p.i.t.a.


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## mitchyz250f

My head feels like it is going to explode. I apologized in advance for saying anything ridiculous. I feel like I should be getting college credit for this thread.



Patrick Bateman said:


> Having said all that, this isn't the final design. I spent a few hours trying to figure out how to mound the midranges, and I'm having a heck of a time. In a lot of ways, too much knowledge is a dangerous thing. For instance, the obvious location for the midranges is to the left or the right of the tweeter, like Gary did. But that creates a big problem for your crossover. Basically you wind up with a situation where the pathlength difference between the midrange and the tweeter varies from one side to the other.
> 
> YES, this can be fixed with delay. But delay won't change the directivity pattern, and I really want the left and the right to match. And that means that midrange needs to be above or below the tweeter. (That's why 99% of the loudspeakers out there have the woofer and tweeter in vertical line.)
> 
> Another possibility would be to cram the midrange and tweeter so close together that the orientation doesn't matter. With a crossover of 2000hz, that would be about one quarter wavelength, or 1.6875"(!)


Isn't this situation typical for most home speakers? Unless the tweeter is mounted further back than the midrange so that the voice-coils are aligned there will be tilting of the sound lobe. This can be mechanically corrected by tilting the speaker upward or using a tweeter in a waveguide so that the coils are aligned. Electronically could this be corrected using an even number crossover and inverting the tweeter? 
https://en.wikipedia.org/wiki/Loudspeaker_time_alignment

In Gary's car the side tweeters are pushed back. I don't know if this was done to take advantage of the windshield/dash wave guide or for time alignment. This my not be possible with your design because your woofer is the size of a tweeter.

In a car everything is a mess. Poor speaker location, reflections, road noise... It seems that if you can get the mids and tweets on the dash and next to each other AND get rid of early reflections you are 95% there.

Very interested in seeing your polar response chart and your thoughts about them.


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## cajunner

I put some thought on this last night and came up with what I think is a move towards the goal.

the D2 by JBL, takes a single 90 turn, and there's no reason for a reflector there, correct?

now why is that?

I see what appears to be tangerine-type narrowing of the L, I think that 2-D visually you don't see it, but if you can do 3-D in your head, you will see an annular wavefront that doesn't recognize the far side of the isobaric dual radiator output.

so, let's just reverse it!

close off the center, but let it vent to the sides.

This will create an output that is perpendicular to the ring radiators, the same as the D2 but there is no 90 to deal with, there's just an aperture that can be controlled like a lens letting light through.

the portion of the driver that faces the interior of the vehicle, that part of the slit between motor halves, is mostly open save for some thin "tangerine" type compression building vanes.

the part that faces the windshield and the side window, have thicker vanes, and allow less sound transmission to the rear but operate much like a dipole, allowing the depth reflecting waves to project onto nearby surfaces and create dimensional sub-strata, like the way an omnipolar can, like the Pluto.

since you can make a D2 clone from 4" ring radiators using much less "power soak" for the output we want, the whole thing can fit into a 5.25" X 3" thick disc that sits 1" below the dash, and since we have a need for rear truncation of the driver output, the 1" of motor that stacks above the vented area, or slit between motors, can extend upward to the windshield on many vehicles with <40 degree rakes.

Or that can be adjusted through experimentation.

what do you think?


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## cajunner

advantages I can see with this design:

two motors, equally yoked yield low distortion.

the unequal pressure loading of the annular vent ring, is going to be distributed against two motors and suspensions, so the forces that cause rocking modes are going to be half as effective, and allow a larger excursion than if one motor/diaphragm were operating against an unequally loaded vent, which should allow the amount of low frequencies through the driver to extend into sub 300 hz regions.

By using an isobaric loading scheme, you could adjust the amount of vent to pressure ratio to compress the output, giving an acoustic lever that would make 2 four inch ring radiators actually louder than their direct radiator counterparts, by quite a bit.

I guess testing this for feasibility one could set a pair of compression drivers face to face, and make the vent ring with the variable tangerine vanes at different opening ratios, using industry standard dome diaphragms and the traditional phase plug correcting aperture, or exit holes.

the dual driver design does everything the Synergy can't, it provides time alignment without electronics, it puts two drivers into synchronous output, doubling the efficiency of a single footprint, and it reduces distortion by not only doing away with the one L (90 degree turn) in the D2 driver, but also can be used as a cardioid device if manipulation of the back-wave through absorbing strata can be accommodated, or more importantly, as an image depth product using the dipole or omnipolar radiating version.

then there's the power of 2 four inch voice coils going on, I imagine with a limber enough suspension, and the control of the isobaric configuration adding to lower distortion the final output of such a driver is easily in the 120 db range, with <1% THD from 300 hz to 14Khz, using low cost materials like mylar or highly oriented polyolefin, in the construction using the single injection molded unit structure, maybe even kevlar, haha...

they say the first 30% of the throat opening is crucial, so giving 1" of vented ring, that makes this speaker 6" wide, easily placed on most dash tops and fitted with either platters to extend the annular waveguide or logistically placed oblong platters, to create a coverage angle that excludes most of the nearby reflecting surfaces and directs the sound toward listeners.

which, I can see a horn with winnowing, open vent/aperture for direct fire to the opposing side listener, with image creation elsewhere through the annular ring. This would build the center image even further and allow some fixes for Haas and crosstalk at the same time...


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## Patrick Bateman

*What if the harmonic distortion is due to the enclosure?*









Here's a pic of one of my 3D printed enclosures. I used 1/5" walls for that enclosure. In the more recent ones, I stepped it up to 1/4". (6mm)

When I measured the harmonic distortion of the little Peerless 830970, I found that harmonic distortion was quite bad.

My initial line of thought was simply that I needed a better driver. But then I started to think about how my software *measures* harmonic distortion. And the way that it does that is by playing a tone, then measuring the harmonics. For instance, it will play 1000hz, then measure the output at 1000hz, 2000hz, 3000hz, etc. *If harmonic distortion was zero, then there would be zero output at 2000hz, 3000hz, etc.* IE, if there was zero distortion, we would only hear the fundamental.

If Erin is reading the thread, I'd be curious to get his thoughts. He's a lot better at me at doing measurements, and I've noticed that he does things like clamping down the driver when doing the measurements. As I ponder how distortion happens, it occurs to me that it's probably not possible to get a valid distortion measurement from a flimsy plastic enclosure, particularly when it's not possible to "clamp it down" so that it doesn't move whatsoever.

*All is not lost however!*

The next two paragraphs are speculation, but I *do* think that I am onto something:









In a conventional loudspeaker, we use something like a 7" woofer, and we mount the woofer to a heavy wooden baffle. We use four bolts to keep the woofer in place. The mass of the entire structure is probably five to ten pounds.









In my 3D printed pods, I am using a woofer that's a small fraction of the size of a conventional midrange. There is no baffle, and the loudspeaker is bolted to the enclosure via four small bolts.









I'm thinking that it might be possible to lower the distortion by doing everything possible to reduce and contain vibration. Basically *we want the cone to move, and NOTHING ELSE.* Pictured above is a JBL cone midrange compression driver. I'm guessing that the diecast aluminum enclosure is there for a reason - it's probably there to reduce vibration.

I'll probably need to think about how the waveguides are mounted to the car itself. There are two ways to reduce vibration I think. The first is to build a very solid connection from the waveguide to the car itself. The second would be to isolate it from the car entirely. (Similar to how subwoofers sit on spikes.) I might simply suspend the waveguide from the windshield using fishing line or the like.


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## Patrick Bateman

Here's a quote from Von Schweikert explaining the phenomenon that I am hearing from these 3D printed midranges:

How to design a low distortion speaker cabinet by Albert Von Schweikert

_"The Blue line is the response of the same driver, hard-mounted on the same baffle, without compliant decoupling. Note how the driver and baffle are still ringing up to 50 milliseconds after the impulse. Since the mid-woofer is mechanically attached to the baffle, and the baffle is mechanically attached to the cabinet, there is a high degree of unwanted transfer of vibration into the cabinet, effectively adding smear (a lack of clarity due to the constant ringing of the cabinet walls). This results in poor sound.

Since the surface area of a speaker cabinet can be up to 10 to 40 times the area of the cones, very little motion of the cabinet walls is necessary to become audible. The implication is that the cabinet vibration might have as much energy as the output of the driver itself, and this unwanted energy must be cancelled if true clarity is desired._"

One interesting thing about those Peerless midranges is that they honestly don't sound bad! It's curious how a LOT of distortion doesn't sound BAD, it just sounds DIFFERENT. The frequency response plots of the Peerless midrange pods I built, they look good. You can see the problem in the distortion plot, and I'd assumed the problem was the driver. But I am starting to believe the problem is the enclosure, particularly the way that the midrange is mounted. It should be easy to fix; since there's a waveguide it is possible to clamp the woofer from the front AND the back.

To my ears, the distortion is mostly euphonic (it's mostly 2nd order.) But it's definitely audible.


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## seafish

Patrick Bateman said:


> *What if the harmonic distortion is due to the enclosure?*
> 
> 
> 
> I'll probably need to think about how the waveguides are mounted to the car itself. There are two ways to reduce vibration I think. The first is to build a very solid connection from the waveguide to the car itself. The second would be to isolate it from the car entirely. (Similar to how subwoofers sit on spikes.) I might simply suspend the waveguide from the windshield using fishing line or the like.



PB, mounting the waveguide isolated from the car will help reduce any harmonics from the car/road from affecting the speaker output, but will NOT prevent a poorly mounted speaker in a light duty (read poorly damped) enclosure from creating it own unwanted harmonics. In other words, while isolating the wave guide from the car is a good idea in and of itself, it will likely not solve your problem of unwanted harmonics coming from the speaker/enclsoure interface. For that, you will need to add mass to the enclosure and tightly secure the speaker to the enclosure.


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## cajunner

and that enclosed CMCD enclosure was used to dissipate heat, along with structural integrity to reduce cabinet vibration.

the aluminum is an excellent conductor of heat energy and wicks away from the voice coil for higher power input/longevity of the driver.

the new drivers by JBL here, are new to me tech and look like a way to bridge Synergy horn time-coherent output with sheer low-distortion volume from the cone midrange with phase plug.

like, if those 3-D printed horn bodies aren't up to snuff you could put a phase plug in front of the cones, making 2.5" versions of the 6.5" and 8" CMCD JBL speakers.

that would be exciting, I think because the motor strength and the moving mass can be held in, maybe allowing 350 hz to 8Khz response at >95 db sensitivity, if the scale can be moved from the results JBL achieved with larger cone drivers.

that might just be what the doctor ordered, a phase plug that balances out the too-small rear enclosure to create a compression driver out of those little cone midrange, maybe the way to fly would be to tune an Aura Whisper's rear to a phase plug front, and achieve some compression ratio near 3:1 where the exit diameter could fit into a 1/2" throat for a real small EOS derivative corner dash horn?

yep, that sounds GOOT.


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## Kevmoso

Patrick Bateman said:


> *This means that you want a midrange that's insanely low in depth.*


Doesn't help the efficiency issue but 0.8" deep and $6.
HiWave BMR12 Compact 2" Full-Range Square Speaker 12W 8 Ohm

Sounds like maybe a B&G Neo8 could work?


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## oabeieo

Wow what a read . I'm anxious waiting the next step


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## Patrick Bateman

seafish said:


> PB, mounting the waveguide isolated from the car will help reduce any harmonics from the car/road from affecting the speaker output, but will NOT prevent a poorly mounted speaker in a light duty (read poorly damped) enclosure from creating it own unwanted harmonics. In other words, while isolating the wave guide from the car is a good idea in and of itself, it will likely not solve your problem of unwanted harmonics coming from the speaker/enclsoure interface. For that, you will need to add mass to the enclosure and tightly secure the speaker to the enclosure.


Agreed - I'll have to battle vibration from the enclosure itself, the driver, and also isolate it from the car.

I haven't seen a lot of people put too much effort into this. I'm guessing it's because the distortion isn't particularly offensive. But it's really apparent in the measurements.

I'm also starting to understand why compression drivers are built like a tank.


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## Patrick Bateman

cajunner said:


> and that enclosed CMCD enclosure was used to dissipate heat, along with structural integrity to reduce cabinet vibration.
> 
> the aluminum is an excellent conductor of heat energy and wicks away from the voice coil for higher power input/longevity of the driver.
> 
> the new drivers by JBL here, are new to me tech and look like a way to bridge Synergy horn time-coherent output with sheer low-distortion volume from the cone midrange with phase plug.
> 
> like, if those 3-D printed horn bodies aren't up to snuff you could put a phase plug in front of the cones, making 2.5" versions of the 6.5" and 8" CMCD JBL speakers.
> 
> that would be exciting, I think because the motor strength and the moving mass can be held in, maybe allowing 350 hz to 8Khz response at >95 db sensitivity, if the scale can be moved from the results JBL achieved with larger cone drivers.
> 
> that might just be what the doctor ordered, a phase plug that balances out the too-small rear enclosure to create a compression driver out of those little cone midrange, maybe the way to fly would be to tune an Aura Whisper's rear to a phase plug front, and achieve some compression ratio near 3:1 where the exit diameter could fit into a 1/2" throat for a real small EOS derivative corner dash horn?
> 
> yep, that sounds GOOT.


I have a couple of the 2.5" drivers from SB Acoustics on the way from Meniscus. Should give me a little bit more performance than the Peerless. The (not so) secret sauce will be overbuilding the enclosure.

As far as compression ratios, I can't really use one easily. Even with a vanishingly small front chamber under the phase plug, you still get a rolloff in the high frequencies. (For anyone that doesn't know, when you put a chamber of air in front of a diaphragm, it creates an acoustic low pass filter. Make the chamber large enough and you have a bandpass enclosure. But even a tiny bit of a chamber will introduce a rolloff. I use this technique in nearly all of my projects, but in a driver that's meant to go to 20khz, it's best avoided IMHO.


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## ErinH

Patrick, in regards to using a 2.5" driver, have you considered the AudioFrog GB25? 
http://www.diymobileaudio.com/forum...ctive-review-audiofrog-gb25-2-5-midrange.html

I've been playing with them off and on for the past couple of months and have really been impressed by them. I shopped a lot of 2-3" drivers as well, so I definitely have done due diligence in money saving (actually just ordered a couple of 2" daytons for $9/each yesterday).

Just mentioning it as an option. If you want, PM me... I'd be willing to loan you a pair.

- Erin


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## mitchyz250f

Gary S. if you are still out there, maybe you could go into some detail on speaker placement testing/listening you did before deciding on placing the tweeters to the inside of the mids in the side speakers.


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## cajunner

Patrick Bateman said:


> I have a couple of the 2.5" drivers from SB Acoustics on the way from Meniscus. Should give me a little bit more performance than the Peerless. The (not so) secret sauce will be overbuilding the enclosure.
> 
> As far as compression ratios, I can't really use one easily. Even with a vanishingly small front chamber under the phase plug, you still get a rolloff in the high frequencies. (For anyone that doesn't know, when you put a chamber of air in front of a diaphragm, it creates an acoustic low pass filter. Make the chamber large enough and you have a bandpass enclosure. But even a tiny bit of a chamber will introduce a rolloff. I use this technique in nearly all of my projects, but in a driver that's meant to go to 20khz, it's best avoided IMHO.


I'm aware that the JBL drivers were produced specifically with parameters conducive to the use of a phase plug.

I believe that a gain from a phase plug in sensitivity due to compression, would benefit these wideband drivers that are more traditionally long excursion, low sensitivity.

it wouldn't be as powerful as JBL designed drivers, but if they can do it, so can we!

now if we had a driver designed similarly to the design goals of the JBL 6.5" Cone Midrange Compression Driver, but it was not as large I believe the window where higher output and small footprint can coalesce, is larger than we think.

A very strong neodymium motor, and a 2" form factor? excluding depth restrictions, how about a large phase plug on the Dayton 2" dome midrange?

I'm kind of hung up on putting a phase plug on just about everything in a smaller more compact design, so that we can finally tackle the little bottom in the male vocals that comes up light or missing in most A-pillars using tiny drivers, and to be able to produce average SPL levels that make 2 fifteens IB out back, work hard to power over the top of the front stage.

This might not be possible unless we use phase plugs of some sort, even perhaps the strange response of the Manger driver (which I haven't heard, or tested).

I was under the impression that 3-D printing lent one access to a heretofore, uncharted territory of tolerances and fitment.

A phase plug that sits very close to the cone to produce the necessary compression without those acoustic impedance changes that a small air volume predicts, seems doable if one attempts?

I mean, give it a try, you've thrown away several horns made out of plastic, I suppose a phase plug that imitates the JBL version on their CMCD drivers wouldn't be that much of a stretch...




and the JBL models play pretty high up, wouldn't it make sense that a smaller driver play at least as high, and possibly higher using a comparison that takes beaming of the larger driver's response into account?

I wouldn't need it to play out to 20 Khz, there's several drivers that take up little room that can get the top of the range like the mini AMT or the AAT/piezo, or even just a silly little Motorola/CTS piezo?

I mean, aren't we trying to replicate the horn experience but above the dash physical mounting?


and do it unobtrusively, using DIY spirit and possibly, purpose-built drivers?

If there is no small diameter drivers out there with the correct parameters, let's get them made!


----------



## Orion525iT

Patrick Bateman said:


> I have a couple of the 2.5" drivers from SB Acoustics on the way from Meniscus. Should give me a little bit more performance than the Peerless. The (not so) secret sauce will be overbuilding the enclosure.


If you really get a design you are happy with, might be worth it to cast it out of aluminum. You could 3d print the parts to make the mold, and try it yourself. Its not that hard, and you get to play with fire. But I know you are the impatient type, not sure how much it would cost to pay somebody to cast the piece for you.


----------



## Patrick Bateman

Orion525iT said:


> If you really get a design you are happy with, might be worth it to cast it out of aluminum. You could 3d print the parts to make the mold, and try it yourself. Its not that hard, and you get to play with fire. But I know you are the impatient type, not sure how much it would cost to pay somebody to cast the piece for you.


I like building bikes, and I was daydreaming about 3D printing a bike on one of my bike forums. Steve Delaire, from Rotator, had an idea that I'd never considered:

*3D print a mold.*

Pretty ****ing brilliant I think. By going this route you get the ridiculous accuracy of a 3D printer, and the strength of carbon fiber or fiberglass.

For speaker pods, it would basically go like this:

1) design the speaker pod
2) Make a mold in 3D
3) print the mold
4) cover the mold in saran wrap
5) press the carbon fiber or fiberglass into the mold

I don't think anyone has done this for loudspeakers OR bikes. If you look at the history of companies like Cervelo, they basically started out by making bikes out of foam, then covering them in carbon fiber. It's an error prone process, and particularly with bikes, you need ridiculous accuracy. I once built a bike without building a jig, and it was basically un-ride-able because small errors in the angles and measurements "cascade" throughout the entire design, and you wind up with a bike that won't go straight, wobbles, etc.


----------



## Patrick Bateman

mitchyz250f said:


> Gary S. if you are still out there, maybe you could go into some detail on speaker placement testing/listening you did before deciding on placing the tweeters to the inside of the mids in the side speakers.


I'm not Gary, but I know that putting tweeters towards the center works fine. Below 1khz, most of our spatial cues are phase. Basically we determine where a sound is based on the time delay between our ears. (Not coincidentally, 1khz is 13.5" long; the reason that we hear this way is because that length exceeds the width of our head.)

Due to that, if you wanted the absolute maximum width you would put your speakers immediately to the left and to the right of you. By doing so, you maximize the interaural time difference (ITD)

Above 1khz it's mostly amplitude, which is why you can get away with moving the tweeters towards the center.

Basically wide midranges give you a wide stage, and tweeters in the center fills in the hole that appears when the midranges are spread too far apart.

Or, you know, you can just put a center channel there 

Gary has been experimenting with coaxes and I really need to stop working so much so I can go hear his car now. (Typing this on a plane on another one of my twenty hour commutes.)


----------



## Patrick Bateman

cajunner said:


> I'm aware that the JBL drivers were produced specifically with parameters conducive to the use of a phase plug.
> 
> I believe that a gain from a phase plug in sensitivity due to compression, would benefit these wideband drivers that are more traditionally long excursion, low sensitivity.
> 
> it wouldn't be as powerful as JBL designed drivers, but if they can do it, so can we!
> 
> now if we had a driver designed similarly to the design goals of the JBL 6.5" Cone Midrange Compression Driver, but it was not as large I believe the window where higher output and small footprint can coalesce, is larger than we think.
> 
> A very strong neodymium motor, and a 2" form factor? excluding depth restrictions, how about a large phase plug on the Dayton 2" dome midrange?
> 
> I'm kind of hung up on putting a phase plug on just about everything in a smaller more compact design, so that we can finally tackle the little bottom in the male vocals that comes up light or missing in most A-pillars using tiny drivers, and to be able to produce average SPL levels that make 2 fifteens IB out back, work hard to power over the top of the front stage.
> 
> This might not be possible unless we use phase plugs of some sort, even perhaps the strange response of the Manger driver (which I haven't heard, or tested).
> 
> I was under the impression that 3-D printing lent one access to a heretofore, uncharted territory of tolerances and fitment.
> 
> A phase plug that sits very close to the cone to produce the necessary compression without those acoustic impedance changes that a small air volume predicts, seems doable if one attempts?
> 
> I mean, give it a try, you've thrown away several horns made out of plastic, I suppose a phase plug that imitates the JBL version on their CMCD drivers wouldn't be that much of a stretch...
> 
> 
> 
> 
> and the JBL models play pretty high up, wouldn't it make sense that a smaller driver play at least as high, and possibly higher using a comparison that takes beaming of the larger driver's response into account?
> 
> I wouldn't need it to play out to 20 Khz, there's several drivers that take up little room that can get the top of the range like the mini AMT or the AAT/piezo, or even just a silly little Motorola/CTS piezo?
> 
> I mean, aren't we trying to replicate the horn experience but above the dash physical mounting?
> 
> 
> and do it unobtrusively, using DIY spirit and possibly, purpose-built drivers?
> 
> If there is no small diameter drivers out there with the correct parameters, let's get them made!


Most of the gain that you get with a horn is simply due to constraining the radiation into a small space.

For instance, if you put a loudspeaker on a stand in the middle of a field, the loudspeaker will (mostly) be radiating into 360 degrees.

Now place that loudspeaker onto the ground, and you're radiating into 180 degrees. Output goes up by 6dB*, but not because of any change in efficiency; it's simply radiating the same amount of sound into a smaller volume.

Now halve it again, and you're radiating into 90 degrees. A cone. Output goes up another six dB.

You can see how this piles up in a hurry; a loudspeaker that puts out 84dB in free air goes up to 96dB on a conical horn.

If you want to increase the dynamics in the midrange, the phase plug won't make much of a difference. 1khz is 13.5" long; the phase plug is too small to make a difference there. To increase output at 1khz, you need a waveguide or horn, and the dash and windshield do the job nicely.

What the phase plug WILL do is reduce the size of your radiator, or change it's shape. For instance, if need to squeeze the output of a 3" diaphragm through a 1" throat, you'll need a phase plug to concentrate the output into a smaller space. But check out a lot of the new JBL designs; they're moving away from the very high compression ratios that were standard operating procedure for the last eighty years. IMHO this is a good idea; high compression ratios can sound kinda strident. Those little Celestion and BMS drivers I use a lot have a low compression ratio, about two to one or less. A lot of older compression drivers have ratios in the neighborhood of ten to one.

* the gain in output was calculated off the top of my head; it would be worthwhile to fact-check with hornresp or the calculators at sengpielaudio.com


----------



## garysummers

mitchyz250f said:


> Gary S. if you are still out there, maybe you could go into some detail on speaker placement testing/listening you did before deciding on placing the tweeters to the inside of the mids in the side speakers.


We put the CDM880 midrange and the MT23 tweeter on a tear shaped plate, just big enough for the drivers. Very little edge. I blue taped the windshield and dash and filled the corners with non-hardening modeling clay. I then spent the next two months listening to the mid/tweet plate in every possible position, vertically and horizontally. The crossovers stayed the same and I did just a basic averaged equalization for the listen tests. 99% of the test was with my ears. Once I narrowed in on this configuration, which I finally decided yielded the best depth without sacrificing any width, we began to fine tune the shape. The shrouds were a later idea which started out as pieces of cardboard with the Alcantara double stuck to it. Listened for a while, liked what I heard and then had Scott Babson build them for real.


----------



## Patrick Bateman

So, um, y'know how I said I was having all kinds of issues with the harmonic distortion from the pods that I built for my Peerless 830987?

Um, I'm a dumbass, I had the gates set wrong. I re-ran the measurements in Arta and the pods are working fine. (I'm referring to my comments here : http://www.diymobileaudio.com/forum...udio-discussion/180497-28-weeks-later-12.html)

There was some harshness that I was hearing, but I now believe that harshness was due to a 5dB peak at 720 hz. There's a 5dB peak at 720hz because the enclosure is so small. You could EQ out the peak easily with any good EQ, or you could simply set the xover point above the peak.

Long story short:

These pods work quite well. My earlier measurements were ****. If you want a wideband that will cover half of the audible spectrum, these 830970 pods will do the job nicely.









Here's the on-axis response of the left and right pod, with the same EQ applied to fix the decaying response of CD waveguides. Note that the response matches within 1-2dB, which is important for a solid center image. (At high frequency, amplitude is everything.)









Here's the frequency response and distortion. Not as epically smooth as a dome tweeter, but that's the price you pay when you're squeezing five octaves out of a single driver. The distortion isn't too bad at all. An array would lower things further, but we don't have room for one...









Here's the polar response. It's not perfectly smooth, but that's because you need quite a large waveguide and a compression driver to get incredibly smooth response. It's +/- 3dB from 650hz to 8khz, and there aren't many drivers that can do that on a car dash. (Putting a driver on a flat baffle smooths out the response tremendously. The dash of a car is a harsh environment.)









For comparison's sake, here's the response of QSC's very nice waveguide. But the QSC is huge (14" in diameter) and would never fit in car. _This response does NOT include CD EQ, and that's why it's falling._


----------



## cajunner

Patrick Bateman said:


> So, um, y'know how I said I was having all kinds of issues with the harmonic distortion from the pods that I built for my Peerless 830987?
> 
> Um, I'm a dumbass, I had the gates set wrong. I re-ran the measurements in Arta and the pods are working fine. (I'm referring to my comments here :
> 
> There was some harshness that I was hearing, but I now believe that harshness was due to a 5dB peak at 720 hz. There's a 5dB peak at 720hz because the enclosure is so small. You could EQ out the peak easily with any good EQ, or you could simply set the xover point above the peak.
> 
> Long story short:
> 
> These pods work quite well. My earlier measurements were ****. If you want a wideband that will cover half of the audible spectrum, these 830970 pods will do the job nicely.
> 
> Here's the on-axis response of the left and right pod, with the same EQ applied to fix the decaying response of CD waveguides. Note that the response matches within 1-2dB, which is important for a solid center image. (At high frequency, amplitude is everything.)
> 
> Here's the frequency response and distortion. Not as epically smooth as a dome tweeter, but that's the price you pay when you're squeezing five octaves out of a single driver. The distortion isn't too bad at all. An array would lower things further, but we don't have room for one...
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's the polar response. It's not perfectly smooth, but that's because you need quite a large waveguide and a compression driver to get incredibly smooth response. It's +/- 3dB from 650hz to 8khz, and there aren't many drivers that can do that on a car dash. (Putting a driver on a flat baffle smooths out the response tremendously. The dash of a car is a harsh environment.)
> 
> For comparison's sake, here's the response of QSC's very nice waveguide. But the QSC is huge (14" in diameter) and would never fit in car. _This response does NOT include CD EQ, and that's why it's falling._


is this in-car measured response from the car seat miking point?

if you put this together with what Orion525 is doing with his Whisper pod that use the windshield/dash juncture to make an extended horn wall seen by the driver, maybe there's a meeting of minds where your early focus, perfect horn geometry can be inset into Orion525's fitted pod?

that seems like what is needed here, because frankly, there's too much going on with those cracks between your horn enclosure bodies and the surrounding parts to be certain of anything, except that as a crude first-time out, it is throwing excellent graphs.


Now how much gain are you getting in the lower octaves by the use of the location?

Is the edge diffraction of the horn enclosure body affecting the upper response that much, or is it symmetrical comb filtering because the horn is centered between the dash and windshield by height and allows for a destructive interference?

looking forward to more experiments, maybe you can press those bodies into place by shaping some modeling clay into the cracks so you can throw out diffraction effects, lens transition, gaps, etc. and design the horns to follow the windshield by placing the horn throat on the dash, or below the center of axis for the location....


----------



## Patrick Bateman

Yeah the reason that the QSC looks like this:









And my pods look like this:









Is because the QSC looks like this:









And my pods look like this:









Basically sound radiates in a sphere. If you want smooth response and constant directivity you want a shape with no sudden changes in angle, sharp edges, etc.

But that's hard to do in a car, unless you're willing to mount the loudspeakers on the other side of the windshield!


My measurements were done quasi anechoically, basically I set up a mic in my living room and I gate out the reflections. In my 2009 thread I used to measure in the car, but I don't think that's a hot idea anymore. It's really difficult to gate out the reflections. So I design them to be anechoically flat and then I tweak them from there.


----------



## Patrick Bateman

Here's the waveguide from here : http://www.diymobileaudio.com/forum/2941337-post1.html
I intend to re-use this design, but with a couple of tweaks to make it fit better on the dash


















Here's some attempts I made to fit the woofers on the waveguide. It's really REALLY hard to make it work. Basically the windshield gets in the way. It's easy to fit one on the waveguide, but I can't figure out a way to fit two without screwing up the polar response, and four is outright impossible.


















At the moment, my plan is to put the woofer where the stock *tweeter* used to be, and put the tweeter in a saw lens right on top of it. As long as the crossover is low enough, the tweeter should be "invisible" to the woofer. Same idea as putting a tweeter in front of a coaxial cone.

If anyone out there has a Mazda 3, 6, or CX-5, there's a ridiculous amount of room under those stock tweeter locations. I could probably fit a small subwoofer behind the dash if I was so inclined. (I'm using dual TC Soudns fifteens for this project, so a sub up-front is unnecessary IMHO.)


----------



## jwsewell01

I have been following your work for a few years but I don't even pretend to understand half of what's going on. Lol

I did come across this convention paper discussing dash mounted speakers that may or may not be of any use to you, I dunno....... 

http://www.jjracoustics.com/128-AES_2010.pdf


----------



## Orion525iT

Patrick Bateman said:


> At the moment, my plan is to put the woofer where the stock *tweeter* used to be, and put the tweeter in a saw lens right on top of it. As long as the crossover is low enough, the tweeter should be "invisible" to the woofer. Same idea as putting a tweeter in front of a coaxial cone.
> 
> If anyone out there has a Mazda 3, 6, or CX-5, there's a ridiculous amount of room under those stock tweeter locations. I could probably fit a small subwoofer behind the dash if I was so inclined. (I'm using dual TC Soudns fifteens for this project, so a sub up-front is unnecessary IMHO.)
> [/font][/QUOTE]
> 
> How low do you think you will need to cross them to avoid issues? How low will that saw lens go?
> 
> The advantage of a higher tweeter crossover is that you can afford to place them slightly inboard of the mid without the risk of loosing width. However, you can't go so high to where you center-center spacing starts to cause issues. In any case, if you are crossing the mids super low, then you need to do everything that you can to get them as wide as possible. At least that is my thinking.
> 
> Is there any way to slot the mid [B]behind[/B] the tweeter? If you are firing them straight up into an obstacle (the saw lens) why not try to route it around back. That way your apparent acoustic center is wider, correct?


----------



## Patrick Bateman

Orion525iT said:


> How low do you think you will need to cross them to avoid issues? How low will that saw lens go?


I'm crossing over at 2khz (7"). I could probably push that down to 1500hz (9") but that's pushing it.

The off-axis lobes of a horizontal array are only a problem if they're, well, horizontal!









So I think they'll basically wind up one on top of each other. The woofer in the stock location, and the tweeter right on top of it in a waveguide.

Note that the off-axis lobing of a horizontal array is simply caused by pathlength differences. For instance, if you have a midrange and a tweeter in a horizontal array, with a center-to-center spacing of seven inches, and a crossover of 2000hz, then they're one wavelength apart. If you're dead center in front of the array, everything is fine, because the midrange and the tweeter are equidistant. But as soon as you move a few degrees off axis, you get a pathlength difference between the midrange and the tweeter. And as soon as that pathlength difference is a mere 3.5", you get a null, because now they're 180 degrees out of phase! That's how we get those nasty off-axis nulls in a horizontal array.

And those nulls really aren't the end of the world; there's plenty of studios that use horizontal arrays. The problem is when you're not smack dab in the center between the two speakers. And that's how we're seated in a car, which makes horizontal arrays a p.i.t.a.



Orion525iT said:


> The advantage of a higher tweeter crossover is that you can afford to place them slightly inboard of the mid without the risk of loosing width. However, you can't go so high to where you center-center spacing starts to cause issues. In any case, if you are crossing the mids super low, then you need to do everything that you can to get them as wide as possible. At least that is my thinking.
> 
> Is there any way to slot the mid *behind* the tweeter? If you are firing them straight up into an obstacle (the saw lens) why not try to route it around back. That way your apparent acoustic center is wider, correct?


Yeah that's basically how I'll do it. One 'neat' thing about putting the midranges under the dash is that it introduces a delay. For instance, with a 4th order Linkwitz Riley crossover at 2000hz, we get a delay of one wavelength on the midrange. (2000hz is 6.75" long.) So by burying the woofer under the dash, we don't just hide it, we also physically delay it.

Chances are I'll have to use some additional DSP to get it all lined up, which kinda sucks, but I couldn't figure out a way to put the midranges more than about 3" below the dash. There's plenty of ROOM under the dash, but my sims indicated that a seven inch long cavity basically rolled off the highs way too much. I had to keep the depth very shallow to get the midranges to go to 2000hz.









I'm doing a manifold setup, similar to this, but with a couple of those $3 buyout midranges from Parts Express.


----------



## Patrick Bateman

After an embarassing number of failed attempts, a lot of time in front of the computer, and a lot of wasted 3D prints, I came up with a setup for the left and right midranges.





















































My design is fairly similar to the Kef eggs. But I'm doing a push-pull setup. The push-pull setup reduces second harmonic distortion. The main reason that I went this route was that I was SEVERELY limited on how large the woofer could be, because the larger the woofer was, the further away it has to be from the windshield. Basically if there was a 2" woofer out there that would get the job done, that would be awesome. By using a couple of 2.5" woofers I get the output of a 4" woofer, with the footprint of a 2.5" woofer.

There IS a bit of a downside however; the enclosure is too small, so my F3 will probably be around 250hz. If I could've given it more space, I could've pushed the F3 down to around 150hz. I tried a TON of schemes to extend the enclosure behind the dash, but none of them worked unfortunately.


----------



## mitchyz250f

Gary in this photo it appears that the side speaker tweeters are set behind the mids. How did you arrive at this position and did you try setups similar to the center speaker. What crossover are you using for the midrange?

Patrick - Where is the tweeter going in your latest setup? Also I read the paper (provided by jwsewell01). What are your thoughts on having a midrange firing up at the windshield. How high could you play before there were issues?



jwsewell01 said:


> I have been following your work for a few years but I don't even pretend to understand half of what's going on. Lol
> 
> I did come across this convention paper discussing dash mounted speakers that may or may not be of any use to you, I dunno.......
> 
> http://www.jjracoustics.com/128-AES_2010.pdf


Pretty interesting


----------



## Patrick Bateman

mitchyz250f said:


> Gary in this photo it appears that the side speaker tweeters are set behind the mids. How did you arrive at this position and did you try setups similar to the center speaker. What crossover are you using for the midrange?
> 
> Patrick - Where is the tweeter going in your latest setup? Also I read the paper (provided by jwsewell01). What are your thoughts on having a midrange firing up at the windshield. How high could you play before there were issues?
> 
> 
> 
> Pretty interesting


In an Opsodis setup the tweeters go in the center, woofers are nine and 3 o'clock, and midranges are in the 'normal' location. 
I'm doing a blend of Opsodis and Dolby PLII. 

So my woofers will be at nine and 3, my midranges wil be in their normal position. But instead of having two tweeters in the center, a la Opsodis, I'll have a derived center via PLII.

I'm hoping this will give me the spaciousness of Opsodis, but without the comb filtering you get when you put two tweeters in the center. I *could* use a mono tweeter - I've tried it before and it works. But I have a hunch that the steering logic of PLII should create a more convincing soundstage. 

So I'll have the following:

1) center channel: about 350-20000hz
2) left and right channel: about 80 - 5000hz, but split between midranges in the corners of the dash and midbasses at nine and 3oclock 
3) rear channels: same frequencies as left and right
4) sub: 20hz-160hz


----------



## garysummers

mitchyz250f said:


> Gary in this photo it appears that the side speaker tweeters are set behind the mids. How did you arrive at this position and did you try setups similar to the center speaker. What crossover are you using for the midrange?
> 
> Patrick - Where is the tweeter going in your latest setup? Also I read the paper (provided by jwsewell01). What are your thoughts on having a midrange firing up at the windshield. How high could you play before there were issues?
> 
> 
> 
> Pretty interesting


The tweeters are set back to get them as deep as possible. Did not try the center configuration on the sides. The midrange and hi-frequencies are crossed over at 4kHz @ 24db/oct.


----------



## cajunner

I believe this project is tailor-made for Orion525iT's pods, if someone could do a 3-D scan of the cavity where the windshield, dash, a-pillar and side windows meet, to make a reverse, or negative space scanned mold of the space, then doing a really cool 2 layer 3-D mold using a vibration-killing soft plastic for the back, or enclosure side and the front face having a harder, less giving substrate in the printer, injection heads.

it would be cool if you had a two head printer where you could run two types of injection plastic at one time, building the pod in one piece, though. Maybe even have metal sintering for the front ring, with elongated "nuts" molded right into the design, for the screws to hold better...

I think that getting the fit perfect is the hardest part of it, but if done right it can be done using very light build thickness on the enclosure walls using bracing built into the 3-D scan using the software.

Then you'd have the ability to shape the enclosure, taking advantage of space in the thin and thick areas behind the compression driver, and with vehicles that have enough rake, a Sausalito/Synergy combination with the space around the CD driver, used for enclosure behind the midrange cone driver.

this works, only with a phase plug covering the midrange cone, a la JBL and their special aluminum driver, but instead of having a big back compartment that's attached to the frame, you're getting a 3-D scan of the vehicle's dash hole, and filling it with a model made in forms that are unique to each vehicle.


this makes the phase plug, compression for the midrange, raising efficiency. The corner dash area, opens up in the way you want, because you design the horn throat however you think, according to Sausalito baffle sides, or according to tractrix design, or a combination that fits aesthetically and with the type of response that an average DSP processor can fix.

Design the nulls, make them coincide with the normal 10-band equalizer frequencies using the software, and even a 5 band graphic with wide Q can help if it hits the right frequencies on the peaks.

That can all be done using software, I believe.


But the enclosure volume in the area surrounding the horn throat will act like "nautilus wings" and provide a resonant chamber that isn't a flat plane for the backwave of the midrange, since it's essentially firing into a triangle corner, this could be the most important part of it, the midrange being small enough to fit where a sausalito back and sides are, and compression driver characteristics adding sensitivity and volume to the natural horn of the dash/windshield juncture.

I like the value that Aura Whispers represent, and I'd be willing to bond a fabric surround covering onto the foam rubber surround surface, to lower suspension compliance and create a more suitable driver for the project.

Stiffening the surround, just makes it that much more reliable since it doesn't have a spider to support, and brings the Fs of the driver higher to a more reliable crossover point. You could conceivably run the driver down to 350 hz, if it's being statically controlled by the compression phase plug enclosure, and the larger enclosure behind and around it.

This would be just like a Synergy but with careful placement, the Whisper's phase plug exits, could be aligned physically with the Sausalito so that no time alignment is necessary, all in the space of the corner below the line of sight to the road, and made virtually invisible to the untrained eye using grill fabric and a raised section of dash across the width of the vehicle.


----------



## Patrick Bateman

It's really difficult to push everything all of the way into the corner.

The funny thing about all of this is that the tweeters are actually the easy part. I've done a lot of screwing around with Opsodis type stuff, and I am convinced that I could 'con' someone into thinking that I have a tweeter in one location when it's actually somewhere else.

But 'faking' a midrange location is basically impossible. There's just too many cues in the midrange, and our ears are too sensitive to problems. The Speakerworks Grand National put the mids behind the driver, but it also used a very very low xover on the tweeter - something like 500hz iirc.

Pushing the midranges into the corners isn't just good for frequency response. It has some other advantages too. First, you can get real horn loading. I know Jason disagrees with me on this, but hear me out. Basically the midrange is radiating into a smaller volume than if it was in the door. In the door, the midrange is radiating into half-space. In the corners of the dash, it is radiating into a volume that is less than 25% of that. By reducing the volume of air that the midrange is radiating into, you raise the on-axis SPL. This is the same way that horn loading works. A horn isn't loud because it's a horn; a horn is loud because the driver mounted on the horn is 'pushing' a smaller volume of air. Some would argue that the horn itself is pushing the entire room. But this is not true; once the horn forms the air into a beam, it does not expand. (Same idea as a flashlight; the light doesn't scatter once it passes from the lens, it stays in a beam.)

TLDR: If you put an 8" woofer into the door of a car, it's radiating into 180 degrees. If you put a 3" woofer into the corners of the car dash, it's radiating into less than 45 degrees. The reduction in beamwidth raises the on-axis SPL, and that little 3" woofer may give the 8" woofer a run for it's money.

I don't think 3D scans of the dash will work. I started out doing 3D scans, two years ago, but gave up. The results just aren't very good unless you put a lot of work into adding 'markers' onto the object that you're scanning. And then you *still* have to clean up the model.

I'm getting stupid-accurate models with nothing more than a tape measure; I routinely get accuracy of a single millimeter. (If you look at my 3D prints, the screw holes line up; if I didn't make accurate measurements I would have to manually drill those holes, instead of having the screw holes printed righted into the model.)

If I were going for a deadly accurate model of the dash, I would spray foam into the corners, let it expand, remove the foam, then slice it into layers and measure the layers one by one.


----------



## mitchyz250f

garysummers said:


> The tweeters are set back to get them as deep as possible. Did not try the center configuration on the sides. The midrange and hi-frequencies are crossed over at 4kHz @ 24db/oct.


Gary what was the crossover on the dome midranges to woofer? I think morel crosses them at 450Hz (Fs is 400) at 6db!


----------



## cajunner

Patrick Bateman said:


> It's really difficult to push everything all of the way into the corner.
> 
> The funny thing about all of this is that the tweeters are actually the easy part. I've done a lot of screwing around with Opsodis type stuff, and I am convinced that I could 'con' someone into thinking that I have a tweeter in one location when it's actually somewhere else.
> 
> But 'faking' a midrange location is basically impossible. There's just too many cues in the midrange, and our ears are too sensitive to problems. The Speakerworks Grand National put the mids behind the driver, but it also used a very very low xover on the tweeter - something like 500hz iirc.
> 
> Pushing the midranges into the corners isn't just good for frequency response. It has some other advantages too. First, you can get real horn loading. I know Jason disagrees with me on this, but hear me out. Basically the midrange is radiating into a smaller volume than if it was in the door. In the door, the midrange is radiating into half-space. In the corners of the dash, it is radiating into a volume that is less than 25% of that. By reducing the volume of air that the midrange is radiating into, you raise the on-axis SPL. This is the same way that horn loading works. A horn isn't loud because it's a horn; a horn is loud because the driver mounted on the horn is 'pushing' a smaller volume of air. Some would argue that the horn itself is pushing the entire room. But this is not true; once the horn forms the air into a beam, it does not expand. (Same idea as a flashlight; the light doesn't scatter once it passes from the lens, it stays in a beam.)
> 
> TLDR: If you put an 8" woofer into the door of a car, it's radiating into 180 degrees. If you put a 3" woofer into the corners of the car dash, it's radiating into less than 45 degrees. The reduction in beamwidth raises the on-axis SPL, and that little 3" woofer may give the 8" woofer a run for it's money.
> 
> I don't think 3D scans of the dash will work. I started out doing 3D scans, two years ago, but gave up. The results just aren't very good unless you put a lot of work into adding 'markers' onto the object that you're scanning. And then you *still* have to clean up the model.
> 
> I'm getting stupid-accurate models with nothing more than a tape measure; I routinely get accuracy of a single millimeter. (If you look at my 3D prints, the screw holes line up; if I didn't make accurate measurements I would have to manually drill those holes, instead of having the screw holes printed righted into the model.)
> 
> If I were going for a deadly accurate model of the dash, I would spray foam into the corners, let it expand, remove the foam, then slice it into layers and measure the layers one by one.



then perhaps the bottleneck here, is not a resistance to idea creation, but a resistance to idea formation, haha...


maybe there's been advancement in the 3-D scan technology that makes it worthwhile.


I believe in 3-D and I want to see it's power. I want to see it make things that weren't possible using a tape measure, or foam casting.


going old school, I believe is for those who didn't do 10,000 filaments before getting it right.

They can do 3-D scans of about anything, I don't see why the process of an enclosure in a dash corner would be such a change from the norm, or proffer any kind of obstacle that can't be overcome with a 2-part build, if you have to bolt it together once it's in position.

at worst, you get a model enclosure that is 2 mm off, too small and cover the piece with a thin silicone layer to decouple the enclosure.

Aura Whisper, on-axis firing towards the car's dome light. In an enclosure that looks just like a Sausalito in the Audi but a tad larger, and clear acrylic wings making the horn shape transition to the side, and middle of the dash.

You could do it in 2.7" of depth, the phase plug vents in front of the Whisper would be immediately adjacent to the baffle edge, forming a vertical column less than 1" from the compression driver's primary exit under the Sausalito lens.

You'd have to use the Celestion .5" exit driver, but that would be fine considering the compression adds sensitivity and the Sausalito adds efficiency too. 

On a dash that's at least 14" deep, and a windshield angle of <45 degrees, you could probably calculate the sensitivity to a .5 db, accuracy using software.

I could probably play solitaire, on the computer while you run the program, haha...


----------



## Patrick Bateman

I just had a random idea:


















If you look at these attempts to push the drivers all the way back, you'll notice that as you get back in the corner, you wind up with a shape that's basically elliptical. IE, if you put a sphere in that corner, there would be a lot of wasted space. The ideal shape, to go all the way back, winds up looking a lot like an ellipse.

*Now hold that thought.*

Ideally, we'd put a driver in that corner that had unlimited output. That's the reason that I started this journey using an unobtanium compression driver from Germany, that cost about three times as much as a conventional compression driver. *I wanted to get as much output as I could, but I didn't have much space.*

Since the space in that corner is elliptical, it's tempting to go with a pair of drivers that are side by side. *A horizontal array.* But the reason that I've never done this is because horizontal arrays have nulls off axis.









Not a problem if you're sitting equidistant between the speakers, and the frequencies are low. But at midrange frequencies in a car, it's a deal breaker.










But what if we put a waveguide in front of *two* woofers, to yield a wavefront that's the size of ONE? The pic above is a crude illustration of what this would look like. (I'm traveling for work, no access to my normal tools.)

















Nexo does this to make one eight inch woofer "look" like two four inch woofers









JBL does this









And so did KEF

But I've never seen anyone do it with TWO drivers. We'd basically be stuffing the output of TWO drivers into a shape that's identical to one. So you'd get the polar pattern of a small driver, but the output of two.

Another nice side effect is that you could stick a tweeter in the center and it would behave like a coaxial.




It's really really tempting to build this. Sucks that I finished printing and finishing two midranges that seemed to be working nicely :O


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## cajunner

the horn will continue to produce gain, as long as it is continually expanding.

the horn can slowly advance towards the dash middle, or centerline, eventually contracting vertically coming to a point.

in the side window area, the horn is expanding vertically quickly, coming to a triangle configuration.

the baffle, the phase plug venting, the Sausalito with compression driver hanging in a dash midrange location or a custom hole in the dash corner, if the vehicle is suitable...

hmm....

gotta make this thing usable in more cars?

maybe not. Maybe just a specialized application, for those unique vehicles where the dash mids are put all the way into the corners for those who don't want to cut.


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## cajunner

What about covering the outside 1/2's of the pair of midranges?

Instead of creating 2 spaces, you'd have a single outlet, using the center to center spacing here doesn't apply because of the compression, not only will it act like a smaller driver on a polar plot but it will not comb filter until much higher out of the pass band of a 2.5" midrange...


right?


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## cajunner

I'm thinking the physical angle of the drivers on their mounting plates, can be as much as 90 degrees. This would collapse the outsides of the enclosure to fit deeper into the space.

what would a pair of midranges, using phase plugs instead of a board over them, do to the output, you ask?


a lot, haha...


that's a great idea, Patrick! I'm glad I came up with it....


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## thehatedguy

The GN played the horns down to 300.

Depending on when you heard Harry's old car, they were crossed 600 or so. Was around 800 later on I think.


----------



## Focused4door

cajunner said:


> I'm thinking the physical angle of the drivers on their mounting plates, can be as much as 90 degrees. This would collapse the outsides of the enclosure to fit deeper into the space.
> 
> what would a pair of midranges, using phase plugs instead of a board over them, do to the output, you ask?
> 
> 
> a lot, haha...
> 
> 
> that's a great idea, Patrick! I'm glad I came up with it....


If you have a pair of drivers with phase plugs mounted 90 degrees to each other, it seems like you have some cancellation from the sound reflecting off of the phase plugs. Hard to put in words but if you draw it out it should make sense. I guess the question is does it matter?

I really want to do a horizontal array for left right and center, but every time I try to mock it up it seems like it won't work either due to size, blocking defrost vents. Just not willing to make a completely custom dash for an idea that may not work as well as expected.


----------



## Patrick Bateman

cajunner said:


> What about covering the outside 1/2's of the pair of midranges?
> 
> Instead of creating 2 spaces, you'd have a single outlet, using the center to center spacing here doesn't apply because of the compression, not only will it act like a smaller driver on a polar plot but it will not comb filter until much higher out of the pass band of a 2.5" midrange...
> 
> 
> right?


That is exactly what I am proposing. 
A horizontal array where only the center of the array is visible. The edges of the array are masked off. 

This has the effect of making the array acoustically small, as small as a single driver. But with twice the output.


----------



## Patrick Bateman

Pic:


----------



## Patrick Bateman

Focused4door said:


> If you have a pair of drivers with phase plugs mounted 90 degrees to each other, it seems like you have some cancellation from the sound reflecting off of the phase plugs. Hard to put in words but if you draw it out it should make sense. I guess the question is does it matter?
> 
> I really want to do a horizontal array for left right and center, but every time I try to mock it up it seems like it won't work either due to size, blocking defrost vents. Just not willing to make a completely custom dash for an idea that may not work as well as expected.


It took me a few years to wrap my brain around it, but sound simply doesn't reflect at all unless the wavelengths are smaller than the object. 

For instance, if you have an eight inch woofer and you put a three inch wide 'bridge' across the cone, you're going to get reflections at 10000hz. That's because 10000hz is 1.35" long. 

But 1000hz will sail right by, because it's 13.5" long. It's so long, it doesn't "see" the bridge.


----------



## mitchyz250f

Patrick is there a formula for how much area the baffle plate/waveguide/phase plug can cover? In your example it looks like you are cover a greater area than the Nexo's.

For my application (rear speakers) I was thinking a baffle plate would be widest right over the dust cap and mount the tweeter in the center. Possible with a small waveguide formed into the baffle plate/waveguide/phase plug . How can I calculate the size of the baffle plate/waveguide/phase plug in the center?

Are there any negative aspects to this such a reflections/refraction or is that avoided with proper crossover selection?

I would like to read more about this. What would be the keywords? Tried phase plug and waveguide without much success.


----------



## Patrick Bateman

cajunner said:


> I'm thinking the physical angle of the drivers on their mounting plates, can be as much as 90 degrees. This would collapse the outsides of the enclosure to fit deeper into the space.
> 
> what would a pair of midranges, using phase plugs instead of a board over them, do to the output, you ask?
> 
> 
> a lot, haha...
> 
> 
> that's a great idea, Patrick! I'm glad I came up with it....


The tricky part about angling drivers is pathlength. I ran into this issue in my "soundbar Bateman style" project over at diyaudio. 

Basically if you're listening off axis, the pathlength from one side to the other can be significant. For instance, I was using an eight inch woofer and I was listening ninety degrees off axis. This meant that one side of the cone was eight inches closer. 

This isn't a big deal at 100hz, but at 1700hz it meant that one side of the cone was a full wavelength closer! (Because 1700hz is eight inches long.)

It also meant that 850hz was out of phase due to the PLD differences.

It was a real p.I.t.a.


----------



## Patrick Bateman

mitchyz250f said:


> Patrick is there a formula for how much area the baffle plate/waveguide/phase plug can cover? In your example it looks like you are more area than the Nexo's.
> 
> For my application (rear speakers) I was thinking a baffle plate would be widest right over the dust cap and mount the tweeter in the center. Possible with a small waveguide. How can I calculate the size of the baffle in the center?


Compression drivers mask off ninety percent of the diaphragm and they play to 20khz. 

So, seriously, you can cover a great deal of the cone. 

Id start with fifty percent, but heck, that's not a lot.


----------



## Patrick Bateman

mitchyz250f said:


> Are there any negative aspects to this such a reflections/refraction or is that avoided with proper crossover selection?
> 
> I would like to read more about this. What would be the keywords? Tried phase plug and waveguide without much success.


Technically, this is a phase plug.

You want the "bridge" to be smaller than the highest frequency that the driver will play. 

For instance, the Nexo plays to about 2000hz. 2000hz is seven inches long. So you'd want the bridge to be smaller in diameter than seven inches.


----------



## cajunner

Focused4door said:


> If you have a pair of drivers with phase plugs mounted 90 degrees to each other, it seems like you have some cancellation from the sound reflecting off of the phase plugs. Hard to put in words but if you draw it out it should make sense. I guess the question is does it matter?
> 
> I really want to do a horizontal array for left right and center, but every time I try to mock it up it seems like it won't work either due to size, blocking defrost vents. Just not willing to make a completely custom dash for an idea that may not work as well as expected.


90 degrees, is an L.

the phase plugs are not conventional looking, because they will be placed over inverted dome diaphragms.


the phase plug exits will be mated to the compression driver's output using physical distance to time-align, so they will be non-concentric, or more like a nautilus than a tangerine for analogy sake.


there are a few ways to do this, but I believe, after looking at Patrick's enclosures for the Sausalito that it's possible to do it modular to make each part simpler for the software programming involved in the 3-D printer operation.


once you get the pieces right, you could probably do a single piece casting.

the issue over phase plug design, patent rights, all that, means that I'd design something that works, but isn't a direct replica of JBL's Cone Midrange Compression Driver, or CMCD, and especially because i'm using a direct radiator that has a single piece of titanium in the cone/cap parts, and inverted.

The way a ring radiator works is surface area, and we won't have a lot of that with the Whisper but we do have a spider-less suspension, albeit needing a little fortification via bonding with mesh to the foam.


so we can optimize the long-ish throw of the Whisper using mild compression techniques by reducing the play space, (90 degrees forward radiation) and by placing a small phase plug over each driver that directs the output into a vertical slot that aligns with the play height of the Sausalito reflector/baffle, or about 1.25" high with the Whisper's exit/vertical slots 1" from the center line.

this would create a time-aligned, horizontal axis Synergy horn, that leads into a dash configuration that by it's shape, allows a strong center image and extremely wide presentation because the tall sided horn structure involving the side windows is going to make a semi-virtual driver out of the door windows.

it'll be the widest stage ever, (for a dash-mounted stage) and the wrap-around effect is going to blow your mind!


haha..

what I like about it is the general low-cost, high engineering, and common sense use of acoustics, like the way you can time-align the phase plugs to the compression driver, possibly, using only passive components in the crossovers, or having the 3 drivers run on a single amp channel due to the proximity of all drivers and the Synergy principle design concept.

I know others would want to use different, basket-type midranges but I think the Whispers have a unique ability to force the rear wave, that can be easily implemented since it's basically a tube. Others with baskets on magnets, you can't get a repeatable enclosure, it's molding around the basket.


----------



## mitchyz250f

Patrick Bateman said:


> Compression drivers mask off ninety percent of the diaphragm and they play to 20khz.
> 
> So, seriously, you can cover a great deal of the cone.
> 
> Id start with fifty percent, but heck, that's not a lot.


Patrick - A 6.5" speaker with a 2.5 - 3khz crossover, could have a 3.5" phase plug (all surfaces and edges rounded to reduce refraction) with an integrated waveguide for a tweeter all in line with the coil. The waveguide would provide proper polar response integration. The waveguide would also limit undesired reflection of the tweeter generated waves from bouncing off the moving cone of the midrange. With time alignment you would have a virtual coincident speaker, at least on axis. Patrick what do you think of placing a speaker of this configuration on the dash; other than a 6.5" is a big speaker for a dash location. Do you think the tweeter waveguide could reduce windshield/dash reflections sufficiently?


----------



## Patrick Bateman

mitchyz250f said:


> Patrick - A 6.5" speaker with a 2.5 - 3khz crossover, could have a 3.5" phase plug (all surfaces and edges rounded to reduce refraction) with an integrated waveguide for a tweeter all in line with the coil. The waveguide would provide proper polar response integration. The waveguide would also limit undesired reflection of the tweeter generated waves from bouncing off the moving cone of the midrange. With time alignment you would have a virtual coincident speaker, at least on axis.


Actually it works on AND off axis. It's still a coaxial, the only difference is that the high frequencies 'lead' the low frequencies. It took me a long time to wrap my brain around this. It's how the Synergy horns image so well. Even though the mids, highs and lows are not physically located in the exact same spot, they EXIT at the same time. Time delay is a wonderful thing. (The Synergy horns don't use DSP delay, they leverage the delay introduced by the crossover network to do the delay.)

Bottom line: multiple drivers, located in multiple locations, but arriving at your ear at the same time. But you don't have the drawbacks that you get with putting a tweeter at ear level and a midrange at waist level, where the off-axis is compromised. *Because the drivers are on the same X and Y axis, but a different Z axis, it all arrives simultaneously.* We're fixing the Z axis with delay.



mitchyz250f said:


> Patrick what do you think of placing a speaker of this configuration on the dash; other than a 6.5" is a big speaker for a dash location. Do you think the tweeter waveguide could reduce windshield/dash reflections sufficiently?




















The larger the woofer is, the more you have to move it forward. Erin's car is a good example of that. Beautiful pods, but you can see that the depth was limited by the size of the woofer.

That's why I keep trying to figure out ways to cram an array of 2" or 3" drivers up there. It's so I can push everything backwards.









Think about the Jericho horn. Here's a loudspeaker that's powerful enough to cover an entire STADIUM. Literally ONE speaker can produce enough output for a stadium, a single speaker. At the center of it we have the high frequencies. They have to emanate from the center, because they're so short.
Next to the tweeters we have the midranges. They're crossed over at 1500hz, which is nine inches long. Due to those wavelengths, they're all bunched up in the center too, but not as tightly. We have a few inches of 'wiggle room.'

But the low frequencies? Those are huge. 350hz is THIRTY EIGHT INCHES LONG. So we have TONS of wiggle room. That's why the cabinet is six feet tall, those low frequencies are so long you can take some liberties with their location.

And once you have everything sorted in the X and the Y axis, you can "fix" the Z axis with delay.

Another "neat" thing about fixing the Z axis is that the depth of the soundstage becomes real nebulous. For instance, I've heard speakers that image really well, like the Wilson speakers. And the soundstage is wide and pinpoint, but you know exactly what the depth of the speakers is.

But the Synergy horns don't sound like that; the depth is very nebulous, because the tweeter is nearly two feet behind the woofer! But, again, the wavefront arrives in phase. What a strange trick huh? Flat response, in phase, from speakers that are nearly a meter apart. But, again, it's all about the Z axis. We can't fix the X, can't fix the Y, *but we can fix the Z.*









Take to it's logical extreme, if you had fifty 2" drivers, a fifty amp channels, and fifty DSP channels, you could put the speakers in a straight line and generate as much SPL as a 15" woofer. But it would basically have the polar response and frequency response of a 2" driver still! (This is called an "end fire array" and they already do this with subwoofers at concerts. It will also work at high frequencies.)


----------



## subterFUSE

That's really the brilliance behind the Synergy Horns. The "delay" is done by physically locating the higher frequency drivers in the back of the enclosure. So it's actually not time alignment at all. It's physical alignment that takes the crossover-induced phase rotations into account. The major benefit is that you get proper impulse alignment AND phase alignment without any DSP, and a true point-source speaker.

I heard the Pure Groove speakers at a club a few months ago, which is the dance club branch of Danley Sound. They are unreal. They were actually imaging like a great home or car stereo.


Sent from my iPhone using Tapatalk


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## Patrick Bateman

Amazing aren't they? Pure Groove is based in Los Angeles iirc. There's a video of their Jericho horns playing the Nocturnal Wonderland event last year.
That was held in the same location as where I went to my first 'massive', way back in 1992 when I was in college. (I did a LOT of raving in the 90s.)

I was pestering Danley to get his speakers into the EDM scene back in the day:

I Don't Understand. - Page 5 - diyAudio

IMHO, a great sound system is particularly critical for EDM shows, because there's so much LFE. I'm so damn sick of going to see DJs and they're playing over a sound system that's twenty years old and optimized for the rock bands that were the 'norm' in clubs in the 80s. DJs need different speakers than rock bands.


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## subterFUSE

Patrick Bateman said:


> Amazing aren't they? Pure Groove is based in Los Angeles iirc. There's a video of their Jericho horns playing the Nocturnal Wonderland event last year.
> That was held in the same location as where I went to my first 'massive', way back in 1992 when I was in college. (I did a LOT of raving in the 90s.)
> 
> I was pestering Danley to get his speakers into the EDM scene back in the day:
> 
> I Don't Understand. - Page 5 - diyAudio
> 
> IMHO, a great sound system is particularly critical for EDM shows, because there's so much LFE. I'm so damn sick of going to see DJs and they're playing over a sound system that's twenty years old and optimized for the rock bands that were the 'norm' in clubs in the 80s. DJs need different speakers than rock bands.



Yeah, I want a pair of the monitors but they are like $3000 each. LOL


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## mitchyz250f

Patrick, My thinking is to modify the dash of a 1989 CRX. 

In the pic below you can see a PHL 1120 frame placed on the dash of a CRX. The speaker would not be in this position but placed into the corners by the A-pillar. The speaker’s rim sits 2.5" above the dash as is. The dash doesn't have airbags and slopes downward steeply from the windshield. If I screw up my dash I can get a replacement dash for $37 at Pull-A-Part. After I remove dash 'ridge/ledge' behind the magnet I should be able to drive the speakers to contact the windshield. The dash will be smoothed/optimized (somewhat) and covered with ¼"- 3/8” sound absorbing foam and Alcantara or something acoustically transparent. But important thing is that the speakers will be driven into the corners with only minor gaps.

In the above condition would an eliptical 5"x 3" tweeter waveguide (long axis vertical) mounted coaxily (3000hz xo) control early reflections sufficiently (by reducing their sound level) such that the refection would not interfere with critical listening? How much lower (dbs) does reflected sound have to be before we ignore it for spacial clues?

The other possible solution would be to slice the waveguide just below the tweeter place it on the dash directly in front of the mid such that the tweeter in contact with the dash. In this way there would be no early reflections off the dash and the waveguide would control refection off the windshield?

Also I understand the phase plug principle correctly I could bury part of the speaker below the level of the dash and all I would be doing is shifting the acoustic center of the speaker. Is this correct


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## Focused4door

Patrick Bateman said:


> Take to it's logical extreme, *if you had fifty 2" drivers, a fifty amp channels, and fifty DSP channels, you could put the speakers in a straight line* and generate as much SPL as a 15" woofer. But it would basically have the polar response and frequency response of a 2" driver still! (This is called an "end fire array" and they already do this with subwoofers at concerts. It will also work at high frequencies.)


You only need one amplifier, and don't even need the DSP.

You can use a LC network to create the delay, JBL does this with the CBT array

http://www.jblpro.com/ProductAttachments/CBT_Tech_Note_Vol1No35_091007.pdf


You don't get a lot of delay, and apparently the drivers impedance needs to be high relative the the termination impedance.


----------



## cajunner

to make my idea more understandable, let's put it into perspective.

A Danley speaker, the GH60, sideways.

GH60 | Danley Sounds Labs | Danley Sound Labs, Inc.

or put another way, the paraline is the exit vents in the baffle that a Sausalito uses.

look at it like a Sausalito with the two wings to the side, as enclosures for the Whispers.

this is elliptical, slid into the dash corner to fit. I believe a smidge of angle, maybe 50 degrees of closing in compared to the standard Sausalito, will add sensitivity and help control reflections.

since you are basically turning the sideways baffle, (Whisper array) sideways to fit into the dash corner, you are also allowing the side window/a-pillars to form a natural extension of the horn that is extended towards the centerline on the other side of the Sausalito lens.

Naturally, this all is built to fit to each vehicle, and windshields that are near vertical will not produce much gain, because they tend to have the shortest dashes....


but those low-raked sporty types, and mini-vans with the long dashes will give quite a bit of natural waveguide gain due to the physical details of the space.


but I'm liking my reverse D2 more and more.


the ability of a dual diaphragm driver to increase power handling, efficiency, and lower end cut-off depth in the vocal band, is where it's at in image drivers up high on a dash.


because this would create a natural response that has everything. Rear reflection from a perfect match, because it's the exact same driver that radiates omnipolar.

No need to wonder about motor structure for rear wave corrupted acoustics, no need to worry about using secondary drivers to produce the ambient field, and their distortion/timbre distinct characteristics giving the whole thing away...

just a dual radiator that makes regular compression drivers sound funny, because the output is direct, there's no phase plug to exit irregularity, since the compression is formed from annular lens built into the driver and coinciding with a flat dash, makes the dashboard a natural extension of the lens.

I could even make this using neodymium slugs, an internal motor approach that would appear to the untrained eye like a hockey puck about 3" around and 1" tall sitting on the dash, with the acoustic lens obscured by a fine mesh screen.

Now that's an idea!

I should draw it up and see what you guys think, eh...


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## Patrick Bateman

Focused4door said:


> You only need one amplifier, and don't even need the DSP.
> 
> You can use a LC network to create the delay, JBL does this with the CBT array
> 
> http://www.jblpro.com/ProductAttachments/CBT_Tech_Note_Vol1No35_091007.pdf
> 
> 
> You don't get a lot of delay, and apparently the drivers impedance needs to be high relative the the termination impedance.


What a great find!

This could be very very cool in the car. The CBT array is something like two feet tall, so it would be trivially easy to fit this up on the dash of a car. The drivers are just two inches tall and would be a lot less obtrusive than most dash pods.









Here's a pic - it's skinny

The REALLY great part about all of this is that you can use the delay to curve the wavefront. What this means is that you can have the drivers pushed ALL the way into the apex of the windshield, *but they'll behave like a point source, not a line array.

What that means is that it will radiate like a regular loudspeaker, it will radiate with a curved wavefront.

The reason that this is really important in a car is because we're seated off axis. If you used a conventional line array, the speaker on the left would be much MUCH louder than the speaker on the right. We want a CURVED wavefront so that we can crossfire the drivers.

Same idea as what they did with horns back in the 90s; the drivers horn is aimed at the passenger seat, and the passenger's horn is aimed at the driver's seat. This gives you an image in the center.

The JBL CBT array is doing the same thing, except it's curving the wavefront via the xover, not via a waveguide.

Another cool thing about this solution is that it should be capable of a LOT of output. The twenty driver CBT from JBL puts out 127dB and can handle transients of 1300 watts. Amazing what you can do with a pile of tiny drivers.

If I wanted to do one of these I'll have to figure out the xover, so I started to dissect it here:

Passive Loudspeaker Delay - diyAudio

*


----------



## garysummers

mitchyz250f said:


> Gary what was the crossover on the dome midranges to woofer? I think morel crosses them at 450Hz (Fs is 400) at 6db!


The CDM880s are crossed over at [email protected]/oct. I arrived at this after much listening and found it yielded the best phase coherent sound stage. The mids are really naturally rolling off and the crossover is more for protection. The Morel CDM880 is very well behaved as it rolls off naturally. The mids are obviously not playing down to 180Hz, but placing the filter at this point again yielded the best sonic result. The woofers are crossed over at [email protected]/oct.


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## subwoofery

garysummers said:


> The CDM880s are crossed over at [email protected]/oct. I arrived at this after much listening and found it yielded the best phase coherent sound stage. The mids are really naturally rolling off and the crossover is more for protection. The Morel CDM880 is very well behaved as it rolls off naturally. The mids are obviously not playing down to 180Hz, but placing the filter at this point again yielded the best sonic result. The woofers are crossed over at [email protected]db/oct.


Crap... Best post I've seen in a while  

I have a pair laying around and was wondering where I could cross it... Guess the myth about dome midrange not able to be crossed low is gone now  
Dome midrange prices might go up now lol 

Kelvin


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## subterFUSE

garysummers said:


> The CDM880s are crossed over at [email protected]/oct. I arrived at this after much listening and found it yielded the best phase coherent sound stage. The mids are really naturally rolling off and the crossover is more for protection. The Morel CDM880 is very well behaved as it rolls off naturally. The mids are obviously not playing down to 180Hz, but placing the filter at this point again yielded the best sonic result. The woofers are crossed over at [email protected]/oct.



Thanks for the details!
I think this post makes a good illustration of the difference between "electronic" crossover settings vs the actual "acoustic" result.

Did you likewise find that the woofers naturally roll off their low pass below the 315 Hz setting you have in the crossover? On first glance, the selection of 180:315 settings looks like a wide overlap. But considering the mids naturally roll off above 180 does make sense.


Sent from my iPhone using Tapatalk


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## cajunner

at first glance such a low crossover on 2" dome midranges, means that it goes against conventional thinking that you could play the driver above 95 db at all, if 390 hz is the Fs and Xmax is limited...

I mean, playing a 2" dome midrange through the resonance with only the suspension to prevent bottoming at high power inputs, sounds like a recipe for disaster, but here we have a dilemma as not only was it arrived at through experimentation but to be landed on as the best presentation...

does it mean that the 2" driver is playing at a nominal level below Fs, or that the phase coherence of a driver up above the dash is more important than the safety concerns of driving a small diaphragm at high excursion, regardless of the consequences?

so the mid bass does add to the stage at those 180 hz to 315 hz frequencies, but having what amounts to a bolstering effect, since Haas dictates that as long as the dome on the dash is less than 10 db beneath the mid bass, precedence goes to the dash, so you can ramp up the overall volume quite a bit before collapsing that stage from non-linear modes out of the dome.

And indeed, it has been supported by those hearing the car, saying it is dynamic like horns, which is probably that nifty phase coherence coming into play, like horns do...

and probably why there is still some ways to go before the ultimate fix steps into a winner's circle, somewhere...


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## mitchyz250f

garysummers said:


> The CDM880s are crossed over at [email protected]/oct. I arrived at this after much listening and found it yielded the best phase coherent sound stage. The mids are really naturally rolling off and the crossover is more for protection. The Morel CDM880 is very well behaved as it rolls off naturally. The mids are obviously not playing down to 180Hz, but placing the filter at this point again yielded the best sonic result. The woofers are crossed over at [email protected]/oct.


We have been told for so long that you cannot play below the Fs except when using subs. This goes against so many things that I have believed for so long to be true. More questions:
-How many db is the woofer crossed at?
-Did you try crossing at higher crossovers? 
-What was the difference in sound that you heard that you describe as phasing.

I may get a few things wrong here but I wonder if what Gary is doing is what Andy W. describes as a 'shelf filter'. Something they do on the MS-8 to make the bass fell like it is coming from the front even if it is behind you.


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## thehatedguy

You can play speakers below resonance...it's just that distortion and excursion greatly increase when you do, so output would decrease too. Just that in a subwoofer, it's the only (pretty much) speaker we have to play below Fs...and distortion in a sub isn't as audible as a midrange or tweeter.

It would be easy to model what the XO at that frequency is doing...would have to trace the FRD and IMP files, load them into your favorite free crossover designer, and apply the filter.

But it's not acting like a shelf filter...it's too far away from the passband to have any effect on anything but maybe (and that's a stretch) the very low portion of the passband.


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## garysummers

i know what I am doing may go against the rules and theory, which is why I spent many hours listening before concluding. I tried every frequency available on the processor from 100Hz to 500Hz to apply the 24db filter and 180Hz sounded the best. When I plot the woofer and mid the actual crossover acoustically (3db down point) is at about 350Hz. I will try to post a plot when I get a chance. 
Also the CDM880 is a 3" mid, not 2".
As far as distortion going up below fs, I don't hear that happening in this application. I have listened to all types of recordings, some very dynamic, even just listening to the mids. They are each getting 300 watts from a bridged Alpine F6. If I remove the hi-pass on the mids they will clip, so the filter is doing its job.


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## thehatedguy

Gary have you seen the new Morel Ingeras yet?


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## garysummers

thehatedguy said:


> Gary have you seen the new Morel Ingeras yet?


Yes I have. I am currently doing some listening tests with the Integra 502 and comparing it with several other point source speakers. This listening is being done through my home system, not in the car.

I see that Morel has a new Integra speaker line. I have not heard the 524 Integra!


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## mitchyz250f

Patrick - Trying to understand why you are planning a waveguide for the side speakers. With a 1" outlet on playing through the bottom of the dash and if you were only playing to 6000Hz (so it would effectively be omnidirectional) would you need any type of directional waveguide for the side speakers? Would the sound just radiate from the corner like a giant horn?


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## Patrick Bateman

mitchyz250f said:


> Patrick - Trying to understand why you are planning a waveguide for the side speakers. With a 1" outlet on playing through the bottom of the dash and if you were only playing to 6000Hz (so it would effectively be omnidirectional) would you need any type of directional waveguide for the side speakers? Would the sound just radiate from the corner like a giant horn?


Actually I'm pretty excited about 'focused4doors' CBT idea.

Seems like the CBT solves a lot of issues:

1) The 2" CBT array can handle something like a thousand watts, way more than I'll ever use
2) The passive delay in the crossover allows us to get the wavefront of a point source, without buying ten channels of DSP that you'd normally need for a horizontal array


What's not to like?

Horizontal arrays have always been the obvious choice. But the pathlength differences that arise have always been a real p.i.t.a.

(If you have two speakers with a pathlength difference of just one inch, you'll get comb filtering above 13,500hz. That's why the delay is so critical. To get to 20khz, the pathlenghts have to be absolutely equal. That's why the passive delay of the JBL CBT is such a big deal.)


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## Patrick Bateman

Looks like it's going to be a piece of cake to do a horizontal array.
Right now I'm looking at eight 2" drivers. That will give me as much cone area as a six inch woofer, but jammed right into the corner of the windshield for maximum horn loading and bandwidth.

Each one of those wood pieces is big enough to accomodate four woofers. I made two of them to see if I'd need to make the baffle concave, or if I could get away with a flat baffle.

My client at work has had the gall to actually make me COME INTO THE OFFICE, which I haven't had to do in eight ****ing years. So I'll probably end up doing this one in wood, just because 3D printing it would take too long and I have to catch a plane soon.


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## oabeieo

Patrick Bateman said:


> Looks like it's going to be a piece of cake to do a horizontal array.
> Right now I'm looking at eight 2" drivers. That will give me as much cone area as a six inch woofer, but jammed right into the corner of the windshield for maximum horn loading and bandwidth.
> 
> Each one of those wood pieces is big enough to accomodate four woofers. I made two of them to see if I'd need to make the baffle concave, or if I could get away with a flat baffle.
> 
> My client at work has had the gall to actually make me COME INTO THE OFFICE, which I haven't had to do in eight ****ing years. So I'll probably end up doing this one in wood, just because 3D printing it would take too long and I have to catch a plane soon.


I'm excited to see what this does for you. This seems like a solution in my car instead of using a horn and a 6.5 combined . Best of luck and happy experimenting .


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## Patrick Bateman

(Hopefully) it should sound similar to having horns up in the corners of the dash. 

The secret sauce is the CBT technology. It basically takes a speaker thats shaped like a ribbon but forces it to n radiate like a point source.

So you get the dynamics and efficiency of a horn, though it LOOKS like a conventional array. Or that's the idea.


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## mitchyz250f

Patrick Bateman said:


>


Does it matter that the speaker are not 'more' on axis like the are in the home/studio?



Patrick Bateman said:


> Right now I'm looking at eight 2" drivers. That will give me as much cone area as a six inch woofer, but jammed right into the corner of the windshield for maximum horn loading and bandwidth.


I have to ask..Is eight 2" speakers enough? When not 12? Why not eight 3" speakers? Also when it comes to speakers producing their lowest notes (how low is that) what is the cone area of those speakers combined? 

This thread has been great. I check it several times a day. And we have talked about so many theories and setups. I am a little confused about the direction. I thought you were heading towards a Opsodis setup. With one tweeter in the center. Is this still the case?


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## cajunner

garysummers said:


> i know what I am doing may go against the rules and theory, which is why I spent many hours listening before concluding. I tried every frequency available on the processor from 100Hz to 500Hz to apply the 24db filter and 180Hz sounded the best. When I plot the woofer and mid the actual crossover acoustically (3db down point) is at about 350Hz. I will try to post a plot when I get a chance.
> Also the CDM880 is a 3" mid, not 2".
> As far as distortion going up below fs, I don't hear that happening in this application. I have listened to all types of recordings, some very dynamic, even just listening to the mids. They are each getting 300 watts from a bridged Alpine F6. If I remove the hi-pass on the mids they will clip, so the filter is doing its job.


when I googled Morel CDM880 I found where they state the voice coil is 2.125" and I usually attribute a dome driver to the voice coil size, but everywhere I look they say these are 3.5" drivers and Morel's site is down right now...

if the drivers you have are not the same as what I googled, then the Fs won't be 390 hz and all, either.

but no matter what, your technique and hearing choosing a non-standard approach to the 3-way is very interesting since we almost always expect to be see the dome mids crossed over at different frequencies than the ones you chose.

edit*

still can't get into Morel's site, but looking on Parts Express I didn't see a CDM880 available, but there was a driver, MDM55 or something, which was 2.125" diameter. Since the CDM880 follows the millimeter to diaphragm size naming, an 88 would be 3.5" or so, going by that rule and definitely not the driver I googled a couple of days ago.

that's a large dome and with the closed back, may be able to produce more output near 180 hz than previously thought, even more so based on a 3.5" size factor. Your tuning method may be unorthodox but using a lower excursion midrange in a chamber may not require a steep high pass filter as would be expected. I'm going to use this information to try and get a 2" midrange dome, the Kappa poly domes, to play under 800 hz using a chamber on the back... and see what I sees.


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## Patrick Bateman

mitchyz250f said:


> Does it matter that the speaker are not 'more' on axis like the are in the home/studio?


Definitely.

If you have a couple of speakers in a horizontal array, and there's a pathlength difference of just one inch, then you're going to start seeing comb filtering at 3,375hz and by the time you reach one wavelength there will basically be no output at all. (Due to comb filtering.)

That's where the CBT processing comes in. We're basically using a combination of power tapering and delay to make the wavefront behave as if there was a point source in the corner.









That's why the CBT array is physically curved, and uses power tapering. My array will be delayed passively (like JBLs.)

I kinda wonder if we could get away with power tapering alone* but that's a conversation for another day.



mitchyz250f said:


> I have to ask..Is eight 2" speakers enough? When not 12? Why not eight 3" speakers? Also when it comes to speakers producing their lowest notes (how low is that) what is the cone area of those speakers combined?


Gary's system is very dynamic, with just a 3" midrange. I think the key is efficiency and output. Gary's mids are very efficient; my mids aren't but I have as much displacement as a 6" woofer. Add in horn loading and I think it should be plenty loud.

As far as using 3" woofers or large, the main problem is the center-to-center difference. The upper range of the woofer will largely be dictated by the center-to-center spacing. (one wavelength.) With a center-to-center spacing of 2.5" I should be able to get to 5400hz, maybe higher. JBL gets to something like 16khz, but a lot of that is due to the time delay.



mitchyz250f said:


> This thread has been great. I check it several times a day. And we have talked about so many theories and setups. I am a little confused about the direction. I thought you were heading towards a Opsodis setup. With one tweeter in the center. Is this still the case?


Thanks!

I haven't decided if I'll do a five channel setup. I probably will. I'm leaving space in the center for a center channel.




* http://www.audioroundtable.com/misc/nflawp.pdf


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## mitchyz250f

So with the current design with two 




Patrick Bateman said:


> As far as using 3" woofers or large, the main problem is the center-to-center difference. The upper range of the woofer will largely be dictated by the center-to-center spacing. (one wavelength.) With a center-to-center spacing of 2.5" I should be able to get to 5400hz, maybe higher. JBL gets to something like 16khz, but a lot of that is due to the time delay.
> 
> * http://www.audioroundtable.com/misc/nflawp.pdf


So could the outside speakers be 3"or larger? Is this going to have 16 tweeters too?


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## oabeieo

I just read all about constant beamwidth technology , wow !!! 
I am very interested in trying this too. Again I anxiously wait what you do with it , I think I would do a array of about 25 2" drivers And use the middle drivers for low frequencies and move the high stuff to the out sides , it would be nice to control the pattern to 50"! That down near 400hz and the careful use of FIR filters. 

So maybe I didn't read enough , and I apologize . But, what dsp does all this processing ? And I would essentially need 50 channels of amp correct?


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## Patrick Bateman

oabeieo said:


> I just read all about constant beamwidth technology , wow !!!
> I am very interested in trying this too. Again I anxiously wait what you do with it , I think I would do a array of about 25 2" drivers And use the middle drivers for low frequencies and move the high stuff to the out sides , it would be nice to control the pattern to 50"! That down near 400hz and the careful use of FIR filters.
> 
> So maybe I didn't read enough , and I apologize . But, what dsp does all this processing ? And I would essentially need 50 channels of amp correct?


Yes, ideally you would create a curved wavefront using an independent channel of DSP and an independent channel of amplification for every single channel.









Short of that, you'd curve the baffle to get a curved wavefront.









But 'Focused4door' found a great way to do it passively. And better yet, you can basically just copy JBL's design. It's all in the patent.

If you want to get creative, you could modify the delays using Bill Waslo's 'xsim' program. 

BTW, all of the drivers are basically driven full range. You're basically recreating the wavefront that would be radiated from a full range point source.

You could probably turn it into a two-way, but that wouldn't be faithful to the CBT patent. (Not saying it won't work, but if you want to copy JBL, follow the patent.)


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## cajunner

but, doesn't CBT make too large a stage, or it just gets out of hand and in the car, the windshield is pretty much a visual connection to the stage size parameters, as if a CBT in the car would make a stage that extends above the roof and below the dash line?

And is this advantageous, or is it just pushing the limits of the technology and the end result is ultimately too diffuse, or similar to Bose 901's, "stereo everywhere" technologies that were considered too much a room factor, which is now too much a DSP factor?


I'm not 100% sold on the idea of CBT as an ultimate design principle, I sort of like the cardioid or reduction in front wall bounce, maybe it extends to why I also enjoy 4 corner sound in the car, (not all the time) and being immersed in the music, I figure if a CBT array is going to produce a sonic field floor to ceiling the players on that stage must be like Clash of the Titans, haha...


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## Patrick Bateman

cajunner said:


> but, doesn't CBT make too large a stage, or it just gets out of hand and in the car, the windshield is pretty much a visual connection to the stage size parameters, as if a CBT in the car would make a stage that extends above the roof and below the dash line?
> 
> And is this advantageous, or is it just pushing the limits of the technology and the end result is ultimately too diffuse, or similar to Bose 901's, "stereo everywhere" technologies that were considered too much a room factor, which is now too much a DSP factor?
> 
> 
> I'm not 100% sold on the idea of CBT as an ultimate design principle, I sort of like the cardioid or reduction in front wall bounce, maybe it extends to why I also enjoy 4 corner sound in the car, (not all the time) and being immersed in the music, I figure if a CBT array is going to produce a sonic field roof to ceiling the players on that stage must be like Clash of the Titans, haha...


I should know soon, it took four hours but I've managed to solder up six of eight drivers!

I'm hypothesizing that the reason the CBT is special is because it mimics the radiation pattern of a point source.

If you look at a really well behaved point source like a synergy horn, the SPL is highest on axis then falls off as you go off axis. The CBT mimics this behavior; the power tapering reduces output off-axis.

Regular line arrays don't do this; the output level is identical from top to bottom. And it's curved, the same way that a wavefront from a point source is.

Ideally, if everything went according to plan, it would sound like any ol' point source, except with higher efficiency and output.


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## Patrick Bateman

Here's a couple pictures showing the back chamber for the woofers (a 2" PVC pipe) and the woofers I'll be using (Gento 2")


















A couple pics of the baffle. Did my best to shape it to fit the windshield.









The primary woofer is a Fostex FF85WK. I'm using a different woofer for the primary driver in the array because it will be getting more power than all the other drivers in the array.









Eight holes routed









After hours and hours of soldering and wiring, we have eight drivers in the driver's side array


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## cajunner

it's a shame we can't get the Aura Cougars for Gento prices.

that little full ranger would be a dandy for this app, cutting the width of the array by half, at least and there wouldn't need to be an anchor since 8 of those babies would produce enough low end to basically mate with subs in the door or floor.

and I'd do a center array of 4 Whispers, they would get down and dirty from the middle and produce an anchor center.

interesting to attempt CBT using DSP but going sideways I'm thinking it's going to be awesome if you can subvert the natural response of the narrow horizontal using CBT techniques in that orientation.

I've thought about trying the linear arrays in the dash many times over several years, it's been a pipe dream of mine since I was first introduced to the CBT design principles many years back, I believe on diyaudio actually...


it did cross my mind that crosstalk could be physically affected using additional drivers such as a Polk SDA uses.

it would require probably, 4 of those Gento in a push pull, all of which would mount behind the pipe, or towards the windshield and ducted using lost foam techniques to vent either under or over the array facing the interior...


then you would have ultimate control, CBT tech with aperiodic damping using image drivers to steer the response and produce the cardioid pattern inside the natural horn beam of the dash/windshield junction.

or maybe that's too much jargon for one exercise, sort of like doing jumping jacks while lifting curls, the jaw may get in the way occasionally...


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## Orion525iT

cajunner said:


> it's a shame we can't get the Aura Cougars for Gento prices.
> 
> that little full ranger would be a dandy for this app, cutting the width of the array by half, at least and there wouldn't need to be an anchor since 8 of those babies would produce enough low end to basically mate with subs in the door or floor.
> 
> and I'd do a center array of 4 Whispers, they would get down and dirty from the middle and produce an anchor center.


The problem with the Cougars and the Whispers in this application is the frame depth. I ran into this issue with my dash pods. Ideally, I would have liked to have pushed them back even further into the dash/windshield junction. But the depth of the frame prevented this. A driver with a traditional frame would allow for this. But, good luck finding one with the capabilities of the Auras.





cajunner said:


> then you would have ultimate control, CBT tech with aperiodic damping using image drivers to steer the response and produce the *cardioid pattern* inside the natural horn beam of the dash/windshield junction.


I tried cardioid with midranges at one point. After a few minutes of testing, I wished I had those minutes of my life back. It was terrible; to be technical, it was fubar. My thoughts as why it was so bad was attributed to the horrible environment of the car interior. Basically, a cardioid pattern could not be predicted due to all the near reflections and related chaos. Hard enough to get control and predicted output in just the forward direction. But now also get that control rearward and somehow get it to combine with the front to produce a cardioid? No chance. 

Which brings me to the current direction of the thread. This all works well in a fairly benign (by comparison) environment that a CBT array is typically utilized, but throw it in to a car, and things may not work out as planned. The instrument cluster alone is going to cause havoc. I guess it comes down to how sensitive the design is to the these issues. If I were to guess, I would say, very. I am not saying the idea as a whole won't work, but a passive arrangement might not be possible.


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## Patrick Bateman

I had really good results with cardioid. I posted a project in 2013 that used cardioid midranges.










If you look at the dipoles from fifteen years ago, and the dipoles of today, * you'll notice the baffles are getting smaller and smaller. * The reason for this is The Dipole Peak. Basically theres a frequency where the energy from the back sums in-phase with the energy from the front. This creates a huge peak in the response.

I have a hunch that your cardioids sounded bad due to the Dipole Peak.

The thing that sucks about the peak is that you can't really fix it with EQ, because if you fix it ON axis you'll scree up the OFF axis response.

Unfortunately, the only reliable solution to the Dipole Peak is to use specific baffle widths combined with the correct xover points and slopes.

It's not like a monopole, where you have a lot of flexibility with the xover points.

In a Dipole, the polar response varies dramatically from octave to octave, and certain xover points and baffle widths simply don't work.









Smaller seems to be better, which is why most modern dipoles use baffles barely larger than the drivers.

Theres some good news though - you can push them quite close to the back wall. In fact, this is why Gradient dipoles are so popular in Denmark, where space is at a premium.

Note - I've used the term Dipole and cardioid interchangeably in this discussion. IMHO, they're two points on the same spectrum.


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## oabeieo

cajunner said:


> but, doesn't CBT make too large a stage, or it just gets out of hand and in the car, the windshield is pretty much a visual connection to the stage size parameters, as if a CBT in the car would make a stage that extends above the roof and below the dash line?
> 
> And is this advantageous, or is it just pushing the limits of the technology and the end result is ultimately too diffuse, or similar to Bose 901's, "stereo everywhere" technologies that were considered too much a room factor, which is now too much a DSP factor?
> 
> 
> I'm not 100% sold on the idea of CBT as an ultimate design principle, I sort of like the cardioid or reduction in front wall bounce, maybe it extends to why I also enjoy 4 corner sound in the car, (not all the time) and being immersed in the music, I figure if a CBT array is going to produce a sonic field floor to ceiling the players on that stage must be like Clash of the Titans, haha...


I thought the same thing, but cbt slightly modded for car and in the vertical plane on a dash makes some sense , so long as the drivers In the middle either play extremely high only or extremely low only and filters are used to control the pattern . I haven't figured out how it would affect imaging , but if only a couple drivers are used it seems like it would work, on another note I have experimented with driver replacement in dashboards Great deal lately and a lot of my experimentation does not show here on the boards mostly because it's not worth mentioning and it's already been done however the way Speakers behave placed against the windshield and path differences i've experienced some very unusual things , I would suggest that the windshield does act like a horn lower frequencies , but doesn't do any real benefits above about 1K , in the reflection and smearing really take charge , I haven't really found a way to take advantage of windshield above one today and it seems that directivity and aiming makes the most difference. I've made cardboard flaps that I've covered in carpet and put it right above speakers that are placed far forward in the dash to minimize first reflections off windshield and that really makes a huge difference above 1K and even though drivers may be placed far apart for some reason the windshield causes a crossed talk in some cases that is uncontrollable like my van, which has 5" point source drivers in the pods firing on axis in far corners , and the windshield has so many reflections that I cannot get it to image properly. Everything is smeared so badly that makes it completely unusable, The direct sound and reflected sound causes a phase disturbance where nothing is really In phase and nothing is really out of phase completely , I like the idea very very small drivers that don't push sound out to the sides so much as a go straight forward so you can control the directivity in such close quarters but some degree of damping I think is an order to really get a dash to work properly. Even with all the chaos that goes On a dash , to me is still a referred location. I love how pat try's stuff and works towards something truly unique. Even if you can get complete phase coherence down to 300hz I would be happy.


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## Patrick Bateman

Managed to get my DIY amplifier installed in the car today, as detailed here : http://www.diymobileaudio.com/forum/3011337-post53.html

This gave me the first opportunity to listen to one of the arrays. Here's some observations:

1) It's REALLY loud. It's outrageous how much output you can get from an array. I am using eight drivers but four would *easily* be more output than I'd need. I'm guessing this is a combination of the horn loading that you get from the windshield, the efficiency gain you get from an array, and the additional power handling you get. This thing is a MONSTER. Just for laughs I tried cranking up the gain on the amp all the way, and I made it to around 80% before the excursion led to distortion. I think I could've gone to 100% if I was using a high pass filter. The SPL dudes really need to try this, this thing is ridiculously loud.

2) I don't have any of the CBT processing in place. Due to this, the response above 5000hz was basically AWOL. I should be able to extend the highs once I add the CBT processing.

3) One thing I like about Synergy horns is that they have this 'x-ray' thing, where they can really extract details in a recording. These arrays seem to do that too. I'm guessing it's because their beamwidth is very narrow, down to around 700hz.

4) On the downside, the top octave just isn't there, and the upper treble isn't as clean as you'd get from a good dome tweeter or even a nice midrange like the Peerless 830970. I'll probably need a tweeter. I'm waiting until I add the CBT processing to decide for certain.


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## Patrick Bateman

I'm working on a crossover for my array. Here's a sim of the frequency response and delay of the crossover in the JBL CBT.

Basically the JBL crossover is mostly just adding delay, to curve the wavefront. There's a little bit of power tapering but nothing substantial. If you want more details on how this works, check out my thread here : http://www.diyaudio.com/forums/multi-way/280664-passive-loudspeaker-delay.html


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## mitchyz250f

Wow. You went from an idea to this in a week. 

How loud in dbs do you think?

Would it be fairly easy from a crossover perspective to match the curve of the windshield?


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## oabeieo

That's super awesome!!! I usually use a crossover for one reason as we all use a crossover , but I also choose the crossover based mostly on how it's polar behavior interacts with other speakers in the system relative to my seat in the car. I usually end up with a 6db or 12db , and only use steep filters up high above 3k. I would be intrested to see how adding a lpf to the cbt interacts with the array , and with let's say a mid bass in a door or kick . I would hope it wouldn't turn to phase nightmares , but would be very cool if one could get it all to pan out.


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## Patrick Bateman

mitchyz250f said:


> Wow. You went from an idea to this in a week.
> 
> How loud in dbs do you think?
> 
> Would it be fairly easy from a crossover perspective to match the curve of the windshield?


I think the xsim prediction is accurate - it's about 96dB efficient.
It's as loud as anything I've ever used, noticeably louder than even prosound woofers like the 3FE20 (90dB) and the 8NDL51 (93dB)

The thing that makes it really ridiculous is the relative lack of power compression. It gets way WAY louder than the 3FE20. Not as loud as the 8NDL51 tho 


That crossover is a real p.i.t.a. by the way. The GOOD news is that it seems really insensitive to your choice of driver. The BAD news is that I'm having a hard time figuring out what the rhyme or reason is to the values. It's clearly a variation on a 5th order xover, but if I adjust the capacitor values by even 25% the delay gets all screwed up.

Basically you probably just want to copy the JBL xover and call it a day.

Further complicating things is that some of those values are really hard to find. For instance, where do you get a 100picofarad capacitor? That's a really strange value for a loudspeaker xover.

Luckily Parts Express *does* have them in stock, but I hate waiting ten days for a ninety nine cent part:

Film and Foil Crossover Capacitors in the Speaker Components Department at Parts Express | 295

I usually buy my parts off of eBay because the shipping is so much faster.


TLDR:

1) If you build this thing, you probably want to stick with the 'stock' xover from JBL. You might even just BUY it from JBL, they WILL sell you the whole board.
2) The crossover is surprisingly cheap. Most of those parts are about $1-$3. This is a relief, considering that due to the high cost of copper, a lot of passive xovers can top $100 these days.


----------



## Patrick Bateman

oabeieo said:


> That's super awesome!!! I usually use a crossover for one reason as we all use a crossover , but I also choose the crossover based mostly on how it's polar behavior interacts with other speakers in the system relative to my seat in the car. I usually end up with a 6db or 12db , and only use steep filters up high above 3k. I would be intrested to see how adding a lpf to the cbt interacts with the array , and with let's say a mid bass in a door or kick . I would hope it wouldn't turn to phase nightmares , but would be very cool if one could get it all to pan out.


The whole array behaves like a point source, so you could add a high pass filter or a low pass filter before the array.

The only thing that gets really tricky is if you try to filter one or two drivers at a time. Due to the fact that all of the parts are interconnected, if you touch one value, it can have weird ramifications on the other values.









This is the JBL xover. Those are the actual values, so if you want to run out and buy the parts, have at it









This is a fourth order xover. If you compare the JBL and the fourth order xover, you'll notice that they're real similar. But the JBL adds one more inductor, for a fifth order rolloff. Where things get REALLY bizarre is that every driver is linked together. So we have a 2nd order rolloff for two drivers, then a 4th order for the next two, then a 5th order for the last two.

So each pair of drivers has a different slope. This is how they achieve the delay. Higher order xovers have more delay than lower order xovers, and that's why the order goes higher and higher and higher.


----------



## Patrick Bateman

It just occurred to me that this bizarre topology is a cost saving measure on the part of JBL.

IE, if you want to come up with a different curvature, and you don't want to do it based on JBL's topology, you *should* be able to achieve the same result with three 'conventional' crossovers. (One crossover for each pair of drivers, a total of six drivers and three low pass xovers.)

But the xover is going to be super-expensive. For instance, if you wanted to do a 2nd order lowpass on two drivers, a fourth order low pass on two drivers, and a fifth order low pass on two drivers, *that's a total of eleven xover parts!*

JBL's xover is bizarre, but it cuts down on the cost by at least 50%, and that's a big deal due to the expense of inductors. (Inductor prices have basically quadrupled in the last twenty years.)


----------



## Rrrrolla

I'm really liking this thread. The ability to steer the dispersion pattern in this manner opens up some new possibilities. My initial thoughts were that it might work very well if a line array was placed at the top of the door panel from the corner of the door where the pillar meets the door, with the line of small speakers riding along the top of the door towards the listener. Instead of directing the sound straight up, direct it towards the driver seat. So the speaker furthest from the listener (in the corner where the door meets the pillar) gets no delay, and each subsequent speaker gets delayed as the array moves toward the listener. This would effectively steer the audio towards the listener but still be at the furthest sides of the car. Might be efficient, wide, and reduce reflections in all other directions. In this case, the cascade of delay would only be in one direction, not from the center to each side.


----------



## Patrick Bateman

What you describe is an "end fire array"
Here's one being set up at a concert

In addition to generating MORE output in the direction of the audience, it also generates LESS output to sides and to the back. This is handy for outdoor stages and festivals where you don't want one stage bleeding into the next. Could also be used to reduce reflections off the windshield and side windows


----------



## BP1Fanatic

Patrick, this thread is off the hook! I found it from the Night Of The Living Bassheads thread on diyaudio. In the words of Public Enemy & LL Cool J, continue to "Rock the bells" PB!


----------



## oabeieo

Patrick Bateman said:


> The whole array behaves like a point source, so you could add a high pass filter or a low pass filter before the array.
> 
> The only thing that gets really tricky is if you try to filter one or two drivers at a time. Due to the fact that all of the parts are interconnected, if you touch one value, it can have weird ramifications on the other values.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This is the JBL xover. Those are the actual values, so if you want to run out and buy the parts, have at it
> 
> 
> 
> 
> 
> 
> 
> 
> 
> This is a fourth order xover. If you compare the JBL and the fourth order xover, you'll notice that they're real similar. But the JBL adds one more inductor, for a fifth order rolloff. Where things get REALLY bizarre is that every driver is linked together. So we have a 2nd order rolloff for two drivers, then a 4th order for the next two, then a 5th order for the last two.
> 
> So each pair of drivers has a different slope. This is how they achieve the delay. Higher order xovers have more delay than lower order xovers, and that's why the order goes higher and higher and higher.


That is kinda wierd , it looks to me and I could be wrong a no xo for the first two , 12 db for next , 24db for next and 30db for last. I immagine the cap values and cool values don't make sense because it takes into account the other speakers load on the line in previous filters in the positive throw, also the.sets of speakers are in series. It looks like , ( scratch head) my first thought is , I doubt this sounds good really close up. I bet it works good for a pass band , maybe for integibile speech or something that's not Hifi. But maybe , it sounds great. Eek . I'm going have to try it .


----------



## Focused4door

Patrick Bateman said:


> 4) On the downside, the top octave just isn't there, and the upper treble isn't as clean as you'd get from a good dome tweeter or even a nice midrange like the Peerless 830970. I'll probably need a tweeter. I'm waiting until I add the CBT processing to decide for certain.


This seems to be the flaw in all wideband speakers. Even a 2" speaker will beam at fairly low frequencies. 



Patrick Bateman said:


> Where things get REALLY bizarre is that every driver is linked together.


Going by memory but I think the pair that are linked are mirrored around the center of the array. The top and bottom speaker are paired, and so on. That way the delay to those speakers is identical. No extra components needed, no mismatch between components.


----------



## Regus

Patrick Bateman said:


> In an Opsodis setup the tweeters go in the center, woofers are nine and 3 o'clock, and midranges are in the 'normal' location.
> I'm doing a blend of Opsodis and Dolby PLII.
> 
> So my woofers will be at nine and 3, my midranges wil be in their normal position. But instead of having two tweeters in the center, a la Opsodis, I'll have a derived center via PLII.
> 
> I'm hoping this will give me the spaciousness of Opsodis, but without the comb filtering you get when you put two tweeters in the center. I *could* use a mono tweeter - I've tried it before and it works. But I have a hunch that the steering logic of PLII should create a more convincing soundstage.
> 
> So I'll have the following:
> 
> 1) center channel: about 350-20000hz
> 2) left and right channel: about 80 - 5000hz, but split between midranges in the corners of the dash and midbasses at nine and 3oclock
> 3) rear channels: same frequencies as left and right
> 4) sub: 20hz-160hz





Patrick Bateman said:


> Do you have a center channel?
> 
> Check out the graphs I posted earlier in the thread, and note that there's quite a bit of bass in the center channel.
> 
> I'm actually considering using a sub for the center channel, along with the mids and the tweets. From what I can see, the center channel in a ProLogic II setup is the trickiest part; the other five channels play a role, but the center channel does most of the heavy lifting.
> 
> Another fundamental problem with a five channel setup is that width will probably suffer. I notice this in my Genesis with the Lexicon processor. It's a tradeoff between the width of stereo or Opsodis, versus the solid center of a five channel setup. Heck, if this experiment is a dud I'll probably just do Opsodis.


Hey Patrick,

I've been following the two threads on your current setup with no small amount of interest. One thing I'm wondering is how you perceive that the setup you describes in this threw will work compared to what you discussed in the five channel thread. Basically, will the Opsodis midbasses still "work" if PLII steers the midbass frequencies to the centre, which will be playing down to 350Hz, or will they be getting a conventional signal?

It seems to me that it would be better to go the same route as home surround systems and match the LCR speaker responses, at least in terms of the midbass, whilst the arrays etc. are placed as described to utilise the windshield.

I'm tempted to play with this myself using the PLII decoding on my HT receiver and see how it sounds, although I think I already known the answer, as my experience of playback without a centre channel (don't ask!) confirms what your graphs say about the steering and frequency filtering that takes place.

P.S. I am also wondering if a Windows Phone would ever be able to do the PLII part - I believe they are working on a mobile version of Foobar2000, but I doubt that even with the OTG cable, it would be possible to add a USB sound card, although I will be happy to be proved wrong!


----------



## sqnut

Patrick Bateman said:


> In an Opsodis setup the tweeters go in the center, woofers are nine and 3 o'clock, and midranges are in the 'normal' location.
> I'm doing a blend of Opsodis and Dolby PLII.
> 
> So my woofers will be at nine and 3, my midranges wil be in their normal position. But instead of having two tweeters in the center, a la Opsodis, I'll have a derived center via PLII.
> 
> I'm hoping this will give me the spaciousness of Opsodis, but without the comb filtering you get when you put two tweeters in the center. I *could* use a mono tweeter - I've tried it before and it works. But I have a hunch that the steering logic of PLII should create a more convincing soundstage.
> 
> So I'll have the following:
> 
> 1) center channel: about 350-20000hz
> 2) left and right channel: about 80 - 5000hz, but split between midranges in the corners of the dash and midbasses at nine and 3oclock
> 3) rear channels: same frequencies as left and right
> 4) sub: 20hz-160hz


1. Isn't 160 very high for the sub? We can tell front and back above ~ 70, plus the risk of resonating something between the sub and your ears. Plus knowing you, you're going to do a first order slope  so you're basically hearing the sub well into 500......

2. Why an octave's worth of overlap between sub and woofer?

3. Hearing the highs from the back, even timed right, is going to pull the stage out into your lap, unless the objective is immersive sound. 

......just curious. In the opsodis setup, what does having only one tweet accomplish?


----------



## mitchyz250f

Sorry more questions for Gary. 

Are the crossovers for the rears speakers the same as the fronts and did you notice a big difference in efficiency due to the horn loading of the fronts? What was your criteria for the rear mid/tweeter locations.

I think you said you didn't experiment with the front side speakers drivers positioning/lcoations, how do you think sides set up like your center would sound? 

Are the front speakers on axis with the driver and if so how much did it affect listening in the passenger seat? 

Also what is the foam that you used to cover the dash?


----------



## Patrick Bateman

sqnut said:


> 1. Isn't 160 very high for the sub? We can tell front and back above ~ 70, plus the risk of resonating something between the sub and your ears. Plus knowing you, you're going to do a first order slope  so you're basically hearing the sub well into 500......
> 
> 2. Why an octave's worth of overlap between sub and woofer?
> 
> 3. Hearing the highs from the back, even timed right, is going to pull the stage out into your lap, unless the objective is immersive sound.
> 
> ......just curious. In the opsodis setup, what does having only one tweet accomplish?


The overlap between midbass and subwoofer is to smooth out the response. Same idea as using multiple subs in a home. But in the car, you move it up an octave, because the Schroeder frequency is higher. 

Also, the octave from 80 to 160hz is incredibly demanding.


----------



## Orion525iT

^ What I did for the same reason. A little math and maybe a measurement or two will show you the way. I don't have any suck out typical in the lower mid bass region. The bass tends do be a bit more amorphous (a trade off of sorts) but I still get very good left, right, front cues. I also have tons of output; I can hit north of 120db from 80-150 hz with ease.


----------



## cajunner

Orion525iT said:


> ^ What I did for the same reason. A little math and maybe a measurement or two will show you the way. I don't have any suck out typical in the lower mid bass region. The bass tends do be a bit more amorphous (a trade off of sorts) but I still get very good left, right, front cues. I also have tons of output; I can hit north of 120db from 80-150 hz with ease.


which brings to mind a new nomenclature necessary for those who respond to such things...


the SPL division from SQ is based on a prevalence of, high pressure scaled into burpage, extended resonant peaks under 100 hz, for SPL derivative board games.

SQ, however is not biased towards any subsect, and a new division can be produced that specifically addresses the mid bass region as a new realm of proficiency.

Some would like to run the SQL designation into a nearby ditch to never be spoken, seen, or heard from again.

I myself have mixed feelings about it, but the creation of something else, something that shakes off all those uncertainties of a dainty little acronym mash-up that served very little real purpose for most, into a suitable naming convention, well that is alright by me.

I want a new class, like I want a new drug. I want the 100 hz to 200 hz region to have it's own unique substance, and those who excel in it to gain recognition. 

I am no longer impressed by burps of 65 hz, with all the intrinsic and extrinsic harmonic modal distortions being plopped willy nilly on the scale and counted, as if wheat didn't have chaff and sound waves didn't have unwanted guests at the table...

something new, forcing the divide between hair tricks and stage presentations, a shot blast of pure percussive qualities, in the body cavity charmed resonant tones.


let me experience the best the industry has to offer, in those frequencies that scare the **** out of me...


that's where the future of car audio is, that's where the Burning Man inside us all, is waiting to be let out...


----------



## Patrick Bateman

It's amazing how frustrating this project has become. Normally I just pull the plug on threads when I lose enthusiasm for them, but I've kept this one running to chronicle the process of engineering a solution. I'm definitely not the type of engineer to do something because it's in vogue or because I like the names of the products. My modus operandi is to generally copy things that work, and adapt them as necessary. (Hence my signature.)

Here's a sad summary of what I've tried so far:









I tried making a mold of the corner of my dash, in order to build some speaker pods. That just made a mess.









Years ago, I tried building some waveguides with a triangular shape, to match the shape of the dash corners. That didn't work because you wind up with frequency response that varies with angle. That's no good - you don't want a speaker that sounds one way when you're seated in front of it, but another way when you're seated 45 degrees off axis.









I tried some synergy horn style waveguide arrays. That became tricky because the waveguides get big in a hurry. Even when using 2" drivers, you run out of room.









I tried putting some 400GTIs in pods in the corner. Once again, too big.
Admittedly, some could probably live with the size; it's not like they don't fit at all. I just thought they looked a little ridiculous. YMMV









I tried this funky looking array with a 29mm dome in a Sausalito Audio Works lens, along with four 2" woofers.
I'm kinda glad I re-read my own thread because this setup actually showed promise. The tweeter that I used didn't work, because it was too big. But if you reduced the size of the tweeter this just might work.









Here are the polars of that midrange setup. You can see that it's very directional. So you might want to reduce the number of midranges, just to make it less directional. (The longer the array, the more directional it gets.)

















I made this weird ass HLCD. This was another one that showed real promise.









While it looks fairly ridiculous, it plays from 2000hz to 20000hz with good directivity. I loaded it with a compression driver. After a lot of experimenting, I've come to the conclusion that small domes work better than anything on SAW lenses. So this particular design might be worth another look, but this time loaded with a SB29 tweeter instead of a compression driver. Another advantage of this design is that the tweeter is mounted from the side. That could be advantageous for putting speakers on the dash, because it's challenging to find space for everything. Being able to put speakers in weird locations, like 90 degrees off axis, can make everything a lot easier.

Hmmm I just might revisit that one...









I tried to copy the SAW lens from one of the Beolab home speakers. That sucked. The enclosure is just way too big. If you're putting things on the dash, you have to make them tiny.









I tried using smaller drivers in speaker pods. I had varying degrees of success with this. When I shrunk down to a 2" driver, the pods fit well.









The problem is, I like it loud, and a single 2" driver isn't going to cut it. I tried making larger pods, and once again, they didn't fit









I tried some horizontal arrays. These were really loud. 
I have a feeling that a lot of people were looking forward to these, as arrays are really "hot" right now. But I wasn't happy with these either. While they DID get loud, they sounded like a loud version of a cheap 2" driver. (I used the 2" Gento woofers that you can get on eBay for about $1 in quantity.)
So the treble on these was completely unacceptable, the midrange was good, and the lower midrange was AWOL. If you used these as a pure midrange, like Bill Waslo does in his Synergy horns, these would probably be a good bet. And very affordable. But I was hoping that I could get them to go to 5000hz at least, and I just wasn't satisfied with the fidelity of these cheap drivers. Arrays might be worth another look with a better driver.


Right now I'm at a fork in the road. I had insomnia and I'd intended to do a new design using a single tweeter in the center of the dash, and some nice wide range solutions for the corners. But after re-reading my own thread, I wonder if these two solutions are worth refinement:









or


----------



## SkizeR

I'm just wondering when your going to cave and do a normal hlcd install lol. Either way, I admire your persistence 

Sent from my SM-G920V using Tapatalk


----------



## rton20s

cajunner said:


> I want a new class, like I want a new drug. I want the 100 hz to 200 hz region to have it's own unique substance, and those who excel in it to gain recognition.
> 
> I am no longer impressed by burps of 65 hz, with all the intrinsic and extrinsic harmonic modal distortions being plopped willy nilly on the scale and counted, as if wheat didn't have chaff and sound waves didn't have unwanted guests at the table...
> 
> something new, forcing the divide between hair tricks and stage presentations, a shot blast of pure percussive qualities, in the body cavity charmed resonant tones.
> 
> 
> let me experience the best the industry has to offer, in those frequencies that scare the **** out of me...
> 
> 
> that's where the future of car audio is, that's where the Burning Man inside us all, is waiting to be let out...


What you need is some seat time in one of Mikey's builds. I'm still eagerly anticipating my first chance to listen to his new Passat. His S10 had me grinning from ear to ear.


----------



## Regus

Patrick Bateman said:


> It's amazing how frustrating this project has become. Normally I just pull the plug on threads when I lose enthusiasm for them, but I've kept this one running to chronicle the process of engineering a solution. I'm definitely not the type of engineer to do something because it's in vogue or because I like the names of the products. My modus operandi is to generally copy things that work, and adapt them as necessary. (Hence my signature.)
> 
> Right now I'm at a fork in the road. I had insomnia and I'd intended to do a new design using a single tweeter in the center of the dash, and some nice wide range solutions for the corners. But after re-reading my own thread, I wonder if these two solutions are worth refinement:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> or


I think this is worth pursuing, as you have the data to support the principle of these designs. Maybe the curved array with three drivers will have the right balance of directivity and output, and have a slightly smaller footprint to boot. Maybe the "funky HLCD" with the SB29 will achieve a synergy that pushes the performance to new heights. If you stop now, we may never know...

I for one (and hopefully many more of the DIYMA community) hope that you persevere with this, as I think you could be on the verge of a breakthrough.

As an aside, I am curious as to whether both designs would work with that SB29 tweeter - maybe an A/B comparison is in order, if that's an option?

In any case, kept on pushing the boundaries of speaker/enclosure design!


----------



## whisky22

Patrick Bateman said:


> In an Opsodis setup the tweeters go in the center, woofers are nine and 3 o'clock, and midranges are in the 'normal' location.
> I'm doing a blend of Opsodis and Dolby PLII.
> 
> So my woofers will be at nine and 3, my midranges wil be in their normal position. But instead of having two tweeters in the center, a la Opsodis, I'll have a derived center via PLII.
> 
> I'm hoping this will give me the spaciousness of Opsodis, but without the comb filtering you get when you put two tweeters in the center. I *could* use a mono tweeter - I've tried it before and it works. But I have a hunch that the steering logic of PLII should create a more convincing soundstage.
> 
> So I'll have the following:
> 
> 1) center channel: about 350-20000hz
> 2) left and right channel: about 80 - 5000hz, but split between midranges in the corners of the dash and midbasses at nine and 3oclock
> 3) rear channels: same frequencies as left and right
> 4) sub: 20hz-160hz


how will this center channel be configured? 1 or multiple speakers?


----------



## BP1Fanatic

Is the sub going to be located upfront to play up to 160hz?


----------



## Patrick Bateman

whisky22 said:


> how will this center channel be configured? 1 or multiple speakers?


A midrange and a tweeter.

If I'm right about the Opsodis stuff, we want to limit the low frequencies going to the centre channel, to prevent narrowing of the stage.

Anything above 2khz shouldn't affect stage width, but as you go lower in frequency it should start to become a problem. Or at least I THINK that's how it works.


----------



## Patrick Bateman

BP1Fanatic said:


> Is the sub going to be located upfront to play up to 160hz?


I think subs up front are unnecessary.

The CX-5 is a crossover, and due to that, there's a ton of space under the dash. So I might consider that simply because there's unused space under the dash. But I don't believe there's any "superiority" to putting subs up front, and I think that if you do it right, it's easy to get the bass up front illusion with subs in the back.

The Navone/Clark paper on this from Autosound 2000 spells it all out well.


----------



## Patrick Bateman

Here's another one that didn't work for various reasons. It's a synergy horn using an SB Acoustics SP19 at the apex, and a couple of Peerless TC6s for the midranges.

First off, it's too small. I thought I could cram it back further, but due to where the tweeter is, the height is too short. (The tweeter was supposed to go in the stock location, in a Sausalito Audio Works lens, at the apex of the Synergy Horn.)

Second off, I discovered that white PLA is really weak. I have no idea why this is, but it's noticeably flimsier than the silver PLA that I usually use. I'm guessing that they must bleach the PLA to make it white, and that makes it brittle and weak. Whatever it is, white PLA sucks. I'm going back to silver.


----------



## Patrick Bateman

About a week ago I was tinkering around with my array software*, and I realized that we could put the midranges in some peculiar locations if we push the tweeter down low enough.

For instance, in a Synergy Horn, the midranges are in a ring around the tweeter. By putting them there, it basically behaves like a coax. But it looks like you have some flexibility with the midrange location IF you push the xover quite low.

With that realization in hand, I threw together a rather unorthodox looking waveguide.




























This is an evolution of the waveguide from this thread : xxx

Basically it's an elliptical waveguide with a Sausalito Audio Works lens at the apex, driven by an SB Acoustics SB19. There's an embarassing number of different waveguides that I've tried, and I haven't been able to come up with one that mounts the midranges coaxially, which would be my preference. The reason I can't mount the midranges coaxially is because the dash and the windshield get in the way.

But the good news is that it looks like it won't matter IF you're prepared to push the xover point quite low.









Here's the frequency response and distortion of the SB19 on the waveguide here. The reason that the response is falling is because the waveguide is a constant directivity waveguide. Basically CD waveguides take the energy of a driver and they 'spread it out' over a wider beam. Since there's only a finite amount of energy coming off of the radiator, when you put it on a CD waveguide, you get a falling response. This is easily fixed with a simple lowpass filter, which flattens everything out.

The good news is that we're playing out past 20khz, with no major dips, and the distortion is 20-25dB below the fundamental across the entire bandwidth.

There's a 3dB dip at 8khz, I can live with that, we're not that sensitive at 8khz









Here's the response with a super-basic first order low pass added in to flatten it out. I specifically avoided using a lot of EQ, because I wanted to see what the response would look like without any sophisticated response shaping. This is a 1st order low pass set at 15khz. With that added into the mix, *distortion is over 25dB below the fundamental.* That's really important here, because it will allow for a low acoustic xover and high power handling.









Here's the polar response of the waveguide and tweeter, with the same ultra-simple lowpass filter. (1st order lowpass at 15khz.) In the polars, we see that the response shape is the same on axis and off, from 1khz to 8000hz. That's three octaves, and that will be important for imaging in the car. Basically we want the left and the right tweeter to have the same response shape, on AND off axis, for a stable center image.


----------



## Patrick Bateman

I've finished printing a waveguide for the right hand side of the car.

So I have a stereo pair now. I need to make the new waveguide airtight - that's what the white gunk is for - and I need to mount the tweeter and the woofers.


----------



## thehatedguy

Those things are pretty big and pretty far to the insides of the car.

Maybe it's just the angle of the photos though.


----------



## Patrick Bateman

I've begun doing measurements of the system in the car.









Here's a measurement of the SB tweeter, in the car, on the waveguide. Measurement was performed at the location of the driver's head.










Here's the same waveguide, measured semi-anechoically. Things are looking good - *we have consistency between the anechoic measurements and the in-car measurements.* This is important, the goal here is to make the entire windshield behave like a waveguide.

The falling response in both measurements is because this is a constant directivity waveguide. I can explain why they do that if anyone's curious. (It's explained a couple of times in the thread, but there's something like 200 posts now...)


----------



## Patrick Bateman

One of the (many) great things about CD waveguides is that they're super-simple to filter, if you're willing to give up some efficiency. And since maximum output is determined by displacement, not efficiency, I don't mind trading efficiency for simplicity. In this measurement, I've flattened out the response of the waveguide with a two dollar capacitor. 3.3mfd to be exact. The capacitor also lowers the noise floor noticeably.

This measurement is in-car, and due to that, it's hard to escape comb filtering in the response. There's a lot of reflections.









Here's a measurement comparing a 3.3mfd cap with a 1.5mfd cap. The 3.3 gives us a flatter response, so that's what I'll use for now.


----------



## Patrick Bateman

thehatedguy said:


> Those things are pretty big and pretty far to the insides of the car.
> 
> Maybe it's just the angle of the photos though.











It's 6" wide, 6" deep, and about 4" tall. It's under a liter in volume; the steep rake of the windshield severely limits the volume. The windshield is raked about 65 degrees. (35 degree angle on the inside of cabin.)

Soda can for comparison. If anyone wants to build one, I'll upload it to Shapeways. The tweeter is $19 and the woofers are $8. It's a real expensive project lol


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## Patrick Bateman

Here's the frequency response and distortion of the woofers mounted on the waveguide, in the car. The frequency response is pretty scary, that's due to the insanely reflective environment up on the dash. In particular, I'm speculating the dip at 1500hz is due to the reflection from the apex of the windshield. Basically energy from the midranges radiates into the windshield, then gets reflected back into the incident wave. But the energy is delayed, and that delay creates a dip when the reflected wave and the incident wave are 180 degrees out of phase. Which looks to be about 1500hz here.

I'm thinking I can reduce the severity of that dip by filling the corner of the dash with felt. Note that this won't effect the tweeter, because the tweeter waveguide focuses it's energy into the forward lobe. It's a problem for the midrange because the midrange isn't at the apex of a waveguide, it's off center.









Here's the response of the tweeter and the woofer on the same graph, with the same input level. Note that the tweeter is STILL more efficient than the woofers. That waveguide really raises the output a lot.


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## mitchyz250f

Anything going on with this?


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## oabeieo

Wowzerz. Dood that is tight. How low are they playing down?


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## Patrick Bateman

mitchyz250f said:


> Anything going on with this?


Yeah I kinda scaled it down a bit. Due to how ambitious everything was, the project was taking fo-rev-er. And I'm also totally ADHD, so I kept re-designing every aspect of it, over and over again.

I was listening to Gary's car a couple of weeks ago and noticed a couple things:

1) He's using a 3" midrange and his car is very dynamic.
2) He's using a couple of subwoofers and his car gets plenty loud.

Based on that, I made a couple of changes:

1) My original plan was to use dual fifteens in a bandpass box. By using a bandpass box I can get about as much output as you'd get from four twelves sealed. I shelved that box (for now) and switched to a single 12" in a bandpass.
2) I've tried about a gazillion different options for the midranges. I really REALLY wanted to squeeze four 2" drivers onto a waveguide but it just won't fit. Up until a month ago, I had dual 2" drivers on a waveguide.
I scrapped that and went with a single 3.5" woofer in the stock tweeter location. I might add one more if I can find a spot for it, but for now, I'm only using one midrange.









3) Chances are good that the front stage will end up looking a lot like an LX Mini


So, long story short, I'm ramping back my own expectations a bit. From listening to Gary's car I don't think it's necessary to have an eight cubic foot sub box, or four midranges.


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## Bluenote

Gary's car provides a great basis for Mobile SQ exploration.


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## pocket5s

Patrick Bateman said:


> So, long story short, I'm ramping back my own expectations a bit. From listening to Gary's car I don't think it's necessary to have an eight cubic foot sub box, or four midranges.


Or waveguides, or other fancy contraptions


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## rton20s

pocket5s said:


> Or waveguides, or other fancy contraptions


But that is what makes Patrick... Patrick. 

No way I would go through the exercises he does. But it can be fun to watch... from a distance.


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## cajunner

rton20s said:


> But that is what makes Patrick... Patrick.
> 
> No way I would go through the exercises he does. But it can be fun to watch... *from a distance*.


cue the (near) missing thumb shot, haha..

with 3D Printer access he's considerably more interesting and safer to boot.


What he's doing now, at his age, (I'm not that far behind) I understand the clutter perhaps, better than the average reader here.

There's a bit of a self-center that the best experimental inventors have, and this site could use 10 more Patrick Batemans.

I keep hounding him with thoughts because in that spare room we all like to throw ideas around in, sometimes if a new idea smashes into an old idea, with just the right velocity...

you can get genesis of the new.

like him, I'm not holding very much back even though at this point he's probably developed physically, a few trademark-worthy designs, even if he hasn't recognized them as such...

but that isn't really the goal, I think? I think we'd like to make that mark, leave some indent in the paragraph of 2000-2025 audio canon, where at least a name is left, in the form of an idea that did some advancement or moved the peg a notch...


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## mitchyz250f

I drift out of car audio every now and then. I visit this website maybe twice a month during that time. But what always fires me up again is one of Patricks threads. It keeps me interested in car audio. Inspiring me want to learn more and make my system sound better.

There are about 5 guys on this site that keep me excited about car audio. Patrick is one of them.

Edison didn't invent the lightbulb he perfected it (for commercialization) when no body thought a light bulb was needed. So I am all for these experiments and accept that most will meet with failure.


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## mitchyz250f

Patrick have you done more experiments? What about improving on Gary's car?


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## Patrick Bateman

mitchyz250f said:


> Patrick have you done more experiments? What about improving on Gary's car?


Thanks!

Back when I lived in Oregon I had a place that was almost 3000', but here in San Diego my place is tiny.

So I've been spending most of the past month making room in the garage so I can actually measure the Mazda. My place is so small, I'm not even allowed to park in the driveway. So the only way I can move forward with this project is to clear out the garage.

I'm about 80% done.

I don't have any expectations that I'll be able to improve on Gary or Jon's setups, but it's nice to have something to shoot for. Those guys have put way, WAY more money and time into their setups than I have.


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## oabeieo

Patrick Bateman said:


> Thanks!
> 
> Back when I lived in Oregon I had a place that was almost 3000', but here in San Diego my place is tiny.
> 
> So I've been spending most of the past month making room in the garage so I can actually measure the Mazda. My place is so small, I'm not even allowed to park in the driveway. So the only way I can move forward with this project is to clear out the garage.
> 
> I'm about 80% done.
> 
> I don't have any expectations that I'll be able to improve on Gary or Jon's setups, but it's nice to have something to shoot for. Those guys have put way, WAY more money and time into their setups than I have.


Come on pat, 
Throw some horns in his car and let him take a breath of fresh "air".


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## Patrick Bateman

I wish someone around here had some horns or waveguides, it would be interesting to listen to. The last time I heard horns in someone else's car was Mikey's Tacoma truck. (I forget his diyma name. He's from Phoenix.)

I'd love to see some people put small drivers on waveguides. Gary's Mercedes is as dynamic as an horn car, but without the HOMs. His mids are just 3" in diameter.


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## Patrick Bateman

Here's an example of what I mean, regarding "small drivers on waveguides." This is a two inch tangband on a horn. They're getting six octaves of bandwidth from a single driver. So they're seeing the benefits of using a single driver:
Good phase response, no crossover, simplicity, etc.

But they're not getting the drawback of low efficiency, because the waveguide raises efficiency by nearly 20dB.

They'll need about ten db of EQ to bring up the top octave. But that's not a big deal because excursion is no issue at those frequencies.

This measurement is from page 108 of the "Trynergy" thread at diyaudio.


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## mitchyz250f

Patrick. I would think that the LX Mini configuration would limit how how high the mids will play before you start having reflections and suck out. With bigger speakers having reflections at lower frequencies than smaller speakers. Can you explain what the critical dimension are and the math? Also how would the phasing be handled?


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## Patrick Bateman

mitchyz250f said:


> Patrick. I would think that the LX Mini configuration would limit how how high the mids will play before you start having reflections and suck out. With bigger speakers having reflections at lower frequencies than smaller speakers. Can you explain what the critical dimension are and the math? Also how would the phasing be handled?



Hmm the LX setup is pretty simple really.









In a sealed box, the sound from the cone will wrap around the box when the sound is larger than the box. That's why these B&Ws have a spherical midrange. The sphere diffuses the sound as it begins to wrap around the sphere. The frequency where that will happen is simple - it happens at the length of the wave. In the case of these B&Ws, the width is about 10". Which means that the sound will 'wrap around' as the sound exceeds 1,350hz. (1,350hz is 10 inches long.)

Dipole does the exact same thing. Except the sound from the front and the back are out of phase. So what happens is that they 'null' each other out below that frequency. So the same driver in a 10" wide dipole would start to roll off around 1,350hz. BTW, check my math on that one. You can check it with "bastas the edge." Dipoles are quite complex because it's not just the width of the baffle, it also depends on the angle. That's why all the modern dipole speakers use these tiny tiny baffles.

Cardioids are somewhere in between sealed and dipole. How far between really depends on the stuffing. If you make a cardioid with tons and tons of stuffing, it starts to act like a sealed box. (See Richard Clark's Grand National.) If you don't use much stuffing at all, it behaves like a dipole.

I think cardioids are neat because they're just about the only way to reduce energy to the back.

Unless you go full retard and do a ninety degree dipole.





http://www.diymobileaudio.com/forum/3235801-post1.html

BTW, I'm going to try and do some measurements to figure out if dipole or sealed works better for midrange and midbass in a car. Stay tuned. I was inspired by the thread above.


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## mitchyz250f

Patrick Bateman said:


>


I think you missed understood my question or I misunderstood your intent. Based on the picture above I thought you were thinking midranges in the dash/windshield corners (your stock tweeter location) with a tweeter with waveguide stuffed into the corner and on axis. That makes sense to me. Is that what you have planned or something else? 

It seems that at lower frequencies the windshield and dash would act as a horn for the midrange, but at some higher frequencies you would begin to get reflections. I suppose just below that point would be the crossover to the tweeter. If that is true how would you calculate the point where would begin to get midrange reflections...the crossover point to the tweeter?


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## Patrick Bateman

Yep, midrange in the stock location for the tweeter, with another 2" "tweeter" above it, a la Siegfried linkwitz.

The pic above gives the general idea, but that's from an older iteration of this project.

As far as reflections go, a cardioid's radiation to the rear is reduced by about 75%. So it won't "see" the windshield, for the most part. It (should) behave as if the windshield isn't there.
The midrange is sealed, so the windshield will act like a giant waveguide for the midrange.

There will definitely be reflections in the midrange, but that's how waveguides work, they focus those reflections in one direction.


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## Patrick Bateman

After exhausting a few ideas, I decided to try a D'Appolito cardioid instead of a waveguide.

I think this has some advantages here:

1) When I tried experimenting with dipoles in the car, it worked REALLY well; it made the car disappear in a way that I'm not accustomed to. http://www.diymobileaudio.com/forum...sion/247921-sealed-vs-dipole-vs-cardioid.html

2) I think that a limited amount of early reflections can improve intelligibility and soundstaging. See Linkwitz Orions beaten by Behringer.... what!!? - diyAudio




























Here's some pics of the model. (It's printing right now.)


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## mitchyz250f

Confused. Typically MTMs are run vertically and have very narrow vertical dispersion. Is your thought to take advantage of this and run them horizontally?


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## Orion525iT

mitchyz250f said:


> Confused. Typically MTMs are run vertically and have very narrow vertical dispersion. Is your thought to take advantage of this and run them horizontally?


MTM is a good way to increase output, especially in the case of passive cardioid. My guess is that the cardioid pattern will constrain radiation in all directions. Also, the wave guide on the tweeter seems to work against the radiation pattern of a typical D'appolito speaker. But since the mids at either end are cardioid, the pattern changes. It seems to me that the wave guide on the tweeter might block part of the cardioid pattern on the edge of the mids closest to the tweeter. As a result of all this, I would expect the radiation pattern to be more like a spotlight.


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## Patrick Bateman

mitchyz250f said:


> Confused. Typically MTMs are run vertically and have very narrow vertical dispersion. Is your thought to take advantage of this and run them horizontally?


I probably could run them horizontally - the Whisper can play pretty low, especially if you stick it on a waveguide.

But I'm going for a vertical D'Appolito.

The reason the tweeter waveguide is wider than the baffle of the cardioid is because you want cardioids and dipoles to have a really minimal baffle. (Or at least that seems to be what John K and Linkwitz have settled on.)

I believe this has to do with something called the 'dipole peak.'

As for the tweeter waveguide, it's width is simply based on the crossover frequency. I'm crossing it around 2000hz, and 2000hz is 7" wide, so the waveguide is too. If I was crossing it higher, I would use a narrower waveguide.

I'm forced to use a low xover point because of the D'Appolito arrangement. In a D'Appolito you want the crossover and the spacing to be the same. IE, if you have a spacing of 7" center-to-center, you have the following crossover options:

2000hz (one wavelength)
1000hz (1/2 wavelength)
500hz (1/4 wavelength)

500hz would be ideal, but I don't want to run the Whisper down that low. 1000hz would be nice too, but that would require a really large waveguide. So 2000hz it is.

The use of a 2000hz xover means that the off-axis lobes will be pretty substantial. So the vertical aiming of the unit will be critical; you wouldn't want to listen off of the vertical axis.









I have four of these JBL Control Now speakers, and they suffer from this too. Due to the shape, if you put it on a bookshelf the listening axis is pointed at the ceiling!


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## Patrick Bateman

Orion525iT said:


> MTM is a good way to increase output, especially in the case of passive cardioid. My guess is that the cardioid pattern will constrain radiation in all directions. Also, the wave guide on the tweeter seems to work against the radiation pattern of a typical D'appolito speaker. But since the mids at either end are cardioid, the pattern changes. It seems to me that the wave guide on the tweeter might block part of the cardioid pattern on the edge of the mids closest to the tweeter. As a result of all this, I would expect the radiation pattern to be more like a spotlight.


I'll know soon, it finished printing this morning!


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## oabeieo

Patrick Bateman said:


> I'll know soon, it finished printing this morning!


Is a 3D printer big enough to make a horn 12" long and 3" high and 11"deep?


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## Patrick Bateman

oabeieo said:


> Is a 3D printer big enough to make a horn 12" long and 3" high and 11"deep?


With enough time, any size is possible.

I've been making most of my waveguides out of multiple pieces lately. The one I posted yesterday is a two-piece unit.


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## Patrick Bateman

Patrick Bateman said:


> After exhausting a few ideas, I decided to try a D'Appolito cardioid instead of a waveguide.
> 
> I think this has some advantages here:
> 
> 1) When I tried experimenting with dipoles in the car, it worked REALLY well; it made the car disappear in a way that I'm not accustomed to. http://www.diymobileaudio.com/forum...sion/247921-sealed-vs-dipole-vs-cardioid.html
> 
> 2) I think that a limited amount of early reflections can improve intelligibility and soundstaging. See Linkwitz Orions beaten by Behringer.... what!!? - diyAudio
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> Here's some pics of the model. (It's printing right now.)


I'm off in the frozen tundra of Utah, but I managed to eke out a few measurements before I ran off to the airport.










Here's the polar response of the cheap $15 Tymphany TC9 in my little cardioid pods.

WOW this is epic performance. Far better than I'd hoped for.

yellow is on-axis
orange is 45 degrees off-axis
red is 90 degrees off-axis, IE from the right
violet is 135 degrees off-axis
purple is 180 degrees off-axis, IE from the back

















To demonstrate how good the response, is, here's the LX Mini response. Dare I say it, my polars are better :O

I'm going to speculate that the reason for the really smooth response is that the rear wave can only exit from one spot - that ring along the circumference of the enclosure.









I stole this 'ring' idea from the Gradient Helsinki, where the rear wave of the midrange is also constrained into a ring. (Rings are good because they're equidistant from the source; it's a way to keep the sound in-phase. JBL uses rings on their master reference, Scan Speak uses rings on their ring radiators, etc.)


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## Orion525iT

^Bravo sir! I was thinking that this may turn out to be one of your best designs yet. It's simple enough, and works off of proven designs.

It might not matter much, but what do you think is going on with the polars at end the range (17 khz or so)?

Any ideas of how to extend the lower end to 800hz? What xover between the TC9 and the Whisper?


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## Patrick Bateman

Orion525iT said:


> ^Bravo sir! I was thinking that this may turn out to be one of your best designs yet. It's simple enough, and works off of proven designs.
> 
> It might not matter much, but what do you think is going on with the polars at end the range (17 khz or so)?
> 
> Any ideas of how to extend the lower end to 800hz? What xover between the TC9 and the Whisper?


Thank you.

I wish I wasn't so damn ADHD, I'm already seeing issues with this setup.









This is the driver's side of my car, a Mazda CX5. Ignore that speaker there, it's one of many misfires sitting in a box in my garage 

Basically there's enough room for a vertical array that's about a foot tall. So far, so good.









Here's the new array, a vertical array that's a foot tall.









Here's the polar response.

Here's the problem:

*Why am I using three drivers?*

Originally, I'd planned on crossing over at about 2000hz. So I'd have a pair of midranges covering two octaves, from 500hz to 2000hz. And a Whisper on a waveguide covering three octaves from 2000hz to 16000hz.

But what's the point? The TC9 can already cover most of that entire span.

The on-axis and the 45 degree off-axis curve are about as good as you're going to get, *and that curve is completely unequalized.* I could easily make that +/- 2dB with very little effort. The TC9 is a heck of a driver.

I'm wondering if I should simplify this beast. (That measurement is of the TC9 alone, not the array.)

As far as your questions:

1) the TC9 should get down to 500hz, no issue. I used a 1000hz highpass simply because I had to catch a plane and I wanted to focus on the polar response since that was what I was after. I can turn off the high pass and lower the F3 easily.

2) The response at 90, 135, 180 is interesting. Here's how this works:
_In a conventional sealed box, the speaker radiates sound in all directions below the point that it's beaming. For instance, if it's 3" in diameter it will be radiating sound in all directions at 4500hz and down.









Here's Tymphany's curve for the TC9, off their website. You can see this behavior; it's omni below 4500hz.

In a dipole, you get a curve like a figure eight; it's loud on axis, and 180 degrees off axis, but it's quiet to the sides. (And this works in three dimensions; it's not just quiet to the left and to the right, it's also quiet to the top and the bottom. You get a 'ring of quiet' that's shaped like a donut.)_

I'd heard good things about resistive enclosures from the folks at diyaudio, and it looks like they're right (as usual.) You get a really nice compromise between the dipole radiation and the sealed radiation. 

You see this in my polar measurement. On axis it's "hot", at 45 degrees off axis it's fallen by about four decibels. Once you're 90 degrees off axis, it's REALLY dropped like a rock, it's over 13 decibels down. This is like cutting the output by ninety five percent(!)

But once you get to the back, the response starts to come back, because it's still acting a bit like a dipole. At the back the output is attenuated by about 10dB.

IMHO, this is great for a car though. We want as little going into the windshield and side windows as possible, if we could eliminate 99.9% of the output in those directions that would be great. I'll settle for 95%


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## Patrick Bateman

Orion, you'd asked about the xover, here's the measured distortion of the cardioid.
There's no real rise in distortion below 1000hz, so it would be easy for me to 'open it up' to a xover of 700hz or even 500hz.

Basically I'll just lower the high pass xover, raise the power, and see how much abuse the TC9 will take.

BTW, check out the consistency of the speaker; it's response curve is darn-near identical to what's published on their website. Amazing quality control, even more exemplary since it's a fifteen dollar speaker.


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## Patrick Bateman

Here's Hanatsu's measurement of the same driver:










Full measurements here: http://www.diymobileaudio.com/forum...-midrange-widebander-review-measurements.html


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## Patrick Bateman

To make this whole thing simpler, I could print a single enclosure, a sphere, something like this:




























I shaved the sides off of the sphere, just to make it fit on the 3D printer. It also reduces the footprint, which is important on the dash.



















It would wind up looking a lot like these spheres I made for my JBL 400GTIs









In order to get something (close) to full range performance, I could load it with a coax like this 5" coaxial from SEAS.









If I'm not mistaken, this is pretty similar to the setup that Gradient uses in their Revolution. (I didn't copy the designer, just wound up converging on the same idea.)


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## Patrick Bateman

I'm too impatient to wait for some SEAS coaxes from Madisound, and my B&C coaxes are too big.










So I just ordered a pair of these from Amazon, let's see how they work out...

Would be funny if they measure well, as they sure are cheap ($40 each)


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## garysummers

Patrick Bateman said:


> To make this whole thing simpler, I could print a single enclosure, a sphere, something like this:
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A concentric driver mounted in the apex of the windshield and dash! 
I have a pair of those SEAS drivers in 3 liter sealed enclosures.
Without any EQ or being hi- passed, so "right out of the box" , they produce a very convincing deep soundstage. I am playing them on my home stereo system.
Very interested in your further investigation of this concept!


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## Patrick Bateman

@Gary, maybe with a little encouragement I'll actually finish something for once :O

Would love to demo my car for you one of these days, once it's actually functional.


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## Patrick Bateman

I discovered something interesting today:

In my subjective listening tests, I noticed that the TC9 dipoles sound 'strained' at fairly low volumes. I didn't have my SPL meter with me, but I'd say it was strained around 100dB.

When I stepped up to a SB Acoustics 5", the strain went away.

I *thought* the issue was displacement, but after doing some sims, I think it's something else. (And I'll explain what that is shortly.)

















Here's the frequency response and displacement of a Tymphany TC9 and a Dayton ND91 in a one liter sealed box. *You can see the TC9 has a lot more output.* This is simulated with 25 watts into 8ohms. (They're 8ohm drivers.)

The TC9 is putting out about 100dB with 25 watts, but that's close to it's thermal limits; it's rated for 30 watts RMS.



















Here's the response and excursion when I remove the enclosure. (This is a dipole.)

*The output has dropped by about ten decibels.*

Obviously, the whole response curve looks pretty weird; in the measurement I posted a couple days ago, you can see that the bandwidth is a lot wider than Hornresp is predicting here. The reason for this is because Hornresp exaggerates the effect of inductance, it simulates the driver as a perfect piston, when in the real world, drivers play past their pistonic limits. (Basically at high frequencies only part of the cone is radiating.)

The bottom line though, is that the efficiency on the dipole is a LOT lower than the sealed. About 10dB lower.

And the displacement isn't as high as I'd expected.

Put all of this together, and it looks like what I need is a driver with fairly high output, or an array of drivers with fairly high output. Displacement isn't the limiting factor here; it's output.

So I'm going to steer away from the ND91, and maybe even the TC9, and look for something that can belt out more SPL.


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## mitchyz250f

Patrick for corner loading of the dash wouldn't the ideal be a speaker with a coincident tweeter that had a integrated horn that was not the speaker cone itself. For example if you are of using a 5" speaker, that will have a 4" cone, As the speaker gets to 3500Hz it would match up perfectly with a 80 degree dispersion horn. Since you said your windshield/dash is at 40 degrees you could make the horn 80 x 30 and really minimize unwanted reflections while still matching polar responses pretty well. Tweeter efficiency would imprve dramatic and with the high crossover you could use a the tiny ND20 or even an ND16. 

Dayton Audio ND20FB-4 Rear-Mount 3/4" Neodymium Dome Tweeter

Dayton Audio ND16FA-6 5/8" Neodymium Dome Tweeter

Check out this very useful polar response chart.


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## Patrick Bateman

mitchyz250f said:


> Patrick for corner loading of the dash wouldn't the ideal be a speaker with a coincident tweeter that had a integrated horn that was not the speaker cone itself. For example if you are of using a 5" speaker, that will have a 4" cone, As the speaker gets to 3500Hz it would match up perfectly with a 80 degree dispersion horn. Since you said your windshield/dash is at 40 degrees you could make the horn 80 x 30 and really minimize unwanted reflections while still matching polar responses pretty well. Tweeter efficiency would imprve dramatic and with the high crossover you could use a the tiny ND20 or even an ND16.
> 
> Dayton Audio ND20FB-4 Rear-Mount 3/4" Neodymium Dome Tweeter
> 
> Dayton Audio ND16FA-6 5/8" Neodymium Dome Tweeter
> 
> Check out this very useful polar response chart.


With a sealed box we definitely want to jam it as far into the corner as possible. If we don't, the sound will 'wrap around' the enclosure, reflect off the windshield, and come back at us. That reflection muddies imaging cues, creates comb filtering, basically ruins everything. *If you have a sealed box, you want it as far in the corner as possible.*









With a cardioid we lose a ton of efficiency, *but radiation to the back is reduced by around 90-95%.* So we don't have to worry about how close it is to the rear wall, or the windshield. This is why the Linkwitz LX Mini is a cardioid, but the LX521 is a dipole. If you're close to a wall, use a cardioid.


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## garysummers

Patrick Bateman said:


> @Gary, maybe with a little encouragement I'll actually finish something for once :O
> 
> Would love to demo my car for you one of these days, once it's actually functional.


Patrick, if you need encouragement there are people on at least 5 continents following all your threads attempting to gleen a little understanding and knowledge. Your persistence in the pursuit of audio excellence is respected by many. ?
When you get to the point your ready to demo we shall meet!


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## Patrick Bateman

garysummers said:


> Patrick, if you need encouragement there are people on at least 5 continents following all your threads attempting to gleen a little understanding and knowledge. Your persistence in the pursuit of audio excellence is respected by many. ?
> When you get to the point your ready to demo we shall meet!


Definitely! I think you'll dig these. I haven't listened to the cardioids yet, but the dipoles imaged like crazy.


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## Patrick Bateman

The output levels from the sims in post 424 looked "off."
I'm not sure if I fat fingered one of the inputs, or if it's something else.

So I re-ran them.

















Here's the output of a Tymphany TC9 with 30 watts into 8 ohms, it's thermal limit. (It only has a 0.75" voice coil.) You can see the output is very low; the dipole radiation costs you a lot of SPL.

*With 30 watts into 8 ohms, one of the Tymphany TC9s is good for 94dB at 2000hz.*

















Here's the output of *four* Peerless TC6s with 60 watts into 4 ohms, their thermal limit. (Each has a 0.75" voice coil.) You can see the output is a little bit higher than the TC9, about 2-4dB; the dipole radiation costs you a lot of SPL.

There are two lines in the graph because I'm comparing the output of four of the TC6s to *one* of the TC9s.

*With 30 watts into 8 ohms, four of the Tymphany TC6s are good for 97dB at 2000hz.*

















Here's the output of a JBL 400GTI with 150 watts into 4 ohms, it's thermal limit. (It has a 2" voice coil.) You can see the output is significantly higher than the TC9, about 10dB; the dipole radiation still costs you a lot of SPL.

There are two lines in the graph because I'm comparing the output of the 400GTI to the TC9.

*With 150 watts into 4 ohms, one of the JBL 400GTIs are good for 102dB at 2000hz.*

Some caveats here:

1) I'm not building a dipole, I'm building a cardioid. But there's no good way to simulate a resistive cardioid right now, so simulating a dipole gets me 'in the ballpark.'
2) As noted in post 424, the thermal limits of the driver seem to dictate the SPL for the most part. I could build a bigger baffle to lower the F3, but I've generally found that the tiny baffles work much much better in this application. When the baffles starts to get large, it winds up sounding like a sealed box... Which is not what I want. To get the 'room' out of the equation you really need a tiny baffle with these


----------



## Patrick Bateman

At nearly $300 a pair, the B&C 5FCX44 isn't cheap, but it looks pretty compelling here. We want something with high output. The 400GTI can take more power, but it doesn't have the efficiency of the 5FCX44. The 5FCX44 also simplifies the tweeter part of the equation, because it's a coaxial.









Here's the output of the 5FCX44 with 100 watts at 8ohms versus the TC9 with 30 watts at 4 ohms. (Each driver's thermal limit.)

Now we're really pulling away from the TC9, the 5FCX44 has a solid twelve decibel advantage here. About the only thing that sucks here is that I'd have to get a new amp, mine can't put out 200 watts into 4 ohms (100 watts into 8 ohms.)









The depth on these is pretty silly, but I think it will fit.









Here's a polar measurement I made two years ago of the 5FCX44, along with an average of the polars. I think I set the gate too long on this measurement; you'll notice my latest measurements are generally cleaner than this one. But it gives you the general idea, this coax should easily cover five octaves, maybe six.

That measurement is from my post here: http://www.diyaudio.com/forums/multi-way/247574-together-one.html#post3741214


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## Patrick Bateman

It just occurred to me - since I have a 3D printer I could do some strange things, as far as mounting these speakers.

I *know* that a minimal baffle sounds good, and most people with minimal baffles use something like this:


















But since I have a 3D printer, I can do some strange things, like have them float in space, suspended by thin 'branches' of plastic.

JL Audio did something like this with a VW Golf a few years back, they put the tweeters in pods, but the pods 'floated' above the dash.










Here's a general idea of some of the strange meshes you can build with a 3D printer

So picture a 'mesh' of tweeters and midranges, but they're positioned in space to form a spherical wavefront. Basically the same thing that a waveguide does, but without the waveguide, because we're getting our directivity control via the cardioid radiation of a resistive enclosure.

Yes, I know this post sounds batshit crazy


----------



## jwsewell01

As I follow along I have been on the lookout for suitable drivers and gave had my eye on this one. At $89 each it's not too bad. The top end looks a little ragged though....

http://www.parts-express.com/pedocs/specs/290-4004--eminence-pro-5mrn-8-spec-sheet.pdf


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## Patrick Bateman

jwsewell01 said:


> As I follow along I have been on the lookout for suitable drivers and gave had my eye on this one. At $89 each it's not too bad. The top end looks a little ragged though....
> 
> http://www.parts-express.com/pedocs/specs/290-4004--eminence-pro-5mrn-8-spec-sheet.pdf


Looks like there's a ferrite version of the same driver, that's cheaper, and is an even better match for this. Nice find!

The parameters on the ferrite version are quite a bit different, but the lower QES helps a lot.


----------



## Patrick Bateman

In post 428, I talked about using B&C's 5" coax for this project.



















A couple of years ago I did another cardioid, in my Mazda6, and it worked pretty darn well. Sounded great. I abandoned the project because the waveguides were hyooooge.

Read more about it here: Edge of No Control - diyAudio



















I think I could use some tricks I've learned in the last two years to improve on that one.

Here's a list:

1) I've generally been using dome tweeters lately, the SB Acoustics SB19 in particular. It's not as efficient as a compression driver but the distortion is lower, particularly on the low end. This is because dome tweeters have a surround and most compression drivers do not. (Less SD but more xmax on the dome.)

2) With a 3D printer I can obsessively tweak the parameters to shrink the size. I literally went through about ten iterations in the last day, to shrink the footprint as small as humanly possible.

3) I'm getting really good at the 3D software, so I'm getting pretty good at packing things in tightly. If you look at my older designs they weren't nearly as elegant.

4) From toying around in Hornresp, it looks like even a little bit of horn loading can really extend the cutoff of those midranges. Basically we get cardioid radiation by having the front and the back of the driver out-of-phase. But we create a DELAY by putting the drivers on a waveguide, *and that delay lowers the F3.* So you get the best of both worlds; the directivity control of a dipole or cardioid, but with a lower F3 caused by separating the front and the back wave by a few inches.


----------



## Patrick Bateman

The off-axis curves of that dipole I made last weekend were REALLY smooth, and I have a hunch that part of the reason was because of the way that I arranged the ports on the enclosure. If you look at them, they're in a PERFECT ring, a type of setup that would be really time consuming to do by hand, but in 3D it's (fairly) easy.









The Danley Synergy Horns use eight holes arranged in a ring, and the tweeter is a ring radiator too. (Rings are good because they keep everything equidistant, this improves your frequency and phase response.)



















Thought I'd try the same thing on the midrange 'taps' of this waveguide, since it worked so well on the one I made last weekend. Same idea as Danley, except he's using eight (relatively) large taps, and I'm using seventy two(!) That many taps would be a nightmare to drill by hand, but with a 3D printer, it's no problem.

The pic above shows the 'taps' before they're 'subtracted' from the waveguide.


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## jwsewell01

Yeah your damn good with that 3D drawing!

What mids are you designing the 72 tap wave guide for?


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## Patrick Bateman

jwsewell01 said:


> Yeah your damn good with that 3D drawing!
> 
> What mids are you designing the 72 tap wave guide for?


Thanks!

I spent about twelve hours making the model, then walked down to the garage to print it. Even if everything went perfectly (and it never does), it was going to take about three days to print a pair of waveguides.









And then I saw this set of waveguides sitting on my bench, ignored for the last month or so, and it hit me that I could turn them into a cardioid easily...

So that's what I did 

As for the midranges, I am using these Peerless TC6s:

Peerless TC6WD02-04 Silver Series 2" Midrange

You can get ten for $37.50. I'm using six, three per side.

I'm not sure if I love these midranges; I hadn't bothered to measure them before using them, because the TC9s are so good. But it looks like the TC6s aren't in the same league, and I probably should have used a Aurasound Whisper or a Peerless 830970.

The TC6s aren't terrible, but they're not as good as the Whispers. Bill Waslo is getting epic results with a really cheap set of 2" woofers in his Synergy Horns, so it's not the end of the world.

Then again, Bill told me that he's been thinking about using the Whispers too...

Here's Bill's Synergy Horn:


----------



## Patrick Bateman

BTW, that waveguide is from this project here:

http://www.diymobileaudio.com/forum...discussion/240586-one-horn-rule-them-all.html


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## Patrick Bateman

I tried something new, which I stole from Earl Geddes. I used to have a set of his flagship speakers, and I think the enclosure was a big part of their excellent sound. The enclosure was solid as a rock; tapping on it was like tapping on a piece of marble. The Summas use a constrainted layer damping construction. The outside layer is carbon fiber, the inside layer is a secret I'm not going to divulge, and the net effect works really really well.

In the car, it's hard to copy that construction, because the inner layer on the Summas is VERY thick; literally over an inch in some locations.

I've had really good results using a CLD sandwich that looks like this:

fiberglass -> PL 375 -> PLA plastic -> fiberglass

The way that this works is that the inner layers are less rigid than the outer layers. So if you try to bend the composite, the energy is absorbed by the inner layer and doesn't reach the next layer.










The net effect is that it's noticeably 'deader' than wood. And since I do nearly everything in plastic these days, anything I can do to improve the performance is great. I'm kinda done with wood these days.

The improvement I made this time around is that I added Jute to the damping layer.










My inspiration was fiberglass reinforced concrete.

At this point I can't tell if the Jute is making a big difference. But I definitely noticed that Jute makes it way way easier to slather on a LOT of PL375. It seems to dry faster too.

Here's how I think this works:

When you use PL 375 as a damping layer, the PL 375 can take as much as two or three days to dry completely. A thin layer will dry in a day, but if you're going to do CLD, you should really use a decent amount of damping. By using Jute, the Jute absorbs the PL375, and it seems to dry faster, likely because there's air in the Jute, and the PL375 needs air to dry.










This is what I use for the damping layer. It's great stuff. Fiberglass sticks to it with no issue, and it sticks to wood too. I think Earl uses liquid nails for subfloors, but that's not always available at my Home Depot.


----------



## Patrick Bateman

Here's the frequency response of the waveguide with the Peerless TC6 midranges on the waveguide, operating as a dipole.









Here's a picture of the waveguide, to give you the general idea. Three midranges, no back caps at all, radiating as a dipole.

The frequency response is really bad. Here's what I think is happening here:

1) There's a dip at 1800hz and a peak at 2200hz. I think this is caused by a reflection from the waveguide mouth, an interaction from the rear wave, or both.

Here's how this works:









When a horn has a really rapid transition from one angle to another, you get a reflection that travels back down the horn. This reflection creates a dip in the response, a peak in the response, or both. The JBL 2397 pictured above is famously bad due to this.









This is why modern waveguides look like this; by having a smooth transition from the throat to the mouth to the room, you get smoother response and better sound.

TLDR: I think that my waveguide needs some termination at the mouth









Here's the same waveguide, but after I added some fiberglass to the rear chambers. They're still "open", but the fiberglass soaks up some of the radiation. This is how we get a resistive cardioid; read this for more info:

Cardioid bass









Here's a graph comparing the waveguide as a dipole and the waveguide as a resistive cardioid. You can see that the resistive cardioid is a LOT more efficient than the dipole, *and* smoother. The bandwidth isn't as wide as it would be if it were sealed, but that's a compromise I can live with for better directivity control.

It should play even lower in the car; these measurements posted above are ground plane measurements, and in the car we'll get added SPL due to the fact that the waveguide is radiating into a smaller space.


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## Patrick Bateman

I used a small amount of EQ to flatten out the response and ran a distortion measurement. This performance isn't terrible, but you can do a lot better. Second harmonic is about 15dB below the fundamental. This is something I noticed with the Faital 3FE20 that everyone loves so much, it also has very high distortion. I'm not sure if the TC6 exhibits this because it's untreated paper, or a problem with the motor, or maybe even the enclosure. I wouldn't rule out the enclosure; it's still pretty flimsy. Nothing a few layers of fiberglass won't cure.









For comparison's sake, here's Erin's measurment of a Scanspeak 10F from his blog. You can see the Scanspeak crushes the TC6 in the distortion department.


----------



## Orion525iT

I mentioned this in another thread after reading about the viability of cork as a core material in aerospace. Cork makes for a dimensionally stable composite when used as a core, while also acting as a constrained layer. I really wanted to try to make a composite using aramid fabric and epoxy with a cork core for my midbass enclosures. But it would have been a huge project. Something like that might work great for midrange enclosures and waveguides. 

Did a search today out of curiosity and found this:

Kuiper sound insulating panels â€¢ Fineer

Same idea, but these are made for marine applications with plywood outer layers.


----------



## Patrick Bateman

Orion525iT said:


> I mentioned this in another thread after reading about the viability of cork as a core material in aerospace. Cork makes for a dimensionally stable composite when used as a core, while also acting as a constrained layer. I really wanted to try to make a composite using aramid fabric and epoxy with a cork core for my midbass enclosures. But it would have been a huge project. Something like that might work great for midrange enclosures and waveguides.
> 
> Did a search today out of curiosity and found this:
> 
> Kuiper sound insulating panels • Fineer
> 
> Same idea, but these are made for marine applications with plywood outer layers.


I need to check that out - sounds like it would work pretty well. Particularly for subwoofers, where there are a lot of flat surfaces.


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## Patrick Bateman

Here's the polar response of this waveguide, with a resistive chamber on the midranges to turn the thing into a resistive cardioid. (TBH, it technically measures like a supercardioid.)

1) the yellow line is on-axis
2) the orange line is 45 degrees off axis
3) the red line is 90 degrees off-axis (to the left)
4) the violet line 135 degrees off-axis
5) the purple line is 180 degrees off-axis

Similar to the cardioid from last weekend, *this is performing really nicely.* In particular, check out the output 90 degrees off-axis (the red line.) The output is reduced by about 13dB, which is equivalent to reducing the power by 95%!

The curves are really smooth below 1500hz too. (I intend to use a tweeter about 2000hz or so.)

This is really remarkable performance, it will really reduce the amount of sound that's directed towards the windshield.

One thing to note is that the sound immediately behind the speaker is only reduced by about six decibels. But that's still equivalent to a 75% reduction in power.


I've used some EQ to widen the bandwidth of the speaker; there's some boost at 500hz and a cut at 1000hz to increase the bandwidth.


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## Patrick Bateman

On a side note, you can see why Linkwitz and John K use baffles like this:


















In my measurements, you can see there's some weirdness from 1500hz to 3000hz, as the speaker shifts from being something of a cardioid to a super cardioid. This is because the wavelengths become larger than the speaker at 1350hz. As that happens, it shifts from cardioid to super cardioid. If the baffle was small and the driver was only used at frequencies below that wavelength, it would be purely dipole or purely cardioid (depending on how the back chamber is setup.)









This is also one of the reasons that the Danley Jerichos are so huge; if you want to maintain a constant beamwidth down to 500hz you need a baffle that's 27" wide! (Again, you can do it with a smaller baffle using a cardioid or a dipole; my speaker is a bit odd in that it's both a waveguide *and* a supercardioid.)


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## Patrick Bateman

Here's a distortion measurement of the waveguide, with three midranges, from about eight hours ago









Here's a distortion measurement of the waveguide, with three midranges, from five minutes ago.

The difference is that I applied a layer of fiberglass - that lowered distortion by about 10dB. Quite a difference.

So that's good news - it looks like the problem isn't the Peerless TC6 midranges, it's the (flimsy) waveguide, which I can fix.









Here's the response of the SB19 tweeter, with a first order highpass at 20000hz. Yes, I said 20,000hz. I basically high pass it at a very high frequency to offset the gain you get from the waveguide. The net result is vanishingly low distortion (second harmonic is over 30dB down, third harmonic is basically unmeasurable.)

Both measurements show a dip, I'm convinced that dip is caused by a reflection from the mouth. It should be (mostly) absent once I put it in the car, where the waveguide is terminated.

Here's an article on waveguide termination if anyone's curious : Factors Affecting Sonic Quality of Mid & HF Horns & Waveguides


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## Patrick Bateman

I'm not a big fan of using dedicated amplifier channels for each driver. Back in the day I generally used three or four channels of power:

channels 1-2 : left and right 
channels 3 and possibly 4 : subwoofer

At that time, I used passive crossovers.

Nowadays I still use passives, but I generally combine them with miniDSP. For instance, I'll use a passive to get *close* to the target response, and then I'll tweak the curve with EQ. It is also possible to do some weird stuff with MiniDSP, like running your tweeters and your subs on the same amp.

Anyways, this crossover will be 'business as usual', a hybrid of passive and active.









Here's the on-axis frequency response of the SB19 tweeter on this Synergy Horn, with three different capacitor values : 0.75mfd, 1.5mfd, and 3mfd. There is also a ten ohm resistor in series with the tweeter. This flattens the impedance curve that the amp "sees" from the tweeter, and it also lowers the noise floor of the system.

I think I'll use the 3mfd cap, which gets me the top curve, and then use EQ to get to the target curve, which is sloooooowly falling as we go higher and higher.

BTW, yes I *do* see that massive dip in the frequency response. I still think that's mouth termination. It may also be caused by the midrange taps.


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## oabeieo

How do those Dash horns sound? Pretty good?


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## Patrick Bateman

Right now I'm working on the crossover, I won't be ready to listen to anything for a while 

(I do the crossover using a combination of my microphone, DATS, and trial and error. If things get particularly difficult I'll create a computer simulation of the circuit and work from that.)


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## oabeieo

Patrick Bateman said:


> Right now I'm working on the crossover, I won't be ready to listen to anything for a while
> 
> (I do the crossover using a combination of my microphone, DATS, and trial and error. If things get particularly difficult I'll create a computer simulation of the circuit and work from that.)


If you like them, but decid to get rid of them , can I buy them from you? Those look like they get down . I would be thrilled to give them a whirl


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## Patrick Bateman

oabeieo said:


> If you like them, but decid to get rid of them , can I buy them from you? Those look like they get down . I would be thrilled to give them a whirl


I've thought about giving away a bunch of my old designs, but 95% of my stuff is half-finished.

In literally twenty five years of doing this I've finished about four or five projects, and I have a hundred that are half-finished.

I'm a big fan of open sourcing this stuff, and I'd be more than happy to post everything you need to replicate this:

1) the 3D model, which can be printed at Shapeways
2) the passive xover
3) the active xover
4) the response curves, etc

I have zero interest in competing, so there's no 'trade secrets' here, I just want to try new **** out, that's what gets me out of bed everyday


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## Patrick Bateman

Here's some pics of the waveguide out of the car...










https://lh3.googleusercontent.com/-GSqXXQw9QxU/Vreh3NHtByI/AAAAAAAAMTM/CPO4mtDUUjI/s800-Ic42/IMGP4603.JPG[img]

[img]https://lh3.googleusercontent.com/-H5scaCdEYw0/Vreh3MATBwI/AAAAAAAAMTQ/ojnEgL94Akk/s800-Ic42/IMGP4602.JPG










...and IN the car




















Here's some pics from the 2009 project, for comparison's sake


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## oabeieo

That dash unity horn. If you ever want to let go of your fab work. I got drivers galore, I have seven kids so I literally don't even have time to work on my own car otherwise I would have a sick install myself you seen pictures my car most people probably laugh at it it's just I don't have time and I love this hobby and like you I know that horn sound awesome on top of the dash . Just sayin , those look like a bunch of fun


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## Patrick Bateman

oabeieo said:


> That dash unity horn. If you ever want to let go of your fab work. I got drivers galore, I have seven kids so I literally don't even have time to work on my own car otherwise I would have a sick install myself you seen pictures my car most people probably laugh at it it's just I don't have time and I love this hobby and like you I know that horn sound awesome on top of the dash . Just sayin , those look like a bunch of fun


I'll upload the models - you can print them yourself. Just go to Shapeways - 3D Printing Service and Marketplace*

This is a ridiculously cheap project, so if you're not happy with the sound, you're not out much money

The tweeter is $25, the midranges are $3.75

Because I have my own 3D printer I'm only spending about ten bucks in PLA plastic. Shapeways has quite a markup, so it would probably cost about $100 to have Shapeways print it.

But I'm fairly confident that it should be competitive with anything that costs about $200 per channel.

It's a unique design - the distortion is NOT as low as you'll get with a Scanspeak or a Dayton reference speaker. But those speakers can't image like a Synergy horn can, and Synergy horns are ridiculously articulate. That means a lot to me - I go to Vegas all the time and when I'm on that six hour drive, I don't particularly care about whether the sound is distortion free, but I *do* care about getting a soundstage that seems bigger than the car itself, and articulate speakers extract details in a recording that you don't hear.

It's basically like a big set of headphones.

Totally different experience than what you get with the typical two-way setup with ScanSpeak drivers and expensive amps.


* don't go there RIGHT NOW, because I haven't uploaded it yet, but give me a day or two and I will


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## Patrick Bateman

Here's another 'money shot.' This is the frequency response and phase of the waveguide, with the tweeter and the midranges running together, and a SUPER basic xover on the tweeter.

You're looking at six octaves of bandwidth from three drivers, and a transition from midrange to tweeter that's so seamless, it virtually behaves like a single driver.

Honestly I could make that phase curve look even *better* with some delay, and I could *really* go nuts with FIR filters, but this is pretty great performance from ten dollars worth of midranges and a $25 tweeter. This is 100% passive (for now.)









Here's a spec sheet from a full-range, for comparison's sake. My Synergy horn has way more output than a Aurasound Whisper, but the response and phase curve should be similar.










Here's the spec sheet from the Danley flagship Synergy Horn. His phase curve is similar, his response curve is better. I'll improve my response curve with EQ. His speaker has more bandwidth, but that's because it's a three-way, mine is a two-way.


----------



## jwsewell01

Oh crap! Are you going to have to destroy it to get the the 2 inch driver out?

Side note: 
I am thinking of trying my 4 inch coaxials in PVC caps. 
Drill rings of holes around the sides of the cap and line it with denim stuffing.
Then stick them in the apex of my windshield and dash.

I currently have the 4's HP at 500Hz 12dB slope firing into my windshield and they are about 3-4 inches from the dash/windshield apex.

I'm still working on getting a decent REW setup running.


----------



## Patrick Bateman

jwsewell01 said:


> Oh crap! Are you going to have to destroy it to get the the 2 inch driver out?


Why would I need to get the drivers out?


----------



## Patrick Bateman

Here's another measurement, now with some EQ applied. Took all of fifteen minutes to flatten it out, crossovers are so much easier when your speakers are close together.

I think this is good enough to replicate for the second channel, and then I'll throw it in the car for some listening. If it sounds OK, all I need to do is add the midbasses and sub, which have been mostly finished for months now.


----------



## Patrick Bateman

Oh, forgot to mention, that curve is downard sloping on purpose.

I believe Andy Wehmeyer posted this target curve?


----------



## oabeieo

It's a cd with three 2" drivers? Those blue golf ball things have 2s right?


----------



## oabeieo

Patrick Bateman said:


> I'll upload the models - you can print them yourself. Just go to Shapeways - 3D Printing Service and Marketplace*
> 
> This is a ridiculously cheap project, so if you're not happy with the sound, you're not out much money
> 
> The tweeter is $25, the midranges are $3.75
> 
> Because I have my own 3D printer I'm only spending about ten bucks in PLA plastic. Shapeways has quite a markup, so it would probably cost about $100 to have Shapeways print it.
> 
> But I'm fairly confident that it should be competitive with anything that costs about $200 per channel.
> 
> It's a unique design - the distortion is NOT as low as you'll get with a Scanspeak or a Dayton reference speaker. But those speakers can't image like a Synergy horn can, and Synergy horns are ridiculously articulate. That means a lot to me - I go to Vegas all the time and when I'm on that six hour drive, I don't particularly care about whether the sound is distortion free, but I *do* care about getting a soundstage that seems bigger than the car itself, and articulate speakers extract details in a recording that you don't hear.
> 
> It's basically like a big set of headphones.
> 
> Totally different experience than what you get with the typical two-way setup with ScanSpeak drivers and expensive amps.
> 
> 
> * don't go there RIGHT NOW, because I haven't uploaded it yet, but give me a day or two and I will



So there's a place that will print out your model here in my town?


----------



## jwsewell01

Patrick Bateman said:


> Why would I need to get the drivers out?


 Well, you might be fine, but I have what you could call stomach hands.

Everything I touch seems to turn to ****.


----------



## Patrick Bateman

jwsewell01 said:


> Well, you might be fine, but I have what you could call stomach hands.
> 
> Everything I touch seems to turn to ****.


Yeah I already had to crack one open already. I broke one of the terminals on the two inch drivers.









I basically cracked it open with a flathead screwdriver, fixed the terminal, and epoxied the cap back on.

Kind of a pain in the ass. In the future I should try making the drivers screw into the waveguide, similar to how compression drivers screw into horns:










It probably wouldn't be too hard to figure out how to print a thread

And screwing in the bolts for the midranges was a complete p.i.t.a. because there's twenty four bolts and they're all mounted in strange locations. Took me literally HOURS to screw all the bolts in.

Come to think of it, it was easier to re-epoxy those blue caps than it was to bolt the drivers in!


----------



## Patrick Bateman

oabeieo said:


> So there's a place that will print out your model here in my town?


Shapeways is online, they ship it to your door


----------



## Patrick Bateman

oabeieo said:


> It's a cd with three 2" drivers? Those blue golf ball things have 2s right?


Yes, a compression driver with three 2" woofers, Peerless TC6 to be specific

The tweeter at the apex is a dome, and there's no compression chamber, it's just a plain ol' 3/4" dome tweeter


----------



## Patrick Bateman

Here's the polar response of the speaker, using my four-element passive crossover, and a little bit of EQ to 'shelve' down the tweeter.

Yellow is on-axis, orange is 45 degrees off axis, red is 90 degrees off axis, violet is 135, and purple is directly *behind* the speaker.

Some observations:

1) There's massive rejection to the sides; over 13dB, this is like reducing the power by 95% to the sides. So this should be quite directional.
2) As noted before, there's a noticeable transition from cardioid to supercardioid around 2000hz. Basically this happens because the waveguide is big enough to constrain the radiation when the wavelengths are smaller than the waveguide, but once they're bigger the resistive enclosure starts doing it's thing. That's why you see a change in the radiation at 2000hz.
3) At 700hz there's quite a bit of output from the *back* of the speaker. I think what's happening here is that the speaker starts to act like a dipole at low frequencies. Basically the fiberglass that's inside those little 'golf ball' looking things is only effect to about 1000hz. But that's fine, the main thing is that the resistive enclosure is keeping the high frequencies from getting sprayed into the windshield; at 1000hz and up the speaker is basically a flashlight, over 90% of the sound is going one direction










For comparison's sake, here's the polar response of my old reference speaker, a Gedlee Summa









Here's my Summas and a Danely SH-50 that I rented, in my living room. These are not small speakers, so I had to come up with a new way to control directivity. (The easiest way to control directivity, by far, is a big ol' waveguide.)

If you want to read more about constant directivity loudspeakers, I took that Summa measurement from Siegfried Linkwitz's website: Constant directivity loudspeaker designs


----------



## Orion525iT

Patrick Bateman said:


> Here's the polar response of the speaker, using my four-element passive crossover, and a little bit of EQ to 'shelve' down the tweeter.
> 
> Yellow is on-axis, orange is 45 degrees off axis, red is 90 degrees off axis, violet is 135, and purple is directly *behind* the speaker.


Is this in car response?


----------



## Patrick Bateman

Nope.

Back in the day I used to do a lot of measurements in the car.

At this point I basically design it anechoically, then throw it in the car. I'll definitely tweak things a little once it's in the car, but there's so many reflections in the vehicle, it's really hard to come up with a proper xover unless it's measured anechoically.

Dan Wiggins used a similar method with his car speakers.


----------



## Orion525iT

Patrick Bateman said:


> Nope.
> 
> Back in the day I used to do a lot of measurements in the car.


Yeah, I am still concerned that the control will fall apart _in situ_. Hoping that I am very wrong, of course.


----------



## Patrick Bateman

Orion525iT said:


> Yeah, I am still concerned that the control will fall apart _in situ_. Hoping that I am very wrong, of course.


Left and right speakers are in the car, we'll know soon...


----------



## Patrick Bateman

I managed to do some subjective listening tonight.

Here's some thoughts:

1) The soundstaging is REALLY pinpoint. I'm not accustomed to hearing loudspeakers that can create a believable sense of space around the elements in the soundstage. On the flipside of this, it was a bit odd how "small" a lot of recordings sounded. For instance, I was listening to "Bound 2" by Kanye West, and most of the recording sounded about as big as a basketball. Occasionally the stage would get MUCH bigger, but a lot of the song is just plain ol' mono. A mono signal on my home stereo sounds about three feet wide; mono on this system in my car sounds about 8" wide. I think the cause of this is the cardioid radiation, basically a regular speaker will radiate to the back, and those early reflections will make the soundstage sound larger.

2) I've always found that Unity and Synergy horns are good at articulation. I think this is an under-appreciated aspect of a good speaker. A lot of people love great bass or great treble, but what's the point of that when you're listening to talk radio? Or a podcast? Or a baseball game on the radio? An articulate speaker makes *everything* sound better, not just audiophile recordings.
These speakers are about as articulate as I've heard. Literally every few minutes I was noticing new elements in my recordings.

3) There were a lot of recordings where the width of the stage exceeded the boundaries of the car. That was pretty cool. 

This system is far from perfect:

1) I'm really sensitive to higher order modes. I think this is due to owning Gedlee Summas. I'm definitely hearing some HOMs with this speaker. I filled the speaker with polyfill and that made a big difference.
2) The speaker isn't as "clean" as some I've heard. I think those Peerless midranges aren't as low in distortion as Aura Whispers or Peerless 830970s.

Hope I don't sound too negative here; I think this may be the best project I've come up with. But I'm very picky.

I can't imagine how I'll improve on the imaging. It's really world class. On some recordings there was real depth; I was listening to a live recording where you could actually perceive the depth of the stage, with the cheering audience in the foreground. Eerie; I don't know that I've heard a stereo do that.

I *do* think I can improve on the tonality. I'm hoping I can reduce the distortion. Though I've applied a few layers of fiberglass to the waveguides, they're still vibrating a little, and I think that could be adding some harshness to the sound.


----------



## Patrick Bateman

I bought a laser cutter six weeks ago. I've been busy with work, renting out my house, holidays, etc. Haven't had a chance to set it up.

Decided to do that today AND I CAN'T FIND THE LASER.

What a First World Problem. I lost my high powered laser.


----------



## BP1Fanatic

Lmao!


----------



## Orion525iT

Glad that you seem to be moving in a positive direction with this.

Any thoughts of trying them out in the kicks? You might loose some staging. But, I am wondering if better tonality or other improvements could be gained by having a little more absorbing materials and space behind the horn, especially in the frequencies before the transition from cardioid to super cardioid.

Did you physically isolate the drivers from the wave guide? Maybe you could design the rear chamber in a way that it would act as a clamp. The clamp would hold the magnet of the driver and then you can use a gasket around the driver flange to float the driver against the waveguide. Then add mounting tabs to the rear camber/clamp to attach to the waveguide. Does this make sense?

I would also suggest taking your time and using fiberglass cloth over mat. You will get more consistent physical properties, and it will be less prone to voids and air bubbles. 7781 E-glass is my favorite cloth because it has a tight weave and it holds together well as you are trying to laminate. 7725 E-glass conforms better, but it pulls apart too easily during hand layups. You could really go nuts and dive into the science of reinforcing fibers and resins and their acoustical properties. In general, I think epoxy might be the best simply because it is the least likely to delaminate from the printed part you are trying to reinforce.


----------



## Orion525iT

Patrick Bateman said:


> Decided to do that today AND I CAN'T FIND THE LASER.
> 
> What a First World Problem. I lost my high powered laser.


Did you check on your shark's head?


----------



## rton20s

Orion525iT said:


> Did you check on your shark's head?


Funny. This is exactly went through my mind after reading his post.


----------



## mitchyz250f

Have we seen pics of this configuration 'on the dash' yet?


----------



## Patrick Bateman

mitchyz250f said:


> Have we seen pics of this configuration 'on the dash' yet?


They're in post 448

here's one of them:










I tried five different setups:

1) on the dash, exactly like pictured above
2) under the dash, cross fired
3) on the dash, basically firing straight ahead (not cross fired)
4) under the dash, firing straight ahead
5) on the dash, firing straight ahead, and flipped upside down

I've generally cross fired my speakers. Geddes recommends this, because when you're using constant directivity waveguides it gives you a wider sweet spot. Basically makes the sound good for passenger and driver.

*I found that fired straight ahead sounded better.* The stage was wider. I think the reason is because these waveguides have *massive* nulls to the left, right, top, and down. (check out the polar responses I posted.) So when it's fired straight ahead, you're pointing the nulls to the left, right, top and bottom. And this has the effect of making the stage wider, because you're pointing the nulls at the side windows, the dash, and the windshield.

Flipping the speaker upside down sounded better; I think this is because it's a better "mate" to the windshield when it's flipped upside down. (This is because there's no midrange on *bottom* of the waveguide, so when you flip it upside down, you can align the waveguide perfectly with the windshield, no gap.)


----------



## Patrick Bateman

I still can't find my ****ing high power laser

I wound up printing some midbass enclosures

I was really hoping to cut them with my laser, but oh well.

If you see a CO2 laser lying around San Diego, LMK


----------



## mitchyz250f

Is that a picture of the horns firing straight ahead? Looks more like cross firing. How are the dynamics?


----------



## Onyx1136

Patrick Bateman said:


> I still can't find my ****ing high power laser
> 
> I wound up printing some midbass enclosures
> 
> I was really hoping to cut them with my laser, but oh well.
> 
> If you see a CO2 laser lying around San Diego, LMK


What laser cutter were you using?


----------



## Patrick Bateman

mitchyz250f said:


> Is that a picture of the horns firing straight ahead? Looks more like cross firing. How are the dynamics?


That picture is cross fired.

It's hard to comment on the dynamics. I did all of my listening with no midbasses, so I used EQ to "fill in" the gap between the midranges and the subwoofers.

Due to that, SPL was severely limited.

I really need some midbasses; when this is done it will look like this:

20hz - 120hz (2.5 octaves) : JL Audio 12" and some more subs (TBD)
120hz - 480hz (2 octaves) : array of ND91 midbasses
480hz - 2000hz ( 2 octaves ) : array of Peerless TC6
2000hz - 20000hz ( 3.5 octaves ) : SB Acoustics SB19

I was able to 'push" the subs up to about 300hz, and 'push' the midranges down to about 300hz, but it really killed the SPL limits


----------



## Patrick Bateman

Onyx1136 said:


> What laser cutter were you using?


"using" is an overstatement, more like "made an impulse purchase of a laser cutter and lost the laser" 

High Precise 40W CO2 Laser Engraving Cutting Machine ENGRAVER Cutter USB Port | eBay


----------



## mitchyz250f

Patrick Bateman said:


>


To me those horns look like they are cross firing.

I think horns are normally rated where they are 6db down off axis. So an 80 degree horn is down 6 db at 40 degrees off axis. Is this correct? So what is the dispersion of this horn? Dispersion seems very narrow in which case you would have very little early reflections which I think is why the stage seems so wide.


----------



## rton20s

Patrick Bateman said:


> That picture is cross fired.
> 
> It's hard to comment on the dynamics. I did all of my listening with no midbasses, so I used EQ to "fill in" the gap between the midranges and the subwoofers.
> 
> Due to that, SPL was severely limited.
> 
> I really need some midbasses; when this is done it will look like this:
> 
> 20hz - 120hz (2.5 octaves) : JL Audio 12" and some more subs (TBD)
> 120hz - 480hz (2 octaves) : array of ND91 midbasses
> 480hz - 2000hz ( 2 octaves ) : array of Peerless TC6
> 2000hz - 20000hz ( 3.5 octaves ) : SB Acoustics SB19
> 
> I was able to 'push" the subs up to about 300hz, and 'push' the midranges down to about 300hz, but it really killed the SPL limits


Patrick, why the use of an array of 3" ND91 midbasses rather than a more traditional low cost 8" midbasses like the W20RC38-4 or RS225-4? I ask because it will take 7+ ND91s to give you the cone area of a single 8" midbass. Granted, the 4.6mm Xmax on the ND91 is quite impressive. Heck, for less than the cost of 14 ND91s, you can just buy a pair of ZR800s.


----------



## oabeieo

Why haven't you made a horn with controlled dispersion for on the dash? Maybe make it a crossfire mouth with a reflector? Steer some of the sound a bit? I ask because I have tryed 11 diffrent PE horns and wave guides. ES minis sound the best. They put the sound where it needs to be ( even on axis) . When I put horns in corners like that it was wider sounding. But didn't represent a sound stage as well. 

What would have to happen to adopt a ES design and a 90° waveguide for a car dash?


----------



## Orion525iT

mitchyz250f said:


> To me those horns look like they are cross firing.
> 
> I think horns are normally rated where they are 6db down off axis. So an 80 degree horn is down 6 db at 40 degrees off axis. Is this correct? So what is the dispersion of this horn? Dispersion seems very narrow in which case you would have very little early reflections which I think is why the stage seems so wide.


Did you miss the fact that they he has hybridized a cardioid with a waveguide? So in fact, the dispersion is more narrow than typical. In order to get the pattern control measured in those plots, a waveguide by itself would have to be much larger.



rton20s said:


> Patrick, why the use of an array of 3" ND91 midbasses rather than a more traditional low cost 8" midbasses like the W20RC38-4 or RS225-4? I ask because it will take 7+ ND91s to give you the cone area of a single 8" midbass. Granted, the 4.6mm Xmax on the ND91 is quite impressive. Heck, for less than the cost of 14 ND91s, you can just buy a pair of ZR800s.


Its not the easy way for sure, but I am fairly certain that he is planning to incorporate some form of midbass arrays. Beyond that, using multiples allows for all sorts of mounting options that would be impossible with larger single drivers. It's I concept I have adopted too. I have 8 8" subs, 4 6.5" midbass, and 4 2" midranges. It all comes down to packaging. You would never know where my subs are if I didn't point them out, yet they have the cone area of 2 15"s.


----------



## oabeieo

Orion525iT said:


> Did you miss the fact that they he has hybridized a cardioid with a waveguide? So in fact, the dispersion is more narrow than typical. In order to get the pattern control measured in those plots, a waveguide by itself would have to be much larger.
> 
> 
> 
> It's not the easy way for sure, but I am fairly certain that he is planning to incorporate some form of midbass arrays. Beyond that, using multiples allows for all sorts of mounting options that would be impossible with larger single drivers. It's I concept I have adopted too. I have 8 8" subs, 4 6.5" midbass, and 4 2" midranges. It all comes down to packaging. You would never know where my subs are if I didn't point them out, yet they have the cone area of 2 15"s.


So do one of the 2s in the far end of the horn run out of phase to try to cancel the sound radiating into the windshield?


----------



## mitchyz250f

Orion525iT said:


> Did you miss the fact that they he has hybridized a cardioid with a waveguide? So in fact, the dispersion is more narrow than typical. In order to get the pattern control measured in those plots, the waveguide would have to be much larger.


Controlled dispersion can be created physically or by cancelation. In either case it has a dispersion rate. It seems that part of the dispersion is being controlled by the horn and the other part by the cancellation.



Patrick the dispersion varies greatly even when it gets into the tweeter range which should be controlled by the horn. Do you think more can be done to control the dispersion variations?

What is interesting is that Patricks and Gary's cars are both set up to control reflections but do it in opposite ways. Gary uses the car as the horn and the sound waves are in contact with the interior of the car constantly and therefore 'ideally' you would not get any early reflections. Patrick creates an acoustic dead zone through the interior of the car to achieve the same thing.


----------



## Patrick Bateman

rton20s said:


> Patrick, why the use of an array of 3" ND91 midbasses rather than a more traditional low cost 8" midbasses like the W20RC38-4 or RS225-4? I ask because it will take 7+ ND91s to give you the cone area of a single 8" midbass. Granted, the 4.6mm Xmax on the ND91 is quite impressive. Heck, for less than the cost of 14 ND91s, you can just buy a pair of ZR800s.


Chances are good I'll do both. A midbass array of an eight inch woofer, along with a pair of ND91s in series.

So if I had a hundred watts on tap, the eight inch woofer would get fifty watts, the ND91s would each get 25 watts.

Basically give you the power handling of an array, with the distributed bass of an array.

I'd prefer to do an array of ND91s, but I don't have eight on hand. I bought eight, but a couple of them died.


----------



## Patrick Bateman

oabeieo said:


> So do one of the 2s in the far end of the horn run out of phase to try to cancel the sound radiating into the windshield?


Nope, they're all in phase.

I tried wiring one out-of-phase, to see if it would reduce distortion. But the overall output dropped by nearly ten decibels, due to the woofers being so tightly packed.

If I was going to do it again, I'd probably invert one of the woofers to lower second harmonic distortion.


----------



## Orion525iT

oabeieo said:


> So do one of the 2s in the far end of the horn run out of phase to try to cancel the sound radiating into the windshield?


No, they are passive cardioids. The rear wave of the driver is not contained; it is allowed to escape through a resistive element and interacts with the front wave to control dispersion. That may be a viable approach with active cardioid.



mitchyz250f said:


> Controlled dispersion can be created physically or by cancelation. In either case it has a dispersion rate. It seems that part of the dispersion is being controlled by the horn and the other part by the cancellation.


Yep, its a hybrid.



mitchyz250f said:


> What is interesting is that Patricks and Gary's cars are both set up to control reflections but do it in opposite ways. Gary uses the car as the horn and the sound waves are in contact with the interior of the car constantly and therefore 'ideally' you would not get any early reflections. Patrick creates an acoustic dead zone through the interior of the car to achieve the same thing.


There was some discussion over this, but in another thread Gary stated that he was not trying to achieve loading. However, it seems there was an obvious attempt to push the drivers into the apex to mitigate very early reflections. 

When I made my pods, I pushed them into the apex has far as possible without resorting to major modifications. I seamlessly blended the pods to the dash and windshield with the intention of preventing early reflections. But I also attempted to get some loading. Measurements showed that loading was achieved. But my approach was less than optimal with horn design. I just made a somewhat educated guess with the design simply as proof of concept. Imagining is great, best I have done yet. But output is limited with using a single Aurasound Whisper. I believe many more improvements could be made. I am 100% certain that Gary's system performs way better than mine.

Patrick blended cardioid with a waveguide, which I think is a very interesting approach. I have argued that the near reflections that cause us so many issues the typical sealed design, would also prevent the control needed to achieve cardioid or supercardioid dispersion. So, Patrick's design may solve some of that. But I honestly don't know what his entire thought process was other than a slow evolution of designs. 

I agree, it will be interesting to see which approach ends up superior. Or, as with so many other things, what advantages and compromises each approach exhibits. In either case, it's great to have people who are pushing boundaries, are open about their process to advance the hobby.


----------



## Patrick Bateman

mitchyz250f said:


> Controlled dispersion can be created physically or by cancelation. In either case it has a dispersion rate. It seems that part of the dispersion is being controlled by the horn and the other part by the cancellation.
> 
> 
> 
> Patrick the dispersion varies greatly even when it gets into the tweeter range which should be controlled by the horn. Do you think more can be done to control the dispersion variations?
> 
> What is interesting is that Patricks and Gary's cars are both set up to control reflections but do it in opposite ways. Gary uses the car as the horn and the sound waves are in contact with the interior of the car constantly and therefore 'ideally' you would not get any early reflections. Patrick creates an acoustic dead zone through the interior of the car to achieve the same thing.


Our cars definitely sound completely different though. Gary's speakers sound way cleaner, those Morels are nice. Then again, my speakers cost between $3 and $25


----------



## Patrick Bateman

oabeieo said:


> Why haven't you made a horn with controlled dispersion for on the dash? Maybe make it a crossfire mouth with a reflector? Steer some of the sound a bit? I ask because I have tryed 11 diffrent PE horns and wave guides. ES minis sound the best. They put the sound where it needs to be ( even on axis) . When I put horns in corners like that it was wider sounding. But didn't represent a sound stage as well.
> 
> What would have to happen to adopt a ES design and a 90° waveguide for a car dash?


The original idea was to crossifre them.

I found that the stage was wider when they *weren't* crossfired.

For better or for worse, the reflector is still there. I'd probably ditch it if I could; when I went to CES and listened to the B&O speakers with the SAW lens, I definitely noticed HOMs, and I notice them in my waveguide. Though I'd studied the SAW lens quite a bit, I'd only heard it once, back in 2007. That was about eight years ago, and I didn't have anything to compare my designs with. In hindsight, the SAW reflector probably generates HOMs 

Jury is still out though; I noticed it in Vegas and I've noticed it in my car but I may be able to treat the HOMs.


----------



## Patrick Bateman

Orion525iT said:


> No, they are passive cardioids. The rear wave of the driver is not contained; it is allowed to escape through a resistive element and interacts with the front wave to control dispersion. That may be a viable approach with active cardioid.
> 
> 
> 
> Yep, its a hybrid.
> 
> 
> 
> There was some discussion over this, but in another thread Gary stated that he was not trying to achieve loading. However, it seems there was an obvious attempt to push the drivers into the apex to mitigate very early reflections.
> 
> When I made my pods, I pushed them into the apex has far as possible without resorting to major modifications. I seamlessly blended the pods to the dash and windshield with the intention of preventing early reflections. But I also attempted to get some loading. Measurements showed that loading was achieved. But my approach was less than optimal with horn design. I just made a somewhat educated guess with the design simply as proof of concept. Imagining is great, best I have done yet. But output is limited with using a single Aurasound Whisper. I believe many more improvements could be made. I am 100% certain that Gary's system performs way better than mine.
> 
> Patrick blended cardioid with a waveguide, which I think is a very interesting approach. I have argued that the near reflections that cause us so many issues the typical sealed design, would also prevent the controlled needed to achieve cardioid or supercardioid dispersion. So, Patrick's design may solve some of that. But I honestly don't know what his entire thought process was other than a slow evolution of designs.
> 
> I agree, it will be interesting to see which approach ends up superior. Or, as with so many other things, what advantages and compromises each approach exhibits. In either case, it's great to have people who are pushing boundaries, are open about their process to advance the hobby.


I may turn this into something great, but at the moment, I think I'd probably emulate this if I could start all over again:










RL 903K

Dave Smith, who worked on the coincident drivers at Kef and TAD has confessed that this 'bridge' setup is superior. He designed something like this for Snell, before they went kaput. Smith has worked at JBL, Kef, TAD, Snell, and now works at Bose. When it comes to audio, I don't think I've seen a better resume.









NEXO does something similar, and KEF did this back in the 80s.









Linn isn't quite the same, but close


----------



## jwsewell01

Every time I do a google search for cardioid midrange the RL 903k and other ME Gaithain speakers pop up. 

This gives me hope for coaxial tweeters on a cardioid midrange stuffed into the dash/windshield apex. 

Now I'm just trying to figure out the best way to reshape the top half of my dash.


----------



## Patrick Bateman

jwsewell01 said:


> Every time I do a google search for cardioid midrange the RL 903k and other ME Gaithain speakers pop up.
> 
> This gives me hope for coaxial tweeters on a cardioid midrange stuffed into the dash/windshield apex.
> 
> Now I'm just trying to figure out the best way to reshape the top half of my dash.


The great thing about dipoles is you don't NEED to put them in the corners










When you have your midranges set up like this, the sound 'wraps around' and you get a really brutal reflection off the windshield. This adds a harsh 'glare' to the sound that can't really be fixed by EQ, adds comb filtering, screws up imaging cues, etc. It's bad news.

With a cardioid or dipole, you're reducing output off-axis by as much as 90-95% at certain angles, and this means less energy going where you *don't* want it, and more energy going where you DO want it.

In my experiments, pulling the speakers *away* from the windshield made it sound better.

This is really easy to experiment with; just get yourself a pair of speakers about 3"-5" in diameter, and put them up on the dash. No enclosure whatsoever. Use a highpass of about 1000hz. Be sure to have your midbasses running; without the rest of the frequency range, your dipoles will basically sound like tweeters. The magic happens when you get the right combination of angle and location, because dipoles are very directional (which is a good thing.)


----------



## Orion525iT

Patrick Bateman said:


> I may turn this into something great, but at the moment, I think I'd probably emulate this if I could start all over again:


The RL901K is pictured, but the link is for the 903K

Taken from their website:

_The RL 901K has been designed for both the professional user at medium-size to large audio, video and film studios and for the discerning music enthusiast.

*By the radiating characteristic within the frequency range from 30 through 250 Hz the reflections on the back walls of listening rooms can be minimized. *The transfer characteristic can be matched to the acoustical conditions of the reproduction room as well as to the set-up situation by a low-frequent infinitely variable adaptation within two adjustable frequency ranges.

The RL 903K makes a similar claim, but actually mentions cardioid.


"The RL 903K is a main studio control room monitor with* cardioid radiation characteristic from 35 Hz through 100 Hz* for universal application. Main operational areas are audio, video and motion picture studios. By the cardioid characteristic those reflections caused by the wall behind the speakers are minimized. To enhance the low-frequency range we combined the coaxial arranged high- and mid-frequency driver unit with a powerful long-voice coil bass driver unit. Its coaxial arranged transducers ensure a sound impression with a high degree of homogeneity to a point source. We spend much effort in developing constructive ways to ensure a low degree of non-linear distortion. To keep short-term reflections small and achieve a high fidelity of sound we used a special arrangement for the high- and mid-frequency drivers and also designed the front side of the speaker asymmetrical. Although the cabinets dimensions a very compact, the system obtains a low-frequency cut-off at 35 Hz."

How in the heck is that thing cardioid? There are no side vents, the back is closed with the integrated amp mounted there, and there is no rear driver. The polar measurements back up the claims. What am I missing? Is the "bridge" somehow responsible? Can't see how because the bridge should be acoustically invisible in the frequency range affected._


----------



## jwsewell01

I think the two black panels on each side of the rear mounted amp are the resistive slots/ports

I would think given the wavelength of bass frequencys there would really be no need for side slots/ports.


I could be wrong though.


----------



## jwsewell01

Patrick, just to clarify, When I say stuff the coaxials in the apex I have an Idea to basically make a cone to house the coaxial that has 1-1.5" of space around a Gradient style radial resistive slot/port.

Just the tip of the cone will be "stuffed" in the corner.


----------



## Patrick Bateman

jwsewell01 said:


> I think the two black panels on each side of the rear mounted amp are the resistive slots/ports
> 
> I would think given the wavelength of bass frequencys there would really be no need for side slots/ports.
> 
> 
> I could be wrong though.












Seems to be a resistive cardioid with the vents at the top on this model. (Note the dual ports at the top?) Not sure if they're on the bottom too.

















On this model, there appears to be a pair of handles on the side, and a thread for mounting to the speaker stands









This coaxial setup seems especially easy to DIY

Here's an article in German on the company:

Fachbereich Ingenieurwissenschaften









The first time you hear cardioid bass is pretty weird. It's so unnatural to hear the bass go away as you move to the back. I did this on the Beolab 90, very odd.

[/font]


----------



## jwsewell01

Here is the back of the RL 901K



I just love the way this speaker looks!


----------



## BP1Fanatic

That speaker does look nice!


----------



## Patrick Bateman

Here's a video showing the CLD construction I'm using for the midbasses:

https://www.youtube.com/watch?v=bOal1ReM5yU


----------



## oabeieo

Patrick Bateman said:


> The original idea was to crossifre them.
> 
> I found that the stage was wider when they *weren't* crossfired.
> 
> For better or for worse, the reflector is still there. I'd probably ditch it if I could; when I went to CES and listened to the B&O speakers with the SAW lens, I definitely noticed HOMs, and I notice them in my waveguide. Though I'd studied the SAW lens quite a bit, I'd only heard it once, back in 2007. That was about eight years ago, and I didn't have anything to compare my designs with. In hindsight, the SAW reflector probably generates HOMs
> 
> Jury is still out though; I noticed it in Vegas and I've noticed it in my car but I may be able to treat the HOMs.


What about lower order modes? 

I've noticed in my horns when the horn can play down to 1k and I choose a crossover above 1k like 2k I get a much more exaggerated accoustical roll off that reaches down to 1k (even with 24db slopes) the extension usually sounds echoed and colored. I've been calling it LOM lately , when I put a towel around the horn body/mouth it goes away for the most part which leads me to poor mouth termination. 

What do you think about LOM? Or is it a HOM that I'm hearing.


----------



## Patrick Bateman

What you're describing is higher order modes; basically when a horn isn't properly terminated you get a reflection at the mouth, and that reflection travels back down the horn, hits the throat, and gets reflected back out.

see : The HOMster! (or How I Learned How to Fix a Horn) - diyAudio

Factors Affecting Sonic Quality of Mid & HF Horns & Waveguides










Here's what they look like


----------



## oabeieo

Patrick Bateman said:


> What you're describing is higher order modes; basically when a horn isn't properly terminated you get a reflection at the mouth, and that reflection travels back down the horn, hits the throat, and gets reflected back out.
> 
> see : The HOMster! (or How I Learned How to Fix a Horn) - diyAudio
> 
> Factors Affecting Sonic Quality of Mid & HF Horns & Waveguides
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Here's what they look like



Ok I understand higher order now. I thought it meant higher order as in the modes in the horn always caused a higher pitch to a fundamental. 

I get it now. High order as in some inter-modulation inside the horn itself caused by the horn it self. Reflected sound bounced around making harmonics to be louder than fundamentals in some instances and potentially out of tune i.e. g# could be a G♭ and entire oactaves out of place as well.

I love that guys towel experiment. That's good I tryed it


----------



## Patrick Bateman

My midbasses were finished about seven months ago. They've been sitting on a shelf while I tried a zillion different options for the front stage.

Here's a repost, from page four, so I can recall what the xover points, bandwidth, etc are :



Patrick Bateman said:


> In post 74, I described how my last Mazda had Dayton ND91s in a push-pull bandpass.
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> The volumes and the tuning are basically the same. The big difference this time around is that I 3D printed it. Also, as noted in post 74, I had some issues trying to cram two woofers into one box. (Couldn't fit them.)
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> Here's some measurements of the midbass enclosure that I did this afternoon. Over the years, I've learned that many enclosure types are INSANELY sensitive to air leaks. I think these measurements are an excellent example of this.
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> The blue line in the measurement is the bandpass response; the green line is the sealed response. I was able to get measurements of both because I left one wall off of the enclosure. IE, I could change it from "sealed" to "bandpass" by closing off the wall. Every one of these measurements shows the progress as I worked to seal the enclosure more and more.
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> 1) The F3 of the enclosure dropped an entire octave. AN OCTAVE. That is huge; that's literally the difference between a 6" woofer and a 12" woofer. And I didn't do anything but seal the enclosure better. In the first measurement the F3 of the midbass is 300hz and by the time I finished it had dropped an octave, down to 150hz(!!!)
> 2) The frequency response had a series of peaks and dips which mostly disappeared by the time I finished sealing it off.
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> If anyone is curious how I fixed it, I basically sealed off the interior and the exterior of the enclosure with Loctite PL 400. My hypothesis was that the Dayton woofers were pushing air right through the enclosure walls. This is because I 3D printed the enclosure. Since the enclosure is built up, layer by layer, my hunch was that there's a "gap" between each layer that's a fraction of a millimeter. The enclosure is even watertight, but air has a way of squeezing through gaps in way that water doesn't. I progressively sealed the enclosure more and more, by slathering the inside with Loctite, and then the outside.
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> The green line in the top graph shows the response of the bandpass box from my old Mazda.
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> The green line in the bottom graph shows the response of the bandpass box from my new Mazda if you "omit" the front chamber, basically turning it into a plain ol' sealed box.
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> The reason that the rolloff on the two graphs looks so different is that the second graph shows 7.5 octaves while the first graph only shows five octaves.


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## Nismo

Patrick Bateman said:


> Nope.
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> Back in the day I used to do a lot of measurements in the car.
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> At this point I basically design it anechoically, then throw it in the car. I'll definitely tweak things a little once it's in the car, but there's so many reflections in the vehicle, it's really hard to come up with a proper xover unless it's measured anechoically.
> 
> Dan Wiggins used a similar method with his car speakers.


Do you know Dan? I've communicated with him a bit, and I'm a big fan of his work. Met him once, and a few of my buddies had heavy involvement in both the design of the Brahma, and the competition with them.

Eric


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## Orion525iT

Dammit Patrick!

Thanks alot! I spent all day yesterday listening to dipoles in my house, and you got me thinking about cardioid again after my first failed attempt. Now you have caused me to pull out my PM-180s with the thought of creating a hybrid of the cardioid midrange of the LX mini with a bridge mounted Aura whisper, ala ME-Geithain, to place in the kicks. There are sooo many other more important things I need to do today.


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## jwsewell01

:snacks:


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## BP1Fanatic

jwsewell01 said:


> :snacks:


Word! PB displaying some great stuff in this thread!


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## j4gates

Late subscription...


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## Patrick Bateman

Sorry I've been kinda quiet, the system is working pretty well and due to that, I haven't been visiting audio sites as much as usual.

I thought I post a few updates:

1) The midbass arrays are working a lot different than I'd expected. I use subwoofer arrays at home and I find that they make the bass sound 'diffuse', basically it's hard to localize the bass and it blends in better. In the car, I'm hearing the same thing. If you put a gun to my head and asked me to point to where the midbasses are, I'd have a hard time telling you. The midbass just surrounds you.
The part that was unexpected was that the SPL level is just nuts. I'll probably re-wire the midbasses because there's just a LOT of midbass. (In the short term, I've cut their level via EQ.)
I'd speculate that the reason that the midbasses sound so loud is because of a couple things. First, there's six of them, and that's a lot of displacement. But I also think it's because the peaks and dips should be smoothed out by the array. IE, if you have two midbasses and there's a big peak in the response, you're inclined to lower their level. But since midbass arrays (seem) to have fewer peaks and dips, they don't sound boomy, they just sound LOUD. (In a good way  )

TLDR: I am currently using an array of six midbasses, but if I had to do it all over again, I'd probably down-size, I have a ridiculous amount of midbass now.

2) It's been a real struggle to resist the temptation to print some new waveguides. The current waveguides do everything I want them to do, but there's still a bit of a rough edge to them. The image is very pinpoint, bordering on clinical. I think this may be due to the cardioid radiation pattern; basically cardioids really reduce the sound of the room, but the room adds some 'bloom' to the image that blurs the image a bit. Basically the soundstaging of these cardioids is razor sharp, but I might prefer them to be a little bigger and out-of-focus. I know this is splitting hairs in a huge way; it's like buying a 4000 square foot house and complaining that it's too big.

3) As noted earlier in this post, these speakers have kinda dampened my interest in audio. They do what they're supposed to do, music sounds great, and I almost feel like I need to find a new hobby. Don't worry though, I'm still ADHD and I'll probably wind up scrapping the midranges and the tweeters to try something different. But those midbass arrays are here to stay, I have no complaints about them whatsoever.


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## Kevmoso

That's really neat regarding your midbass performance. 
Mind elaborating on where you put them? 
Actually everything about this current configuration intrigues me. Clinical is my favorite quality in a playback sound system.


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## BP1Fanatic

Please post some in-car pics of the 6 midbasses! Are you running the 4 or 8 ohm ND91?


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## Patrick Bateman

Kevmoso said:


> That's really neat regarding your midbass performance.
> Mind elaborating on where you put them?
> Actually everything about this current configuration intrigues me. Clinical is my favorite quality in a playback sound system.


My original plan was to do four bandpass midbasses in series-parallel. Basically I'd have the displacement of a seven inch woofer, but it would be distributed throughout the cabin. I created some enclosures that were *just* big enough to fit under the seat rails and I'd planned to put two under the seat (one at the front, one at the back.) The locations for the other two wasn't determined, I was probably going to put one under the dash and one on the floor *behind* the seat. So each midbass would be spaced out about eight inches from each other, and distributed along a line that's about two feet long. (The one under the dash is the exception, and I figured that though it wasn't close to the others, it would probably be OK because it was only contributing 25% of the SPL.)

So, that was the plan. I've posted two different sets of measurements of bandpass midbasses, one from this car and one from my previous car, a Mazda6.

I was getting realllly frustrated with how long it was taking to make the midbasses. Each one is like a tiny subwoofer. So it's like building eight subwoofers, only more time consuming, because everything goes slower when the parts are tiny.

So I ended up mixing it up. I made two bandpass midbasses with ND91s, two sealed midbasses with ND91s, and two bandpass midbasses with B&C 8ndl51s. The eights are currently on the front floor of the car, but they won't stay there. I'll be putting them under the seats. The bandpass midbasses are under the seat, but they'll be likely moved to the floor in front of the rear seats. (They're about 5" wide, so they don't take up much space, and I basically use my CUV like you'd use a truck, so I rarely use this car to haul people around, I use my Hyundai Genesis for that.) The sealed midbasses will definitely go under the dash; they're currently on the rear floor.

So I currently have it set up like this:

front floor: B&C 8NDL51 in a bandpass box
under seat : ND91 in a bandpass box
rear floor : ND91 in a sealed box

The B&C is an 8ohm driver, so the load is still a 4ohm load when I wire everything in series parallel. I may have to get creative with that wiring because the midbasses are about 6dB louder than the waveguides right now. The waveguides are a twelve ohm load.


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## Orion525iT

How do you manage TA? I had posted in the past that I thought you could cheat a bit with distributed midbass by leveraging precedent, but I didn't know to what extent you could get away with it. 

Where are your xover points? I assume all sense staging must come from the mids on up. I still wonder if you can get some cues out of your midbass with very careful placement and individual processing. I am not technically using and array now, but my subs are crossed at a higher xover than typical right where I observed a problem area. I also want to try asymmetrical midbass placement to try match L/R itd. If that doesn't work out well, I can go to an array fairly easily; but I only b want to use 4 midbass total in plain old sealed boxes.


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## BP1Fanatic

I'd be really curious how you have 8" BP4's on your front floor????


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## Focused4door

Patrick Bateman said:


> My original plan was to do four bandpass midbasses in series-parallel. Basically I'd have the displacement of a seven inch woofer, but it would be distributed throughout the cabin. I created some enclosures that were *just* big enough to fit under the seat rails and I'd planned to put two under the seat (one at the front, one at the back.) The locations for the other two wasn't determined, I was probably going to put one under the dash and one on the floor *behind* the seat. So each midbass would be spaced out about eight inches from each other, and distributed along a line that's about two feet long. (The one under the dash is the exception, and I figured that though it wasn't close to the others, it would probably be OK because it was only contributing 25% of the SPL.)
> 
> So, that was the plan. I've posted two different sets of measurements of bandpass midbasses, one from this car and one from my previous car, a Mazda6.
> 
> I was getting realllly frustrated with how long it was taking to make the midbasses. Each one is like a tiny subwoofer. So it's like building eight subwoofers, only more time consuming, because everything goes slower when the parts are tiny.
> 
> So I ended up mixing it up. I made two bandpass midbasses with ND91s, two sealed midbasses with ND91s, and two bandpass midbasses with B&C 8ndl51s. The eights are currently on the front floor of the car, but they won't stay there. I'll be putting them under the seats. The bandpass midbasses are under the seat, but they'll be likely moved to the floor in front of the rear seats. (They're about 5" wide, so they don't take up much space, and I basically use my CUV like you'd use a truck, so I rarely use this car to haul people around, I use my Hyundai Genesis for that.) The sealed midbasses will definitely go under the dash; they're currently on the rear floor.
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> So I currently have it set up like this:
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> *front floor: B&C 8NDL51 in a bandpass box
> under seat : ND91 in a bandpass box
> rear floor : ND91 in a sealed box*
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> The B&C is an 8ohm driver, so the load is still a 4ohm load when I wire everything in series parallel. I may have to get creative with that wiring because the midbasses are about 6dB louder than the waveguides right now. The waveguides are a twelve ohm load.


I am curious if you are getting *some* directivity in midbass frequency range and possibly even some nulls to the sides. I don't think that would be a bad thing in a car, but kind of curious what your setup would simulate as. Probably far quicker to simulate than actually measure.


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## T3mpest

Patrick Bateman said:


> Here's a video showing the CLD construction I'm using for the midbasses:
> 
> https://www.youtube.com/watch?v=bOal1ReM5yU


Have you thought about putting some BB's or something on the liquid nail mixture to mass load it as well? I had an idea of suspending a bunch of metal BB's into a mixture like that, since the soft layer would dampen them and then glassing over it for kickpanels. 

Haven't tried it myself, but it seemed a cheap easy way to mass load, dampen and stiffen all at the same time.

Not sure if you'd need it on something small like this, maybe for the 8's though 

I'm thinking very hard about doing a midbass array myself. I dont' want to go the route of doing a bunch of midbass in my doors like a lot of people tend to do. I'm thinking a pair in the doors, a pair down in my floorboards and maybe a small set under the seats or under a false floor in the back seat footwell area.


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## Patrick Bateman

Orion525iT said:


> How do you manage TA? I had posted in the past that I thought you could cheat a bit with distributed midbass by leveraging precedent, but I didn't know to what extent you could get away with it.
> 
> Where are your xover points? I assume all sense staging must come from the mids on up. I still wonder if you can get some cues out of your midbass with very careful placement and individual processing. I am not technically using and array now, but my subs are crossed at a higher xover than typical right where I observed a problem area. I also want to try asymmetrical midbass placement to try match L/R itd. If that doesn't work out well, I can go to an array fairly easily; but I only b want to use 4 midbass total in plain old sealed boxes.


I'm not 100% convinced it's necessary. Here's why:

1000hz is 13.5" long. So when you're listening to a pair of stereo speakers playing 1000hz in your car and you're one foot closer to one than the other, *you're over one wavelength closer to the speaker.*

So at midrange frequencies, *time alignment is really important.*

But when you move down one octave to 500hz, that wavelength is 27" long. So if you're one foot closer to the speaker, it's kind of a big deal, but not nearly as important as 1000hz.

Move down to 250hz, and a difference of one foot is just barely a problem.

By 125hz, a pathlength difference of one foot is really no big deal at all.

Of course, if the pathlength difference was three feet, that would be a problem. But we're not dealing with pathlength differences that are that large.


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## Patrick Bateman

BP1Fanatic said:


> I'd be really curious how you have 8" BP4's on your front floor????





















It's a pretty basic bandpass box. I didn't even model TBH. I just put the 8" woofer in a small enclosure, then built another enclosure around that. The whole thing is under 4" tall, so it will fit under the seat. I used a sonotube for the inner enclosure. I did this because a tube is stronger than a box. The pics above show the bandpass box with the top removed. (It's not 100% finished here; this is from a week ago.)

One thing I did this time around was that I slathered the entire interior in that liquid nails for subfloors that I used for the plastic enclosures. This stuff really works well. I measured the impedance curve of the speaker before and after the liquid nails, and the liquid nails measurably improved the curve. In the real world this should make quite a difference; even a tiny air leak can cost you 1-3dB easy. It also raises your F3. This is one of the reasons I'm so opposed to putting woofers in doors; I don't think people grasp how much SPL they lose to leaks. With the midranges I made them leaky on purpose, because I wanted a cardioid, but with the midbasses I really need them to play down to 100hz, so leaks cannot be tolerated.


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## Patrick Bateman

Focused4door said:


> I am curious if you are getting *some* directivity in midbass frequency range and possibly even some nulls to the sides. I don't think that would be a bad thing in a car, but kind of curious what your setup would simulate as. Probably far quicker to simulate than actually measure.


I don't perceive any directivity from the midbasses. The low frequencies basically sound like they're coming from everywhere. If you put a gun to my head and asked me to point to where the bass is coming from, I wouldn't be able to tell you.

I think there's definitely an argument for directional midbass, but I don't know where I'd put it. The 8NDL51s would probably fit under the dash, but in a dipole the F3 would rise from around 100hz to about 500hz. So the 8" woofer would basically become a midrange.

In the car, I find that the whole thing images REALLY well. This is definitely a step up from the 2009 project (http://www.diymobileaudio.com/forum...ussion/60146-creating-perfect-soundstage.html)

I spent seven hours in the car yesterday night, for a trip, and it really gave me a chance to do some serious listening. It definitely images better than the 2009 project, probably better than anything I've done. I was thinking about why this is, and my 'hunch' is that the distributed midbass array eliminates imaging cues from the midbasses.

IE, in a perfect world we'd want to put midbasses in exactly the right spot, and they'd be perfectly free of resonances. In the car, I don't think this is practical. Even if you made a midbass enclosure out of titanium and put the midbasses in the kick panels, *the car itself will introduce audible resonances.* You can see this in any measurement of a midbass in a car; there are noticeable resonances introduced by the geometry of the cabin.

So the midbass array reduces the severity of those resonances by spreading them out. The interesting part is that it also destroys the cues that tell you where the midbasses are. The bass "surrounds you."

If we were only listening to bass, the system wouldn't soundstage at all. But here's the curious part; the midranges and the tweeters 'anchor' the soundstage, and the absence of low frequency imaging cues basically robs your brain of the cues that would tell you if the sound is coming from somewhere besides the midranges.

On this forum I've mentioned the reason that I killed the 2009 project: I found that the music I listen to basically sounds like mono 75% of the time.

This time around, I'm not finding that. I'm not sure if it's because I got the phase right this time around, or if I'm a better listener, or if it's the cardioids, the midbass array, or all of the above. But there's no doubt about it - these things image. One example of this was a Madeon set I was listening to yesterday. In one of the tracks he did this 'trick' where he mapped the keys on the keyboard to the entire stage. So some notes came from the left, others from the center, others from the right. The trippy part was that some of the sounds were somewhere in between, and this was audible. Quite a neat trick!

Another thing I noticed from literally 80% of my albums was a pattern where the recording engineer had put the lead singer in mono, and the band out of phase. For instance, on a Morrisey track from 'Viva Hate' the vocal track was dead center and about the size of a basketball, but the band itself was audibly out-of-phase, which made the band sound very wide and large, but with a bit of a 'hole' in the center of the soundstage. Even my Vandersteen speakers don't have this level of clarity in the sound stage. My Vandersteens have a huge stage, but they don't have this freaky level of clarity around the objects in the sound stage.

Another fun thing about the midbass array is that you can play my system at quite a shocking level. I don't think people really appreciate how much power and displacement it takes to do justice to the midbass. For instance, I was listening to Porter Robinson's set from Coachella yesterday. (BTW, it's ****ing embarassing how many times I've listened to this set, if anyone reading this is into EDM and hasn't listened to "Worlds", you're in for a treat. I've probably heard the Coachella set a hundred times now.) Anyways, in Porter's set he mixes 'Fresh Static Snow' into 'Divinity*.' The first track has a computer generated vocal that's in mono which literally hovers over the dash, and then Divinity comes on with a full-on sonic assault. On a system with limited dynamics this will probably sound muted, but with six midbasses on tap, the second track just blows you out of your chair. (Due to the former track being so quiet, the latter track comes on like a freight train.)

I'm definitely curious if one could combine this concept with something simpler than a Synergy Horn. Perhaps one could have a satisfying full-range system by combining a midbass array with a simple full range cardioid on the dash, something like the Tymphany TC9s.

* here's the setlist, for anyone who's curious : http://www.1001tracklists.com/track...chella-festival-united-states-2015-04-10.html


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## BP1Fanatic

Patrick Bateman said:


>


Nice! I use liquid nails on all my enclosures.


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## BP1Fanatic

Could you have designed the enclosure to have the basket mounted in the vented area for the pole piece?


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## I800C0LLECT

This makes me want to throw in my hybrid audio i6sw's as midbass along side the gb60's. I love reading your journals


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## Patrick Bateman

I800C0LLECT said:


> This makes me want to throw in my hybrid audio i6sw's as midbass along side the gb60's. I love reading your journals


Yeah it's working really well.
I brought my mic with me to work this week and I'm hoping to do some tuning to get the frequency balance better. Right now there's too much midbass. It's a real luxury problem, I have more midbass than I need.

On the upside, I'm getting really excellent pitch definition with the low frequencies. This is the first thing I notice with The Magic Bus, the pitch of the bass notes are as clear as a bell. I assume this is due to all the room treatment in the bus. My 'hunch' was that midbass arrays could achieve something similar and that seems to be correct.

It doesn't sound exactly the same; the bass in the Magic Bus doesn't surround you, but that goes back to my point from yesterday, basically we don't have the luxury of having our cake and eating it too, unless we're willing to design the entire vehicle around the speakers, like Jon did.


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## mitchyz250f

Please describe the dynamics and power compression if any of the midbass and midrange.


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## Patrick Bateman

mitchyz250f said:


> Please describe the dynamics and power compression if any of the midbass and midrange.


Well that's the funny part about this whole setup. For years I'd been arguing on the forum that you can get as much output from an array of small drivers as you can from a single unit. And the arguments against me were basically that it was too much hassle, and a single unit was a simpler and easier solution.

Now that I've actually got the thing installed in my car, I've found that I have a real strange problem, which is that I just have TOO MUCH output. The midbass array is way way WAY more efficient than the midrange, tweeter, or subs.

So if I were to scrap this thing and do it all over again, I'd probably use even MORE drivers, and make them smaller. Because the cosmetics on this setup are just dreadful. I have wires going all over my car, I need a spreadsheet to keep track of all the connections, the midbass enclosure for the eights is just a little too big to fit under the seat, so now it's sitting on the floor in front of the rear seats... It's quite a mess.



But dynamics? Wow, that's something they DON'T lack. These things will blow you out of your seat.

To me, the most impressive thing about the midbass arrays isn't the dynamics, it's how the midbass arrays make you re-think what's important in a car stereo. For instance, I've mentioned that the lack of imaging cues from the midbasses seems to make your brain focus on the soundstage that's being presented by the midrange and tweeter.

Another weird aspect of the midbass arrays is that it seems to mask issues with the subwoofer. I'm trying to figure out why this is, but I've noticed that the sub seems to integrate a lot better than I'm accustomed to. At the moment I am using an incredibly basic subwoofer design, I am using a JL Audio twelve in a bandpass box. I haven't talked much about the sub, because I'd never intended for the sub to be a permanent part of this install. Basically the reason that the sub is there is that I'd put in a few weekends building an elaborate sub box using dual TC Sounds fifteens. And it's still on my bench in the garage, because the stupid thing was taking FO-REV-ER to finish. I was frustrated that I had no subwoofer, so I made an impulse buy of a JL sub off of Craigslist. I paid a whopping $40 for two of them. And though it's a completely cheap solution, there is something about the midbass array that seems to be masking the crappiness of my subwoofer.










I can only speculate, but maybe it's the Fletcher Munson curves? IE, we all know that we get tons of gain at low frequencies from cabin gain. In the octave from 100-200hz we don't get much gain, and that means that it's actually harder to generate SPL at 150hz than it is at 75hz. It's really really easy to post big numbers below 80hz, above 80hz, not so much. So maybe that's part of the reason that my midbass array seems to 'mask' the crappiness of my sub box. Basically it's relatively difficult to generate high SPL at midbass frequencies, AND we're more sensitive to those frequencies, compared to sub-bass frequencies.

Again, I can only speculate. All I know is that these midbasses seem to mask any deficiencies in the subs, and their lack of imaging cues seems to make your brain focus on the front stage instead.

The midbass arrays are a home run; I really can't imagine a scenario where I won't be using midbass arrays in the future.

The only complaint I have, besides the fact that they were a ton of work and I have a mess of cables, is that I'm starting to think that I need some DSP to 'tighten' them up a bit.

Here's what I mean by this:

As noted in a previous post, the pitch definition of the midbass is REALLY good. The first time I heard a system do this really well was Jon's Magic Bus. It does midbass in a way that I've rarely heard; only cardioids and dipoles come close to what it does.

The pitch definition of my midbass array comes real close, and I think the reason is because it spreads out the resonances that are generated by the room/car.

So far, so good.

Orion had wondered if I needed delay, and I figured that I wouldn't, because the wavelengths are so long. Basically the pathlengths are all within a fraction of a wavelength, so I figured I'd be alright.

But now that I've had it in the car for a few weeks, and I've made a couple of long trips, I've noticed that percussion suffers a TINY bit. When I say "tiny", I mean it, this isn't a huge problem. But what I think is going on is that the wavefronts need to be a little bit better aligned to get a really tight definition on percussive sounds, like drums.


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## Patrick Bateman

Here's a wacky idea that I had today:

As noted in this thread, *these midbass arrays work really really well.* It's amazing to play something with a bass guitar, and the pitch is SO GOOD. Being able to hear each note with such distinction, it's eerie. It's like you never knew how good bass could sound.

But I've also noted that it is a MESS of speaker cables, and building the enclosures took a RIDICULOUS amount of time.

Consider the fact that it usually takes me about one whole weekend to build a subwoofer. Then realize that I have SIX midbass enclosures. Then consider that each one of those enclosures takes more time to build, because they're so small. I know the updates to this thread have slowed recently, but that's largely because these midbass enclosures are TREMENDOUSLY time consuming.

And the crummy part is that I'm only halfway there. All of the enclosures are fully functional, but they just look ridiculous. I'd love to play the stereo for someone, but my car is a rat's nest of speaker cables now, and you have to be REAL cautious about those wires, because they're all uninsulated, unlabeled, and if a single wire gets disconnected it takes me about thirty minutes to sort it all out. (Because there's so many.)

On top of all that, I have hours and hours left to finish up the enclosures. (Paint, sand, etc.)

And I've mentioned that the SPL levels of the array are just ridiculous - I have way more than I need. The midbass array exceeds the output of the subs and the mids and the tweets.



Okay, here's where things get crazy:

*What if I just used computer speakers?*

I kept thinking about that today.

I'd probably be the laughing stock of this forum, but computer speakers would sure solve a lot of problems here.










Basically I'd go on eBay, and buy about six or ten computer speakers. The enclosures are already finished, and they're small enough to hide. I can fit them under the dash, under the seats, I can discretely mount them just about anywhere.

And I know everyone would wonder how you can get good sound out of ****ty computer speakers, but the truth is that a lot of these speakers perform pretty darn good. Years ago I had a set of Cambridge Audio satellites in my garage, and on a whim I measured the cubes. They perform as good as 90% of the drivers out there! The cubes had a bandwidth of six octaves, the response was as flat as my Vandersteens, and the distortion was low too. The major problem with the Cambridge satellites was that they won't get loud, due to limited xmax. But as noted in this thread, when you array a bunch of speakers, the SPL goes up in a hurry, particularly when they're close together.

So as insane as this sounds, I'm not ready to rule out the idea of taking all the midbasses out of the car, and replacing them with a bunch of cheap Cambridge satellites. I know I'll lose all credibility, but I'm really not thrilled about spending another weekend painting and fiberglassing my enclosures.


----------



## Focused4door

With the bandpass, you should have lower harmonics from the midbass, do you think that is a big part of the improvement to the sound?


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## mitchyz250f

Patrick said you had 6 midbasses and that was too much. Possibly 4 would do. If thats the case why do you think that people with 4 midbasses (1 in each door) have such crapy midbass?


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## I800C0LLECT

mitchyz250f said:


> Patrick said you had 6 midbasses and that was too much. Possibly 4 would do. If thats the case why do you think that people with 4 midbasses (1 in each door) have such crapy midbass?



Because time alignment doesn't fix location issues. I think doing some math and using the cone of confusion would be much more beneficial. However, keeping the midbass speakers within 1/4 wave length of each other(from first to last) in reference to crossover point should remove any issues with location as well.

Patrick, I LOVE the idea of going with the satellites. I've been eye-balling PC satellites for years to be used in my install. That's the heart of this site and I'm glad to see somebody bringing it back!!! Depending on your success I may go down that road myself. Since my speakers are already sealed under the seats I might revisit changing them to match yours. I may even add the i6SW's to my doors since they're sealed from the factory...

But for the sake of testing I may just steal this idea from you


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## mitchyz250f

Most car doors speaker locations will be within the 5 degree angle needed to meet the requirements of cone of confusion. 

I don't think it's the location either. 1/4 WL for 200Hz is around 15" which is less than distance from the floor of my car to the center of the door speakers.

Regarding time alignment everyone with 4 door speakers and a DSP would have the correct time alignment and should therefore have tremendous, killer and pounding midbass. But from my experience that is not what happens. 

I think it has to be something else.


----------



## seafish

I800C0LLECT said:


> . I think doing some math and using the cone of confusion would be much more beneficial. However, keeping the midbass speakers within 1/4 wave length of each other(from first to last) in reference to crossover point should remove any issues with location as well.


I have read the thread on midbass placement using the CoC. That being said, I do NOT understand how to "do the math" despite reading it several times and TRYING to understand the intricacies of CoC midbass placement. More then likely I am geometrically challenged …lol… but can anyone explain SIMPLY what parameters I need to measure in my truck and then help me "do the math".


----------



## Patrick Bateman

mitchyz250f said:


> Patrick said you had 6 midbasses and that was too much. Possibly 4 would do. If thats the case why do you think that people with 4 midbasses (1 in each door) have such crapy midbass?


Hmmm that's an interesting point.

I never considered the fact that anyone with midbasses in the front and the rear doors will have a midbass array.

In my car it's REALLY easy to flip between the stock system and my aftermarket system; all I have to do is turn on Bluetooth and the sound will flip between the two. (My stock system is Bluetooth.)

Perhaps part of it is because my midbasses aren't putting much energy into doors of the car?

IE, there's a couple of schools of thought on mounting drivers to a car door. One school of thought is to rigidly mount the driver to the door. I think this is what most people do; they build a MDF ring, and then bolt the driver into the door of the car. The downside of this approach is that metal rings like crazy, so a ton of the energy from the driver is going to get into the door, and that energy will be re-radiated as sound.

The output of a radiator is related to two things : the surface area of the radiator and the excursion of the radiator. Mass does not change the output level. For instance, if you have a fifteen inch woofer with a heavy aluminum cone, and you have a fifteen inch woofer with a light paper cone, the SPL won't vary as long as the excursion is identical. It's just two variables, surface area and excursion.

The same thing applies to a car door. While the door may only be moving a fraction of a millimeter, the surface area is huge, and the output will be accordingly huge.

My midbasses don't suffer from this, thought this wasn't by design. The reason that I don't put midbasses in doors is because I don't want to screw up my car, and my projects tend to change five times a year, and opening up my doors five times a year would surely ruin them.

By the way, the other school of thought, which you don't see too much would be to 'float' the drivers. Kef does this in their home speakers IIRC. The idea of 'floating' the driver is to basically use something that will isolate the driver from the structure. I think Geddes is keen on this too. The method that Geddes has mentioned is ingeniously simple, basically just suspend the enclosure with bungie cords. The rear deck would be an obvious place to do this. In the door is trickier; you could use a sorbothane ring, but a few millimeters of sorbothane probably won't be as effective as suspendinding with a bungie.
Jon Whitledge uses this approach with his subs, but instead of suspending the subs he floats them on a damper that was intended for air conditioning units. (This is off the top of my head - check on Jon's web site to confirm.) Another way to do it is with tennis balls. Jon went to college for this stuff, and I write software for a living, so follow what Jon does


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## Patrick Bateman

I800C0LLECT said:


> Because time alignment doesn't fix location issues. I think doing some math and using the cone of confusion would be much more beneficial. However, keeping the midbass speakers within 1/4 wave length of each other(from first to last) in reference to crossover point should remove any issues with location as well.
> 
> Patrick, I LOVE the idea of going with the satellites. I've been eye-balling PC satellites for years to be used in my install. That's the heart of this site and I'm glad to see somebody bringing it back!!! Depending on your success I may go down that road myself. Since my speakers are already sealed under the seats I might revisit changing them to match yours. I may even add the i6SW's to my doors since they're sealed from the factory...
> 
> But for the sake of testing I may just steal this idea from you


I came close to pulling the trigger on them, but wound up buying different midbasses to replace the B&Cs instead.

I looked at a TON of different models, but wound up getting some Pyles. I feel a little silly replacing $300 in midbasses with $40 worth of midbasses, but I've generally been pretty happy with Pyle's products. The number one criteria by far was depth, and the Pyle midbasses are three tenths of an inch shallower than the 8NDL51.

I came pretty close to going full retard and buying sixteen MCM 55-1870s; the MCM drivers are shallow enough, and they might as well be free they're so cheap. Bottlehead uses the 55-1870 in their line array and it sounds great. I used the same driver in my first line array project, and while I didn't like the sound of the array, the driver performed great. It's as good as anything at twice the price, and I kinda like the idea of using stiff cones in bandpass enclosures, because woofers seem to behave better under high compression when their cones are particularly stiff.

Anyways, the current plan is to basically build a midbass enclosure that's virtually identical to the B&C bandpass enclosure, except about 80% the size, using a pair of Pyle PPA600s.

I also have an idea for the sub that I'll post shortly...


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## Patrick Bateman

mitchyz250f said:


> Most car doors speaker locations will be within the 5 degree angle needed to meet the requirements of cone of confusion.
> 
> I don't think it's the location either. 1/4 WL for 200Hz is around 15" which is less than distance from the floor of my car to the center of the door speakers.
> 
> Regarding time alignment everyone with 4 door speakers and a DSP would have the correct time alignment and should therefore have fabulous pounding midbass. But from my experience that is what happens.
> 
> I think it has to be something else.


The thing I notice with midbass arrays isn't so much that you get pounding midbass, it's that the pitch of the bass notes is much more distinct.









I've posted this measurement a million times, but here's a measurement of a sealed enclosure with an 8" woofer from my Honda accord. The thin lines are polar measurements; the thick line is the average.

*You can see that the average response is fairly flat* but the polars are just ****ing insane. In the midbass frequencies the response varies by over TWENTY DECIBELS.

That's just freaken nuts; our ears can perceive a difference of about 1-3dB, so swings of TWENTY dB are just terrible.

In a nutshell, when you tune with an RTA you can get a nice looking curve on the screen, but the midbass can sound godawful because the RTA can't pick up on these insane swings in the amplitude.

Midbass arrays clean this up. Once you clean it up, the pitch of bass notes sound more distinct. It's particularly noticeable on anything with a bass guitar.


----------



## Patrick Bateman

In this 1991 interview with Richard Clark, he explains on page 74 why an RTA won't cut it:

Richard Clark Interview - 1991 CA&E

This interview had a big impact on me; it was basically what got the gears turning in my head, twenty five years ago. Tom Danley also uses TEF.


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## danno14

Fun stuff!

have a listen to some Dean Peer when you have a chance.....Airborne is fun for midbass


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## danno14

Fun stuff!

have a listen to some Dean Peer when you have a chance.....Airborne is fun for midbass


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## mitchyz250f

Patrick what do you mean by pitch? Are you saying that sound is more "accurate' with a midbass array than with a single pair of woofers? How would the pitch/frequency change?


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## I800C0LLECT

Patrick Bateman said:


> I came close to pulling the trigger on them, but wound up buying different midbasses to replace the B&Cs instead.
> 
> I looked at a TON of different models, but wound up getting some Pyles. I feel a little silly replacing $300 in midbasses with $40 worth of midbasses, but I've generally been pretty happy with Pyle's products. The number one criteria by far was depth, and the Pyle midbasses are three tenths of an inch shallower than the 8NDL51.
> *
> I came pretty close to going full retard and buying sixteen MCM 55-1870s*; the MCM drivers are shallow enough, and they might as well be free they're so cheap. Bottlehead uses the 55-1870 in their line array and it sounds great. I used the same driver in my first line array project, and while I didn't like the sound of the array, the driver performed great. It's as good as anything at twice the price, and I kinda like the idea of using stiff cones in bandpass enclosures, because woofers seem to behave better under high compression when their cones are particularly stiff.
> 
> Anyways, the current plan is to basically build a midbass enclosure that's virtually identical to the B&C bandpass enclosure, except about 80% the size, using a pair of Pyle PPA600s.
> 
> I also have an idea for the sub that I'll post shortly...


Lol...I'm a huge fan of getting high end performance from low excursion with multiple drivers. I just can't get the balls to put the stuff in my car and deal with my wife's brf. I'm pretty sure that's what she'd tell everybody too...."robert went full retard..."


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## BP1Fanatic

Patrick Bateman said:


> In this 1991 interview with Richard Clark, he explains on page 74 why an RTA won't cut it:
> 
> Richard Clark Interview - 1991 CA&E
> 
> This interview had a big impact on me; it was basically what got the gears turning in my head, twenty five years ago. Tom Danley also uses TEF.


I remember having that magazine! Your midbass array goes against RC's minimal speaker principle.


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## pocket5s

Patrick Bateman said:


> In this 1991 interview with Richard Clark, he explains on page 74 why an RTA won't cut it:
> 
> Richard Clark Interview - 1991 CA&E
> 
> This interview had a big impact on me; it was basically what got the gears turning in my head, twenty five years ago. Tom Danley also uses TEF.


Mark Eldridge used to use a TEF. it now sits in his shop collecting dust. Sometimes he brings it out for his workshops/seminars as a gee-wiz thing, but no longer uses it during tuning.


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## Focused4door

Seeing the polars of the single 8" and the fact that four midbass with one in every door doesn't work as well as we might expect reminds me of the Harman white paper on multiple subs. Its for home audio and dealing with subwoofers, but midbass in a smaller automotive environment is a very similar problem.

We have identified two things that don't work very well, and one that does. What is the minimum number of drivers we need, and what are the best locations? Harman did this with Matlab simulations I believe, but that seems impractical for the automotive environment. Cars vary quite a bit relative to mostly rectangular rooms.


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## Patrick Bateman

pocket5s said:


> Mark Eldridge used to use a TEF. it now sits in his shop collecting dust. Sometimes he brings it out for his workshops/seminars as a gee-wiz thing, but no longer uses it during tuning.


Of course. In 2016 there are better options. In the 90s it was ahead of its time.


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## Focused4door

Patrick Bateman said:


> The thing I notice with midbass arrays isn't so much that you get pounding midbass, it's that the pitch of the bass notes is much more distinct.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I've posted this measurement a million times, but here's a measurement of a sealed enclosure with an 8" woofer from my Honda accord. The thin lines are polar measurements; the thick line is the average.
> 
> *You can see that the average response is fairly flat* but the polars are just ****ing insane. In the midbass frequencies the response varies by over TWENTY DECIBELS.
> 
> That's just freaken nuts; our ears can perceive a difference of about 1-3dB, so swings of TWENTY dB are just terrible.
> 
> In a nutshell, when you tune with an RTA you can get a nice looking curve on the screen, but the midbass can sound godawful because the RTA can't pick up on these insane swings in the amplitude.
> 
> Midbass arrays clean this up. Once you clean it up, the pitch of bass notes sound more distinct. It's particularly noticeable on anything with a bass guitar.


What are the different locations for the polars?

I reread the Harman multiple subwoofer paper again today, and a few things stood out.

The setup where the four subwoofers are 1/4 away from the side wall, and 1/4 away from the other wall works very well by their simulations. 

Going from four midbass one in each door to your array setup is a very similar looking setup. Seems like your speaker locations are very good.

The other thing that stood out is that two subwoofers in good locations was almost as good as four subwoofers. Are two midbass speakers close enough with a great location? What is that best location? 

How does a BMW with the underseat woofers measure?

It's tempting to get an MS-8 and a bunch of cheap cube speakers. The MS-8 would simplify the cabling/wiring, it's perfect amount of power for small speakers, and the time alignment would be quick and easy. It would be fairly quick to try multiple locations, and placing several of the cube speakers together could then replicate the door and kickpanel locations commonly used without other variables in the way.



BP1Fanatic said:


> I remember having that magazine! Your midbass array goes against RC's minimal speaker principle.


Pretty much everything in car audio is a huge compromise. In that time there was no $250-300 eight channel DSP with time alignment. The tradeoff with the DSP is complexity and cost and extra amplifier channels.

Cars still win competitions with minimal speakers to this day. Winning without a DSP seems highly unlikely.


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## BP1Fanatic

Is anyone winning world titles with 6 speakers?


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## pocket5s

BP1Fanatic said:


> Is anyone winning world titles with 6 speakers?


many are. one back to back winner in meca did it with 5 (two-way front with single sub). 6 to 8 is the most common, just depends on if they use a 2 or 3 way front and 1 or 2 subs.


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## Focused4door

pocket5s said:


> many are. one back to back winner in meca did it with 5 (two-way front with single sub). 6 to 8 is the most common, just depends on if they use a 2 or 3 way front and 1 or 2 subs.


7 speakers in the HAT car. https://www.youtube.com/watch?v=DPBJQ9OSG4g

More isn't always better, but there is more than one way to skin a cat. We can't ignore math science and physics in audio and expect good results, and what Patrick is trying to do with the midbass array makes sense and is backed by solid logic

Reading the Harman white paper again makes me think that he nailed the locations for the drivers, especially when working within the practical limitations of a car, and not cutting up dash and doors.


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## BP1Fanatic

Patrick is doing excellent work! It was strange for him to bring up the RC link referencing minimal speakers in the middle of his midbass array experiments.


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## Patrick Bateman

mitchyz250f said:


> Patrick what do you mean by pitch? Are you saying that sound is more "accurate' with a midbass array than with a single pair of woofers? How would the pitch/frequency change?


Without a doubt.

My favorite example of this phenomenon is when I heard the Magic Bus for the first time. Jon spent the first hour or so playing tracks that he'd selected, and then he gave me an opportunity to pick my own songs. All I listen to is EDM and hipster music, so I don't have many 'reference recording.' I put on 'Billie Jean' by Michael Jackson, because it was one of the few recordings in Jon's playlist that I was familiar with.

For the first 10-15 seconds of the recording, *I literally thought it was a cover of the song.* The song sounded so different in the bus, I thought that it was a newer recording of the song. And since Jackson was dead as a doornail, my brain immediately thought "I wonder who did this cover of 'Billie Jean', because this is obviously a cover of the original, this song sounds completely different."

Lo and behold, it wasn't different, the bass in The Bus is *that* revealing.









Going back to this measurement of my old Accord, *you can see that the response curve can vary by twenty decibels if you move your head six inches.*

And you can *also* see that the response swings are most severe in the midbass frequencies.

So...

*Why is this?*

The answer is fairly straightforward:

The length of a car interior is about 10'. Some will be longer, some shorter. 113hz is ten feet long. So *below* the Schroeder frequency a speaker is just going to pressurize the car, and that's why the response doesn't vary too much at bass frequencies. At low frequencies, the waves are so long, they don't even form, and since the waves don't even form, we FEEL the bass more than we hear it.

Above 1000hz, it's fairly easy to get some directivity with our speakers. For instance, if you're using a 6.5" midrange, that midrange will control directivity above 2000hz due to the size of the cone.

So...

That leaves us just THREE octaves where the sound is pretty much going EVERY direction. These octaves:

125hz - 250hz
250hz - 500hz
500hz - 1000hz









And you can see the issues in this polar measurement; the lower two octaves of the midbass are a freaken MESS when you use a single loudspeaker.



If you agree with all of that, then the trick is to come up with a solution. There are a TON of possible solutions; multiple midbasses is simply the one that I am using. Some others include:

1) dipole bass. John Kreskovsky explains how it solves the problem here : Dipole on axis and here : Dipole_modesA
There's a loooooong thread about multiple subs vs dipole subs over at diyaudio; Kreskovsky has posted in it quite a few times

2) cardioid bass. This one is trickier. At concerts it sounds AMAZING but it hasn't really caught on at home yet. Nobody has documented it better than Kimmo Saunista : Cardioid bass









3) Helmholtz traps. This is what Jon Whitledge does. They're all over the Bus; you can see them along the walls in the pic above.

4) end fire arrays

5) I forget what it's called, but there's an array type where you put the subs on one side of the room, and then you have subs on the *other* side of the room, and the subs on the opposite side of the room are designed to cancel out the wave arriving from the *opposite* side of the room.

6) If I'm not mistaken, some of the stuff than the MS-2 and the MS-8 does is based on these ideas. I haven't tried either, because I've generally found that programs designed to 'automatically' fix a room make a slight improvement in the bass, but frequently at the expense of the rest of the spectrum. And the solutions listed above just work SO MUCH BETTER, it's hard for me to get excited about 'automatic' solutions. Dipole in particular is just incredibly easy to implement, it's really difficult to screw up a dipole, It Just Works


----------



## Patrick Bateman

BP1Fanatic said:


> I remember having that magazine! Your midbass array goes against RC's minimal speaker principle.


On page 75, Richard Clark states that 'multiple sources radiating the same frequencies is one of the worst things you can do in a system. A basic understanding of time domain spectrometry will teach you this in a hurry.'

Here's the thing - *I don't disagree with Richard at all.*









In the Grand National, Richard has one set of drivers covering as much of the spectrum as humanly possible. He has a set of Altec compression drivers covering over five octaves.









I have a set of Synergy Horns covering the same range. And this type of setup has virtually been a constant in my projects; although I've messed around with many different geometries and driver combinations, nearly everything I've done has featured one speaker covering 500hz-20,000hz. When you get the crossover correct and you get the drivers close enough together, it virtually looks like one driver. I'd be willing to bet that I can reproduce a square wave with more accuracy that Clarke's horns can; when you push an Altec to such a wide bandwidth it's hard to keep the phase correct, because that wide bandwidth requires steep filters that introduce ringing. I can get away with shallower and more phase-accurate slopes because I have more displacement than the Altec does.

My subs are pretty boring, nothing to write home about there.

The midbasses *appear* to depart from Clarke's recommendations, but then again, they may not. Here's why:

In a perfect world, all of the bass would go ONE direction, then fade to black as soon as the note finished.

If only cars were a perfect environment 

If you look at the impulse response of a speaker in a car, it is a MESS. As mentioned in the last post, there's lots of ways to clean up the impulse response, and even get some measure of directivity at low frequencies. Bass waveguides are not practical, but dipoles cardioids and bass arrays ARE.

Even with a single midbass in a car, you're going to get a HUGE amount of reflections, because the sound is radiating in every direction. (This is not true of higher frequencies; they can be quite directional, even without waveguides.) So even if you have a single midbass, the reflections can frequently be louder than the original wavefront. Even worse, the reflected energy is delayed, which screws up the pitch of low frequencies, and masks the impact of instruments like drums.



TLDR : it's 2016 and we have ways to improve the impulse response of midbasses. One midbass would be ideal if the room was ideal, but the room ain't, so we gotta deal with it.
[/font]


----------



## Patrick Bateman

Here are my current waveguides. They sound awesome. Probably the best system I've ever made, even exceeding the 2009 project.




























Never one to leave well enough alone, I wanted to improve upon them.

First off, the current waveguides are horrendously ugly. While I could paint them and that would help a little bit, they look so ridiculous, I don't even want to explain what the hell is going on. For the past couple weeks I've been parking my car in the back of the parking lot just so I don't have to explain why there's a white and blue thing on my dash that looks like a bomb. These waveguides were actually designed for a different project, where I'd expected to put a proper baffle on them.

So... The new waveguides are a little bit prettier.

The big change in the new waveguides is that they're vertical instead of horizontal. The reason that I did this is that I've noticed that dipoles seem to image best with really REALLY narrow baffles.









10-15 years ago Siegfried Linkwitz made dipoles that look like this









And now they look like this.









So I'm moving the same direction.

The other big change is that these are dipole, not cardioid. For the most part, I'm doing this because of cosmetics. Cardioids are ugly. Another thing is that I've noticed that the super-analytical sound of cardioids takes a little getting used to. At first the sound was a bit odd, because it's hard to get used to a speaker that doesn't have much of a 'room' sound. At some point I'd like to demo this thing and I don't want the speaker to sound COMPLETELY different than everything else out there, just a little different and better.

But I might go back to cardioid, we'll see. It would be simple enough to go cardioid, just add some back chambers and fill them with fiberglass insulation.

Another potential advantage of dipole is that dipole radiation illuminates that back wall. This can add some ambience that can be pleasant. With the current set up, there's so little energy going into the windshield, some recordings can sound "small." (Again, this is a bit of a luxury problem, admittedly.)

Another change with the new setup is that it has the same radiation pattern across the entire bandwidth. This may be the most important change. One thing that I noticed with the current setup is that the treble measures well, but it can sound a bit 'off' compared to the midrange. I think what's happening is that the directivity pattern changes as you go from treble to midrange, and that change in directivity can make things sound a bit wrong, even if they measure right.









In the polar response of the current setup, you can see what I mean at 700hz and 2000hz. The change in directivity at 700hz is because cardioids radiate more to the back than the sides. At 2000hz the change is due to the transition from midrange to tweeter.

Clearly this is splitting hairs, because the performance is already really good. And I think it was a mistake to abandon the 2009 project so quickly; I had it running for all of a week or two before I trashed it and started all over again.

So with this new set of waveguides, I'm keeping the original waveguides completely intact. I am not re-using the waveguides or the crossover or the drivers, everything is new.

The new waveguides are using a Dayton RS75 as a dipole tweeter from 2000hz to 20000hz.
The new waveguides are using a pair of Tymphany TC7s as dipole midranges from 500hz to 2000hz.
As usual, it's a Synergy Horn.

The TC7s should be able to generate as much output as the TC6s in the current setup. (The current setup uses three, the new one uses two.)


----------



## Focused4door

Patrick Bateman said:


> 1) dipole bass. John Kreskovsky explains how it solves the problem here : Dipole on axis and here : Dipole_modesA
> There's a loooooong thread about multiple subs vs dipole subs over at diyaudio; Kreskovsky has posted in it quite a few times
> 
> *2) cardioid bass. This one is trickier. At concerts it sounds AMAZING but it hasn't really caught on at home yet. Nobody has documented it better than Kimmo Saunista : Cardioid bass*
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 3) Helmholtz traps. This is what Jon Whitledge does. They're all over the Bus; you can see them along the walls in the pic above.
> 
> 4) end fire arrays
> 
> *5) I forget what it's called, but there's an array type where you put the subs on one side of the room, and then you have subs on the *other* side of the room, and the subs on the opposite side of the room are designed to cancel out the wave arriving from the *opposite* side of the room.*
> 
> 6) If I'm not mistaken, some of the stuff than the MS-2 and the MS-8 does is based on these ideas. I haven't tried either, because I've generally found that programs designed to 'automatically' fix a room make a slight improvement in the bass, but frequently at the expense of the rest of the spectrum. And the solutions listed above just work SO MUCH BETTER, it's hard for me to get excited about 'automatic' solutions. Dipole in particular is just incredibly easy to implement, it's really difficult to screw up a dipole, It Just Works


2) I am pretty sure cardoid subwoofers don't work when placed against or near a wall which could potentially be a problem in a vehicle. Lots of software to simulate cardoid subwoofers though, so easy to verify. 

4) There was a member here who was doing an endfire on the top of the doors, but can't find the thread at the moment.

5) Double bass array, the waterfall plots look impressive on them. I contemplated doing a single bass array but the amount of bass trap you have to build its probably easier to do a double bass array. 

6) APL does some sort of power average based on multiple mic positions but don't think I have ever seen midbass polars of one. I know we have a few members who are using the APL, so maybe one could take some data.

I really like the idea of getting midbass out of the doors, but at the same time keep thinking my next vehicle is going to get the doors and dash chopped up to do whatever needs to be done. It's been a long time since I have cut up dash and doors, and for good reason but about back to that point again. I keep cars forever, so not as big of a deal.


----------



## Patrick Bateman

A member of the diyaudio forum mentioned that he didn't think dipoles or cardioids would work in a car because 'you need to get them away from the wall.'

This didn't make sense to me for a few reasons:

1) You can see the directivity of a dipole or a cardioid with the mic just inches away from the driver. In fact you can try this with your own two ears, take a 'naked' driver and hold the edge to your ears, it is noticeably quieter. (Due to the dipole null.)

2) companies like Gradient use dipoles and cardioids *specifically* because they work better in small rooms.


One of these days I'll have to try a dipole sub. Back in the day when I moved into my new house in Oregon, I set up a dipole sub in my bedroom. I didn't do a dipole because I wanted a dipole sub, I did a dipole because it was the easiest and fastest way to set up a subwoofer in my bedroom, and I basically didn't have time to build the type of subs that I normally do. (Horns.)

The irony was that the thing kicked ass. Loud, tight and massive. And the construction was so simple it was stupid. It was literally a bed-sized piece of plywood, with dual TC Sounds fifteens. Dipoles roll off at 12dB octave, but due to the massive displacement and power handling of the fifteens, I was able to EQ them flat.

The sub that replaced it was ten times as much work and sounded much worse. (The one that replaced it is here (Night of The Living Bassheads - diyAudio). Due to the fact it went down to ten hertz, it required much better construction than I used, and my SPL was severely limited by squeaks and creaks from my crummy construction.


----------



## Patrick Bateman

Hmmm now I'm tempted to see what those TC Sounds subs would do. They've been collecting dust in my garage for months. I originally intended to do a massive bandpass box with them in the trunk of the CX5, but the project went off the rails a few months ago because I got distracted by working on the mids and tweets.


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## Orion525iT

I tried out a simple cardioid today. I tested them at 400hz-20K and 600hz-20K. I tested three locations; kicks, dash (pointed forward), and dash (pointed to bounce of the door windows).

Kicks were pretty decent with some rainbowing and lightly lower stage. I also needed to attenuate the subs and midbass a bunch to keep levels matched.

dash (pointed forward). No attenuation needed on the other drivers. Great detail. Not sure about this arrangement. Listening fatigue was setting in.

dash (pointed towards the windows) This is the weird one. The idea was to use the cardioid pattern to bounce directly off the door glass to produce I phantom source. It worked pretty darn well. Very wide stage, lots of spaciousness. Center image was a bit thin and slightly amorphous; might be because of the distance to the glass vs wavelength at higher frequencies.











*facing forward*










*the bounce*


----------



## Orion525iT

Patrick Bateman said:


> A member of the diyaudio forum mentioned that he didn't think dipoles or cardioids would work in a car because 'you need to get them away from the wall.'
> 
> This didn't make sense to me for a few reasons:
> 
> 1) You can see the directivity of a dipole or a cardioid with the mic just inches away from the driver. In fact you can try this with your own two ears, take a 'naked' driver and hold the edge to your ears, it is noticeably quieter. (Due to the dipole null.)
> 
> 2) companies like Gradient use dipoles and cardioids *specifically* because they work better in small rooms.


Might have been me? I still think they are less them optimal when stuck very tightly against boundaries. Dipoles typically have a more narrow pattern than cardioid. But the trade-off is the backwave. If you look at the LX-mini. It's a dipole made to be used close to walls. It's a dipole, except that the stuffed tube behind it "eats" the back wave of the dipole. This is so you can use it very close to a back wall. What you end up with is a narrow dispersion cardioid. With that said, my recent experiments with a LX-mini inspired design holds promise.



Patrick Bateman said:


> One of these days I'll have to try a dipole sub. Back in the day when I moved into my new house in Oregon, I set up a dipole sub in my bedroom. I didn't do a dipole because I wanted a dipole sub, I did a dipole because it was the easiest and fastest way to set up a subwoofer in my bedroom, and I basically didn't have time to build the type of subs that I normally do. (Horns.)
> 
> The irony was that the thing kicked ass. Loud, tight and massive. And the construction was so simple it was stupid. It was literally a bed-sized piece of plywood, with dual TC Sounds fifteens. Dipoles roll off at 12dB octave, but due to the massive displacement and power handling of the fifteens, I was able to EQ them flat.


My best home sub was a dipole, and like you, more of an accident then anything else. I had built PPSL manifolds for my 8s, and on a whim I cut a slot in a 2.5ft x 3ft piece of MDF and screwed the manifold to that. Set the thing in the middle of the room about 10ft away with the slot firing toward my back. It was amazing. Tight and articulate.


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## Patrick Bateman

The frequency response on dipoles and cardioids is utterly hopeless without EQ. They're going to sound REALLY shouty without it.

Pictured above is the response of my RS75s, without EQ, and then with it.

Obviously this opens up a whole 'nother can of worms, which is whether you build and measure the speaker anechoically, then place it in the car, or put it in the car, and measure it. At the moment, I'm in the former camp. I basically build it in the garage, and then listen in the car, and then tweak the response a lil' bit.

These dipole things are really difficult to get right without EQ and a mic, definitely trickier than a plain ol' sealed box.


----------



## BP1Fanatic

Patrick Bateman said:


> Hmmm now I'm tempted to see what those TC Sounds subs would do. They've been collecting dust in my garage for months. I originally intended to do a massive bandpass box with them in the trunk of the CX5, but the project went off the rails a few months ago because I got distracted by working on the mids and tweets.


I say put em back on track and get that bassline humming!


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## thehatedguy

I have to ask...

How can you terminate the mouth of the horn properly and still have the cardoid response?


----------



## Patrick Bateman

thehatedguy said:


> I have to ask...
> 
> How can you terminate the mouth of the horn properly and still have the cardoid response?


Great question.

I'm super-sensitive to higher order modes, due to owning Gedlee Summas for six years. With the current waveguide, I noticed a bit of HOMs. Not a huge amount, but they were definitely there. I tried jamming the waveguide into the dash so that the top of the waveguide touched the windshield, which basically terminates the waveguide the same way that bolting an HLCD under the dash does:









^^ Similar to this, but firing straight forward

Pushing it against the class made most of the HOMs go away, (subjectively), but there's still a touch of it. I've been building clones of the Sausalito Audio Works lens for years, yet the last time I heard a Beolab 5 was in Portland eight years ago. So though I'd happily been building my own, *I hadn't heard the real deal in nearly a decade.* Even worse, a bunch of my lenses died on the vine, I basically lost interest and didn't listen to 'em much.

At CES this year I had a chance to hear one of the Beolab speakers with the SAW lens, and I *immediately* heard HOMs. Unmistakably there.

So my 'hunch' is that the rest of the HOMs in the current waveguide are due to the SAW lens in there. I could be wrong, but we'll know soon.


Another thing that I did with the new waveguide is that I made the coverage angle wider. Since HOMs are generated when you have a sharp edge, widening the waveguide should reduce the HOMs. (In this case, the 'sharp edge' is the edge of the waveguide; widening the waveguide gets you closer to a flat baffle.)


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## Patrick Bateman

Here's a pic of the current waveguide, to give you an idea of it's scale. It's not huge by any means, but it's not small either.




























The new one is definitely "small." Just big enough to hold the drivers, and no bigger.









I'm definitely taking some inspiration here from John Kreskovsky and Siegfried Linkwitz. (Did you know he used to work at the same place I work at? Ha, that trips me out.)




























I put a fair bit of effort into having a really smooth transition from the tweeter to the waveguide, to keep the HOMs to a minimum and also improve the frequency response.


----------



## mitchyz250f

Patrick-Lets see it in your car.


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## Patrick Bateman

mitchyz250f said:


> Patrick-Lets see it in your car.


Will do.

Right now there's a layer of fiberglass drying on it so I can't move it, and the other waveguide is nearly finished on the 3D printer.


----------



## Patrick Bateman

Here's the frequency response and distortion of the Dayton RS75 on the waveguide, with no EQ. There's a 2nd order highpass at 250hz to protect the driver from overexcursion.









Here's the frequency response and distortion of the RS75 with no enclosure whatsoever. (From my thread a couple of days ago: 

http://www.diymobileaudio.com/forum...-discussion/256098-best-cardioid-tweeter.html

I *think* that the overall level has gone up a bit, but it's hard to tell from the measurement because I didn't calibrate the SPL on either one. You'll notice that the distortion has gone *down* on the one with a waveguide.

Obviously, both of these require EQ, but that's the nature of the beast when you're doing dipoles.


----------



## Patrick Bateman

Here's the response of a single Tymphany TC7 midrange on the waveguide

















The two lines at the *bottom* of this measurement are the unfiltered frequency response of the Tymphany TC7 on the waveguide. One measurement is with one driver; the other is with two. The reason that the SPL doesn't go up is because I wire them in series. Basically I want to "pad" them down so that they don't overpower the RS75 tweeter.

You'll notice that the response of all three drivers is fairly similar; that's because they share a common baffle and they're all about 2-3" in diameter. To get full range response I'll require a crossover of course.









Here's the response and distortion of the Tymphany TC7 with no enclosure whatsoever. The response is more extended because I don't have a chamber in front of it. The chamber in front of the cone on a Unity or Synergy Horn is there to roll off the high frequencies. (Similar to a bandpass subwoofer.) Note that the distortion of the TC7 has dropped like a rock, thanks to that chamber. It's doing it's job.


----------



## Patrick Bateman

Here's the impedance curve of the midranges. An easy load, about 9ohms.









Here's the response and distortion of the midranges after I applied some filters. There's a high pass filter at 250hz to protect the midranges. There's a lowpass at 2500hz so that I can cross them over to the tweeter. Most importantly, there's a LOT of boost at 400hz to widen the bandwidth. I added twelve dB of boost(!) The woofers seem to be holding up alright; you can see in the graph that distortion is under control.

You can see why John K and Linkwitz use Seas and ScanSpeak; to widen the bandwidth of a dipole you have to apply a LOT of EQ and that's quite punishing on the voice coil. To put this in perspective, twelve dB of gain at 400hz is like raising the power level from 10watts to about 150 watts!


----------



## Patrick Bateman

Here's a polar measurement of the dual midranges on the waveguide. Yellow is on-axis, orange is 45 degrees off axis, red is 90 degrees off axis.









From three weeks ago, here's the midrange response of the waveguide currently sitting on my dash. *From the prior measurements, we can see that the cardioid appears to work better.* More details here : http://www.diymobileaudio.com/forum/3408122-post441.html

I'll still tinker with this thing, but there's a fairly good chance that I'll wind up adding some back chambers to it to convert it from a dipole to cardioid.

First I'll do some listening though; three weeks ago I definitely heard some 'magic' with the dipole.



Here's what I think is going on here:
A perfect dipole would have literally ZERO output off axis. No SPL whatsoever. We can't get a perfect dipole because our radiator isn't infinitely small. IE, if you had a driver that was 1" in diameter, it would (almost) act like a perfect dipole because it's so tiny. (And this is likely the reason that Linkwitz and John K have progressively shrunk their baffles.) Since there's a baffle there, we're going to get unequal pathlengths from the back side of the baffle to the front side. And it's those unequal pathlengths that contribute to the ragged frequency response between 1000hz and 2000hz.

In a cardioid, we still have output from the back, *but the output is attenuated by the fiberglass.* And I think that's why you see smoother curves from the cardioid, both ON and OFF axis.

At the lower frequencies in the measurement, BOTH devices are acting like a dipole. Basically the cardioid that's in my car doesn't have enough fiberglass to attenuate 500hz. (You'd need about 3" of it to have any real effect.)

Then again, our ears are funny things, and sometimes comb filtering is just plain inaudible.


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## Patrick Bateman

Here's the current waveguides in my car. They're really ugly.









Someone at "pakwheels.com" posted this pic of Gary's car and my old Accord. Gary's car is a good example of how to blend speakers into the dash seamlessly. My Mazda? Not so much lol









Here's the new waveguides mounted horizontally. I don't intend to mount them this way; response should be better vertically. Then again, with some DSP I could probably make it work horizontally too. I'd have to step up to a four channel DSP, at least.









Here's the waveguide mounted vertically. I drew a couple of red lines to visualize how I'd *like* to mount it. Basically use some aluminum or carbon fiber rods to move the pods away from the windshield. My thinking on this is that we'll get reflections off the windshield, but if we can get those reflections at least a millisecond away from the incident wave, the reflections should contribute some spaciousness to the sound instead of screwing up the incident response.









According to this graph, the precedence effect says that I'd have to delay the reflected energy by about 20dB.









My cardioids pulled this off; above 1500hz the rejection to the sides was over 15dB, which is way WAY higher than you'd get from a monopole.

So it's really looking like I'll do the following:

1) add some aluminum or carbon fiber rods to get the speakers about 6-12" away from the windshield
2) add some caps over the back of the drivers to turn them into cardoids
3) Probably put some felt on the A-Pillars to absorb some of the reflected energy.


----------



## Orion525iT

I probably missed it, but were the cardioid polars with eq?

In free space, every polar graph I have seen shows better polar attenuation with a dipole. This is not reflected in your measurements, which makes me think something else is in play. Is it simply due to the larger waveguide with cardioid?

Also, it just seems to me that any advantage a cardioid could offer in free space is mitigated greatly once you shove it into a corner where you are essentially dealing with less than 1/4 space. I would expect it to act much like a monopole in that you still have considerable wrap around of the wave front which will interact with near boundaries. With very close surfaces, you really need very good control and narrow beamwidth to get the most benefit. Of course pulling them away from the surfaces helps, but is this less intrusive (aesthetically) in the end?


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## Focused4door

Patrick Bateman said:


> Here's the waveguide mounted vertically. I drew a couple of red lines to visualize how I'd *like* to mount it. Basically use some aluminum or carbon fiber rods to move the pods away from the windshield. My thinking on this is that we'll get reflections off the windshield, but if we can get those reflections at least a millisecond away from the incident wave, the reflections should contribute some spaciousness to the sound instead of screwing up the incident response.




I hate to think what it would cost to have made, but something machined out of clear plastic would avoid having so much stuff in the way visually. Would probably distort pretty badly and may not hold up to uv well either.


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## Patrick Bateman

Orion525iT said:


> I probably missed it, but were the cardioid polars with eq?


I think it's earlier in the thread, I'll take a look shortly



Orion525iT said:


> In free space, every polar graph I have seen shows better polar attenuation with a dipole. This is not reflected in your measurements, which makes me think something else is in play. Is it simply due to the larger waveguide with cardioid?


Great observation. I was surprised by this also. I wonder if it's the waveguide? I did those measurements before fiberglassing it, and before damping it. It's ringing quite a bit.



Orion525iT said:


> Also, it just seems to me that any advantage a cardioid could offer in free space is mitigated greatly once you shove it into a corner where you are essentially dealing with less than 1/4 space. I would expect it to act much like a monopole in that you still have considerable wrap around of the wave front which will interact with near boundaries. With very close surfaces, you really need very good control and narrow beamwidth to get the most benefit. Of course pulling them away from the surfaces helps, but is this less intrusive (aesthetically) in the end?


Subjectively, the cardoids in my car have a lot less of the 'room sound.' In fact, there's so little that it's a bit of a luxury problem! I think I may need to add a little 'room sound' back into the mix because the cardioids are so dry.









If this speaker was a monopole, we'd have output getting directed towards the listener, towards the side window, towards the windshield, etc

If this speaker was a cardioid, most of the energy goes towards the listener. A fraction of the energy goes into the windshield and the side window and dash, but it's so little that it's mostly masked by the on-axis sound.

If this speaker was a dipole, the response would be similar to a cardioid, except there would be a lot more energy going into the windshield. At this point I don't know if that will sound like an acoustic mess, or if it will add some ambience to the sound that I'm experiencing already.


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## BP1Fanatic

I love this thread! There is so much education and eye candy going on that it's ridiculous!


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## SSSnake

> How can you terminate the mouth of the horn properly and still have the cardoid response?


You know the answer...

Patrick don't you think the delaminated strands entering into the "lens" of the mids are causing defraction? I was ALWAYS under the impression that problems/distortions at the throat of a horn were MUCH worse than problems at the mouth (reference pics in post #564).

I admire the tenacity.


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## Patrick Bateman

SSSnake said:


> You know the answer...
> 
> Patrick don't you think the delaminated strands entering into the "lens" of the mids are causing defraction? I was ALWAYS under the impression that problems/distortions at the throat of a horn were MUCH worse than problems at the mouth (reference pics in post #564).
> 
> I admire the tenacity.


Nah. The midrange frequencies are long enough that diffraction isn't much of a worry. For instance, the midranges on my waveguide cut off at 2000hz. That's seven inches long. At these lengths, the 'fins' in the phase plug are about as inconsequential as a pebble on the beach getting hit by a wave that's a foot tall.

Diffraction IS an issue at high frequencies, which is why we want a smooth surface for the waveguide, which is why I use a phase plug. Another benefit is that it gets the apparent source of the midranges closer to the tweeter, and the chamber in front of the mids reduces distortion.

Danley probably pioneered all of this, but now it's basically standard operating procedure:









EAW does it in their Anya speaker









NEXO does it









JBL does it


----------



## I800C0LLECT

So here's a thought...ever since the question was asked about why TA'd mid-bass in each door has a poor response...

I've been wondering how much those same speakers play a role in system response when left unpowered? Shouldn't they respond similar to a passive radiator? The thought came to mind when you stated you had an abundance of mid-bass. I thought maybe your OEMs in the doors would just pile onto what you installed.

Anyways, I'm still perplexed at the idea of that original question. I've always had decent mid-bass the more I add into the mix.


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## thehatedguy

They would as would every other speaker in the car that was not shorted as to keep the cones from moving.


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## thehatedguy

But I don't think they would effect things a great deal.

There is a whole lot of vibration happening in the interior already.


----------



## SSSnake

> Nah. The midrange frequencies are long enough that diffraction isn't much of a worry. For instance, the midranges on my waveguide cut off at 2000hz. That's seven inches long. At these lengths, the 'fins' in the phase plug are about as inconsequential as a pebble on the beach getting hit by a wave that's a foot tall.
> 
> Diffraction IS an issue at high frequencies, which is why we want a smooth surface for the waveguide, which is why I use a phase plug. Another benefit is that it gets the apparent source of the midranges closer to the tweeter, and the chamber in front of the mids reduces distortion.


I agree with your statements but the tweeter is using the waveguide as well. One of the reasons you keep the openings from the mid into the waveguide small is so that it does not cause issues with the tweet that is emitting into the same waveguide. The opening for the mid, circled in the attached pic, is so rough that it does not appear to actually perform much of the acoustic transformer function that it is intended for and appears that it would cause diffraction problems with the high frequencies emitted by the tweet as well. Do you have any measurements of the speakers in the waveguide but outside of the car and at fairly hi res? freq response, impulse response, and a polar plot of the freq response would be interesting. These won't explicitly show diffraction but they would likely provide some clues that diffraction is present.

To be frank I am having a tough time believing that the tangerine portion of the waveguide is doing much more than causing issues. As the flaws in the construction are nearly as large as some of the features, I am unsure what value the features contribute. I am also fairly sure the tangerine portion of the waveguide provides large enough discontinuities to the horn surface to cause the diffraction I was referring to earlier. If not then I am just missing something about how horns work. Which is quite possible but every horn I have constructed to date performed audibly better with a smooth horn surface. 

Not trying to nitpick or detract from your efforts as I find them very informative and thought provoking. So much so I may pop for a Taz 5 myself.


----------



## Patrick Bateman

SSSnake said:


> I agree with your statements but the tweeter is using the waveguide as well. One of the reasons you keep the openings from the mid into the waveguide small is so that it does not cause issues with the tweet that is emitting into the same waveguide. The opening for the mid, circled in the attached pic, is so rough that it does not appear to actually perform much of the acoustic transformer function that it is intended for and appears that it would cause diffraction problems with the high frequencies emitted by the tweet as well. Do you have any measurements of the speakers in the waveguide but outside of the car and at fairly hi res? freq response, impulse response, and a polar plot of the freq response would be interesting. These won't explicitly show diffraction but they would likely provide some clues that diffraction is present.
> 
> To be frank I am having a tough time believing that the tangerine portion of the waveguide is doing much more than causing issues. As the flaws in the construction are nearly as large as some of the features, I am unsure what value the features contribute. I am also fairly sure the tangerine portion of the waveguide provides large enough discontinuities to the horn surface to cause the diffraction I was referring to earlier. If not then I am just missing something about how horns work. Which is quite possible but every horn I have constructed to date performed audibly better with a smooth horn surface.
> 
> Not trying to nitpick or detract from your efforts as I find them very informative and thought provoking. So much so I may pop for a Taz 5 myself.


When you're making a Synergy Horn, you have to be careful about the effect of the ports.


















Here's an example of when Things Go Badly. This was my "Monster Massive" project from diyaudio. Basically I used a conventional horn profile with a Synergy Horn type concept, midranges bolted onto a conventional horn. *And I found out in a hurry why Danley uses constant directivity waveguides.* If the walls are too narrow, the energy from the tweeter goes right into the midrange cavities and creates a null. *The top measurement is the tweeter with no midrange taps; the bottom is the tweeter with the midranges bolted to the waveguide and taps drilled into the waveguide walls.*

I also found out from Art Welter that you have to be careful how you measure it; basically the tweeter will excite the midrange cones like they're a really efficient passive radiator. Imagine a 15" woofer with 60" of port and you get the general idea. That's probably a large part of why this setup worked so poorly.

















Here's the response of the RS75 completely "naked", no enclosure whatsoever.
Below it is a measurement of the midranges on the waveguide and the RS75 tweeter. There's no obvious null; I don't see any evidence that the tweeter is interacting with the midrange ports to any large degree.


A lot of this isn't about the midrange ports, but the angle of the waveguide. I know Art Welter would argue with me, but I've generally found that wider and shallow waveguides measure better than deep and narrow waveguides. I think that when you 'open up' the walls you lose efficiency but gain smoothness.









While the surface of the waveguide is certainly important, the bigger issue is the chamber in front of the mids. The tweeter will excite the air in that chamber, no different than blowing over the top of a coke bottle. IMHO, widening the walls lessens that effect; you basically have more of the energy going straight down the center, instead of exciting the mass of air trapped under the woofer cones. Reducing the area of the woofer ports will lessen that effect, but will cost you midrange output! Basically the bigger the ports are, the more midrange output you get, but the greater risk of generating HOMs and screwing up your tweeter response.


----------



## Patrick Bateman

I800C0LLECT said:


> So here's a thought...ever since the question was asked about why TA'd mid-bass in each door has a poor response...
> 
> I've been wondering how much those same speakers play a role in system response when left unpowered? Shouldn't they respond similar to a passive radiator? The thought came to mind when you stated you had an abundance of mid-bass. I thought maybe your OEMs in the doors would just pile onto what you installed.
> 
> Anyways, I'm still perplexed at the idea of that original question. I've always had decent mid-bass the more I add into the mix.


**** that's a good point

I should probably turn on the stock system and turn the volume down

As I understand it, the speakers won't act like a passive radiator if they're powered up?

Or are you supposed to short them out?

I know there's a 'best practices' for this. At audio shows you see a lot of companies demoing speakers with OTHER speakers in the room, and that's a bad idea for the reasons you pointed out.


----------



## Focused4door

I800C0LLECT said:


> *So here's a thought...ever since the question was asked about why TA'd mid-bass in each door has a poor response...*
> 
> I've been wondering how much those same speakers play a role in system response when left unpowered? Shouldn't they respond similar to a passive radiator? The thought came to mind when you stated you had an abundance of mid-bass. I thought maybe your OEMs in the doors would just pile onto what you installed.
> 
> Anyways, I'm still perplexed at the idea of that original question. I've always had decent mid-bass the more I add into the mix.


I think it's just a bad location. Read the Harman white paper on multiple sub locations, it's an interesting read and I think it's relevant. I think it's as simple as Patrick has found a better location (or locations) The midbass array is getting the increased output and smoother response as expected. I think it's worth experimenting, as there is likely the possibility of finding the better of the locations he is using and minimizing drivers and amplifier channels. Granted that might only hold true for his particular vehicle or maybe vehicle type, but think the location matters. 

I think the only way to know is to run a bunch of simulations like Harman did, which is much harder to do for an automotive environment, or run lots of measurements in different locations. I will likely do some experiments this summer, no way I will have time to do so before then. I also don't have appropriate drivers at the moment.

I also think there is the possibility that there is some directivivity going on, but Patrick didn't think there was. I think it might be worth simulating.

I don't think this is a passive radiator effect. Even with out shorting the driver, the motor adds some resistance to motion. I wouldn't think you would get much excursion out of them. 

If this is really the case, the stock system should be able to achieve great midbass response as well by exciting the non powered midbass array. If this is true, Patrick has discovered a huge breakthrough and we could add passive radiators throughout the vehicle and achieve great midbass without even powering them. I doubt that is the case though.

Me being completely wrong is certainly an option though.


----------



## Focused4door

Patrick Bateman said:


> **** that's a good point
> 
> I should probably turn on the stock system and turn the volume down
> 
> As I understand it, the speakers won't act like a passive radiator if they're powered up?
> 
> Or are you supposed to short them out?
> 
> I know there's a 'best practices' for this. At audio shows you see a lot of companies demoing speakers with OTHER speakers in the room, and that's a bad idea for the reasons you pointed out.


You should play the stock system with the midbass array turned off to see if that increases the midbass. If it does, you have discovered something really cool.

Shorting the drivers would work. The amplifier output impedance should be really low though, so turning it on with low volume likely works good enough.


----------



## Orion525iT

Focused4door said:


> I reread the Harman multiple subwoofer paper again today...
> 
> ... thing that stood out is that two subwoofers in good locations was almost as good as four subwoofers. Are two midbass speakers close enough with a great location? What is that best location?


I started a thread a few weeks back that introduced this idea with eccentrically located midbass. I was focused on trying to match and maximize ITD between left and right midbass, but I also theorized that it might add some of the benefits found in midbass arrays. I am still curious about this possibility.


----------



## mitchyz250f

Focused4door said:


> I think it's just a bad location. Read the Harman white paper on multiple sub locations, it's an interesting read and I think it's relevant.



Has this link been posted?


----------



## I800C0LLECT

Focused4door said:


> *I think it's just a bad location.* Read the Harman white paper on multiple sub locations, it's an interesting read and I think it's relevant. I think it's as simple as Patrick has found a better location (or locations) The midbass array is getting the increased output and smoother response as expected. I think it's worth experimenting, as there is likely the possibility of finding the better of the locations he is using and minimizing drivers and amplifier channels. Granted that might only hold true for his particular vehicle or maybe vehicle type, but think the location matters.
> 
> I think the only way to know is to run a bunch of simulations like Harman did, which is much harder to do for an automotive environment, or run lots of measurements in different locations. I will likely do some experiments this summer, no way I will have time to do so before then. I also don't have appropriate drivers at the moment.
> 
> I also think there is the possibility that there is some directivivity going on, but Patrick didn't think there was. I think it might be worth simulating.
> *
> I don't think this is a passive radiator effect. * Even with out shorting the driver, the motor adds some resistance to motion. I wouldn't think you would get much excursion out of them.
> 
> If this is really the case, the stock system should be able to achieve great midbass response as well by exciting the non powered midbass array. If this is true, Patrick has discovered a huge breakthrough and we could add passive radiators throughout the vehicle and achieve great midbass without even powering them. I doubt that is the case though.
> 
> Me being completely wrong is certainly an option though.



I only thought about the idea because below 100Hz you start to pressurize the vehicle. I do believe that the other poster was just dealing with bad locations and TA can't fix that.

Even if the mids were moving a fraction of a mm it's adding "something" to the system response. It may not be worth a bother. If it is benefecial...again, worth any effort adding more?


----------



## 1fishman

Focused4door said:


> I think it's just a bad location. Read the Harman white paper on multiple sub locations, it's an interesting read and I think it's relevant. I think it's as simple as Patrick has found a better location (or locations) The midbass array is getting the increased output and smoother response as expected. I think it's worth experimenting, as there is likely the possibility of finding the better of the locations he is using and minimizing drivers and amplifier channels. Granted that might only hold true for his particular vehicle or maybe vehicle type, but think the location matters.
> 
> I think the only way to know is to run a bunch of simulations like Harman did, which is much harder to do for an automotive environment, or run lots of measurements in different locations. I will likely do some experiments this summer, no way I will have time to do so before then. I also don't have appropriate drivers at the moment.
> 
> I also think there is the possibility that there is some directivivity going on, but Patrick didn't think there was. I think it might be worth simulating.
> 
> I don't think this is a passive radiator effect. Even with out shorting the driver, the motor adds some resistance to motion. I wouldn't think you would get much excursion out of them.
> 
> If this is really the case, the stock system should be able to achieve great midbass response as well by exciting the non powered midbass array. If this is true, Patrick has discovered a huge breakthrough and we could add passive radiators throughout the vehicle and achieve great midbass without even powering them. I doubt that is the case though.
> 
> Me being completely wrong is certainly an option though.


Is that Harman white paper on subwoofer available to read somewhere? The links i found to the Harman site say no longer available.


----------



## Patrick Bateman

Focused4door said:


> I think it's just a bad location. Read the Harman white paper on multiple sub locations, it's an interesting read and I think it's relevant. I think it's as simple as Patrick has found a better location (or locations) The midbass array is getting the increased output and smoother response as expected. I think it's worth experimenting, as there is likely the possibility of finding the better of the locations he is using and minimizing drivers and amplifier channels. Granted that might only hold true for his particular vehicle or maybe vehicle type, but think the location matters.
> 
> I think the only way to know is to run a bunch of simulations like Harman did, which is much harder to do for an automotive environment, or run lots of measurements in different locations. I will likely do some experiments this summer, no way I will have time to do so before then. I also don't have appropriate drivers at the moment.
> 
> I also think there is the possibility that there is some directivivity going on, but Patrick didn't think there was. I think it might be worth simulating.
> 
> I don't think this is a passive radiator effect. Even with out shorting the driver, the motor adds some resistance to motion. I wouldn't think you would get much excursion out of them.
> 
> If this is really the case, the stock system should be able to achieve great midbass response as well by exciting the non powered midbass array. If this is true, Patrick has discovered a huge breakthrough and we could add passive radiators throughout the vehicle and achieve great midbass without even powering them. I doubt that is the case though.
> 
> Me being completely wrong is certainly an option though.


The effect of multiple midbasses is definitely similar to what I experienced with multiple subs at home. Basically smoother sound, the notes are better defined and they don't 'stand out.' I was a bit nervous about using so many bandpass boxes, because bandpass boxes have a tendency to sound "one-note", but this is anything but.

If anything I'm curious how high you can take this; what if I did it all the way to 2000hz?


Cars have terrible acoustics, but we have two things in our favor:

1) We know exactly where our ears will be
2) DSP and amps have never been cheaper

In a conventional car stereo we put the speakers in the best location possible. Sometimes we try to put more sound in one direction with waveguides, arrays, dipoles, or cardioids. Those solutions can cut down on the reflected energy, they basically send more sound into a narrower beam.

*But what if you just put the speakers in semi-optimal locations and lined everything up via DSP?* It's the same idea as what we do with our midranges and midbasses already, just extending the concept to multiple drivers.

On the surface, it seems that this would be no different than what we're doing already with DSP. But there's ONE key difference : the sound that arrives at your ears would be in-phase, but the REFLECTIONS wouldn't.

Does that make sense?









For instance, you can use DSP and delay the sound from a single driver so that it arrives in-phase with the driver on the other side of the car. *This is how we get a rock solid center image.*








Now what if you did the exact same thing, but with an array? So the sound arriving at your ears is in-phase; but the reflected energy is not.

I wish I had time to draw a diagram; you'd basically create a converging wavefront.









It would do *electronically* what this array does *physically.* Bill Waslo used to run one of these; he said it sounded great, but you had your head in a vise because it only sounded good in one spot. But maybe in a car, that's what we want.

And note that you can't easily recreate this effect in a car physically, because the curvature varies for each side. (Because your distance to the left speaker is less than the right speaker.)

Well I guess you COULD do it physically, but it would look quite bizarre, the arrays would be asymmetric.

I'm reluctant to drop another $150 on four more amp channels and another miniDSP, but it's tempting, particularly since I got rid of my MiniDSP noise issues by running it on batteries.


----------



## Patrick Bateman

If my comment about the reflections being out of phase didn't make sense, let me elaborate a little bit.









With a flat or a diverging array, the sound going FORWARD spreads out. If the array is flat, *all the sound arrives at your ears in phase.* But the reflection does too; this can create a REALLY strong reflection off of the walls. Particularly since the walls are closer to the speaker than you are; you can have a situation where the reflection can be even louder than the speaker itself! This really destroys the imaging cues on the recording. I think this is a big part of why my cardioids sound so damn good, they just don't send much energy into the windshield.









Make that array converge, *and all of the forward energy is focused at a single point.* So the coherence and the SPL will be at their peak right where you focus it, which should be your ears. Same idea as a satellite dish.

You'll still get energy going backwards, that is unavoidable, but the energy going backwards isn't going to hit the wall at the same time. The drivers at the center of the array will send sound into the back wall first, and the drivers at the edge will illuminate the wall last. *The sound going backwards will not be 100% in phase.* And because the sound isn't 100% in phase, you should get quite a bit of destructive interference, which will basically reduce the reflected energy.

And you can curve an array electrically or physically.


----------



## Focused4door

Harman white paper for multiple subwoofers, looks like previous links for this are dead.

INNOVATION | Harman

Click on view more, then look for subwoofers
Then "optimum number and locations"
click download and it will download/open a pdf

I think Patrick has 6 total midbass, but I think he is _kind of sort of_ close the setup in figure 40, where the subs are 1/4 away from the walls.

I suspect that a center channel that plays low enough would also work well. 

Andy's car has a pair of 4" drivers in the center, and one of his comments was that it was to get the output low enough (I hope I am not misquoting). He also mentioned some possible phase issues, and I wonder if that was due to the center horizontal array in the center. 

The Harman paper figure 42 B setup is basically a center channel and a rear sub if you think about it, so it would help at around 80 Hz where both the center and sub were both playing (assuming you could get a center to play that low)

If you look at lots of songs in Audacity, most of the content is mono so losing some left right imaging might be a decent tradeoff in the midbass region. Unfortunately not many cars have much room in the center of the dash for large drivers.

Patrick,
One of your cardoid threads had the speaker aimed at the side window, and it looked interesting and possibly useful. One of your previous line array comments was something about the driver close to the windshield/pillar corner was to high/hot and had high reflections, or something like that. 

What if you moved the line array further inward, and then aimed the beam at the side window like you did with the cardoid?


----------



## Patrick Bateman

I think I've come over to the dark side, where the car is completely optimized for one seat.

Up until a few weeks ago I generally followed the Geddes approach, where the speakers are cross fired and the sweet spot is wide.

But I gotta admit I like the rock solid image you get when the car is optimized for exactly one point in space.









With the dipoles and the cardioids you'll notice that the output to the sides is *hugely* attenuated - about twenty decibels - but the output to the back is quite high. (The purple curve.)

Due to that, pointing them straight ahead seems like the best option, because that points the nulls at the side windows. If you cross-fire them the output from the rear, which is quite loud, is pointed straight at the corners of the dash, where it's amplified because corners do that.


----------



## mitchyz250f

Patrick Bateman said:


> Without a doubt.
> 
> My favorite example of this phenomenon is when I heard the Magic Bus for the first time. Jon spent the first hour or so playing tracks that he'd selected, and then he gave me an opportunity to pick my own songs. All I listen to is EDM and hipster music, so I don't have many 'reference recording.' I put on 'Billie Jean' by Michael Jackson, because it was one of the few recordings in Jon's playlist that I was familiar with.
> 
> For the first 10-15 seconds of the recording, *I literally thought it was a cover of the song.* The song sounded so different in the bus, I thought that it was a newer recording of the song. And since Jackson was dead as a doornail, my brain immediately thought "I wonder who did this cover of 'Billie Jean', because this is obviously a cover of the original, this song sounds completely different." My system was tuned by MS8 with the midbass turned down 2db.


Patrick I think it is interesting that you brought up Billy Jean because it is one of my favorite demo recordings. A lot of recording effort went into the first 10 seconds of that song. In most systems the first 5 drum beats sound very ordinary. On my system with only two 12" midbasses the first five drum beats of the song are incredibly powerful and savagely sharp. In fact at volumes that seem normal for the rest of the song this portion will cause pain. If this is what you are hearing with your midbass arrays or in the M bus I think it is mostly about efficiency and head room. In any standard 'midbassed' system this sound cannot be reproduced at any volume or and eq'ing cannot make it sound like it was intended.

https://www.gearslutz.com/board/bruce-swedien/84587-real-story-billie-jean.html

Still not sure what pitch means.


----------



## funkalicious

mitchyz250f said:


> ........ On my system with only two 12" midbasses the first five drum beats of the song are incredibly powerful and savagely sharp. In fact at volumes that seem normal for the rest of the song this portion will cause pain.


Ppfffttt. Lol. Yeah, it's "_only_" two 12" midbasses. Spoken like a true horn/high efficiency aficionado.


----------



## BP1Fanatic

Lol!


----------



## mitchyz250f

Not being a snob what I meant by 'only two 12" midbasses is that it is not an array.


----------



## funkalicious

mitchyz250f: No no no my friend. My humor was genuine and most definitely not meant in any negative way. I have 12" midbasses myself and am considering adding two more 8" in an array (two JBL 2206 and two JBL 2118) :laugh:! I don't want to derail Patrick's thread but just wanted there to be no misunderstanding . Trust me, it's all good.


----------



## Patrick Bateman

Here's a quick update on this project:









Up until a few weeks ago, this system consisted of cardioid Synergy Horns for the 5.5 octaves above 400hz, an array of midbasses for the two octaves from 100hz to 400hz, and a single bandpass sub.

















The midbass array was a smashing success, and it got me curious about whether you could do it with midranges. I posted a couple threads about it, and my takeaway was that you CAN use multiple midranges, but you need to line up the wavefronts. To me this was a bit of a breakthrough. It means I can have my cake and eat it too; I can use a small full range in the optimum location, and then I can reinforce the output of that driver by putting additional drivers somewhere else. *The key is that all the drivers are EQ'd to the same response shape and they arrive at the same time.* That's how you make them blend together.

With that knowledge in hand, I made a waveguide for the SB Acoustics 2.5" woofer.

Here's a review from Vance Dickason, author of the loudspeaker cookbook: Test Bench - SB Acoustics SB65WBAC25-4 2.5” full-range driver | audioXpress

In a nutshell: the tiny SB 2.5" woofer and waveguide will replace the big ol' Synergy Horn. There will be additional midranges in the car that will be time aligned and EQ'd to match the SB, but only in the midrange. (The SB will play all the way to 20khz.)









My 12" bandpass sub is being replaced with an Alpine SWS-15D4 in a tapped horn. Go big or stay home, right?  This is the biggest sub I've ever had in my car. Write-up is here: Maximum Bass for $1000 - Subwoofers / Enclosures - SMD Forum

The midbass array is great, but I think I'll replace the eight in the array with a 6.5". Simply to make it fit under the seat really. It sounds fine the way it is, it just doesn't fit.


----------



## BP1Fanatic

Are you posting the sub build pics here or SMD?


----------



## Patrick Bateman

BP1Fanatic said:


> Are you posting the sub build pics here or SMD?


Basically I'm stuck in Texas on the world's most boring assignment, and out of sheer boredom I tried to figure out how much bass I could make for $1000. As the thread moved along I ended up ordering a subwoofer, and next thing I know I blew my whole weekend building a sub 

So, yeah, the subwoofer build will be documented at SMD. But that wasn't intentional, when I started the thread I only planned on it being a "what if" type of thing, and next thing I know I'm busting out my credit card.

I really wish I got the sub finished yesterday, but I'm really taking my sweet time and trying to make the box as good as possible. Literally 75% of my sub projects have failed because I rushed the construction and leaky horns don't work.


----------



## BP1Fanatic

You know I had to setup an account there!


----------



## whisky22

Patrick, which cell phone charger are you using to power the miniDSP? I tried the cheap Dynex from Best Buy but there was lots of noise. 

whisky


----------



## Patrick Bateman

whisky22 said:


> Patrick, which cell phone charger are you using to power the miniDSP? I tried the cheap Dynex from Best Buy but there was lots of noise.
> 
> whisky


I'm using one of those cel phone battery packs

zero noise - the mini dsp isnt plugged into the car at all


----------



## Kevmoso

I freaking love that waveguide for the SB Acoustics 2.5!!! Just on looks alone it's awesome. What other midranges are you planning on using, how many and where will you place them? Have you taken measurements of that waveguide???


----------



## Patrick Bateman

Kevmoso said:


> I freaking love that waveguide for the SB Acoustics 2.5!!! Just on looks alone it's awesome. What other midranges are you planning on using, how many and where will you place them? Have you taken measurements of that waveguide???


Haven't measured anything, have mostly been focused on the subwoofer. Details here : Maximum Bass for $1000 - Page 2 - Subwoofers / Enclosures - SMD Forum









I sealed off the waveguides using T-88 epoxy. I tried tinting them black using graphite powder, but apparently didn't use enough

















The inside of the waveguide was kinda rough, after it had been 3D printed. I used a layer of mortite, then epoxy, to smooth things out. I'm not too thrilled about how 'lumpy' the mortite is, but once I applied the mortite I couldn't get it off. That **** REALLY sticks to plastic. Once I sand it and paint it black the 'lumpiness' should be less apparent.


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## danno14

Lol! Good luck sanding mortite..... It's good for some things though. What sort of epoxy did you use, as one of its "benefits" has been that many epoxies don't bond to it?


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## Lord Raven

Subscribed, I think I need to go through the entire thread to see the end result...

Edit: If there is any


----------



## rton20s

Lord Raven said:


> Subscribed, I think I need to go through the entire thread to see the end result...
> 
> Edit: If there is any


This is a PB thread. The end result is, "I've moved on to... Check out my new thread..."


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## gijoe

rton20s said:


> This is a PB thread. The end result is, "I've moved on to... Check out my new thread..."


Haha, and I'm not even mad about that.


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## douggiestyle

I looked on craigslist and didn't see your sub on there anymore. Too bad... with you being so close to me (my folks still live in SD) talking shop would have been worth the price of admission. And I drive a CX-5 as well.


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## Lord Raven

LOL Exactly what I was hoping for  If he does all this R&D on his home audio, he might just discover something new rather than imitating home audio in car environment...


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## Patrick Bateman

douggiestyle said:


> I looked on craigslist and didn't see your sub on there anymore. Too bad... with you being so close to me (my folks still live in SD) talking shop would have been worth the price of admission. And I drive a CX-5 as well.


I look at my email about twice a year, but I always follow my threads, so if you want to hear the TH-Mini clone, or just talk shop, just let me know. Best way to do that is just make a post indicating that I have mail.

At the moment I'm working out of state so I'm only around on weekends.


----------



## Patrick Bateman

On Friday I managed to get most of the system hooked up.

I still have a lot of work to do on the crossover, but at least it's making music.









Here's a gated measurement of the system in my car. I set the EQ curve using my phone, my ears, and an RTA app.

Some random observations:
1) I wish the sub digged a little lower, but I designed it for the maximum possible output without upgrading my electrical system. It's a six cubic foot tapped horn with an Alpine SWS-15D4. Details here : Maximum Bass for $1000 - Page 4 - Subwoofers / Enclosures - SMD Forum
2) There are no crossovers on any of the drivers, just the subwoofer. So forgive the rise in the midbass; that's caused by the much higher efficiency of the B&C midbasses I'm using.
3) The midbass arrays aren't wired up yet; I'm only using the B&Cs for midbass at the moment.

The SB Acoustics waveguides don't have the pinpoint imaging of the dipole Synergy horns. But they're much much smaller and much much simpler. There's also a "thinness" that I notice with dipoles and cardioids, I think it's caused by the change in radiation patterns as you move from the midrange to the midbass. My homage to the Linkwitz LX-Mini had the same problem. Basically it imaged like crazy, but it was hard to "fix" the transition from the cardioid tweeter to the monopole midbass.

I'm not traveling for work this week, so hopefully I can tame the midbasses and make a proper xover for the SB Acoustics waveguides.


----------



## BP1Fanatic

Install pics!


----------



## Orion525iT

Patrick Bateman said:


> 3) The midbass arrays aren't wired up yet; I'm only using the B&Cs for midbass at the moment.


Do you think you will still run the arrays? Out of curiosity, where did you tune the B&Cs? I modeled some of those for ****s, and they do an excellent job between 80-280hz in a tiny bandpass box (~6 liters total box volume).


----------



## mitchyz250f

Patrick I have been thinking about using a point source in the windshield/dash cornersas Gary is investigating. 

We know that placing a speaker in the corner of the dash is like basically like placing the speaker in a horn. In that circumstance we try to get the edges of the speakers radiating surface as close to the windshield/dash as possible to reduce reflections. But in the case of a point source or coaxial the tweeter is relatively far from the windshield and dash. Would this cause problems? Have you run simulations in horn response.

What works so will in the home environment may not work on a car dash.


----------



## Patrick Bateman

rton20s said:


> This is a PB thread. The end result is, "I've moved on to... Check out my new thread..."


Totally. I already have some new midranges printing as we speak. (See thread "it'll end in tears")


----------



## Patrick Bateman

BP1Fanatic said:


> Install pics!











SB Acoustics fullrange loaded in a Sausalito Audio Works lens that I designed and printed, covering 500hz to 20khz









3D cutaway of my bandpass midbasses









bandpass midbasses in the car. There's one on each side under the seat, a B&C 8NDL51 about a foot behind that in the passenger footwell, and a sealed 3.5" midbass under the dash. Six midbasses total, three per side, wired series parallel so the 8" midbass gets twice as much power.


















the amplifier is in the mouth of the horn









measured response of tapped horn in my garage (not in the car)


----------



## Patrick Bateman

Orion525iT said:


> Do you think you will still run the arrays? Out of curiosity, where did you tune the B&Cs? I modeled some of those for ****s, and they do an excellent job between 80-280hz in a tiny bandpass box (~6 liters total box volume).


Yeah the midbass arrays are my favorite part of the whole setup. They sound great. 

The SB Acoustics midranges sound pretty clean, but they can't get as loud as I'd like.

The tapped horn is doing it's job, but I found that my output was severely limited by my ****ty wiring, basically I have an 800 watt amp that's getting choked out by my wiring.


----------



## Patrick Bateman

mitchyz250f said:


> Patrick I have been thinking about using a point source in the windshield/dash cornersas Gary is investigating.
> 
> We know that placing a speaker in the corner of the dash is like basically like placing the speaker in a horn. In that circumstance we try to get the edges of the speakers radiating surface as close to the windshield/dash as possible to reduce reflections. But in the case of a point source or coaxial the tweeter is relatively far from the windshield and dash. Would this cause problems? Have you run simulations in horn response.
> 
> What works so will in the home environment may not work on a car dash.


The really difficult thing about using coaxes at the throat of a horn is that you want the driver at the throat to be as small as possible.

With a 1" driver you can get gain and directivity control all the way up to 13,500hz. (Because 13,500hz is one inch long.) When you start using throats that are larger and larger, you lose the gain and directivity above a certain point. For instance, if you use a 3" driver, your gain and your directivity drops down to 4,500hz. Go down to a 5" driver, and now you lose gain above 2700hz.









That's why the Danley SM60F uses a fairly complex phase plug, along with a coaxial driver.

The reason that I've never gone the route of the Danley SM60F in the car is that the motor gets in the way. Basically you can't put the driver as far back as you'd like, because the motor of the driver gets in the way.

If you were willing to sacrifice the top two octaves I definitely think you could horn load a neodymium 3" driver and gets some fairly outrageous output. With the right driver you might even get away with a 5" driver.

The trick to making this work is to come up with some type of a phase plug so that the throat is smaller than the driver.










Here's the phase plug of my current horns, designed for an AuraSound Whisper. I'm taking a 2" driver and squeezing it's output through a 1" hole.









Here's an Aurasound Whisper, note that the phase plug is a mirror image of the driver cone.

The next challenge, which is a bit of an art, is figuring out the compression ratio. I'm using a ratio of four to one, but that might be too high. If it is, I'll probably bore out the throat using a 1.25" drill bit to reduce the compression.

A lot of this is trial and error


----------



## mitchyz250f

Patrick in the configuration that Gary is using on his C230 (speakers on the dash) if you were to reduce the size of the horn throat you would also be increasing the distance on the horn throat from the windshield which will cause unwanted reflection and a suck out a the 1/4 wave cone to windshield distance. Is this correct? Is there a way to do this wo creating new issues?


----------



## Patrick Bateman

mitchyz250f said:


> Patrick in the configuration that Gary is using on his C230 (speakers on the dash) if you were to reduce the size of the horn throat you would also be increasing the distance on the horn throat from the windshield which will cause unwanted reflection and a suck out a the 1/4 wave cone to windshield distance. Is this correct? Is there a way to do this wo creating new issues?


Yep. You basically have three options:

1) Use a driver that's so small that you can push it all of the way into the corners of the dash

2) Use a larger driver and live with the fact that the curvature is going to be parabolic for part of the radiation.

3) Try to figure out some way to put the speakers beyond the edge of the windshield, like when Mark Eldridge put speakers up near the headlights of the car.


----------



## mitchyz250f

Patrick a cone speaker with a horn in the center would work on a dash correct. Such as this Beyma, Urei and JBL Control would work. This is one of the patent for the JBL Control.

Patent US8130994 - Waveguide - Google Patents

BTW is the foam on the Urei for deffraction? Do you know anything about this foam density, name...?


----------



## Patrick Bateman

mitchyz250f said:


> Patrick a cone speaker with a horn in the center would work on a dash correct. Such as this Beyma, Urei and JBL Control would work. This is one of the patent for the JBL Control.
> 
> Patent US8130994 - Waveguide - Google Patents
> 
> BTW is the foam on the Urei for deffraction? Do you know anything about this foam density, name...?


All of my latest tinkering seems to indicate that you want a really really diffractionless enclosure, especially at high frequencies.

For instance, check out the post here, and note how gorgeous those polars look:

http://www.diymobileaudio.com/forum/4368042-post60.html



















The problem with 95% of the coaxials is that there's just too much diffraction. For instance, here's the published frequency response of the B&C coaxial.

















Compare the frequency response of the KEF LS50 to the response of the B&C coax. And note how much better it is?









To demonstrate how critical diffraction is, compare the response of this speaker above with the KEF LS50. The speaker above is something I built using a $10 Tymphany full range and a $20 SB65. The total cost for the contraption is under $50 and it's noticeably 'flatter' than the LS50. The reason that this is possible is that it's a full range; it's really difficult to get a woofer and tweeter to play nice when there's any sharp edges nearby.










Note how Kef has gone to a herculean lengths to smooth out the face of their speakers


----------



## Patrick Bateman

Encourage by the results from 'diffractionless' enclosures, I decided to resurrect this project.


















Those 3D printed blue satellites work ridiculously well. But my 3D printer is busted at the moment. So I tried to get 'in the ballpark' using wood. 

Another nice thing about wood is that the new enclosure is noticeably better damped than the 3D printed enclosure. But the 3D printed enclosure looks a million times better.


----------



## Patrick Bateman

I am a dummy. It never occurred to me until a minute ago. But the solution is obvious:










Buy a set of Kef satellites and replace the drivers. Here's why:

1) it gets me a diffractionless enclosure with virtually no effort
2) I won't have to wait DAYS for my (now broken) 3D printer to print the enclosure
3) they're cheap and ubiquitous. 
4) Look how ****ty my wood enclosure looks, for comparison's sake. And keep in mind that this enclosure will likely be sitting on the dash of the car :O

So... Will the SB Acoustics SB65 fit?


----------



## Patrick Bateman

Here's some measurements. I'm trying to figure out what the best option is for a speaker that covers about 250Hz to 20,000Hz.

















Here's the frequency response, distortion, and polar response of a Tymphany TC7 in a 3D printed egg. As noted before, the great results were completely accidental. But at the moment, this $10 speaker seems to be the 'gold standard' here.

















Here's the frequency response, distortion, and polar response of the satellite from the KEF KHT1005.2 speakers. The KEF has a lot of added complexity over my 'blue eggs', but my speaker demonstrates why sometimes K.I.S.S. is the way to go. The Kef speaker has a two-way crossover, and it's a coaxial design. Yet the blue eggs exceed the Kefs in distortion and smoothness. The KEF isn't BAD by any means, but the blue egg is simpler, cheaper, and performs better. The Tymphany TC9 is an absolute steal.

But, again, the KEF isn't bad at all, it's just unnecessarily complex. It would be really interesting to see what the KEF would sound like with some help from MiniDSP. Basically filter out that rise in the upper treble. The KEF sounds 'bright' but not harsh. It's basically a good speaker that needs a little TLC to be truly great. 

Newegg used to sell the entire set - with a powered sub(!) - for $200. Quite a deal.

















Here's the frequency response, distortion, and polar response of the SB Acoustics SB65 in that wooden enclosure pictured in the top of this post. That wooded enclosure was an attempt by yours truly to replicate the performance of my 3D printed 'egg', but without 3D printing. 

IMHO, the performance is CLOSE, but the 'blue egg' is better, and the blue egg looks a million times more polished. With a coat of paint, I could live with the blue egg on the dash of my car. The same cannot be said of that wood enclosure.

At this point, 90% of you are probably wondering why I don't just use the blue eggs and 'call it a day.'

Here's why:

_If you look at the distortion graph of the SB Acoustics SB65, you'll notice that it's a little bit cleaner than the Tymphany TC9._ Also note that I'm using a decent amount of horn loading on the SB65 in that wood enclosure; the SB65 is horn loaded down to about 1500Hz. You can see the difference in the graphs of the two; the SB65 is about 6dB louder than the blue egg. Admittedly, this horn loading leads to a 'forward' midrange; in the measurement of the SB65 you'll notice that there's a broad rise in the midrange. *But that can be smoothed out with EQ, and when it is, we'll have a midrange with really REALLY low distortion.* We're talking Scanspeak levels of performance or better. Even in it's current state, the SB Acoustics SB65 enclosure has 3rd harmonic distortion lowered by 30dB at 2000Hz. Compare that to the TC9, where it's about 3dB louder. Naturally, that's a small difference, but I think I can 'widen the gap' between the two, with a little bit more horn loading. (Not a lot.)

But I really need to get my 3D printer back online. That wood box ain't gonna cut it.


----------



## Patrick Bateman

I'm really stuck between a rock and a hard place at the moment.

I am loving the results that I am getting with 3D printed enclosures.
But my 3D printer just keeps ****ting the bed, day after day after day.

Here's what happened on Saturday:

I'd spent the entire workweek looking forward to the day that I could sit down, and crank out a 3d printed enclosure for my car. I literally bounded out of bed in the morning, excited to get to work on this.

I wound up sitting in front of the computer for about twelve straight hours. I wound up making three different designs, each better than the last. If anyone wonders why my psuedonym is "Patrick Bateman", it's because I get REALLY ocd when it comes to this stuff. I can work on a project for twenty hours straight, no breaks. My wife calls it "mad scientist mode."

So I finally had a design ready to print by 10pm on Saturday. And then I spent the next four hours battling my 3D printer. The first print failed inside of 30 minutes.

I spent another hour "babysitting" the 3D printer. What I mean by this is literally watching the printer print, and making small adjustments to (hopefully) insure a successful print.

I managed to get a whopping four hours of sleep, and on Sunday I woke up to this:



















*There's nothing more satisfying than spending twenty hours working on something that fails miserably.*

I'm not quite ready to throw the printer in the trash, but I'm definitely getting there.

Just in case anyone thinks this is an isolated incident, here's some of the other 3d printed disasters that I've made in the past month. I've basically wasted all of my free time making 3D printed spaghetti.




























The ones pictured above don't look quite as bad, but they're still virtually useless. I'd considered cutting them in half and then gluing them back together, but at these sizes, the tolerances are just too tight. Even a 'glitch' of a couple millimeters means that the driver won't fit in the enclosure. Particularly since I 3D print the screw holes, everything needs to line up.


----------



## Patrick Bateman

I've generally held a negative view of line arrays. This is for a couple reasons:









1) A lot of line arrays that I've heard basically sound like a louder more dynamic version of the speakers in a TV. And that's because a lot of line arrays are cost-constrained, and due to this, they're using drivers that cost less than five bucks. So the array basically sounds like a really loud version of an inexpensive driver.









The use of high quality drivers definitely improves the quality of a line array, but they still didn't "grab" me. Not saying they were bad, they just didn't seem to be competitive with comparably priced speakers.









At CES I had an opportunity to hear the new CBT speakers. *While they weren't the best speaker at CES, they are very very good.* And the CBTs do something very interesting for car audio:

The soundstage of the CBTs basically doesn't move. It's quite a weird phenomenon; if you walk to the left of the CBTs, the soundstage stays in the center.

The closest thing to this phenomenon that I've experienced is the Danley Synergy Horns. I've told this story a million times: when I had the Danley SH-50s in my house, our daughter actually asked if they were turned on. And she was sitting three feet from them. In other words, the soundstage of the Danley SH-50s is so solid, she literally couldn't tell if there was sound coming out of the loudspeakers, or from somewhere else. It's eerie. 

The CBTs aren't quite at that level of soundstaging freakiness, but they're very good. And, obviously, it's a lot more practical to throw an array in the car than a SH-50. (I literally bought a new SUV to replace my sedan, just to get the SH50s into my house. They're THAT big.)









One thing that's kept me from doing CBTs in the car is that the cabinet is quite difficult. My woodworking skills are terrible, and though I've desperately tried to 3D print one of these, my printer just isn't cutting it these days.

The author of hornresp added an enhancement to his software for me, and over the last month that's enabled me to tinker with some things to get some of that "CBT magic" without building a curved cabinet. If you're interested in how I did that, read this:

An Improved Array - Page 6 - diyAudio









I'd always known that it was possible to make a CBT that's straight, not curved, as JBL sells straight CBTs, as pictured above.


















Now that I know how to make a line array that's physically "straight" but generates a curved wavefront, I've started to build one.

My line array uses five drivers:
1) there are four AuraSound Whispers
2) and one SB Acoustics SB65 in the center

My plan is to build the array, and then try it in various locations in the car. Here are the locations I'm going to try:

1) horizontally across the dash
2) horizontally under the dash, in the same spot as where you'd put a HLCD
3) vertically in the kick panel
4) horizontally under the dash, all the way at the firewall
5) possibly vertically on the dash, if it will fit. 

I'm hoping that it will work well in the same location as an HLCD, that's my preferred location for a box this big. Picture something like this, but an array:










This is what it would look like on the dash:








If you want to read about that project, it's here : http://www.diymobileaudio.com/forum/3008450-post350.html
That project fizzled out because I used $2 drivers, and it had that 'giant clock radio' type of sound that's endemic to a lot of cheap arrays.


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## Patrick Bateman

Here's a quick explanation of why the line array is "do-able" now:









In a conventional "straight array", the sound is tightly confined into a narrow beam, particularly at high frequency.









If you've ever heard one of the shorter line arrays, you may have noticed this. If you move your head above or below the line, the treble just disappears.









If your array is mounted horizontally, like an HLCD, that narrow 'beam' is going to be a problem. Basically the driver won't hear the passenger-side speaker properly, and vice versa. Even EQ can't fix this, because the response curve outside of the 'beam' is very poor.

So...

You want to widen that beam.

Easiest way to widen the beam, by far, is to curve the array. It's the reason that prosound arrays are shaped like a "J"









But it looks like shading the array will widen the beam too. "Shading" an array is the process of reducing the voltage to the elements on the edges of the array. The Keele CBT does this. The pic above shows how the beam widens with shading. And note that the overall shape of the wavefront is much better.









I am going to use "log shading." This is a new shading technique. From the sims, it doesn't appear to work quite as well as conventional shading. But it offers much higher output and it is simpler to implement.

Altec Lansing patented this : https://www.google.com/patents/US7260228

But since I'm not selling these, I can use it.

BTW, if anyone reading this is into horns, the dude that patented log shading is also the dude who wrote this:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.536.5361&rep=rep1&type=pdf

There seems to be a pattern here, of horn dudes going over to arrays. Don Keele was a horn guy, he's doing CBT arrays now. Charlie Hughes was a horn guy, he's doing log shaded arrays for Altec Lansing now.


----------



## subterFUSE

Charlie Hughes was my instructor at my SysTune training in October.


Sent from my iPhone using Tapatalk


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## Patrick Bateman

As noted a couple weeks ago, I've found myself between a rock and a hard place:

My printer has been consistently failing, but my handmade enclosures look terrible. It seemed like a no-win situation.

*I think I may have come up with a novel solution.*

Here's my solution:









Everyone here has seen a conventional line array. Basically we take a pile of drivers and we put them in a line. By doing that, we get higher power handling, directivity control, potentially improved dynamics, etc etc. There's a lot to like about arrays.









I've tried arrays in my car, but the arrays always end up dominating the entire dash. Or taking over the kick panels. Plus, I have a hard time making them look acceptable.

















Over at diyaudio, I stumbled across an interesting array called a "Costas Array."

This is an odd looking array, and the way that it works may not be immediately obvious. Here's what's going on in the Costas array:

In a conventional line array, we have a series of drivers arranged in a line, and the distance is (approximately) equidistant. We can vary the shape of the line to create various wavefront shapes, but the idea is pretty simple; a pile of small drivers work together to behave like one big driver.

The Costas Array works the exact same way *except their positions on the X axis are not constant.









The net effect is that you wind up with a radiation pattern that's similar to a flat radiator, like the BG planars.

Easiest way to visualize this is if you took a NEO 10, and you masked off part of the diaphragm, it will still work. The upper limit of the array will suffer, but you'll still have tons of output and very narrow directivity.



So...

The idea that I have is something like the Costas array, but in the car:

A series of approximately four midrange drivers, each located equidistant from the listeners on each side. By keeping the distance to the listener equal, we'll raise the output level and the dynamics. (When compared to a single driver.) But by NOT having the drivers located along the same X or Y axis, the array should become very very directional. Basically we'll hear the speakers clearly, but the reflections off of the car will be minimized.










An easy way to visualize this is if you had four midranges, all located at *exactly* the same depth. But the vertical and the horizontal location varies. Those drivers are going to sum very strongly at the driver's position (because the distance is identical for all four) but they will not sum well off-axis (because the off-axis distances vary.)














































Here's some pics of one of the four midranges I'll be using for this setup. It's basically designed to go as far in the corners of the dash as possible. The midrange is an SB Acoustics SB65





* my inspiration for the Costas array came from here : http://hannover-hardcore.de/infinity_classics/!!!/Dokumentation Quasikoax Prototyp.pdf

*


----------



## rton20s

Interesting. So where do you plan to place the other 2 drivers (or 3, if there isn't one in the opposite dash corner) within the cabin? 

Will on/off axis orientation matter much with your use of wave guides?


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## BP1Fanatic

I love how you continue to experiment for the ultimate setup!


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## Patrick Bateman

rton20s said:


> Interesting. So where do you plan to place the other 2 drivers (or 3, if there isn't one in the opposite dash corner) within the cabin?
> 
> Will on/off axis orientation matter much with your use of wave guides?












Here's what I'm thinking:

1) The heart of the stage is those SB65s, in their own sealed enclosure with a waveguide. I put a lot of effort into blending them into the windshield, to reduce diffraction, basically do all I can to make them "one with the windshield." *The SB65s will run from about 200Hz to 20,000Hz*

2) I'll put another midrange right UNDERNEATH the SB65, in the stock speaker location. So the other midrange fires UP and into the corner

3) I'll put another midrange under the dash. I'll get out a tape measure and insure it's exactly the same pathlength as the speakers on the dash

4) The fourth driver is the wildcard. I'm kinda leaning towards putting it BEHIND me. But if that doesn't work I'll figure something out.



I intend to run one of the drivers full range, and the other three will be lowpassed. So it will basically be a "two and a half way", if you count the sub.


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## Orion525iT

I messed with arrays quite a bit in the car. The best arrangement was horizontal under the dash much like a traditional horn. The biggest issue, was the low stage, I could not resolve to my liking. Horizontal at the firewall didn't work at all. Vertical in the kick panel was super sensitive to head position. I didn't try on top of the dash mainly because of the visual cues 

Another interesting aspect is that it didn't take much of an array to get a lot of directivity. Maybe because you are positioned so near field?

I also did blended pods in the corner but with a single 2". They worked very well. But again visual cues in addition to a lack of output.


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## solacedagony

With both the egg and the wooden waveguide thing, are the top and bottom steeper than the left and right? Was it a particular function you were trying to fabricate in each direction or just testing at this point?

I came up with idea on how to make a sphere out of wood that I was going to try this coming weekend. But if you're saying that a sphere with a waveguide is even better then I'll attempt that instead.


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## mitchyz250f

Orion525iT said:


> I also did blended pods in the corner but with a single 2". They worked very well. But again visual cues in addition to a lack of output.


I've been intrigued with the small midrange dash setup. Did you ever consider using a high output midrange like a GB25?


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## fredswain

Back in the early 90's, I'm going to say in the 92-94 time frame, we were installing 8 Infinity emit tweeters in line arrays under the dash. There were 4 per side lined up end to end. These were the old rectangular tweeters. We used pvc pipe for mounts and then covered the whole thing with grille cloth. The installs looked a lot like horns. The results were interesting to say the least. The sound stage was actually high even though these were only tweeters. When I say high, I mean really high, like mid windshield, even though the mids were in the doors. What was really weird about them though was that the height wasn't stable with frequency. That's not that unexpected since so much energy was coming out of the doors but there were certain tracks where a singer sounded like they were on the sun visor over your head and then sometimes at your knees. I've never heard a sound stage height change that drastically before. Those planar ribbons were very directional so the way we had them placed sideways, you really didn't get much width from the sound stage. It went from a-pillar to around halfway across the dash and then fell in height. We tried angling them inwards and later on tried line arrays with conventional tweeters and small cone speakers. I don't remember but I think we tried up to 3-1/2's. The idea was fun to play with but ultimately a flop. I have no desire to ever play with the concept ever again.


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## BP1Fanatic

Lol!


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## Patrick Bateman

solacedagony said:


> With both the egg and the wooden waveguide thing, are the top and bottom steeper than the left and right? Was it a particular function you were trying to fabricate in each direction or just testing at this point?
> 
> I came up with idea on how to make a sphere out of wood that I was going to try this coming weekend. But if you're saying that a sphere with a waveguide is even better then I'll attempt that instead.


Yes, you want to vary all of the dimensions if at all possible. Here's why:

The sound is going to wrap around the enclosure.
If the enclosure is a perfect sphere, when the sound wraps around the enclosure it's going to create peaks when the wavefronts are in-phase, and dips when the wavefronts aren't.

So varying the height, width and depth will reduce the amplitude of these peaks and dips. 

I've always wondered why people worry about the golden ratio *inside* of their enclosures when the real issue is *outside.*

But note that spherical enclosures still sound pretty awesome; making them in the golden ratio just makes them even better.


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## Patrick Bateman

mitchyz250f said:


> I've been intrigued with the small midrange dash setup. Did you ever consider using a high output midrange like a GB25?


I'm pretty cheap; I rarely spend more than $20 on a driver. But let's see how the SB65 ($28) compares to the GB25 ($200)

















Here they are









Here's how the two compare, in a half litre sealed box. Each is powered with 50 watts into their respective impedances.









Here's how the excursion looks


TBH, I'd expected that they'd perform just about identically. I've tried a TON of these small drivers, and all of them are really close in performance. I personally like the SB65 because it behaves a lot like the Thiel full range drivers that Mic Wallace used to run. Basically the fabric dust cap 'decouples' at high frequencies, which makes the SB65 almost behave like a woofer *and* a tweeter.

But you can see in the sims, the AudioFrog is capable of about 3-4dB more output at the same power.

I'm a little stumped on how this is possible. The obvious way to do it would be to reduce the mass of the cone. But the SB65 actually has lower mass.



In summary: The SB Acoustics SB65 is quite extraordinary; there are very few drivers that can reach up to 20KHz, but also DOWN to 200Hz. It looks like the AudioFrog GB25 can do it too, and even offers additional output, due to it's higher efficiency bandwidth product.



















If anyone wants to tinker with this, here's the Hornresp models

Here's Erin's review of the GB25 : http://medleysmusings.com/afgb25/
Vance Dickason, author of the Loudspeaker Design Cookbook, reviewed the SB Acoustics SB65 here: http://www.audioxpress.com/article/Test-Bench-SB-Acoustics-SB65WBAC25-4-2-5-full-range-driver


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## rton20s

With the database that I have been building for a couple of years now, I can pretty quickly do comparisons of quite a few driver specs and FR graphs (when available). Admittedly, my database is limited. But, it does contain quite a large selection of popular raw drivers as well as some car audio branded drivers where information was available.

Below you can see how the SB65 and GB25 stack up. Not doubt, the SB65 is a great driver for the price. Not as cheap as it once was, but it still seems like a great deal at $28/ea. So, what differentiates the $200 GB25 from the inexpensive SB65? First and foremost Andy has said from the very beginning that the GB25 has been designed as a midrange driver for three way applications. The SB65 on the other hand is marketed as a wide band or extended range driver. For some of the answers, take a look at the data below.

*Driver Specs*









*Frequency Graphs (Corrected for Scale)*









Going down the line, the first thing you'll notice is the disparity in sensitivity. Out of the gate the SB65 gives up more than 3 dB to the GB25. 

Inductance in both drivers is quite low, with the slight advantage going to the GB25. 

Qes, Qms and Qts are strikingly similar between the two. 

The lower Vas on the GB25 could be an advantage if you plan to use them in small sealed pods. 

The GB25 has a stiffer suspension and a heavier cone (by more than 1/3). 

Then we get into what I consider a couple of the largest advantages of the GB25, Xmax and cone area. 

In my database of drivers only one other 2"-2.75" driver matches the Xmax of the the GB25 at 4mm and that is the Sundown SA-2.75FR. (I've owned and used the Sundown, and I wouldn't even put it in the same ball park, but it can certainly get loud for its size.) Even looking at the 3" and 4" driver in my database, there are only two other drivers that match or exceed that 4mm figure. And while I freely admit that Xmax likely isn't a concern for a mid/wideband driver, if accurate, it can give us some idea of how a driver will perform once power is applied. 

Moving into cone area, this is another spot where the GB25 has a significant advantage over other drivers of similar size. At 20 cm^2 of cone area, the SB65 is pretty typical for drivers in this 2"-2.75" range. At 26 cm^2, the cone area of the GB25 has a distinct advantage over any other driver in that range. The 26 cm^2 cone area is more consistent with what you would see in a smaller 3" driver. 

We would also be remiss to ignore the quality, durability and installation/integration options of the drivers. I don't think anyone could argue that the GB25 is the better built driver. From the aluminum basket (rather than polymer) to the screw terminals (rather than spade). And of course, there is all of the installation accessories that are included with the Audiofrogs.

Now, do all of these differences justify a 700%+ cost increase? That would be entirely up to the end user, their application, installation and budget. Is there another driver somewhere between the two in price and similar in size that will give you everything that the GB25 has at a much better price? If there is, I haven't seen it.


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## brumledb

rton20s said:


> Going down the line, the first thing you'll notice is the disparity in sensitivity. Out of the gate the SB65 gives up more than 3 dB to the GB25.
> 
> Inductance in both drivers is quite low, with the slight advantage going to the GB25.
> 
> Qes, Qms and Qts are strikingly similar between the two.
> 
> The lower Vas on the GB25 could be an advantage if you plan to use them in small sealed pods.
> 
> The GB25 has a stiffer suspension and a heavier cone (by more than 1/3).
> 
> Then we get into what I consider a couple of the largest advantages of the GB25, Xmax and cone area.
> 
> In my database of drivers only one other 2"-2.75" driver matches the Xmax of the the GB25 at 4mm and that is the Sundown SA-2.75FR. (I've owned and used the Sundown, and I wouldn't even put it in the same ball park, but it can certainly get loud for its size.) Even looking at the 3" and 4" driver in my database, there are only two other drivers that match or exceed that 4mm figure. And while I freely admit that Xmax likely isn't a concern for a mid/wideband driver, if accurate, it can give us some idea of how a driver will perform once power is applied.
> 
> Moving into cone area, this is another spot where the GB25 has a significant advantage over other drivers of similar size. At 20 cm^2 of cone area, the SB65 is pretty typical for drivers in this 2"-2.75" range. At 26 cm^2, the cone area of the GB25 has a distinct advantage over any other driver in that range. The 26 cm^2 cone area is more consistent with what you would see in a smaller 3" driver.
> 
> We would also be remiss to ignore the quality, durability and installation/integration options of the drivers. I don't think anyone could argue that the GB25 is the better built driver. From the aluminum basket (rather than polymer) to the screw terminals (rather than spade). And of course, there is all of the installation accessories that are included with the Audiofrogs.
> 
> Now, do all of these differences justify a 700%+ cost increase? That would be entirely up to the end user, their application, installation and budget. Is there another driver somewhere between the two in price and similar in size that will give you everything that the GB25 has at a much better price? If there is, I haven't seen it.



How does the Wavecor FR070WA01 compare with these other 2" drivers (assuming you already have it easily accessible in your database)?



Sent from my iPhone using Tapatalk


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## rton20s

brumledb said:


> How does the Wavecor FR070WA01 compare with these other 2" drivers (assuming you already have it easily accessible in your database)?
> 
> Sent from my iPhone using Tapatalk


Not only in my database, but I actually own a pair. I have not had a chance to listen to them though. I am not sure if the price listed for the Wavecor is currently accurate. 

*Driver Specs*









In comparing the data, we can see that sensitivity of the Wavecor is closer to the Audiofrog, but Fs is closer to the SB and that inductance is nice and low, falling right between the SB65 and GB25. 

Qts is a little lower on the FR070 compared to the others while Vas is slightly higher than the SB65. 

You'll see that the suspension is softer (Cms) while the cone is lighter (Mms). Xmax on my table is estimated based on the formula of VC Height (7mm) - Gap Height (3mm) / 2 = 2mm. (Take a look at Vance Dickason's tests in Voicecoil for the SB65 and FR070 drivers for more detailed information here.)

And while the Wavecor is shortest on Xmax, it does have a bit more cone area than the SB Acoustics. This isn't enough to match the displacement though. The SB65 has 50% of the displacement and the FR070 has 40% of the displacement of the GB25. 

Looking at the testing done on these drivers, it would also appear that the Wavecor probably has the highest distortion of the bunch. Not that it is horrible. 

Another thing to consider is that when placed in a 0.2l enclosure (300 Hz BW2 HPF), the SB65 and FR070 are going to have similar output when driven to Xmax. The Wavecor takes about 50W to get there and the SB takes about 75W. The GB25 doesn't hit Xmax until North of 400W! That would give it 10 dB more output. Since this is an unlikely scenario, if you gave it a similar 75W, you're back to about a 3 dB gain. Bottom line, if you want to play one of these drivers low AND give them power for output, the GB25 is the only one that can really handle it. 

Bump your crossover up and keep your power levels reasonable (<150W) and output between the GB25 and FR070 become very similar while the SB65 will lag behind by about 3 dB.

*Frequency Graphs (Corrected for Scale)*









I am fully aware that this is very difficult to read with three drivers overlaid. Especially since this image includes Erin's measurements of the GB25 with off-axis plots.

For reference...

Wavecor: On (purple) - 15 (green) - 30 (yellow) - 45 (red) - 60 (blue)
(From left, highest line on the graph, starts smooth in purple)

SB Acoustics: On (blue) - 30 (green) - 60 (red)
(From left, starts jagged multi-color line)

Audiofrog: On (black) - 15 (red) - 30 (blue) - 60 (aqua-green)
(From left, starts smooth in black)


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## Patrick Bateman

Someone really needs to throw a pair of the AudioFrogs on a horn.

At this point, the SB65 *appears* to be the 'king of the hill' when it comes to horn loading small full-range drivers.

People have had success with drivers from TangBand, AuraSound, and Peerless, but the SB65 is just a little bit better. Mostly because the SB65 has that 'decoupling' dust cap that provides output beyond 20khz.

But the additional power handling and displacement of the AudioFrog leads me to think that the GB25 could knock the SB65 off it's throne.

As you observed, I wish I knew of something that was more than $28 but less than $200. The only thing I can think of is the ScanSpeak 4", but that's too big. I want something right around 2-3".


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## rton20s

Believe it or not, I would be curious how the Wavecor SW070WA01 would stack up. Yes, it is a "subwoofer." However, based on the specs and the FR graphs, I would be curious how it compares. I'll skip the specs, but here is the FR graph overlay. I imagine that distortion could be an issue here, but I haven't seen any independent testing of the SW070WA01. These currently run about $78 shipped each from Solen in Canada.


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## Patrick Bateman

Here's a pic of what my waveguides look like, at the moment. The ones I'm running are basically identical to this, but bigger.









Here's the published response of the speaker, the SB Acoustics SB65









Here's the frequnecy response and distortion of my SB65s in my waveguides.
You'll notice there's a gradual rise in the midrange.
This is normal. The reason that this happens is that waveguides 'focus' the sound into a smaller angle. IE, a speaker that's flat on a baffle will have a rising response, particularly at low frequency, because the waveguide is constraining the output to a narrower angle.

The "trick" is to design the waveguide in such a way that the response shape is smooth.









Here's the same speaker, but with EQ to flatten out the 'hump' that comes with waveguides.
I hate to 'pat myself on the back,' but *this is ridiculously good performance.* You're looking at six octaves of bandwidth from a single driver. And though it's true that lots of speakers can cover six octaves, there are very few that can also offer high output and directivity control.

This is very very cool.


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## BP1Fanatic

Can we get a full dash shot?


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## Patrick Bateman

These SB Acoustics drivers are so good, it just occurred to me that you could probably do an entire system with just four drivers. Here's how:

1) You take the SB65, stick it on a waveguide like mine, but add a first order high pass around 500hz. That will knock down that rise in distortion you see in the pic above

2) 500hz is twenty seven inches long. That means that we need to put the woofers within nine inches or so to keep them in-phase.

That gives you quite a bit of leeway. You could put a ten inch woofer under the dash, maybe even in the doors. (I think my stock door speakers are eights.)

If you were willing to cut into the firewall, you could do twelves.

Long story short, I think you could conceivably do a rull-range system with four drivers. It would be a two-way, with the SB65 covering 500Hz - 20,000Hz. It's true that the SB65 can play all the way down to 200Hz. The idea here is to limit it's bandwidth so you can apply more power. The AudioFrogs would work even better I think.


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## rton20s

Fitting a 10" up under a dash and within 9" could present quite a challenge. Perhaps looking at something slightly smaller with low inductance and reasonably long throw? There are some fairly priced 8" models out there (and even some 6"-7") that could fit your bill. I am thinking Tang Band W8, Dayton HO and even the SB SB23. 

I look forward to seeing what you come up with next.


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## douggiestyle

PB: Stock front drivers are 8". I'm running SLS8 in the doors and Founteks in the dash. It's OK but certainly not ideal. I love the waveguide idea but I'd need it to be better integrated with the dash for aesthetics reasons (not all of us are mad scientists!)


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## Patrick Bateman

douggiestyle said:


> PB: Stock front drivers are 8". I'm running SLS8 in the doors and Founteks in the dash. It's OK but certainly not ideal. I love the waveguide idea but I'd need it to be better integrated with the dash for aesthetics reasons (not all of us are mad scientists!)


You're referring to a CX5, right?

I was running my 'stock' system yesterday and noticed I can make the rear view mirror vibrate with the stock drivers. There's quite a lot of cone area. Not sure if the rear doors are the same size.


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## Patrick Bateman

Patrick Bateman said:


> Here's a couple pictures showing the back chamber for the woofers (a 2" PVC pipe) and the woofers I'll be using (Gento 2")
> 
> 
> 
> 
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This horizontal array design didn't work out so well, because it had a REALLY narrow beamwidth and the treble sounded like a clock radio.

A potential solution may be here: An Improved Array - Page 16 - diyAudio

That link is basically a "twist" on a Bessel array. But it's well suited to putting a tweeter in the array, which should provide some 'sparkle' that an array of paper cone midranges can't achieve.


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## GEM592

I admit I love your posts PB, they are part of the reason I continue to hang around.

My .02 is simply that I don't like all that high end output so close to the glass. And, I know you're trying to work with the glass, and that's kind of the point. But still, I have to submit that I have just two mids pretty low in the doors, off axis, they sound great, are highly tunable/responsive, etc, and I just don't get it.


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## Elgrosso

PB, I'm sure you have tried but can't remember the post, but why didn’t you go vertical array in the pillar?
That’s something I wanted to try, still have 12 Peerless TC6FC02 and my old 8x12 for that.


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## GreatLaBroski

Elgrosso said:


> PB, I'm sure you have tried but can't remember the post, but why didn’t you go vertical array in the pillar?
> That’s something I wanted to try, still have 12 Peerless TC6FC02 and my old 8x12 for that.


I really like the idea of that.


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## Patrick Bateman

GEM592 said:


> I admit I love your posts PB, they are part of the reason I continue to hang around.
> 
> My .02 is simply that I don't like all that high end output so close to the glass. And, I know you're trying to work with the glass, and that's kind of the point. But still, I have to submit that I have just two mids pretty low in the doors, off axis, they sound great, are highly tunable/responsive, etc, and I just don't get it.


I go back and forth on this one. When I have speakers up on the dash, I like how the soundstage is at the height of the dash.

With speakers UNDER the dash, the midrange and treble sounds "smoother", I think because the carpet keeps the amount of reflected energy down. The soundstage is noticeably deeper, because pathlengths are longer. I find that the soundstage is more believable when I can't see the speakers.

But the soundstage is definitely lower.


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## Patrick Bateman

Elgrosso said:


> PB, I'm sure you have tried but can't remember the post, but why didn’t you go vertical array in the pillar?
> That’s something I wanted to try, still have 12 Peerless TC6FC02 and my old 8x12 for that.


I don't do it because you'd need a ton of DSP to align the wavefronts.

A straight array sucks when it's mounted horizontally, but there are tons of array types that DO work horizontally:

CBT

log shaded

Bessel

All the Bessel variants

"conventionally" shaded

Another cool thing about CBT-ish type designs is that they seem to sound good in either orientation. 

I have a CBT-ish thing on my desk that I listen to for about 40 hours every week, and though I designed it to be listened to vertically, I flipped it horizontally because the treble measured a little bit better that way.


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## Patrick Bateman

Here's what I listen to on my desk, at the moment. This might be an interesting option for a dash mount, basically remove the wooded part of the waveguide and just jam it into the corners of the dash. My efforts linked in the post from yesterday were an attempt to add some 'sparkle' to this array.

Above 10khz, it's a little dull, but everywhere else it sounds great.


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## Elgrosso

GreatLaBroski said:


> I really like the idea of that.


&



Patrick Bateman said:


> I don't do it because you'd need a ton of DSP to align the wavefronts.
> 
> A straight array sucks when it's mounted horizontally, but there are tons of array types that DO work horizontally:
> 
> CBT
> 
> log shaded
> 
> Bessel
> 
> All the Bessel variants
> 
> "conventionally" shaded
> 
> Another cool thing about CBT-ish type designs is that they seem to sound good in either orientation.
> 
> I have a CBT-ish thing on my desk that I listen to for about 40 hours every week, and though I designed it to be listened to vertically, I flipped it horizontally because the treble measured a little bit better that way.


Yeah it could be fun, trying to optimize with enough channels and 2/3 micro amps, TA, power and coupling.
I think I got the idea from one of your threads, when I removed my 8x12 I thought hell why not trying that before selling it? (well it's been quite some time now )

But I did try, quickly zip tied all together as a test on only one channel, must have some measurements somewhere. Of course without individual TA and with the acute angle of my pillar they pushed everything into my chest.
If I remember I could only fit 5 of them, and they were still protruding too much.

And after my test I found this little driver that might be even better, less output but so thin I could fit 8 or 10 per side and still get OEM look: https://www.parts-express.com/peerl...37mm-aluminum-cone-transducer-4-ohm--264-1560
But with a break up to manage.


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## Focused4door

Patrick Bateman said:


> I go back and forth on this one. When I have speakers up on the dash, I like how the soundstage is at the height of the dash.
> 
> With speakers UNDER the dash, the midrange and treble sounds "smoother", I think because the carpet keeps the amount of reflected energy down. The soundstage is noticeably deeper, because pathlengths are longer. I find that the soundstage is more believable when I can't see the speakers.
> 
> But the soundstage is definitely lower.



If I were going to go under dash, it would be pretty tempting to buy the replacement parts for the three way JBL VTX, midranges, horn and compression driver and saw it in half to get it lower in height for under dash mounting.


That or just DIY it using a 3D print


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## JCsAudio

You may want to look at the Celestion AN2775 2-3/4” full range driver. See attached picture of this little gem’s FR curve in REW. These are installed in the dash of my Mazda CX-5 shown with and without EQ. The FR in red is without EQ and there are no HP or LP filters applied when measuring this. It sounds amazing to me! Currently testing this driver HP @ 500 Hz 24 db LR to 20k and another tune HP at 1500 Hz 12 db LR to 20k. Haven’t decided which tune I like best yet. This driver was designed to be used in a line array but it’s also on the pricier side at $36 each at the time of purchase. 

Also this FR curve is 30+ degrees off axis. In fact it looks similar to the FR curve listed on Parts Express where I found it.

https://youtu.be/OkUgGYxBtgo


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## Elgrosso

V8toilet said:


> You may want to look at the Celestion AN2775 2-3/4” full range driver. See attached picture of this little gem’s FR curve in REW. These are installed in the dash of my Mazda CX-5 shown with and without EQ. The FR in red is without EQ and there are no HP or LP filters applied when measuring this. It sounds amazing to me! Currently testing this driver HP @ 500 Hz 24 db LR to 20k and another tune HP at 1500 Hz 12 db LR to 20k. Haven’t decided which tune I like best yet. This driver was designed to be used in a line array but it’s also on the pricier side at $36 each at the time of purchase.
> 
> Also this FR curve is 30+ degrees off axis. In fact it looks similar to the FR curve listed on Parts Express where I found it.
> 
> https://youtu.be/OkUgGYxBtgo


Don’t know if it’s for me too, but yes it looks really good, flat etc
But too deep to fit discreetly in my case.
Thought about the bmr, but same issue.


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