# Creating The Perfect Soundstage



## Patrick Bateman

Last week I finished a tapped horn for my car, so now I need a front stage.

Thought I'd blog how I'm going to do it, in case there's anyone else who's interested.

In my opinion, the best way to get a good stage in a car is using waveguides. I have personally tried conventional drivers in every location, as well as horn loaded compression drivers. A carefully designed waveguide seems to work the best.

So that's what I'm going to do.

Getting a solid image at home isn't rocket science, just point your speakers at your head and be sure each side measures the same across the whole spectrum.

But it's a lot trickier in the car, because you're listening off-axis.

At home I use waveguides too, and they image quite well because their response is consistent on AND off axis.

Here's a pic of what I'm talking about. It's kinda small, if anyone wants the full sized files, I can email them to you. (Can't post anything over 800 pixels wide...)

This is a Geddes style waveguide, set up in the recommended manner:









This is an Old School constant directivity horn. Performance is similar; the big difference is that it uses diffraction to cover the whole stage equally. And diffraction sounds terrible.










This is what it would sound like if we took some Geddes-style waveguides and threw them up on the dash. Which is basically what I did in 2006.










And here's the same concept perfected. By widening the angle of the waveguide, we can get identical response for the passenger AND the driver. The key is to adjust the angle of the waveguide's mouth AND to adjust how it's aimed.










Image Dynamics and USD Audio sell waveguides that you can stick under the dash. But I've found that putting waveguides ON the dash solves a lot of problems. You don't get a reflection off the kneecaps and the steering wheel. More importantly, the windshield extends the waveguide all the way to the ceiling if you mount it properly.


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## Patrick Bateman

I'm interested in using a ring radiator instead of a compression driver this time around. I saw some measurements online that showed excellent directivity when a ring radiator is mounted on a waveguide.

Here's a pic comparing the world-class directivity of a Gedlee Summa versus a ring radiator. Note the Summa completely embarasses the Vifa on a flat baffle:










But once you put the Vifa in a waveguide, it starts to look very good:


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## tspence73

:surprised:


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## thehatedguy

I'm still wanting molds.


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## cvjoint

Are you doing this just to get a two seater sound stage LR output equal? I see that the whole exercise is to equalize amplitude unless there are other things I'm missing. If that is so than why is your output dropping 6db/meter, waveguide design? You must care a bunch about your passanger and or they he/she really likes car audio lol


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## drtool

What car is this going into?


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## TREETOP

I'm tuning in for this.


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## shadowfactory

I will be watching this with great interest.


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## dbiegel

Interesting stuff. I was following your threads on other forums when you were experimenting with the windshield corner loaded ring radiator compression drivers (I think they were BMS 4540nd's) and thought it was awesome. I take it you weren't fully content with the results -- why? Geddes' theories and posts are what pushed me to try a ring radiator compression driver with horns in my car. So far I'm having mixed results, but my horns are just thrown in temporarily, and they're just horns of course, not custom waveguides. Kudos to you for pioneering the way with this in a car. I'm looking forward to seeing how it turns out!

BTW -- have you had any success with Geddes' anti-HOM foam plug techniques in a car? I'm using a small piece of the fish filter foam he recommends (30 PPI pu) in the throat at the moment and it doesn't seem to have any effect as far as I can hear or measure.


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## br85

Whoa. I too am doing an XT-25 based dash-top waveguide using the windscreen anddash to continue the mouth (I personally think that tweeter will work well because they have no dedicated "surround" and the propagation is much more planar than most other dome tweeters which have an awkward not-quite spherical-but-not-so-well-aligned-planar propagation)

My reasons were not so much to get the ultimate soundstage, but to enable me to play the bastards a bit below 2khz (where the 2nd order HD becomes a bit problematic) and increase sensitivity a bit.

I will be watching your build very closely, might be doing a bit of "borrowing" to tweak my design. And I'll send you a PM.

Are you going to use those foam inserts that Geddes loves too?


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## thehatedguy

The foam should cover the entire volume of the horn.



dbiegel said:


> BTW -- have you had any success with Geddes' anti-HOM foam plug techniques in a car? I'm using a small piece of the fish filter foam he recommends (30 PPI pu) in the throat at the moment and it doesn't seem to have any effect as far as I can hear or measure.


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## thehatedguy

I'm still wanting to do unity horns in my car...lol.


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## br85

thehatedguy said:


> The foam should cover the entire volume of the horn.


I don't even think Geddes himself does that with the summas, otherwise the foam should extend out on to the baffle?


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## Patrick Bateman

br85 said:


> I don't even think Geddes himself does that with the summas, otherwise the foam should extend out on to the baffle?


That's correct - the foam plug should be semi-spherical at the mouth. Here's a profile view:










That's a tapped horn in the corner, Summas in the foreground, 18Sound XT1086 sitting on the Summas.

(I took this pic to show the size difference between the two.)


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## Patrick Bateman

thehatedguy said:


> I'm still wanting molds.


They need a lot of work, but I have waveguides from the molds I made last summer. You'd have to fix the throat and use a ton of bondo to smooth out the rest of it. But if you want a pair...

I need to hold onto the molds myself, I might need them for this.


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## tspence73

I don't have much info on waveguides but has anyone tried different materials from plastic to metal to rubber to cloth and figure out if the material the waveguide is made of effects the sound? I've always wondered that.


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## shadowfactory

tspence73 said:


> I don't have much info on waveguides but has anyone tried different materials from plastic to metal to rubber to cloth and figure out if the material the waveguide is made of effects the sound? I've always wondered that.


All the body of the waveguide needs to be is as non-resonant as possible, and have a smooth throat. The purpose of the waveguide is to direct the sound, NOT to color it.


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## Eric Stevens

Amplitude being equal is a good start and that is all you address, this is not a complete discussion without including time and phase arrival and early reflections. 

Two basic elements go into recreating a sound stage in any listening environment; 1- Amplitude including equal frequency response 2- time arrival including proper phase response. you can over come a deficiency in one element with an increase of the other element. 

In my experience and understanding you want more volume form the farthest speaker to overcome the late arrival.

Your basic discussion fails to address the horrible acoustic environment of the car. Early reflections degrade both elements used to create a sound stage by affecting both time and amplitude. The effects of reflections are a lot more important than most people would believe.

Eric


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## Eric Stevens

I would like to mention one other thing, The importance of the elements that re-create a proper sound stage are of different importance at different frequency ranges. Imaging and staging will always be best when you get all the elements working their best together. 

Here is an over simplified description:
High Frequencies- Amplitude dominated

Mid frequencies- Time/phase dominated 

Low frequency- Phase dominated

Eric


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## Patrick Bateman

Someone over at diyaudio clued me in to the fact that I need to consider the Haas effect. Basically I designed these wavguides to be equally loud, but that's not wise. Due to the Haas effect, the speaker that's *further* away needs to be louder.

Since I want the image to work on both sides of the car, it sounds like I need to narrow the coverage angle of my waveguides. That will reduce the level of the driver side, while keeping the SPL of the passenger side intact.

(Because I'm listening off-axis to the waveguide on the driver's side, and ON-axis to the passenger's waveguide.)

Haas Effect:

Rane Professional Audio Reference Home


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## cvjoint

Patrick Bateman said:


> That's correct - the foam plug should be semi-spherical at the mouth. Here's a profile view:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> That's a tapped horn in the corner, Summas in the foreground, 18Sound XT1086 sitting on the Summas.
> 
> (I took this pic to show the size difference between the two.)


How acoustically transparent is this foam piece? Does it not affect 2nd, 3rd order products, decay etc? 

I still don't know if this is just to get a two seater. I mean for a one seater you can easily adjust the level of the farthest speaker to make up for the distance differences. The amplitude shouldn't be that different I would think, My left and right kicks are less than 1m difference from listening position. I never had to adjust more than 2db to make them arrive at the same output level subjectively or objectively on the WinMls.


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## thehatedguy

Foam is transparent. Read about it on DIYAudio in Dr. Geddes's posts on waveguides.


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## Eric Stevens

From experience to get the top of the dash to work the path length difference must be equal to or better than if you mounted them under the dash. I would say if you can get the PLD below 8" it will work well. This is difficult at best and why most cars will do better with under dash horns. PLD of 6" or less is the holy grail and makes things really nice.

Also with horns they project more of a spherical wavefront rather than spurious wave forms like a direct radiator so the effect of knees and steering wheel etc are minimized. 

This is the fun part of designing an audio system, with the laws of physics at work you are making a series of trade offs to achieve the best possible sound in a given situation.

Eric


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## slvrtsunami

No time to read... Sub'd for later


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## reindeers

Interesting. Sub'd


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## Patrick Bateman

Eric Stevens said:


> From experience to get the top of the dash to work the path length difference must be equal to or better than if you mounted them under the dash. I would say if you can get the PLD below 8" it will work well. This is difficult at best and why most cars will do better with under dash horns. PLD of 6" or less is the holy grail and makes things really nice.
> 
> Also with horns they project more of a spherical wavefront rather than spurious wave forms like a direct radiator so the effect of knees and steering wheel etc are minimized.


Imagine that you're standing on your lawn, watering it with a hose. If someone walks in front of you, it's not going to be a problem, unless they stand direcly in front of the hose.

That's how traditional horns work; they focus all their energy into a tight beam at high frequencies. I've tried a ton of horn geometries, and I've found that waveguides are particularly sensitive to obstructions.

Going back to the water hose analogy, imagine if you're watering your lawn, but you're using a sprayer to cover the whole thing. Now you can water the entire lawn, but anyone who happens to get in the way of the hose is going to obstruct everything behind them.










Here's the polar response for an OS waveguide, you can see it's "fanning" the sound out across a wide path.










Compare that to this B&C exponential horn; you can see from their data that it's beaming at high frequencies:

http://www.bcspeakers.com/PDF/PRD/ME20.pdf

Horn "beaming" is one of the reasons that a lot of people complain that HLCDs have a narrow, almost mono soundstage. All of the treble energy is confined to a narrow beam, particularly at high frequencies. This increases efficiency, but at the cost of imaging.

Here's a pic of the waveguides I built for the dash back in 2006; you can see that they're dramatically wider than a horn.


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## Patrick Bateman

Patrick Bateman said:


> Someone over at diyaudio clued me in to the fact that I need to consider the Haas effect. Basically I designed these wavguides to be equally loud, but that's not wise. Due to the Haas effect, the speaker that's *further* away needs to be louder.
> 
> Since I want the image to work on both sides of the car, it sounds like I need to narrow the coverage angle of my waveguides. That will reduce the level of the driver side, while keeping the SPL of the passenger side intact.
> 
> (Because I'm listening off-axis to the waveguide on the driver's side, and ON-axis to the passenger's waveguide.)
> 
> Haas Effect:
> 
> Rane Professional Audio Reference Home


A fellow Summa owner was kind enough to post a graph of the Haas effect. Very handy:










Keep in mind that sound travels 13.8 inches in 1ms.

This morning I measured the path length difference. In the illustrations it's about 1.5 feet, but in "the real world" it's about six inches.

But do I include the width of my head? That seems like a silly question, but that changes the distance quite a bit.

Is the path length from the speaker to my ears, or from the speaker to an identical point in space? (IE, the headrest or something???)


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## cvjoint

Patrick Bateman said:


> A fellow Summa owner was kind enough to post a graph of the Haas effect. Very handy:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Keep in mind that sound travels 13.8 inches in 1ms.
> 
> This morning I measured the path length difference. In the illustrations it's about 1.5 feet, but in "the real world" it's about six inches.
> 
> But do I include the width of my head? That seems like a silly question, but that changes the distance quite a bit.
> 
> Is the path length from the speaker to my ears, or from the speaker to an identical point in space? (IE, the headrest or something???)


I tune to the midpoint between the ears, some folks like npdang tune with two mics and sum using an algorithm, I'm not that good...yet 

Are you going to implement this for midrange drivers too? The waveguide would be huge I would think.


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## BMWturbo

As cvjoint commented I use the centre point between both ears as the datum for taking my impulse response/TA measurements for each driver.

I'm interested to see where this takes you however and as mentioned on the other forum how you intend to tackle the midrange frequencies, where PLD's will come in to play.


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## Eric Stevens

Patrick Bateman said:


> Imagine that you're standing on your lawn, watering it with a hose. If someone walks in front of you, it's not going to be a problem, unless they stand direcly in front of the hose.
> 
> That's how traditional horns work; they focus all their energy into a tight beam at high frequencies. I've tried a ton of horn geometries, and I've found that waveguides are particularly sensitive to obstructions.
> 
> Going back to the water hose analogy, imagine if you're watering your lawn, but you're using a sprayer to cover the whole thing. Now you can water the entire lawn, but anyone who happens to get in the way of the hose is going to obstruct everything behind them.


Well in some ways you are correct but with a horn/waveguide a better analogy is to think of waves in a pond made by dropping a rock, They will be affected by the obstruction but not blocked by the obstruction, the wave will reconstruct as is passes the object. This is obviously affected by the shape of wavefront that was created and the actual frequency being discussed.

Your hose sprayer analogy is how a direct radiator projects sound and fits perfectly for discussing dispersion and placement of a direct radiator.

Your thoughts on dispersion need some more thought and discussion as well I will address that later.

Eric


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## Patrick Bateman

BMWturbo said:


> As cvjoint commented I use the centre point between both ears as the datum for taking my impulse response/TA measurements for each driver.


I'll get some proper measurements of the path lengths today then. And I'll adjust the diagram to reflect the measurements.

I'm beginning to think it would be smarter to do polar measurements using the waveguide that I already have, rather than run out and build a new mold. By using the existing waveguide I can calculate the beamwidth, then create a new waveguide once I know how the existing one needs to be improved.

In other words, if I measure the polar response of the existing waveguide and discover that the driver's response is 2DB down from the passenger's response, I can build a new waveguide with a narrower coverage angle.




BMWturbo said:


> I'm interested to see where this takes you however and as mentioned on the other forum how you intend to tackle the midrange frequencies, where PLD's will come in to play.


It's probably going to be a Unity. I measured the frequency response of my Unity in 2006 and the -3db point was about 300hz. That's because the windshield extends the flare of the waveguide all the way to the roof.

Hooray for steep windshields.


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## dbiegel

Hey just wondering... how do you go about measuring polar response in a car?


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## Patrick Bateman

dbiegel said:


> Hey just wondering... how do you go about measuring polar response in a car?


To measure a speaker's polar response, you rotate the speaker.

In the car you can't do that, so you just have to move the mic.

In this application I'm mostly looking for two things:

#1 : measure the response of the passenger's waveguide at the passenger's seat.
#2 : measure the response of the passenger's waveguide at the driver's seat.

If I build the waveguide properly, I think that I can tailor the coverage angle so that the response at the driver's seat is about 3db louder. According to what I read, that will give me a rock solid center image from both seats (due to Haas effect.)


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## Patrick Bateman

Patrick Bateman said:


> I'll get some proper measurements of the path lengths today then. And I'll adjust the diagram to reflect the measurements.
> 
> I'm beginning to think it would be smarter to do polar measurements using the waveguide that I already have, rather than run out and build a new mold. By using the existing waveguide I can calculate the beamwidth, then create a new waveguide once I know how the existing one needs to be improved.
> 
> In other words, if I measure the polar response of the existing waveguide and discover that the driver's response is 2DB down from the passenger's response, I can build a new waveguide with a narrower coverage angle.
> 
> 
> 
> 
> It's probably going to be a Unity. I measured the frequency response of my Unity in 2006 and the -3db point was about 300hz. That's because the windshield extends the flare of the waveguide all the way to the roof.
> 
> Hooray for steep windshields.


#1 - I did some proper measurements of the pathlengths. For waveguides on the dash, it's 45" from the driver's side to the driver, and 57" from the passenger's side to the driver. For horns under the dash, it's 52" and 66". 

#2 - I'm too busy w/work to re-do the diagrams at the moment. According to the Haas curves, the driver-side speaker should be about 4.5db lower in level, based on a path length difference of 12-14". Note that mounting the speakers on the dash in my car is superior to putting them _under_ the dash, if judged strictly on pathlength. In addition, it's easier to drive the car and you can reduce the size of the waveguide dramatically by using the windshield to extend the curve 
To get the driver's level down by 4.5db, using a waveguide that's listened to at 45 degrees off axis, we need a coverage angle of 120 degrees. I just did that off the top of my head, so I'll crunch the numbers later.
Rough estimates:
0 degrees : 0db
-15 degrees : -1.5db
-30 degrees : -3.0db
-45 degrees : -4.5db
-60 degrees : -6.0db

So, yeah, looks like 120 degrees is the magic number.

Here's what a 120 degree waveguide looks like:










We're talking shallow here.

#3 - I downloaded a copy of arta and found my microphone. Installed Windows on a PC in the garage, so I can do measurements. (I used a laptop last time around, unfortunately it died  ) I'll run over to Guitar Center and buy some cables later on.


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## Patrick Bateman

Just got my deliver of the XT19s from Madisound, along with some Peerless 2" woofers.

WOW these are gorgeous driver!

I took a few pics of them, to show how amazing they look. In the pics are the Peerless, along side the Aura Sound 3" and 2" woofers that I evaluated last time around. (I wound up using the 2in woofers last time.)










The Peerless is the same size as AuraSound's 3in woofer 










Nice motor.










TC Sounds Fifteen that I had laying around, for reference


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## blamus

interesting that the peerless 2" makes the aura 2" looks like a 1.5inch. I've got the peerless 2" coming in from the PE buyout for a simple fullrange on the dash mated to a midbass in the doors. I have always wondered if I should get the auras instead, maybe you can tell me which is better 

very interesting looking project, but way too complicated for me >.< I'll keep reading though! Especially when u have more of these nice speaker porn!


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## SSSnake

Patrick (nom de plume?),

What will be the cutoff freq of the waveguides pictured?

While I am interested in using a waveguide in my latest vehicle the constraint that I struggle with the most is waveguide size. The waveguide you pictured above would not constrain midrange freqs to a radiation pattern of less than 120 degrees (unless I'm missing something).

The Geddes waveguides range from 10 to 15 inches across (if memory serves me). Even with the windshield and dash extending the waveguide effect (or limiting the solid angle of radiation) the guides will have to be large, VERY large for dash mounting.

Having said all of this... I will be attempting a 5.1 music system utilizing a center of the dash waveguide and two under dash waveguides. The biggest issues at this point is how to get the dash waveguide to fit, couple effectively to the dash, and provide directivity control down as low as possible down into the mid range freqs.

I would love to hear both your and Eric's thoughts on the subject...


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## Patrick Bateman

SSSnake said:


> Patrick (nom de plume?),
> 
> What will be the cutoff freq of the waveguides pictured?
> 
> While I am interested in using a waveguide in my latest vehicle the constraint that I struggle with the most is waveguide size. The waveguide you pictured above would not constrain midrange freqs to a radiation pattern of less than 120 degrees (unless I'm missing something).
> 
> The Geddes waveguides range from 10 to 15 inches across (if memory serves me). Even with the windshield and dash extending the waveguide effect (or limiting the solid angle of radiation) the guides will have to be large, VERY large for dash mounting.
> 
> Having said all of this... I will be attempting a 5.1 music system utilizing a center of the dash waveguide and two under dash waveguides. The biggest issues at this point is how to get the dash waveguide to fit, couple effectively to the dash, and provide directivity control down as low as possible down into the mid range freqs.
> 
> I would love to hear both your and Eric's thoughts on the subject...


To get pattern control in a waveguide down to 300hz, you'd need a waveguide that's 46" across. The waveguide that I used in 2006 measured about 12" across, and had reasonably flat response down to 300hz.

So I'm fairly confident that the windshield extends the flare.

To be sure I'd have to do some polars. I'll be doing those this week, and posting the results.

I believe the best results would be found using a waveguide which mates as perfectly as humanly possible to the windshield, which basically means the mouth is triangular, not elliptical.

So that's why I built the triangular mold last Summer, but never finished that project:



















The idea is that the point mates with the far corner of the windshield, and the wide side aligns with the left side of the dash.


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## Patrick Bateman

Patrick Bateman said:


> I'm beginning to think it would be smarter to do polar measurements using the waveguide that I already have, rather than run out and build a new mold. By using the existing waveguide I can calculate the beamwidth, then create a new waveguide once I know how the existing one needs to be improved.


As promised, I did some measurements of the polar response of my Unity waveguides that were built two and a half years ago.

First some pics from back in the day...

Here's an overhead pic of the waveguide. You can see it's aimed straight at the driver's head. (IE, the waveguides are crossfired.)










Here a look right down the throat.










Here's a pic of the mold being built. It's an oblate spheroidal waveguide, with a horizontal coverage angle of 108 degrees and a vertical of 72. One of the reasons I wanted to measure the polar response of the existing waveguide is that it appears that I should have made the coverage angle narrower. At the time I built this, I didn't consider the Haas Effect in my calculation.










Here's the actual polar response, which I measured today. It's take at 0,15,30, and 45 degrees. Unlike the picture, the waveguide now has a Geddes-style foam plug. Note that the mids aren't attached; this is just the compression driver.










Just for fun, here's a polar plot of the same compression driver on an MCM H-65, which costs a whopping $12. You can see that it's efficiency is a bit higher (there's no foam plug) but the response is basically omnipoloar for most of the bandwidth. That's cool at home, but we need a waveguide with a narrower pattern.


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## Patrick Bateman

This weekend I'll be building and measuring the midrange drivers for the waveguide. The Synergy Horn uses a frustrum instead of a hole for the mids.

If anyone wants to read the patent, here it is:

http://www.wipo.int/pctdb/en/wadLis...WEEK=NA&TYPE=NA&DOC_TYPE=PDOC&ACCESS=D&PAGE=0

Here's a pic of what the mids in the Synergy Horn look like.

The reason why we want to use a frustrum is that it allows us to make the holes smaller. This improves the frequency response of the speaker, by minimizing reflections inside of the waveguide. My simulations indicate it should improve the bandwidth of the mids as well.










According to the patent,

"Referring now to FIGS. 9 and 10, the port length, or acoustic length can be minimized significantly for horn walls that are relatively thick. Referring to FIG. 9, a lower frequency driver 20 is shown mounted to horn wall 130. A tapered port 132 is formed in horn wall 130. The tapered port 132 is preferably defined by frustoconical wall 134 having a large end adjacent driver 20 and a smaller end adjacent the outer surface 136 of the horn wall. Referring now to FIG 10, a stepped port 140 is formed in horn wall 130, and is defined by stepped wall 144. The port defined by the stepped wall has a larger diameter adjacent driver 20 and a smaller diameter adjacent the outer surface 136 of the horn wall. As shown in FIG 10 it is generally preferred that the step or transition 145 in wall 144 is located relatively close to the outer surface 136. With either port treatment show in FIG 9 or FIG 10, the overall opening in horn wall 130 can be made substantially smaller than if a "straight" or cylindrical hole were employed.


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## Patrick Bateman

The instructions for building the midranges is here:

diyAudio Forums - Another Unity Horn - Page 9

I must have ten or twelve of these laying around, so I'll probably build three and use the design that measures the best.

The model above uses a hole that's 1/2" wide by 1/2" deep. I'm going to go with a frustrum, but I'll probably build one of those too, just to see which performs better.

If anyone is building one of these, the size and depth of the holes, and the volume of air in front of the midranges, is critical.


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## Patrick Bateman

Here's some pics of the measurements being made in this post:

http://www.diymobileaudio.com/forum...creating-perfect-soundstage-2.html#post753488










The waveguide from 2006's Unity horn being measured. The documentation for that project is over on the carsound forums.










The $12 MCM waveguide on my dash, with a BMS 4540ND, getting measured. Fits up there quite well. It would need a baff to mate with the windshield. If you just plop it up there, there's gonna be a ton of reflections in the corner to the left.










The view from outside the car.










I actually wanted a silver car, but wound up with black-on-black-on-black-on-black. Six speed Accord coupes aren't easy to find.


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## cvjoint

Patrick Bateman said:


> I actually wanted a silver car, but wound up with black-on-black-on-black-on-black. Six speed Accord coupes aren't easy to find.


Bah... you think your generation is hard to find stick? I had to drive out of state to get my 5speed.


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## Patrick Bateman

I spent a half hour typing a post and it disappeared?!

Oh well, if this is here twice, blame Internet Explorer.

(I'd use Chrome, but it's banned by the IT department.)










This is a pic of the throat of my friend's Unity Horn. Note the holes are humongous. About 3/4" across. Small holes improve the response of the waveguide, but they limit the SPL at the same time.










This is a pic of my new waveguide. It's different than the one from 2006, it's triangular, to mate with the dash better. The big improvements are in the midranges. In 2006 I used a midrange enclosure that was way too big. That allowed the mids to play very low, but not very high. Due to that fatal mistake, the upper limit of my Unity was reduced by at least 15db, if not more. I didn't make that mistake twice; the new enclosures are a tenth the size.



















The holes on my waveguide are just 1/4" across. I can get away with a much smaller size because the "real" Unity uses cylindrical holes, and the holes in mine are a frustrum. (see previous post.)










Basically it's an improved waveguide, with midranges that should work a LOT better than the last time around.


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## dkm201

blamus said:


> interesting that the peerless 2" makes the aura 2" looks like a 1.5inch.


That's because the Peerless in question is actually a 3".

Peerless 830987 3" Full Range 8 ohm from Madisound


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## Patrick Bateman

Last night I did some polar measurements of the mids on the new waveguide. I only measured one midrange, as I'm still deciding whether I should use the existing molds, or build a new one. And I haven't decided if I'm using a Vifa ring radiator or a BMS 4540ND.










The polar response of the waveguide, with the midranges.
Wow, that just looks like hell doesn't it?
But I gave it some thought, and it's not as bad as it looks. All we can get out of these mids is a bandpass response. And that's what we're getting. It's centered at 1khz. On the low end it's falling quite gently, just 10db/octave beginning around 640hz. At the high end it's dropping quicker, at 18db/octave from 1500hz.

The good news?

With a bit of frequency response shaping in the crossover, I can sacrifice six db at 1khz and bring my F3 from 640hz to 300hz. Try doing THAT with a compression driver; it's impossible. There just isn't enough excursion, but three of the Tangbands have plenty of excursion to go down to 300hz.










A picture is worth a thousand words...










As I've mentioned a few times, my fatal mistake with the Unity I made in 2006 was that the midrange chambers were too big. I just didn't see it at the time, as I didn't understand what was going on in the midranges. The midrange drivers are the most complex part of a Unity horn. If anyone has specific questions on how they work, ask away, because I feel like I have a good grasp on it after years of study. But it's a really complex beast. Three years ago one of the guys that worked with Danley on the original Unity told me to use a very small enclosure and I couldn't figure out why. The reason (as he stated at the time) is that we need to drive the Fb of the enclosure right into the midrange. If we use an enclosure that's too big, all of our efficiency will be down low, and we'll never get the mids to play into the midrange. These midranges are in a _bandpass_, so our bandwidth is limited.

So one thing I wanted to do right away is measure the mids in a sealed enclosure, and compare them to our waveguide, to see if they're tuned too low. If they're tuned too low, the waveguide will have too much output down low, and not enough in the midrange.

That's what the graph above shows us; the response of the waveguide versus a single mid in a sealed enclosure. We can see that in the midrange frequencies, they're comparable. There's a big bump at 1khz in both, which is likely due to the "Q" of the enclosure being very VERY high.

That's another reason that we can't use 90% of the midranges out there; we need a mid with a low QTS, otherwise we get too much bass, not enough midrange. It basically disqualifies all kinds of wonderful aluminum cone midranges from Tangband, Aurasound and Peerless. The cones are too heavy, and the QTS is too high.










This is the simulated response of the midranges on a much larger waveguide, from Hornresp. Note that it resonates an octave lower than what we're seeing in my measurements. If you'd like to get the details on how to model Unity horns in Hornresp, read my thread here.

There's two ways of looking at this:

#1 - Re-build the mids so they play lower, and are closer to the simulation.
#2 - Stick with what we got. The hardest part of a Unity is getting the midranges to play above 1khz, and my mids are playing up to 1500hz. Leave it alone.

I'm inclined to go with option 2.


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## Patrick Bateman

Oh, forgot to mention.

In all of my polar measurements, the light color is on-axis, and the darker color is off-axis. For instance, white or yellow is on-axis, and red is off-axis. From zero to forty five degrees, it goes yellow-light orange-orange-red.

The on-axis measurement is done by putting the waveguide on the passenger side, pointing it at the driver's side, and measuring it. Then I measure from driver side to passenger side, in fifteen degree increments.


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## Patrick Bateman

This post is going to be a bit long. If you're a fan of horns at home or in the car, I think it's going to thought provoking. A series of measurements I've just finished are a real eye-opener, and I'll explain why in this post.

To start off with, I need to explain what the goal of this project is. It's to create the best soundstage possible in a car. Creating a soundstage is relatively easy; just match the left speaker to the right speaker, and sit equidistant between the speakers.

Of course we can't do that in a car. A lot of guys use DSP and EQ to adjust the sound and the delay for the driver, but that ruins the image for the passenger. But there's a bigger problem. The ambience of your soundstage depends on those reflections, and there's literally no electronic way to fix every single point in your car. That's the inherent flaw when using EQ, and particularly time delay via DSP, to fix your car.

Believe me, I have personally tried, and it sounds weird. It doesn't sound natural. Richard Clark, who's Grand National is possibly the most famous sound quality car of all time, also experimented with DSP, and shelved it.

It's a band-aid, and there's a better way.

In my opinon, that way is via the use of waveguides. According to Wikipedia, "a waveguide is a structure to guide waves." In the car, I'm using waveguides because I want the sound at the passenger to sound the same as the sound at the driver, with no DSP. And I don't mean for one speaker; I mean for both. I want the speakers to sound the same, no matter which one you're listening to, no matter where you are seated.

Get that right, and the soundstage just falls into place, because the sound _and it's ambient sound field_ is perfect.

Now that we've established _why_ we want to use waveguides, and why DSP and EQ are an inferior solution, let's discuss what the perfect speaker would look like.

IMHO, the home speakers from Earl Geddes come about as close as you can get. Their hallmark is amazing polar response; in other words they sound the same on axis _and off._ Not coincidentally, Geddes wrote the book on waveguides.

Here's an example of their amazing polar response; this graph shows the response of the Summa loudspeaker. The various colors denote the response off axis. As you move off axis, the shape of the curve doesn't vary. That's the key to good imaging on _and_ off axis. The polar response.










Here's the polar response of my oblate spheroidal waveguides, from 2006, in my car. These polar curves are from on axis to 45 degrees off axis (white, yellow, orange, red.) While it's not as good as the Summas, compare that response to a dome tweeter without a waveguide (the second pic.) And that's not a cheap tweeter; it's $450 a pair, a Seas Excel T25CF.



















What is particularly exciting is the measured response of that OS waveguide, with midranges. Based on my measurements today, it looks like the OS waveguide controls the polar response of the midranges.

Now think about that for a second, because that's *huge.* For close to twenty years we've done all kinds of crazy things to our cars, all to get a good soundstage. Guys like Richard Clark put gigantic horns in their cars with expensive, hard to find speakers. Other guys like Earl Zausmer cut up their cars to mount huge woofers up front. What I'm about to show you proves that a tiny little waveguide, on the dash of a car, works all the way down to 200hz.

I wouldn't believe this myself if I didn't have the measurements to prove it!

First, a graph of my new waveguide. The next two graphs show the response of the _midranges_ on two different waveguides. If you'd like to review the treble performance of this waveguide, please review my previous posts. This midrange is crucial, because it's the most important part of the music experience. It's the range that we're most sensitive to, and where all the vocals are. It's really easy to screw up the midrange, because you have to get the timing and the frequency response correct. If you fail at either, there goes your soundstage.










Remember, our goal is that the sound on-axis _and_ off is the same. In this pic, that's only happening for an octave and a half, from 1khz to 3khz. Everywhere else, the sound changes as you move off axis. In the upper octaves it actually gets LOUDER as you move off axis, while at lower frequencies it gets quieter. As you can imagine, this isn't good, it means that instruments and sounds will meander all over the soundstage, depending on frequency.

Now a graph of my _old_ waveguide, from the 2006 Unity project, with the new midranges.










I hate to brag, but this is just gorgeous. The *entire* frequency range is the same. It doesn't matter if you're the driver or the passenger, _it all sounds the same._

Can you imagine a stereo like this in a car? A stereo where the sound stage is rock solid, and the ambience is deep and wide? This kind of soundstage performance is unheard of.


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## slvrtsunami

Very interesting reading. I would love to have the opportunity to listen to an example. Based on the pictures, I just cant grasp how they can sound as well as the graphs present. 

Just how well do they blend with midbass drivers and the rest?


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## Patrick Bateman

slvrtsunami said:


> Very interesting reading. I would love to have the opportunity to listen to an example. Based on the pictures, I just cant grasp how they can sound as well as the graphs present.
> 
> Just how well do they blend with midbass drivers and the rest?


In a Unity horn the midrange and the treble drivers are literally centimeters apart, so integration is pretty easy really. Here's a pic of a commercial Unity horn. Note the three midranges and the compression driver are right on top of each other. I have a pic of mine in a previous post.










The tricky part is getting the frequency response correct, and getting the directivity correct.

We can always fix the frequency respone with the crossover or the EQ, but there's literally no way to fix directivity electronically.

That's why I was so excited to find out that this waveguide works all the way down to 200hz. It's really quite a breakthrough I think.

I'll admit, this thread is a bit complex, but it's the ultimate solution as I see it. There's no other way to go about this that yields such even and consistent imaging for everyone in the car. And even if you go the DSP route, your soundfield will be a mess.

To give you an idea of what the horizontal directivity of most commercial speakers looks like, here's a couple plots of a Focal speaker.

Here's the JMLab Diva Utopia Be. In the pic, note how the directivity narrows between 1.5 and 5khz:










That was actually good performance; here's a pic of their center channel's performance. As the graph shows, it's just a total mess off-axis. If you think this is bad, just imagine what the average car stereo is like!










pics from here: UltimateAVmag.com: Focal-JMlab Diva Utopia Be Surround Speaker System


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## cvjoint

Patrick Bateman said:


> Last night I did some polar measurements of the mids on the new waveguide. I only measured one midrange, as I'm still deciding whether I should use the existing molds, or build a new one. And I haven't decided if I'm using a Vifa ring radiator or a BMS 4540ND.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> The polar response of the waveguide, with the midranges.
> Wow, that just looks like hell doesn't it?
> But I gave it some thought, and it's not as bad as it looks. All we can get out of these mids is a bandpass response. And that's what we're getting. It's centered at 1khz. On the low end it's falling quite gently, just 10db/octave beginning around 640hz. At the high end it's dropping quicker, at 18db/octave from 1500hz.
> 
> The good news?


Ok, maybe I'm the only one here that doesn't get it but what's the benefit of this waveguide? These graphs look awful no matter how you try to sweeten it up. I see a 200hz-2000hz graph that is + - 13db or so. That's worse than any setup I started with. Even the off axis curves which you say follow each other very well have rather large variations if you take into account the scale, not to mention is rather random. 

Out of the box a 3 inch driver is well outside of beaming well over 2000hz and has a much broader FR with even less variation off axis. You say all these things how DSP ruins the sound but you will be highly dependent on it to get any sort of usable output out of this thing. You also gotta think beyond xover point, if the response drops like a rock like you say than they won't sum up well with the rest of the gear. I don't mean to be a ball buster but all this talk about perfect complex soundstage doesn't match the data.


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## Patrick Bateman

cvjoint said:


> Ok, maybe I'm the only one here that doesn't get it but what's the benefit of this waveguide? These graphs look awful no matter how you try to sweeten it up. I see a 200hz-2000hz graph that is + - 13db or so. That's worse than any setup I started with. Even the off axis curves which you say follow each other very well have rather large variations if you take into account the scale, not to mention is rather random.
> 
> Out of the box a 3 inch driver is well outside of beaming well over 2000hz and has a much broader FR with even less variation off axis. You say all these things how DSP ruins the sound but you will be highly dependent on it to get any sort of usable output out of this thing. You also gotta think beyond xover point, if the response drops like a rock like you say than they won't sum up well with the rest of the gear. I don't mean to be a ball buster but all this talk about perfect complex soundstage doesn't match the data.


I agree with you, a three inch driver will have good polar response on AND off axis. It's the reason that so many people are discovering that small full-range drivers can image very VERY well.

Until I finish my waveguides, guess what's in my car?

Yep, an Aurasound three-inch, running dipole, in my kick panels.

So I agree with you 100%, full range drivers can work very well.

Unfortunately, a three inch full range has terrible power handling, and it will beam beginning at 4600hz. That gives you a couple of choices. You can sacrifice the top two octaves, and never turn up the volume very loud.

Or you can go with a waveguide.

Now a lot of people will just put two-ways in the kicks, so lets examine how a two-way speaker behaves in a car.

To start with, I took a popular Polk two-way, and I measured it outside. I used my own mic, and the same settings that I used for yesterday's measurements in the car. So we're comparing apples-to-apples, this isn't some spec sheet that was sent out from Polk's marketing department.










Measured outside, it looks exactly like I'd expect it to look. It's a bit heavy in the bass, and the treble is tipped up. When you move off axis, the midrange starts to get sucked out. This is completely typical behavior for a two-way, and these Polks actually sound damn good. (Once you accept they're bass heavy, and a bit hot.)










Here's the exact same speaker, but sitting in the kick panels of my Accord. On-axis, the response is about the same. A little bass heavy, and the treble is tipped off.

But look at those off-axis curves! OMG. They're atrocious. The suckout in the midrange is even worse, and where did that peak at 5khz come from?

The reason the off-axis in the car is so much worse than outside is due to all the reflective surfaces in the car. It just wreaks havoc with off-axis measurements.

Subjectively, the reflections collapse the soundstage, and they make the sound less "intelligible."

So that's why I'm using waveguides. I want the on-axis and the off-axis curves to look exactly the same.










Here's the measured response of my midranges on the new waveguide. This is actually better than what I achieved in 2006, but it's still got tons of problems. The area highlighted in green shows the "perfect" bandpass response. But you can see in the pic there's a nasty peak at 8khz, and the polar response from 1500hz and down is anything but consistent.

My waveguide is tiny, so these results would indicate I should have made it bigger. I'd hoped that it would "couple" with the dash, but it doesn't apear to be doing it consistently. If it wasn't working at all, the response would drop like a rock below 900hz or so. So it's working, but not as well as I'd hoped.










And here's the OLD waveguide. From 2006.

The green area would be the "perfect response"

This is really REALLY close to perfect. I'm astounded that it works this well, I would have settled for what I was getting from the new waveguide, but the old one obviously works a million times better.

I'll explain why the green response is "perfect" in a future post. Gotta get to Home Depot and buy some stuff.


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## donkeypunch22

Dude, looks killer for what you are trying to achieve: a band passed on axis = off axis. How are you going to approach the upper octaves?


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## cvjoint

I see what you are saying in that car audio looks like crap once you account for off axis behavior and reflections by testing in car. I don't claim we get what the manufacturer's spec sheet shows.

Here's the deal, with the right scale on both graphs I have no reason to believe a standard 5inch woofer and a tweeter will look worse. That is using a 5 and not a 3 inch combo because I'm with you on not using a 3 that low, 400hz would be the lowest decent spot to cross. I see the comparison as being viable, now plot them on the same graph. The magnitude variation in FR on your waveguide are much larger, as well as the off axis measurements. You wouldn't even be able to EQ down the areas with lots of gain using a standard bit one or 701 at the limit not to mention you would need lots of EQ gain at lowest frequency reducing the output gains of the waveguide system. 

I understand what you are trying to achieve, I would like to see it work. I don't think you are there yet. I'll be watching.


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## Patrick Bateman

cvjoint said:


> I see what you are saying in that car audio looks like crap once you account for off axis behavior and reflections by testing in car. I don't claim we get what the manufacturer's spec sheet shows.
> 
> Here's the deal, with the right scale on both graphs I have no reason to believe a standard 5inch woofer and a tweeter will look worse. That is using a 5 and not a 3 inch combo because I'm with you on not using a 3 that low, 400hz would be the lowest decent spot to cross. I see the comparison as being viable, now plot them on the same graph. The magnitude variation in FR on your waveguide are much larger, as well as the off axis measurements. You wouldn't even be able to EQ down the areas with lots of gain using a standard bit one or 701 at the limit not to mention you would need lots of EQ gain at lowest frequency reducing the output gains of the waveguide system.
> 
> I understand what you are trying to achieve, I would like to see it work. I don't think you are there yet. I'll be watching.


The graph I posted this morning is of a Polk 2-way with a 1 inch tweeter. While it's performance is good on-axis, OFF axis it goes to hell.

And unfortunately, there's no way to electronically fix polar response. If you apply EQ to fix the midrange suckout, you just created a bump on-axis.

Now the response of the midranges on the waveguide, and the compression driver on the waveguide aren't flat, but they're consistent, and that means if we fix it in the crossover at one point, it will sound the same off-axis. That's the key.



















The only way to solve the problem is via a waveguide.

Believe me, I don't like making molds, if there was another way to do this, I'd be all over it.


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## Patrick Bateman

donkeypunch22 said:


> Dude, looks killer for what you are trying to achieve: a band passed on axis = off axis. How are you going to approach the upper octaves?


On a Unity horn, the compression driver and the midranges are on the same horn. I'm just measuring them seperately to figure out which waveguide I want to use. The midranges are Tangband 2" paper cones, and the tweeter will likely be a BMS 4540ND.

I'd purchased some Vifa ring radiators, but they don't perform as well as the BMS unfortunately.


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## Patrick Bateman

A week ago I took some pics of the waveguides and horns that I've built or bought, thought I'd post them.





































These are just the ones I've built recently; I've been putting horns in cars since the 90s. I've never been a fan of buying horns, it's more fun to build them. And I've never heard a horn that can compete with the ones that I build. I bought the USD ones mostly to hear if they were better, but the ones that I build play lower. (And no wonder - they're a lot bigger, except for my new ones, which use the windshield to extend the curve.)


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## Patrick Bateman

Here's how my "perfect soundstage" project is coming along.

My theory is that the ideal soundstage requires that both the left and the right speaker in the car sound the same on axis AND off. This is because we're listening off axis. The best way to make a speaker sound good on AND off axis is to use a waveguide.

Based on that, I created a waveguide a year ago which mated with the dash of my car, so that the windshield and the dash would continue the curve. That's because the _ideal_ waveguide would be four feet across. No seriously!

Last weekend I measured the polar response of the new waveguide, and it was "alright", but the _old_ waveguide, from 2006, was almost perfect.

So I should just use the old waveguide, right?

Unfortunately, the old waveguide is a little bit too wide. It has a beamwidth of 108degrees wide, by 72 degrees tall. That works out to an average beamwidth of ninety degrees.

A narrower waveguide will make the soundstage move in the opposite direction. For instance, if you're the driver, a narrower waveguide will make the soundstage move to the right. I didn't include the Haas effect when I calculated the dimensions of my waveguide in 2006, I know better now.

Yes, I know that rebuilding the waveguide is completely OCD, but I'm a perfectionist, and I want the soundstage to be anchored to the center of the dash, with a wide and deep presentation. While the old waveguide measures very well, the soundstage will be biased too far to one side. The measurements I did last weekend demonstrate this.

Here's some pics to illustrate what I'm talking about.










This is the mold for the NEW waveguide. I used a triangular mouth to mate with the dash as closely as possible. Unfortunately the polar response that I measured last weekend shows that it's not a proper waveguide.










Here's the mold for the old waveguide. Note the sidewalls are flat. That's why it works so well; it directs the sound the way that a flashlight directs light.

So I need a waveguide that's like the old one, but narrower. I put my USD waveguides up on my dash, to figure out what will fit up there.










USD waveguides on my dash










Now that I know what will fit, I figured out the size of an _ideal_ waveguide, and cut a piece of wood to match the foot print. That hunk of wood in the pic is sixty eight degrees wide. But here's the *key*; I sawed off half the mouth, so it will fit in the car. All that brown part will be discarded. Obviously we can't put a waveguide on the dash that's a foot tall, so we chop off part of the mouth, foreshortening the waveguide in the process. Does that make sense?










My waveguide "footprint", with my compression driver, on the dash.










Here are the plans for a new waveguide. This one has a horizontal coverage of 68 degrees, and a vertical coverage of 34 degrees, for an average beamwidth of 46 degrees. In other words, the beamwidth is about half of what the old one was. The advantage of a narrower beamwidth is described earlier in this post.










Here is the 2nd page of the plans. Anyone who's messed around with waveguides will note that this waveguide isn't conical, but it isn't oblate spheroidal either. It uses a bezier curve; I haven't seen anyone else use this before, but I read a paper that demonstrated that the beamwidth of this type changes gradually, without any abrupt changes. I can dig it up if anyone wants to read the paper.

If anyone wants to build this waveguide, each segment is an inch thick, and the dimensions are listed. Just buy a $10 sheet of foamboard and cut 12 ellipses out of it, then stack them together.










I just draw the segments on the computer, print them, and staple them to the foam board.



















Just have to smooth things out, then saw the mold in half, and we're done.


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## splicer

you ever look at rapid prototyping/3d printing to make waveguides? I know there are a bunch of places that will 'print' a design into plastic, and I have seen some up to a cubic foot, but don't know how much it costs...


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## Fast1one

splicer said:


> you ever look at rapid prototyping/3d printing to make waveguides? I know there are a bunch of places that will 'print' a design into plastic, and I have seen some up to a cubic foot, but don't know how much it costs...


Cal Poly San Luis Obispo ( my college) has one. If its for a project and/or I can come up with a good reason, I get free access including free materials. 

Any ideas on how to convince them that acoustics is directly applicable to mechanical engineering?


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## Patrick Bateman

splicer said:


> you ever look at rapid prototyping/3d printing to make waveguides? I know there are a bunch of places that will 'print' a design into plastic, and I have seen some up to a cubic foot, but don't know how much it costs...


That would be almost ideal, since the mold doesn't have to be sturdy. You could do a 3D print, and then fill it with expanding foam or plaster of paris to make it rigid.

My Dad used to own a boat building company, so a lot of my methods are swiped from that field.


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## Patrick Bateman

Someone on another thread was asking about making a front stage, so I thought I'd throw out some advice on how to do it.

I don't want this to turn into a big debate, but I think I have a pretty good idea on how to get a good image in a car. This thread is highly technical, so taking it "back to basics" for a moment might be welcome.

So....

*How to Create a Stereo Image*

To create a stereo image you basically need identical frequency response from the left and the right side. In a car, this is difficult, because we're too close to one side. The easiest way to compensate for this, IMHO, is to cross fire the speakers. So the passenger's speaker is pointed at the driver, and vice versa. If you're using a carefully constructed waveguide, you can control how loud the opposite speaker is.

If you're NOT using a waveguide, you can still adjust the volume, the old fashioned way. Use the balance control.

Since we're listening off-axis, we'll need speakers where the on and the off-axis response is as close as humanly possible. All speakers beging to "beam" at a specific frequency. To figure out when that happens, get out your mic, and measure your speakers on and off-axis. If you can't do that, look at the response plots from the manufacturer. If you can't even do that, there's a mathematical formula that can get you in the ball park.

That formula is (speed of sound / speaker diameter.)

For instance, if you have a 6.5" woofer up front, and it's cone is about 5" across, it will start to beam at approximately 2700hz.

So what does that mean? Why should you care if it's "beaming?"

The reason you should care is that you're listening *off axis.* If you use your speakers above the point where they're "beaming", the sound from the left and the right will not be the same, and your stereo image will collapse. And the ONLY way we're going to get an image is if the sound from both sides is identical. If it's not, it's game over. You can buy a set of $2000 component speakers sprinkled with magic pixie dust, hook it up to a gold-plated $5000 amplifier with $10,000 cables, and it still won't image. You HAVE to get the left and the right to match.

In fact, I'd strongly recommend using your speakers well outside of the range in which they are beaming. That's because the crossover will allow them to play 1-2 octaves above that point, depending on the slope.

So in our example above, the upper limit for our 6.5" midrange is 1350hz. (that's one octave below 2700hz, which is the upper limit dictated by the woofer size.)

Does that make sense? Based on these formulas, your crossover points are practically set in stone. You'll have to cross the woofer over at 1350hz, using a steep slope, and bring the tweeter in at the same frequency. If you cross over higher, the speakers will start to beam. If you cross over lower, it's going to be murder on your tweeter.

A lot of people have reported excellent results using small midranges in the car, and rave about the amazing stereo image. These results aren't due to the quality of the midrange; they're due to the fact that small midranges fit the criteria for imaging a lot better. For instance, let's take our example above, and re-work it for a 3" midrange instead.










The Fountek FR88 has a cone diameter of 2.3". Based on the formula above, our upper limit is 2934hz. Now there aren't may tweeters that will play low enough to cross over to an 8" or a 6.5" woofer using our formula, but there are literally hundreds that will work with the Fountek. The icing on the cake is that using the Fountek gets our crossover frequency out of the midrange, where any little glitch or error is easy to notice, because that's where our ears are the most sensitive.


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## Patrick Bateman

In this post I'm going to show you how to clone a waveguide. I'm going to take an 18Sound XT1086, create a mold from it, and then a new waveguide from the mold.

The process is fairly simple. You buy an 18Sound XT1086, fill up "the bell", and then pull that plug out of the bell. I used aluminum foil and foam to fill it up, but you could use whatever you'd like. Perhaps plaster of paris?

If you want to make a perfect clone of a waveguide, you'd stop at this point, and start cranking out clones using your mold.

But I wanted to put this waveguide in my car, so I shaved off about 50% of the mold, to create a triangular mouth, so that it will fit in the corners of my dash. In the 4th and the 8th pic, you can see this clearly.

Once the mold had been modified, I created two clones, with fiberglass and tinfoil. That's how I make most of my waveguides; I cover the mold in aluminum foil, and then I put fiberglass right onto the aluminum foil. It looks ugly from the outside, but the aluminum foil follows the curves of the mold quite well.

Best of all, I've never trashed a mold. I've tried the "traditional" methods, which require wax and mold release and all kinds of nonsense, and my molds always get destroyed sooner or later. Sound waves are very VERY long, so a rough surface on the waveguide has no effect, except at the throat. (And I bondo that up so it's smooth as glass.)










Here's an XT1086 waveguide from 18Sound. It's $88. Plastic waveguides built for your car cost around $900, and they're mounted under the dash. There's a lot of good reasons not to put them there. There's one problem with the 18Sound waveguide, and that's the funky kink in the throat, which creates diffraction. I'll show you how to fix that.










Waveguides don't photograph easily. This is the waveguide getting filled with aluminum foil. I actually used a combination of aluminum foil and expanding foam, which is easier to cut. So we're talking about two dollars worth of aluminum foil, and an ounce of expanding foam. I use Great Stuff, which sells for six bucks at Home Depot.

Be sure to use a huge piece of foil, otherwise your mold will separate into pieces. I used duct tape as I laid up the layers to be sure each layer was attached to the previous.










Here's the clone, and the original waveguide. In this pic I've covered the mold with bondo, which I then sanded to eliminate the texture of the aluminum foil. Honestly, this is overkill, because sound waves are so long. A sound wave a 2khz is 7" long, so a small bump or a ridge won't make a difference. It IS important at the throat though.










In this pic I've sawed off half the mold, so that it will fit in my car. The wet stuff on the mold is spackle. It's a great substitute for bondo when you're working on a mold, because it cleans up with water, and it doesn't make your place smell like a meth lab.










My buddy Stephen Spielberg made a movie about waveguides. It's called Close Encounters. Here's Richard Dreyfuss in HIS kitchen, doing his best Patrick Bateman imitation. Unfortunately, he didn't take my advice, and used mashed potatoes for this mold.










Here's the waveguide with wax in it. I tried to build a mold the "traditional" way, and it just made a big mess. The foam stuck to the bell and I had to use solvents to get it off. Aluminum foil is definitely a lot easier to work with.










Here's the aluminum foil "plug" that's created from the XT1086 waveguide. This will become our mold. In this pic, you can clearly see there's a kink in the XT1086. That kink creates diffraction, which makes the waveguide sound harsh. In the mold that I built, I used bondo and spackle to smooth out the kink. The idea is that the transition from throat to mouth should be as gradual as possible, with no abrupt changes in angle. It sounds better, and it measures better that way.










The BMS 4540ND uses a threaded adapter. I didn't have any on hand, so I carved up a $12 MCM waveguide, just to get the adapter. The throat of our waveguide must be smooth, so be sure to sand and file after you glue the two pieces together.










The adapter, now glued to our waveguide. At this point the waveguide has been covered in a single layer of fiberglass. That's why it's green, it's the color that the resin turns to after drying.


----------



## tspence73

OMG, this is utter insanity meets uber diy mobile audio. These things may one day take over the earth.


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## finbar

Riveting, keep it coming. Subscribed.


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## Patrick Bateman

In a unity or synergy horn, the midranges and the compression driver are mated to the same horn or waveguide. Here's a couple examples:










This is a Lambda Unity horn. To give you an idea of it's scale, those midranges are 5" across, and the compression driver is as big around as a 2 liter bottle of soda. It's B-I-G. This is the real deal, engineered by Tom Danley and sold by Lambda Acoustics.










These are the holes in that Unity horn. They're close to an inch across IIRC.










Here's a side view of my new waveguide. To make the holes as shallow as possible, I'm using aluminum this time around. (Last time I used wood.) The reason that we want the holes as shallow as possible is that the deeper the holes are, the bigger they have to be. Conversely, if we want to use small holes, they need to be shallow. Hence, the use of aluminum instead of wood. Take a look at the synergy horn patent for more details.










Here's a side pic, with two woofers mounted to the waveguide.










Here's a pic with the waveguide in the car. It's hard to tell from the pic, but the gap between the windshield, the waveguide, and the dash is less than a quarter of an inch on the top and the bottom. Is basically perfectly flush, and the compression driver and the midranges are tucked neatly into the corner. There's no room for midranges on the top or bottom, due to the close fit. That's why there's dual midranges on each side of the waveguide.


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## pwnt by pat

Are you worried about having the midranges at different locations causing problems with dispersion? I had thought unit horns keep the midrange at the same spot on the throat to allow the different firing directions of the midranges to form in to a single wave.


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## Patrick Bateman

pwnt by pat said:


> Are you worried about having the midranges at different locations causing problems with dispersion? I had thought unit horns keep the midrange at the same spot on the throat to allow the different firing directions of the midranges to form in to a single wave.



Directivity is related to the length of the sound wave. Or to be specific, the aperture must be equal to or greater than the wavelength to control it's directivity. For instance, a tweeter on a 3.5" baffle will become directional from 4khz and up, due to the dimensions of the baffle.

So we can answer your question by looking at the dimensions of the waveguide where the midranges enter. It's about 1.5" wide. So what does that dimensions correspond to?

(speed of sound / dimension) =
(13500 inches per second / 1.5" ) =
9000hz

Based on the location of the midranges, the waveguide will provide directivity for frequencies above 9khz.

But the midranges aren't playing above 2khz. Therefore, the direction they're pointed is completely irrelevant. They can fire up, left, right, whatever. It won't make a difference - the sound waves are too long.

Now it DOES make a big difference where the compression driver is pointed, because it's playing frequencies up to 24khz.

One of my gripes with the waveguides from USD and Image Dynamics is that they're fire the compression driver at a wonky angle as it enters the waveguide. Admittedly, it makes a small difference, since that last octave is practically inaudible. But it *does* affect the directivity of sound above 10kz.

But again, the direction that the midranges are pointed is irrelevant.


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## Patrick Bateman

I was looking at some threads on the board, and noticed that some people were spending over ten thousand dollars on their car stereo.

OMFG you people are rich

I thought I'd upload a system diagram, to give you an idea of how much it would cost to install a stereo like this. If I went out and bought all the parts today, it would be about $1500. If you buy your amps from a pawn shop, you could probably get the tab under $1000. (Right now I'm running an old-school amplifier from the 90s that I found at a pawn shop. It's built better than anything I could buy for under $500 new, and they thought it was junk because it was old. I paid $40 iirc.)

But honestly the only thing I've bought for this project was a $1 can of white spray paint and $3 worth of nuts and bolts. Everything else is left over from the 2006 project. Even the amplifiers.

This project uses no DSP whatsoever, and the crossovers will be 100% passive. I'm using dual amplifiers simply because I want a fader. Otherwise I could run the whole thing with a single amp.


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## pwnt by pat

That makes sense. I was considering the diameter of the midranges as opposed to the fact that on the unity, the holes through which the midrange travels through becomes the point of radiation.

Any chance I could bum the waveguide to make a mold of  I would love to play with this to see how it fares against some onaxis a-pillar MTMs

And I feel you on the money thing. The total cost of speakers and subs for the setup I'm working on is roughly $750, including a pair of scan 7's in the floors - I would use something cheaper if I could do it again bringing total moving parts cost down to under $250.


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## Patrick Bateman

pwnt by pat said:


> That makes sense. I was considering the diameter of the midranges as opposed to the fact that on the unity, the holes through which the midrange travels through becomes the point of radiation.
> 
> Any chance I could bum the waveguide to make a mold of  I would love to play with this to see how it fares against some onaxis a-pillar MTMs
> 
> And I feel you on the money thing. The total cost of speakers and subs for the setup I'm working on is roughly $750, including a pair of scan 7's in the floors - I would use something cheaper if I could do it again bringing total moving parts cost down to under $250.


The waveguide is cheap! Just $88

18 Sound XT1086

If anyone wants to build one of these, you should be able to re-sell it on Ebay for $70 - $80. That's an investment of twenty bucks 

If building your own waveguides is too much work, Earl Geddes has been known to build one-offs. He doesn't advertise it on his website, but he's done waveguides for cars before. He might still have the mold. I haven't seen what they look like personally.

GedLee Abbey 12 Loudspeaker Kit Immediately appealing with lifelike dynamics and great clarity. Article By Mike Galusha

I have a set of his home speakers, they are my reference.


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## pwnt by pat

Bah I hate ebay now, especially because you have to wait 20 some days to receive payment through paypal if they don't leave feedback. That and $88 is about $3588 more than I have right now haha


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## ehiunno

The system diagram shows 4 TB's on each waveguide, but I can only see 2 in each picture. I assume the other 2 are on the other side similar to the two visible in the pics?

Also, I notice you are running no midbass with these. How low are these going to play? It seems crazy to imagine you could run them low enough to cross over to a sub without localization issues. Unless I missed something important...


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## pwnt by pat

That's what I assumed (4 on each waveguide). He said earlier that 4 tb 2's should have enough swept volume to play down to 300hz.


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## ehiunno

Thanks pat.

300Hz is definitely localizable though, in just about every way. Even if the tapped horn for the sub was located up front (which seems unlikely), you would lose separation in the midbass which would kill your soundstage for male voices, bass guitar, etc.


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## Patrick Bateman

Here's some more speaker porn.

From left to right, we have a Misco KCN5FD, a Misco JC5RTF-B, a Tang Band W2-852SH that I sealed, a Seas L11RCY/P, and a Parts Express 5" professional midrange.




























According to Tom Danley, the midranges for the original Lambda Unity were made to his spec by Misco. I looked through their catalog, and the 2nd woofer in the picture above seemed to be the same woofer. The first one is a newer model, and appears to be an excellent candidate if you can live with a higher crossover to the subwoofers.

Here's the link:

diyAudio Forums - Another Unity Horn - Page 9


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## Patrick Bateman

ehiunno said:


> The system diagram shows 4 TB's on each waveguide, but I can only see 2 in each picture. I assume the other 2 are on the other side similar to the two visible in the pics?


I've only mounted two at this point. In fact I took both of them off, and re-measured them. I'll explain why later in this post. There will be four on each waveguide when this is all done, just like a real unity.



ehiunno said:


> Also, I notice you are running no midbass with these. How low are these going to play? It seems crazy to imagine you could run them low enough to cross over to a sub without localization issues. Unless I missed something important...




Before I tried to build a Unity in 2006, I had the same thought process.

"how low can I get this waveguide to play???"




























There's a whole gallery of horns I built prior to 2006. By 2004 I was using a compression driver that's the size of a subwoofer, just to lower my F3.

But once you throw a Unity horn up on the dash, getting low is a piece of cake. I mean, the dash is HUGE. And we're not only using eight midranges, they're _horn loaded._ So playing low is NOT a problem at all. As long as the waveguide mates with the dash, you're good to go.

No, the problem with a Unity is getting the mids to play *high.* That's the tricky part. It's especially difficult with a Unity because the ideal midrange requires a weird set of parameters.

As I understand it, here's how you do the math.

You figure out how low you can play your tweeter, then figure out where you're going to bring the subs in, and that dictates your midrange specs.

It's not like you can go out and buy any ol' midrange. Our specs are literally set in stone, depending on how the pieces of this puzzle fit together.

For instance, in the original Unity horn, the compression driver comes in at 1400hz, and the subs come in at 200hz.

Then we plug it into this equation:
*sqrt(lower range * upper range)*

For instance, sqrt(200 * 1400) = 529hz

That frequency is the key; it tells us the Fb of our midranges. Note that's not the Fs; Fb is the frequency of our speaker _in a box._

In my case, I didn't purchase midranges that have a closed back. So we use this equation instead:

*529hz = 2*fs/qes*

Since spec sheets are totally unreliable, I bought about ten different drivers, and measured them to see which would work well. The best candidate was the Tang Band W2-852SH. Here are the specs. I measured four to be sure they're consistent.

TangBand W2-852SH
FS 192hz
QMS 4.28
QES 0.54
QTS 0.48

So the TB works out like this:
*2 * fs / qes = 738hz*

Based on that, we could probably run the Tang Bands quite high. For instance, what if we set an upper bound of 2khz, and a lower bound of 250hz? In that case, we'd need an Fb of 707hz.
sqrt(250x2000)=707

But what if we went the other direction? What if we tried to push the midranges down to 100hz, with a top end of 1.5khz? In that case we'd need an Fb of 387hz. That might be do-able, but in my experience, trying to get a bandpass to play two octaves is tricky, getting it to play four is impossible. 

Then again, who knows? Maybe with the right combination of port depth, port diameter, and box volume we could squeeze four octaves out of the mid. I'm already getting output up to 2khz, which is much higher than I expected. I don't think I've posted those measurements yet, I did them on Sunday.

So now that we know what our midrange should measure, we have to make a box. I started out by putting the TBs in a box, which was too big.
Then I tried a sphere, and THAT was too big (even though it was less than half the volume.)
Finally I just blocked off the driver's frame, and it was about right. That's why the midranges look like hell, I literally blocked off the frames, then added a bunch of polyurethane glue for damping and to seal it.










I have some bad news though. If you're going to try this project yourself, you'll need some way to test impedance. It's the only way to figure out if you've got the enclosure size correct. For instance, here's an impedance plot of four woofers. The orange, yellow and red lines are Tang Band. The blue line is a "real" unity midrange. You can see that the Unity midrange has an Fb of about 500hz, and so does one of the Tang Bands. But *two* of the Tang Bands have dual humps in the impedance plot, which indicates that there's a leak, or the enclosure is acting like a passive radiator.

Basically you have to stiffen and seal the enclosure until the impedance curve is correct.










The Unity midrange is basically ideal. Danley says it was custom made for the project. I don't know if I have a "real" midrange from a Unity, but it sure looks like the real deal.

Six years ago, Tom Danley said this to DIY'ers:

_"Locate some "nothing special" 4” or 5 ¼ inch sealed back mid drivers with a resonance around *500Hz.* Make a scratch horn of the size and angles you want, mount the drivers near the apex but on the horn walls with say 2, ¾ inch holes at the horn corners for each driver, entering the horn about 1/4 wl forward of the apex at the intended Xo. Measure the actual response and HF cutoff. In addition to the normal horn stuff, one also has a hf limit set by the distance of the holes to the apex. When this is about 1/4 wl away or more one gets a hf attenuation (acoustic low pass filter effect starting with a deep notch). Adjust this distance so that this roll off you measured is just above where you want to crossover to be. Make the real horns (same size etc), mount the drivers and go to work on the xover. "_

High Efficiency Speaker Asylum: Re: Tomservo, validity of Leach's math model - conical horn? by tomservo

Here's what I got when I measured the midrange that I suspect is in the Unity:
* f(s)= 490.60 Hz
* R(e)= 6.43 Ohms
* Z(max)= 23.20 Ohms
* Q(ms)= 7.192
* Q(es)= 2.757
* Q(ts)= 1.993
* L(e)= 0.14 mH

Here's the measured parameters of my Tang Band mids, in a sealed enclosure:
* f(s)= 528.20 Hz
* R(e)= 3.66 Ohms
* Z(max)= 11.47 Ohms
* Q(ms)= 2.971
* Q(es)= 1.395
* Q(ts)= 0.949
* L(e)= 0.00 mH

So we're right in the ballpark. If anything we might have a little more bandwidth, due to lower LE and QTS.

Of course it begs the question, why not just use a REAL Unity midrange? Well it won't fit in the corner of the dash will it?


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## Patrick Bateman

ehiunno said:


> Thanks pat.
> 
> 300Hz is definitely localizable though, in just about every way. Even if the tapped horn for the sub was located up front (which seems unlikely), you would lose separation in the midbass which would kill your soundstage for male voices, bass guitar, etc.


It's almost trivial to add a bass driver to a Unity. The trickiest part of the Unity is the midrange, and then the compression driver. The woofer part is easy.

Fer instance :

The upper frequency of our midranges is set by a number of factors, detailed in the last post. The big one is the distance to the throat. Take the distance from the throat to the midranges, divide by four, and there's going to be a big fat null due to the reflection.

Let's say it's located 2" from the throat:
*(speed of sound / 2in) /4 =
(13500 inches second / 2") / 4 =
1688hz*

So that's the brick wall on the midranges. All output above 1688hz will be unusuable.

But let's throw a woofer into the mix.

Let's say it's located 8" from the throat:

*(speed of sound / 8in) /4 =
(13500 inches second / 8") / 4 =
422hz*

Eight inches is pretty generous, we could probably get it closer than that. Just wanted to show how much leeway we have with a woofer.

Now we need to figure out it's Fb. Our poor Tang Band woofers have gobs of efficiency on a horn, but playing more than an octave below their Fb is hard on them. So let's move their crossover point up to 500hz. So we'll run our theoretical woofer for two and a half octaves, from 100hz to 500hz, K?

*Fb = sqrt(100 x 500)
Fb = 224hz*

Now we need to figure out it's Fs and it's Qes.

*224hz = 2 * Fs / Qes
Fs/Qes = 112hz *

The next step is to find a driver that fits the bill. There are at least a hundred options for a Unity woofer, because there are tons of woofers that have an Fb of 112hz in a sealed box. It's the midrange that's so tricky, because it requires an Fb of about 500hz. That's tweeter territory!

Here's one candidate, which I just happen to have laying around. It's $15. Our "ideal" Fs/Qes is 112hz, and it's Fs/Qes is 126hz.










I should mention, GM over on Diyaudio showed me the math for this three years ago, I didn't figure any of this out on my own.

diyAudio Forums - Suitable midrange cone, for bandpass mid in Unity horn. - Page 1


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## pwnt by pat

Since you have ways to measure impedance, could I send you some mids to test out? Or maybe you already have a set. They are the infamous Gentoos


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## ehiunno

I really have nothing more to contribute, I just wanted to say thanks to "patrick" for the most thorough response to a question I have ever asked . I'm following this thread closely!


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## lilmike

I'd like to add another thank you. That was the most informative set of posts I've found so far with respect to unity horn design theory.


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## numbskull

+1 To the above posts!
This stuff is confusing and interesting in equal parts.
Please keep it coming


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## marstedt

I was sure that adding mids to a waveguide required them to intersect at (or before) the cross-section where it was approx one wavelength at the highest frequency for that driver. A mid covering 300 - 3000 Hz should connect with the waveguide where it is no larger than 4.5 inches diameter assuming it is conical.

Wavelength at 3000 Hz is approx 4.5 inch.

But in your pic you show a second mid connecting further out. Is this an issue or will it be only adding to the lower end? Or, is it still within the one-wavelength rule?


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## Patrick Bateman

marstedt said:


> I was sure that adding mids to a waveguide required them to intersect at (or before) the cross-section where it was approx one wavelength at the highest frequency for that driver. A mid covering 300 - 3000 Hz should connect with the waveguide where it is no larger than 4.5 inches diameter assuming it is conical.
> 
> Wavelength at 3000 Hz is approx 4.5 inch.
> 
> But in your pic you show a second mid connecting further out. Is this an issue or will it be only adding to the lower end? Or, is it still within the one-wavelength rule?


The uppper frequency on my mids is about 1.4khz, or 10". If I can get them to play higher, great, but if not...

The bigger issue is the notch that's created when the sound reflects off the throat; that comes in at 1/4 wavelength. So if the mids are 2" from the throat, there will be a notch at 1750khz.

That's definitely one of the biggest challenges with the Unity, and one of the reasons I have the midranges hanging right off the throat almost.

There's actually an upside to that notch though; because it's so deep, it does an excellent job of obliterating 2nd harmonic distortion, and steepens the crossover dramatically.

You can see the notch in some of my measurements from two weeks ago. The notch gets deeper and more pronounced as you go from 1 to 2 to 4 woofers.

Also, if you're into tapped horns, everything I've said applies there too. In fact it was the Unity midranges that inspired the tapped horn.

It would be interesting if someone built a Unity horn with the rear wave of the midranges tapped into where the woofers belong. I think it might work. Haven't simulated it though.

Picture this, but replace the woofers with the back wave from the mids, and you get the general idea.


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## Patrick Bateman

Here's some pics of the waveguides on the dash. This is far from finished, and I painted them white to make them easier to photograph. When it's all said and done they'll be cover in black cloth.

It will be a few weeks (or months) before this is all finished.










waveguide from the unity clone i made in 2006, with damping near the waveguide to make them easier to measure.










early version of the 2006 waveguide, with only two mids instead of four.




































2009 unity waveguide pics


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## bassfromspace

Patrick,

Do you plan to drive your car with these waveguides on the dash?


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## Patrick Bateman

cvjoint said:


> How acoustically transparent is this foam piece? Does it not affect 2nd, 3rd order products, decay etc?
> 
> I still don't know if this is just to get a two seater. I mean for a one seater you can easily adjust the level of the farthest speaker to make up for the distance differences. The amplitude shouldn't be that different I would think, My left and right kicks are less than 1m difference from listening position. I never had to adjust more than 2db to make them arrive at the same output level subjectively or objectively on the WinMls.


The foam reduces "higher order modes" - go to diyaudio for more info.

Horns, waveguides, and bandpass enclosures all have an acoustic lowpass function.

In other words, the device _physically_ filters out high frequencies.

This is important to understand, because it has some exciting advantages.

For example, a physical lowpass filter reduces 2nd and 3rd order harmonic distortion.

But an _electronic_ lowpass does not.


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## dbiegel

I've been following your projects for a long time and I think it's awesome that you're pushing the envelope and posting here for us all to learn and discuss. I've never seen anyone else try this stuff in a car and I'm looking forward to seeing how it turns out. I hope I can hear your setup at some point!

Anyway, I'm a little confused on a few things:
1) Why not extend the waveguide to couple with the side glass via the a-pillar and side mirror areas?

2) What made you choose to go dash mounted, rather than below the dash? Wouldn't down low give better pathlengths? What about reflections from the opposite side glass?

3) Lastly, I'd like your advice on something. I'm using a very similar compression driver (JBL version), but with ID mini horns. The screw-to-bolt on adapters I'm using (from parts express) push the driver away from the horn by a half inch or more (there's a gap in the adapter's "tube")... is this really bad, and if so, do you know of any adapters that don't have this problem?


----------



## Patrick Bateman

dbiegel said:


> I've been following your projects for a long time and I think it's awesome that you're pushing the envelope and posting here for us all to learn and discuss. I've never seen anyone else try this stuff in a car and I'm looking forward to seeing how it turns out. I hope I can hear your setup at some point!


Yeah, I really need to demo this one or compete with it. I've heard a lot of show cars and there's only been two or three that really made much of an impression. Harry Kimura's Acura Legend comes to mind.

Richard Clark's Grand National actually got me into horns over 15yrs ago, but I've never heard it.

Eric Holdaway from Speaker Works demo'd the Acura for me, and also gave me some good info on making my own horns years ago. Great guy!



dbiegel said:


> Anyway, I'm a little confused on a few things:
> 1) Why not extend the waveguide to couple with the side glass via the a-pillar and side mirror areas?


You're one step ahead of me. There *will* be a baffle for the waveguide, once this is all done. I can't build one yet, as I may hack down the waveguide further. The reason there's wool and towels in the pictures of the waveguide that I've posted is to approximate the effects of a baffle.



dbiegel said:


> 2) What made you choose to go dash mounted, rather than below the dash? Wouldn't down low give better pathlengths? What about reflections from the opposite side glass?


Imagine if you're standing in a room, lit by a lamp with no lampshade. All the walls are painted white; it's highly reflective.

Would the light that you receive depend on where you were standing? Or would the reflections from the walls, and the omnidirectional light bulb insure that you received light, no matter where you stood?










Now imagine the exact same room, but it's lit by a very powerful and tiny flashlight, with a tightly focused beam.










The reason we want the waveguides up high is that they're like a flashlight. Any little thing that obstructs the beam causes big problems, and screws up our "cone of sound."

I'll post the measurements I did of my USD waveguides. You'll see what I mean. The response is remarkably consistent, but there's all kinds of dip and peaks as you move around the cabin. That's because of reflections and interactions with the USD's weird dimensions.

Many people haven't heard this phenomenon, as they're accustomed to conventional speakers. We can see what's going on by examining the polar response of a conventional speaker and a compression driver mounted on a waveguide.

With a conventional tweeter, the sound radiates in all directions in the midrange. You can see this in a polar plot.

Here's one from a Seas T25CF002. ($224)



















SEAS Excel T25CF-002 (E0011) Millennium Tweeter from Madisound

Now compare that Seas tweeter to my compression driver on the waveguide from 2006.










In the Seas plot, the 2nd line is 30 degrees off axis. The plot above is measured in my car, using a compression driver, on the waveguide from 2006. The orange line is about 30 degrees off axis. What you'll note is that it's down about 3db.

It's hard to tell from the graph, because there's a fair amount of reflections, and the range is quite high.

Basically, from 1500hz to 8khz, the waveguide is down about 3db from the on-axis response. That's like cutting the power in half.

Basically, the sound is being funneled into a cone, just like a flashlight. Due to the wavelengths, it doesn't drop off to infinity like a flashlight.

But 6db down at 45 degrees is like cutting the power by 75%. That's a pretty big drop.



dbiegel said:


> 3) Lastly, I'd like your advice on something. I'm using a very similar compression driver (JBL version), but with ID mini horns. The screw-to-bolt on adapters I'm using (from parts express) push the driver away from the horn by a half inch or more (there's a gap in the adapter's "tube")... is this really bad, and if so, do you know of any adapters that don't have this problem?


Any kind of gap or discontinuity in the throat of a horn is a HUGE problem. At the mouth it's no big deal, but at the throat, it's disastrous.

For instance, a bump or a gap of 1/4" is enough to prevent a "real" waveguide from forming the wave properly. That screws up your polar response.

Another problem is that it creates reflections, which screw up your frequency response.

The thing that's a bummer is that it might not be immediately audible, but it will definitely hose your image.

So yeah, you definitely want to fix that. If you can post some pics I can tell you what to do. What you use to fix it will depend on how big the gap is.


----------



## Patrick Bateman

I'm going to start working on the crossover for the new Unity.

I dug up my notes from three years ago, with the crossover, so I have something to work with.










This is the simulated response of the first crossover from 2006. Looks like the compression driver is covering 2khz - 24khz.

A few days later I changed the crossover from what's in this picture. I don't have a graph of the changes, but my notes say this:

_I reduced the resistor from 5ohms to 1.5ohms. This brings down the volume of the compression driver.
I increased the first cap from 1.5uf to 3.0uf. This flattens out the curve up high, while also increasing the overall level of the compression driver. Which offsets that resistor by a db or two._

What's confusing is that the diagram shows a 50ohm resistor, not a 5ohm resistor. Hmmm...










This measurement shows the frequency response of the Unity from 2006. There's a wide trough that spans two and a half octaves, beginning at 900hz. This was the fundamental flaw of the 2006 Unity, that I've mentioned a bunch of times. The enclosure for the midranges was too big, and their parameters weren't correct. At the time I didn't understand that the Unity requires a very specific set of midrange parameters. There was nothing I could do to fill in that trough, short of replacing the midranges.

But it's still interesting to see the 2006 crossover, because it gives me a starting point for the new crossover.










This is the response of the new midranges on the 2006 waveguide. You can see that we're getting output all the way to 2khz, which will make it possible to fill in that trough that I mentioned above.


----------



## Patrick Bateman

cvjoint said:


> Ok, maybe I'm the only one here that doesn't get it but what's the benefit of this waveguide? These graphs look awful no matter how you try to sweeten it up. I see a 200hz-2000hz graph that is + - 13db or so. That's worse than any setup I started with. Even the off axis curves which you say follow each other very well have rather large variations if you take into account the scale, not to mention is rather random.
> 
> Out of the box a 3 inch driver is well outside of beaming well over 2000hz and has a much broader FR with even less variation off axis. You say all these things how DSP ruins the sound but you will be highly dependent on it to get any sort of usable output out of this thing. You also gotta think beyond xover point, if the response drops like a rock like you say than they won't sum up well with the rest of the gear. I don't mean to be a ball buster but all this talk about perfect complex soundstage doesn't match the data.


The measurements I did last night are beginning to demonstrate what I'm trying to achieve here. I appreciate the patience of everyone who's following this, as it's a bit arduous.











Here's the response of a single midrange on the waveguide, with no compression driver. I was excited about these results because there an almost perfect bandpass response with no crossover. That's key, because we can only play our tweeter down to 1500hz or so. Richard Clark used a compression driver that's the size of a grapefruit, but I don't have that luxury due to the confines of the dash. A larger compression driver could go lower.










As mentioned in the last post, I re-assembled the crossover from 2006's waveguide. The Achilles Heel in the old design was the midranges. Everything else was solid. Here's the response of the new waveguide, new midranges, and old crossover and compression driver.










Here's the exact same measurement, with single octave smoothing. With the new midranges, there's no midrange suckout any more, and the BMS compression driver plays out to 24khz. (Measurement is capped at 16khz btw.)

Basically we're covering seven octaves from a point on the dash that's the size of a 3inch full-range.

Of course, you could just BUY a three inch full range and skip all this nonsense  Honestly, a Unity sounds a lot like a full-range speaker, except with heart-stopping dynamics. 

Here's a few reasons to use a Unity:

*- You'd need four hundred watts to get as loud with a 3" as the Unity gets with ten watts
- We've got directivity control, to improve the polar response (see page 1 of the thread.)
- The image will be good for driver AND passenger
- This is a passive crossover. No DSP and zero EQ.
- If everything goes according to plan, this car will have the efficiency and slam of Richard Clark's Grand National, with the soundstage of Bigg's Buick. (crosses fingers)* :worried:


----------



## donkeypunch22

"If everything goes according to plan, this car will have the efficiency and slam of Richard Clark's Grand National, with the soundstage of Bigg's Buick. (crosses fingers) "


That's some lofty goals. I really hope it turns out as you plan, because that would be sick. 

Didn't Clark use 12" woofers for his mid bass and a ton of processing?


----------



## Patrick Bateman

donkeypunch22 said:


> "If everything goes according to plan, this car will have the efficiency and slam of Richard Clark's Grand National, with the soundstage of Bigg's Buick. (crosses fingers) "
> 
> 
> That's some lofty goals. I really hope it turns out as you plan, because that would be sick.
> 
> Didn't Clark use 12" woofers for his mid bass and a ton of processing?


Make no mistake, I am literally cloning a speaker that's known to be one of the best in the world, and putting it in a car. My intention is to create the finest front stage that's ever been done in an automobile. I am definitely gunning for something that will _exceed_ the Grand National.

The Grand National used waveguides, and it's not a coincidence that my reference speakers were literally handbuilt by the author of "acoustic waveguide theory(1)." I believe it's important to have a home speaker that can act as a reference for the car. This project will re-define what a car stereo can sound like.

In an interview in CA&E, Clark described the perfect speaker, a point source that covered the entire audio bandwidth. The heart of his Grand National are the waveguides, which cover over half the audio bandwidth. Covering over five octaves with a single driver isn't unheard of. For example, the Fountek FR88 can do it. The problem with the Fountek is that it won't get LOUD. A pair will struggle to hit 100db. Richard's waveguides could play louder than that with a fraction of a watt!

So how did the Grand National pull off this stunt?

Well imagine if you wanted to improve on the Fountek. It can already cover most of the spectrum; how would you improve it?

Perhaps you'd give it a bigger voice coil, so it can play louder? Unfortunately, that won't work, because a larger voice coil will roll off the top, due to inductance.

Perhaps you'd make the cone bigger, so it's more efficient? That won't work either, because a larger cone rolls off sooner too.

Here's how the Grand National solved that problem. It used a GINORMOUS driver, an Altec 288C, with the biggest motor you've ever seen on a tweeter. That increases the efficiency through the roof. To combat the roll off, there are shorting rings in the motor. That extends the top end. Last but not least, Clark claimed in CA&E that he had the diahpragms coated with a diamond composition, to extend the top end further.

So THATS how Clark managed to get outrageous efficiency and wide bandwidth out of his driver. Good ol' fashioned engineering overkill.

I followed a similar path with my last Accord, which used a JBL 2470 and custom diaphragms.










The JBL is freaken *huge.* Would you want this under your dash? It's practically the size of a paint can!!










One problem that I had with the JBLs was that they wouldn't play low with much authority. Sure, they went down to 500hz. But they were struggling; they sounded strained. Here's a graph someone posted online of an Altec 288s response. The black line is unequalized, the blue line is with EQ. You can see that it will play down to 400hz, but you need a lot of EQ to get it flat. In my last project, you could "hear" that it was struggling to play low. And obviously, the top octave is completely AWOL.

This isn't a knock against the GN - I'm just saying you have to jump through some serious hoops to get five octaves and a hundred and thirty DB out of a single driver. If you are willing to sacrifice SPL, just buy a full range speaker. That's what I'm running in my car *right now*, and they give you a taste of what a wideband waveguide can do. Honestly, they sound better than most of the expensive two-ways out there.

The next problem that Clark had to solve was the waveguide. Clark used hyoooooge waveguides. They published pics in CA&E; they're bigger than the ones in the pic above. They're ridiculous.










I noticed the dash approximates the shape of a waveguide pretty darn well. The giant pink hunk of foam is a 500hz waveguide mold. Yes, they're THAT big. (Clark's xover was at 400hz.)










From outside the car, you can see the windshield itself extends the curve nicely.










From the passenger side, you can see it's a _really_ close fit. The dash and windshield approximate the curve of a real waveguide almost perfectly.










While the windshield makes a nice waveguide, how on earth are you going to get an Altec 288 up there? Here's my JBL for comparison. It's about the same size.

The compression driver on the right is the BMS 4540ND, a nifty little device that will play to 24khz.










Here's why the JBL and the Altec can play to 400hz. Their diaphragm is the size of a midrange. Unfortunately, it's also the reason they're struggling to play above 10khz.

The little BMS has no problem playing past 20khz, as it's diaphragm is a fraction of the size. It also uses a ring shape to reduce cancellation and increase efficiency. (Like the Vifa XT25, only larger.)










You can see I've kept the amazing JBL motor, but replaced it with a diaphragm that can play higher. It's aluminum, instead of fiberglass. The only thing better would be Beryllium or diamond. Clark used a titanium/diamond composite IIRC.

The diaphragm of the BMS isn't as exotic, but it doesn't need to be, because it's much smaller. It plays to 24khz because it's light and it's small.










The BMS motor has a slug of neodymium in it that's big enough to power a woofer. Despite it's small size, the BMS is actually MORE efficient than Clark's Altec 288!










So there you have it. The old school used an incredibly sophisticated compression driver on a VERY big waveguide to cover over five octaves. I'm using four woofers and one compression driver on a compact waveguide, to do the same. The key is that the dash and the windshield extend the curve, and the Unity concept did not exist when Clark was refining the Grand National.

(1) if anyone's interested in acoustic waveguide theory, here's the paper: AES E-Library: Acoustic Waveguide Theory


----------



## pwnt by pat

How are you planing to compensate for the gauge cluster?


----------



## Patrick Bateman

pwnt by pat said:


> How are you planing to compensate for the gauge cluster?


Fire right over it. That will raise the soundstage. I'd rather have a soundstage near my ears than my kneecaps


----------



## Patrick Bateman

Here's some quick subjective observations, now that I have the Unity playing full-range.

All four mids are on the waveguide now, and I threw together a crossover to compensate for the higher efficiency of the midranges.










My reference speakers are Gedlee Summas. All subjective observations are based on listening to the tracks back-to-back on each system.

Also, I should mention that I don't use many "audiophile" tracks as a reference. Whenever I go to audio shows I noticed that they demo speakers with a lot of jazz and female vocals. IMHO, those recordings sound good on everything from a set of $100K Pipedreams to a $10 clock radio. There's no bass and no treble, and no real dynamics. If you really want to give your speakers a workout, look elsewhere. YMMV

Anyhow...

*Track 1 - Silversun Pickups - "Lazy Eye"*

If there's one thing the Unity excels at, it's articulation. This is a heavily processed, multi-layered track, with a lot of things going on simultaneously. Picture layers after layers after layers of guitars. The Unity is a real champ at articulating the sounds of distorted overdubbed guitars, separating each instrument into it's own "space." At 2:52 in the track, the track builds to a shattering crescendo that's painful on a lot of speakers, but is downright gorgeous on the Unity. If you're a fan of electric guitars, you'll love the Unity. The cymbals on the Unity sound more realistic than on the Summa, likely due to the extra extension of the BMS compression driver. (The BMS goes out half-an-octave higher.) The bass authority of the Summa is incomparable however. It's going to take a lot of work to get the subs in my car to sound as good as the subs in my listening room.

*Track 2 - Meat Beat Manifesto - "Radio Babylon"*

This is a heavy track with a complex and notable bass line, layered with a ton of samples. The Summas absolutely own this track, with their incredible low end and huge dynamics. This track is a great "torture test" for ported subs, as a sub with poor group delay sounds like mush with this track. (seven of my subs are sealed, and the eight is a tapped horn.) OTOH, the Unity has an obvious edge in the top octave. This was a bit of a surprise. The BMS extends to 24khz, and there isn't much going on in the top octave of this track, but the BMS sounded much more "extended." The samples in the track were also easier to spot; the Unity is like an x-ray when it comes to details buried in the mix.

*Track 3 - The Chemical Brothers - "Life is Sweet"*

When a friend of mine demo'd his Lambda Unities for me, the first track he played had a ton of percussion. Now I see why! The Unities have a freakish ability to reproduce drums, integrating the percussive sounds with the bass. It's difficult for me to describe; I've never heard another speaker that can do this. The sound of the drum, from the lowest note to the highest harmonics, is seamless. In this track there are synthesized bass lines combined with sampled drums, and the Unity clearly delineates each one in the mix. While the Unity cannot compare with the Summa's dynamic impact on the synethesized bass hits, on the percussive sounds of a real drum, it's no contest. The Summas can play this track with more dynamic authority, thanks to their dramatic size advantage.

*Track 4 - Johnny Cash - "Hurt"*

If you ever demo a wideband speaker, give this track a try. It's a spare, simple track, and a good wideband speaker will bring out every last detail in the closely mic'd vocals. The track builds to a climax at the end where distortion sets in. It's particularly interesting to listen to on a LOW distortion speaker, as the distortion in the mix is clear as day. On a cheap wideband, the distortion will be masked by the distortion in the speaker. So this track is an excellent "litmus test" of a low distortion wideband speaker. If there's one track that shows off the Unity design, this is it. With the entire vocal range covered by a single waveguide, the articulation and intelligibility of the lyrics is breathtaking.

Keep in mind all of these comments are based on my Unity _clone_, which is much smaller than "the real deal." My clone is optimized to work in a smaller footprint, and sacrifices midbass impact to do so.


----------



## Patrick Bateman

I need to re-vamp the crossover from 2006 for the new midranges, so let's get started.

First we have to measure the impedance of the midranges and the compression driver on the waveguide.

Here it is:








The blue line is the four midranges, in series-parallel. Orange line is the compression driver. The simulations I did on the computer predicted two impedance peaks. (The trough between the peaks corresponds to the tuning frequency of the midranges.)

I am not getting that trough. Not sure if that's due to the unorthodox port configuration, or the very shallow ports, or something else entirely. The ports are about 1/8" of an inch thick, so I'm guessing that's what's causing this.

The efficiency and the bandwidth is good, so I'm not going to complain too much.

Here's the prediction for the mids, from Hornresp:


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## Patrick Bateman

Here's the impedance with a zobel circuit. The zobel is used to flatten out the impedance. Without a zobel, it's almost impossible to design a proper filter, because our filter is dependent on the impedance.

For more information on impedance compensation networks, see Vance Dickason's Loudspeaker Cookbook, or this page:

Series Notch Filter Designer / Calculator Help

Here are my values, at the moment:

R=10ohm
C=28uf








The circuit is on the compression driver, of course.

Here's the new impedance. Look at the previous post for the old impedance.








With the network:

_From 250hz to 2500hz, the compression driver's impedance fits in a window of 7ohms +/- 10%._

WITHOUT the network:

_From 250hz to 2500hz, the compression driver's impedance fits in a window of 15ohms +/- 60%._


----------



## Patrick Bateman

On another thread I posted measurements of the Unity waveguide with a preliminary crossover. I also posted measurements of a commercial car stereo waveguide, for comparison's sake. If anyone's interested, go here:

http://www.diymobileaudio.com/forum/diy-mobile-audio/62160-new-myth-truth-3.html#post781662


----------



## ehiunno

Hey patrick,

I noticed your results are fantastic above 1.5kHz, but below that the dominant side takes over. That is, below that it seems like on axis response is stronger. As you go down in frequency, the imaging becomes more time/phase dominated and less amplitude dominated, certainly, but this still seems kind of high. This leads to the basic question: How is the imaging of male vocals in that setup as you have it?

Also, have you considered using a basic EQ? I know you want to keep processing minimal, but a stereo eq could flatten those dips and peaks without killing the image for passenger and driver because the variations are so symmetric. To be honest I am super jealous that you got FR that flat and symmetric this early in the design! If I ever have a car with a larger, more symmetric dash, this WILL be my next project.

Actually... how feasible do you think this is from the kickpanels?


----------



## Patrick Bateman

ehiunno said:


> Hey patrick,
> 
> I noticed your results are fantastic above 1.5kHz, but below that the dominant side takes over. That is, below that it seems like on axis response is stronger. As you go down in frequency, the imaging becomes more time/phase dominated and less amplitude dominated, certainly, but this still seems kind of high.


A waveguide controls directivity down to a point that's determined by it's dimensions. So if you want to play down to 500hz, you'll need a waveguide that's 27" in diameter. (speed of sound / 500 hz)

In a previous post I'd surmised that the dips at 1200 and 2400hz were caused by reflections off the window near the mic.

I'm having second thoughts on this one.

1200hz is 11.25" long, which is suspiciously close to the size of my waveguide.

So I think what we're seeing here is that the waveguide loses directivity control at 1200hz, because the waveguide has no baffle. When I do my measurements I've been creating a "fake" baffle with sound damping around the waveguide.

But that's not the same thing as a real (solid) baffle.

So stay tuned! I think you'll see a big improvement in the measurements once I baffle the WG.



ehiunno said:


> This leads to the basic question: How is the imaging of male vocals in that setup as you have it?


I only have one waveguide.

The illusion of stereo is created when the left and right speakers are equally loud when equidistant. When they're not equidistant, there's a few tricks we can use to center the image. (see page one of the thread.)

So I haven't bothered making a second waveguide because I wasn't 100% certain that I'd get the midranges to mate up with the compression driver properly. If I couldn't pull off that trick, I'd scrap the whole project.



ehiunno said:


> Also, have you considered using a basic EQ? I know you want to keep processing minimal, but a stereo eq could flatten those dips and peaks without killing the image for passenger and driver because the variations are so symmetric. To be honest I am super jealous that you got FR that flat and symmetric this early in the design! If I ever have a car with a larger, more symmetric dash, this WILL be my next project.


The speakers response is shaped by the waveguide, the foam in the waveguide, and the compression chambers in front of the midranges.

The reason I haven't used an EQ yet is that I have to get those parts perfect first.

It's particularly tricky with the midranges, since the width and the shape of the midrange holes alters the response.



ehiunno said:


> Actually... how feasible do you think this is from the kickpanels?


Remember how I said you'd need a waveguide that's 27" in diameter to control directivity down to 500hz? That's one of the reasons the waveguides are up on the dash.

But that doesn't mean that the Unity concepts are worthless in the kick panels. The only difference is that you would use a flat baffle instead.

Picture a coaxial speaker in the kick panel, but with ONE big difference. The midranges are in bandpass enclosures. Because the sound radiates from a port instead of the cone, you can get the sound from your tweeter and your midranges to couple perfectly.

That's the key to this whole business - we're creating a point source. A point source is the ultimate speaker.


----------



## ehiunno

Patrick Bateman said:


> So I think what we're seeing here is that the waveguide loses directivity control at 1200hz, because the waveguide has no baffle. When I do my measurements I've been creating a "fake" baffle with sound damping around the waveguide.
> 
> So stay tuned! I think you'll see a big improvement in the measurements once I baffle the WG.


Thats exactly what I was implying . I'm excited to see what happens when everything is baffled.



Patrick Bateman said:


> I only have one waveguide.
> 
> The illusion of stereo is created when the left and right speakers are equally loud when equidistant. When they're not equidistant, there's a few tricks we can use to center the image. (see page one of the thread.)


Thats my whole point. Below the 1.2khz mark, you lose your directivity control and your imaging is skewed to the side, at least thats how it seems it would be. However if the baffle helps this, then you might be fine. The majority of interesting imaging is IIRC happening around this mark, so it seems like a crucial area to get right.


My mistake on the EQ/listening impressions, I thought you had two guides done


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## western47

Great work Mr Bateman!!

I am also an owner of Geddes home gear. If anyone out there is really into home audio or HT then stop screwing around and get his stuff as it's the real scientific gear. 

I would like to surmise the basics of where you are at on the build just so I am sure that I'm on the right page so far. You have built a WG using the elliptical profile set documented in this thread. Once this was completed you have trimmed it accordingly. The throat of the WG is mated with the BMS 4540ND-16. There are two pair of TB W2-852SH drivers flanking each side of the WG. The TB drivers were sealed on the backside creating a bandpassed enclosure which ports into the throat area through a 1/8" hole. 

To this point you have a useable frequency range of 300Hz-20kHz. Someone made mention before of 300Hz and down. If this all works out, I would like to use the multi-sub approach that works so well in the home. Will the woofers involved need to reach from sub frequencies up to 300Hz or will there be another step such as a mid-woofer involved?


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## Patrick Bateman

western47 said:


> Great work Mr Bateman!!
> 
> I am also an owner of Geddes home gear. If anyone out there is really into home audio or HT then stop screwing around and get his stuff as it's the real scientific gear.


Get it while you can. I've seen a lot of guys try to make money with good speakers, but it rarely works out. The audio market rewards charlatans. Take a look at this forum, or any forum for that matter. 75% of the people think that cables and amplifiers are the road to audio nirvana.

I would do this for a living if it paid the bills, but it doesn't. So I write software. I read in another forum that Dr Geddes went and got a day job, so draw your own conclusions...



western47 said:


> I would like to surmise the basics of where you are at on the build just so I am sure that I'm on the right page so far. You have built a WG using the elliptical profile set documented in this thread.


Any good waveguide will do. I used an 18Sound XT1086 to make a mold, since that's more "accessible" to the folks on this forum. I could have re-used the OS waveguide from the 2006 Unity that I documented on audiogroupforum. But I figured most people wouldn't want to build a mold.



western47 said:


> Once this was completed you have trimmed it accordingly. The throat of the WG is mated with the BMS 4540ND-16. There are two pair of TB W2-852SH drivers flanking each side of the WG. The TB drivers were sealed on the backside creating a bandpassed enclosure which ports into the throat area through a 1/8" hole.


The volume of the enclosure and the size of the holes is quite critical. And they're not holes, they're "frustrums." (See the synergy horn patent, or the pics I posted on page 2 or 3 of this thread.)

Everything else you noted is true. Also, there are only four or five woofers in the world that work well in this application. So if you build one of these, be sure to use the same woofer. The best candidates are the two from Misco. If I had the space, I would use those instead of the Tang Band woofers.



western47 said:


> To this point you have a useable frequency range of 300Hz-20kHz. Someone made mention before of 300Hz and down. If this all works out, I would like to use the multi-sub approach that works so well in the home.


I had that idea a few years back, but Winslow talked me out of it. Because the wavelengths are so long, the use of multiple subs is unnecessary in the car. For instance, a 100hz soundwave is thirteen feet long. Due to those dimensions, the Geddes multiple sub approach is moot in the car. It only makes sense in a room, where the dimensions are ten feet or greater. The interior of my car is about four feet wide.



western47 said:


> Will the woofers involved need to reach from sub frequencies up to 300Hz or will there be another step such as a mid-woofer involved?


I'm still "on the fence" on this one. 281hz is four feet long. So the Geddes approach may work well from about 150hz to 600hz.

Here are a couple ideas I've had.

*The obvious approach*
The obvious approach is to add a set of woofers to the Unity waveguide. In a previous post I demonstrated that you could put a set of three inch woofers on the waveguide, and extend the response down to 80hz. Basically the three inch woofers would cover two octaves from 80 - 320hz.

*The not-so-obvious approach*
Psychoacoustics demonstrates that imaging cues are dominated by timing differences between 1khz. People have argued that you can't put your midbasses behind you. I've done it with super low-distortion prosound woofers, and it works damn well. The key is low distortion. A lot of people try it with conventional woofers, and wind up disappointed. The problem is that you can't filter out distortion with a crossover, you have to do it in the speaker. So you can't just slap a couple of 6" woofers on the rear deck. You have to use something with insanely low distortion. More importantly, the timing difference has to be PERFECT. In my car I was able to detect a time differential of less than 1/10000th of a second(!!!)

It's really amazing how sensitive we are to timing differences below 1khz. I could post some papers if anyone's interested.

Anyways, the point I'm trying to make is that one solution to the midbass problem is to use four or even eight midbasses, of exceedingly low distortion, and distribute them at very specific places in the cabin. A bandpass enclosure can lower the 2nd and 3rd harmonic distortion dramatically. A Geddes-style distribution of the midbasses smooths out the frequency response better than any EQ or DSP.

Are you seeing where I'm going with this?

Instead of using one 8" midbass, you can use four 3" midbasses, in bandpass enclosures, to get comparable efficiency and low-distortion. Picture a midbass cube that's the size of a Bose Satellite. Even better, you can hide them. The cubes are playing wavelengths that are four feet long; it won't make a damn difference if they're under the dash, on top of the dash, on the rear deck, the floor, etc...All that counts is that each one of them is exactly equidistant, down to a single inch. 

Of course this is all "in my head" at the moment. I have tried using four midbasses instead of one yet. I *was* pleasantly surprised by how much output you can squeeze out of 2" drivers as long as you use enough of them. With the proper engineering, I think the same trick should be possible with the midbasses.

So when this is all done, it will likely use two tweeters (BMS 4540-16), eight mids (TB W2-852SH), eight midbasses (undecided brand), and one sub (P-Audio SN12MB)


----------



## western47

Geddes took a job teaching a physics class or two at a local community college. The primary reason for this was that he wanted to teach. This same sentiment is reflected from his postings over on diyaudio. I understand why so many of the greats will start out posting on different forums and then give up once the attacks start.

Like you, I have a gen 7 accord. Our dashes work well for this sort of setup. If you are using the reverse engineered WG for your car then I can probably do the same thing. It would be even better if I could clone your WG's once they are completed

According to Earl, doing the multi-sub approach in the car is just as justified as in the home. If this is correct, which I think it would be, then having different woofers in different locations covering different bands then we can probably intergrate well up to 300Hz. Using the small BP mids in different locations with similar path lengths sounds interesting as not having anything located in the factory door locations opens up some decent possibilities.

I will certainly be willing to follow your lead on this project!!


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## western47

An XT1086 has been ordered. Once I receive it I will make a plug, fix the crease and glass a clone'.

From the picture of the WG it seems as though the driver mount is still an ellipse in nature. I know that you turned down some other threaded mounts to apply to this scenario but did you deal with this transfer situation in any way?

From the two midbass solutions that you mentioned, my vote would be for the small bandpass enclosures. If the distance issue is a delicate as you state then locating them could be interesting. I don't think that mating more drivers to the WG will be a viable solution as it is relatively full at the moment. Any more thoughts on this? I would love to read a little more about the timing sensitivities below 1k if you have the links.

Thanks.


----------



## Patrick Bateman

western47 said:


> An XT1086 has been ordered. Once I receive it I will make a plug, fix the crease and glass a clone'.
> 
> From the picture of the WG it seems as though the driver mount is still an ellipse in nature. I know that you turned down some other threaded mounts to apply to this scenario but did you deal with this transfer situation in any way?
> 
> From the two midbass solutions that you mentioned, my vote would be for the small bandpass enclosures. If the distance issue is a delicate as you state then locating them could be interesting.  I don't think that mating more drivers to the WG will be a viable solution as it is relatively full at the moment. Any more thoughts on this? I would love to read a little more about the timing sensitivities below 1k if you have the links.
> 
> Thanks.


When I started this thread I was working from home, but I got laid off a few weeks ago. Since I'll be driving a lot more, I am going to shelve this project for the moment, and focus on something that's more practical for a daily driver.

(I probably use this car once or twice a week lately.)

Anyhow, I'm posting all the details here:

diyAudio Forums - Creating a Soundstage with Waveguides and Psychoacoustics - Page 1

Since it's going to be heavy on the psychoacoustics, I'm putting in on diyaudio, as there are a number of experts on the subject who post on that forum.


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## keep_hope_alive

awesome read. waveguides are very cool, i've never seen them studied to this extent in a car before. 

granted, it's waaaaay too much effort for me, but to see it analyzed to this extent is very cool. sub'd.


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## ctrhenry

I hate to hear about the layoff, telecommuting is a sweet set up. Glad you found work though.


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## western47

PB,

I spent the good part of today looking over my gutted car and doing as much reading as possible regarding a car audio system. There are various threads from here as well as diyaudio that have a few different projects at various points of completion. It looks as though the 'Creating a soundstage using psychoacoustics' thread over at diyaudio have a totally different unity than the one last shown in the posts in this thread. Could you clarify for those of us in mid-stream where you are on these projects/thoughts?

It turns out that getting a WG/unity up on my dash should be a doable solution. Unless you say otherwise I will most likely follow your path and attempt the unity design in page 3 of this thread with the 18 sound modified plug, BMS 4540nd and TB drivers. 

If the triple-8 tapped horn is used for the sub then all that is left is the midbass region if I am not missing anything. I did a good bit of looking and fitting of various midbasses in my car today. Knowing that we have the same car, getting a larger midbass far and wide on the drivers side is relatively easy if they are small (3"). The passenger side is going to be a bit trickier as there only seems to be enough space behind the cabin fan for four, 3" drivers. This would place them as far and wide as possible.


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## mpaschetto

Subscribed!


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## mosconiac

Thanks once again for sharing your findings with the board, "PB"!


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## Patrick Bateman

western47 said:


> PB,
> 
> I spent the good part of today looking over my gutted car and doing as much reading as possible regarding a car audio system. There are various threads from here as well as diyaudio that have a few different projects at various points of completion. It looks as though the 'Creating a soundstage using psychoacoustics' thread over at diyaudio have a totally different unity than the one last shown in the posts in this thread. Could you clarify for those of us in mid-stream where you are on these projects/thoughts?
> 
> It turns out that getting a WG/unity up on my dash should be a doable solution. Unless you say otherwise I will most likely follow your path and attempt the unity design in page 3 of this thread with the 18 sound modified plug, BMS 4540nd and TB drivers.
> 
> If the triple-8 tapped horn is used for the sub then all that is left is the midbass region if I am not missing anything. I did a good bit of looking and fitting of various midbasses in my car today. Knowing that we have the same car, getting a larger midbass far and wide on the drivers side is relatively easy if they are small (3"). The passenger side is going to be a bit trickier as there only seems to be enough space behind the cabin fan for four, 3" drivers. This would place them as far and wide as possible.


The last couple of projects have been an attempt to take some of the ideas from the Unity horns, and "scale them down" to something that won't look like ass.

Over on Diyaudio I started a thread called "creating a soundstage with waveguides and psychoacoustics." In that thread, I used a fairly large horn under the dash so that the waveguides ON the dash could be reduced in size.

On this forum, I also posted some information on how to improve the performance of conventional under dash horns, loaded with compression drivers. That thread is called "Grand National in a Box."

The first project really hit a wall, because the under-dash horns just aren't working properly. I put a lot of work into taming their distortion, but it's coming from both the horn AND the driver itself. So even if I fix the horn, the driver is going to be a problem. That's one of the reasons I turned the waveguides on the dash into a Unity - it was an easy way to mask the problems with the horns under the dash.

At this point, I'm really frustrated with under-dash horns. I'm not saying that they're completely hopeless, but almost. It's kind of amazing to me that putting horns under the dash is what USD and Image Dynamics do.

I've noticed that a lot of competitors have bolted large-format compression drivers to horns under the dash, to lower the F3. My measurements seem to indicate that this solution isn't terribly effective; there is a point where the compression driver is simply limited by the under-sized dimensions of the horn itself. It's like trying to get more bass by putting a fifteen inch woofer in a box that's big enough for an eight. At a certain point, the bigger woofer just makes things worse.

That's one of the reasons I *haven't* put a Unity under the dash. The under-sized horn will screw up the frequency response.

This is basically a long and convoluted way of saying that I wouldn't recommend building the under-dash horns from the diyaudio thread. And I haven't come across ANY under-dash horn that works really well. They're all kinda flawed.

Once you get the waveguides up on the dash, the difference is quite a revelation. And there doesn't seem to be a limit to how small you can make the waveguides *if you blend them into the dash.* That last part is the number one most critical part of the "waveguide on the dash" trick. If the transition from the waveguide to the dash is wrong, it WON'T work. 









Here's a pic of the waveguide on the dash. The vertical angle is *exactly* the same as the windshield. Had to compromise on the horizontal angle, but careful attention to the baffle improves the polar response.

I need to get back to work, but here's a quick "brain dump" of what I've learned from building and measuring more horns in cars than just about anyone:


Waveguides on the dash work really well. Good polar response, high efficiency, and an amazing sound stage.
Waveguides on the dash look like ass. There doesn't seem to be a limit to how small you can make them *if you mate with the windshield and the dash very carefully.* If it's not terminated properly, it won't work. Let the curvature of the dash and windshield do the work for you.
Horns under the dash are riddled with problems. The polar response is quite bad. Check out my Homster thread on Diyaudio - the tweaks on there make a huge difference. If you don't believe me, check out some of the threads on here from people who've heard an audible improvement.
My measurements seem to indicate that the 90 degree bend in the USD waveguides creates a notch in the response, due to a reflection that's sent back to the compression driver's throat. If you must use horns under the dash, you should consider building your own. It's not rocket science - even a simple conical horn is a step in the right direction.
The QSC waveguides, at seven bucks a pop, measure better than anything else I've come across. Better than my own OS waveguides, and better than the USD horns. Getting them up on the dash would be a challenge, but if you don't mind your soundstage at kneecap level, they'll work very well in the kick panels too.
You should be able to turn just about anything into a Unity horn. It's really easier than it looks. Basically buy four of the TB midranges that I use, mount them as close to the throat as you can possibly get, then seal off the back of the basket. The FB goes up to 500hz, which is right where it needs to be. Then drill a couple holes that are about 1/2" in diameter, or better yet, use a slot port. Check out the pics - you can see exactly how to mount and configure the midranges from the diyaudio thread. The Unity horn does an amazing job of extending the low frequency output of the waveguide. It's not difficult to lower the F3 of the waveguide from 1500hz to 300hz with the Unity midranges "in the mix." The crossover is fairly simple too, since a simple lowpass and highpass is all that's needed. I am using simple 1st order slopes on the midranges, nothing fancy at all. You'll need a microphone to get the polarity right though. Don't bother trying to make a Unity if you don't have a measurement set up.


----------



## western47

I think I may give this a go. I have cut out cardboard templates to replicate what I would see with the waveguides on the dash. I will drive with them in this position for a couple of days to see if I have any quirky things that come up. It was cold this morning and the defrosting of the complete windshield was a minor issue.

If I do go forward with this then I will document my build process. I have a measurement setup. I also have a QSC waveguide. The supplement needs to be a couple of BMS4540ND's and some TB drivers to get me rolling.


----------



## Patrick Bateman

western47 said:


> I think I may give this a go. I have cut out cardboard templates to replicate what I would see with the waveguides on the dash. I will drive with them in this position for a couple of days to see if I have any quirky things that come up. It was cold this morning and the defrosting of the complete windshield was a minor issue.
> 
> If I do go forward with this then I will document my build process. I have a measurement setup. I also have a QSC waveguide. The supplement needs to be a couple of BMS4540ND's and some TB drivers to get me rolling.


Any small compression driver will work. The Celestion is a better buy. The BMS measures better. (More high frequency extension.)

I've posted some measurements, but they were on different waveguides.

I was kind of amazed by how much you can "tilt" the compression driver. I wouldn't use a 90 degree bend like USD, but I'm using a 30 degree bend and it's not causing any issues.


----------



## western47

If the Celestion is a better buy then I will go for that.

Will the QSC WG give the coverage angles needed to support the Haas Effect properly?

Still awaiting the proposal in the 'Natural Bass' thread. If we are talking as far and wide as possible then we are really limited to mounting locations. Under the already occuring line of the dash just doesn't seem to work for me. Getting something up on the package deck is possible but I am a bit concerned regarding bringing the soundstage back to the front.


----------



## vactor

just an fyi, the qsc horn is here:

HPR122i Horn


----------



## monkeyboy

I have read the threads, and I have to ask... Have you tested any of the car horns other than the USD horn? You lump them all together as one, but I am interested to know if they have all tested the same, or are you assuming that they will? If so, what would lead you to believe that they all work the same?

Not meaning to be arguementative, but I have wondered if other designs have been tested as the USD's have.


----------



## Patrick Bateman

monkeyboy said:


> I have read the threads, and I have to ask... Have you tested any of the car horns other than the USD horn? You lump them all together as one, but I am interested to know if they have all tested the same, or are you assuming that they will? If so, what would lead you to believe that they all work the same?
> 
> Not meaning to be arguementative, but I have wondered if other designs have been tested as the USD's have.


Based on my experience building and measuring horns and waveguides, I believe that the mouth termination and the choice of compression driver will have a greater impact on how the system sounds than whether you go with USD or Image Dynamics. A poorly terminated horn just sounds awful, and both the USD and the Image Dynamics horns are completely unterminated on the bottom half. If the horns aren't properly mounted to the dash, they'll be unterminated on the top half too.

But that's not to say that they're unlistenable; in fact I just finished a set of USD style horns about 30 minutes ago.

If you terminate them properly, it's a night and day difference from what we normally hear in a horn system in the car.

Once you have the termination down, I'd recommend using a good compression driver. For instance, there's no good reason to use a piezo driver when the Celestion compression driver is just $90 a pair. And if you don't mind spending $400, the neodymium models from BMS are very nice.

Of course, I still haven't answered your question.

Have I tested the Image Dynamics unit? No. But I don't see a good reason to. I have tested about a dozen different horns and waveguides, and they all perform fairly predictably. IMHO, people obsess way too much over the curve, and ignore termination entirely. If you get the throat right, the mouth right, use a good compression driver, and terminate it properly, what happens between the mouth and the throat isn't really a huge deal.

If you don't believe this, try this experiment:


Measure a horn in the car
Saw the horn in half!
re-measure it

If it's properly terminated, the frequency response will be virtually the same, because the dash of the car itself forms the majority of the horn. I discovered this a few years ago, when I was trying to fit a horn in my car. It was a real eye-opener. That's why the termination is so important. It smooths out the response to an enormous degree, and lowers the F3 at the same time.


----------



## Amadeuz1

shadowfactory said:


> I will be watching this with great interest.


X2 we will follow


----------



## rawdawg

Patrick,

Have the latest set of USD styled horns been terminated in the same style as your previous offerings or have you finessed things a bit?


----------



## Patrick Bateman

rawdawg said:


> Patrick,
> 
> Have the latest set of USD styled horns been terminated in the same style as your previous offerings or have you finessed things a bit?


Yes, I terminate all my horns and waveguides now. I built a Unity horn last night and the termination changed the response from +/-2db to basically +/- 0db. It also reduced the F3 by half an octave, which was a bit unexpected to tell the truth.


----------



## Patrick Bateman

I've been rather frustrated with a hole in the response of my system. Basically the F3 of my Unity waveguides is about 400hz, and there's a two octave hole between the subs and the waveguides.

So for the heck of it, I built a new Unity horn, with an F3 of about 200hz. Might even get it down to 100 or 150hz with some work.

Details are here:

Creating a Soundstage with Waveguides and Psychoacoustics - Page 10 - diyAudio

Thought I'd note it in this thread, since it's related to this project.


----------



## monkeyboy

Patrick Bateman said:


> Based on my experience building and measuring horns and waveguides, I believe that the mouth termination and the choice of compression driver will have a greater impact on how the system sounds than whether you go with USD or Image Dynamics. A poorly terminated horn just sounds awful, and both the USD and the Image Dynamics horns are completely unterminated on the bottom half. If the horns aren't properly mounted to the dash, they'll be unterminated on the top half too.
> 
> But that's not to say that they're unlistenable; in fact I just finished a set of USD style horns about 30 minutes ago.
> 
> If you terminate them properly, it's a night and day difference from what we normally hear in a horn system in the car.
> 
> Once you have the termination down, I'd recommend using a good compression driver. For instance, there's no good reason to use a piezo driver when the Celestion compression driver is just $90 a pair. And if you don't mind spending $400, the neodymium models from BMS are very nice.
> 
> Of course, I still haven't answered your question.
> 
> Have I tested the Image Dynamics unit? No. But I don't see a good reason to. I have tested about a dozen different horns and waveguides, and they all perform fairly predictably. IMHO, people obsess way too much over the curve, and ignore termination entirely. If you get the throat right, the mouth right, use a good compression driver, and terminate it properly, what happens between the mouth and the throat isn't really a huge deal.
> 
> If you don't believe this, try this experiment:
> 
> 
> Measure a horn in the car
> Saw the horn in half!
> re-measure it
> 
> If it's properly terminated, the frequency response will be virtually the same, because the dash of the car itself forms the majority of the horn. I discovered this a few years ago, when I was trying to fit a horn in my car. It was a real eye-opener. That's why the termination is so important. It smooths out the response to an enormous degree, and lowers the F3 at the same time.


Thanks for the very detailed response.


----------



## thehatedguy

<- has done the unity style horn with my ID bodies back when you were talking about it on Carsound. I used a pair of the sealed back Pionner mids from PE that came recommended from the guys at Yorkville. Might revist it if the large format CDs don't work out.


----------



## Eric Stevens

Patrick Bateman said:


> Of course, I still haven't answered your question.
> 
> Have I tested the Image Dynamics unit? No. But I don't see a good reason to. I have tested about a dozen different horns and waveguides, and they all perform fairly predictably. IMHO, people obsess way too much over the curve, and ignore termination entirely. If you get the throat right, the mouth right, use a good compression driver, and terminate it properly, what happens between the mouth and the throat isn't really a huge deal.
> 
> If you don't believe this, try this experiment:
> 
> 
> Measure a horn in the car
> Saw the horn in half!
> re-measure it
> 
> If it's properly terminated, the frequency response will be virtually the same, because the dash of the car itself forms the majority of the horn. I discovered this a few years ago, when I was trying to fit a horn in my car. It was a real eye-opener. That's why the termination is so important. It smooths out the response to an enormous degree, and lowers the F3 at the same time.


Patrick I really enjoy your enthusiasm. You are tireless in your search to improve things and that is very commendable.

That being said your understanding of horn theory and the physics at work is limited and you are drawing some strong conclusions based upon flawed theories and tests. 

The most and I STRESS "the most" important factor in any horn is the horn design itself this consists of throat, flare and mouth. The termination of said horn when designed properly will have its largest effect on diffraction at a given frequency range and the diffraction effects amplitude will be well below the pass band if crossed over and used properly. 

If you understood horn theory you probably placed the USD horn in the receptacle most suited for it long ago. Read up on the basics and then review the USD's throat, flare and mouth as I previously mentioned.

To say our Horns sound anything like the USD is absurd and only discredits you and your efforts. 

You can take the TAD TD2001 a $1500 ea compression driver and what is the best 1" compression driver IMHO and listen to it on a crappy horn and guess what it WILL SOUND CRAPPY, take a mediocre compression driver on a well designed horn and compare it to the TAD 2001 on a crappy horn and you will choose the sound quality hands down of the mediocre driver on the good horn over the best compression driver on a crappy horn.

To use an analogy like you use often, to say that all horns are alike is the same as saying all 15" speakers sound alike. bottom line is it just aint so.

A horn needs to be designed for the frequency range in which you intend to play it with a proper throat, flare and mouth area, when these this are done right you will find that you dont need the termination to get it to work correctly. I am not saying the termination does not have an effect I am just saying it is not as important as you state in your comments. A large part of this working correctly in the car is you need to design the horn for proper dispersion. 

If you want a better understanding of creating a good sound stage in a car start measuring amplitude of the first reflection versus the direct sound, do this using a impulse response and look at the initial arrival of the direct sound and then look at the 1 st reflection. Wide dispersion and some of what Geddes suggests are actually counter productive in the car because of the early reflection that is generated. Geddes is a brilliant theorist but hasnt done enough practical testing to prove all of his theories. 

Stepping off the soap box for now.

Eric 
Image Dynamics


----------



## western47

Eric,

I for one find your inputs quite valuable. Like many others, I also find Patrick's posts very intriguing. On the flip side, having industry experts whom have dedicated their lives to such said designs and installs will have a wealth of beneficial information to provide. I would love to see more two sided communications about certain aspects of designs similar to those that have been happening over at diyaudio as of late. It would further the knowledge of a comparatively small group of enthusiasts that may be taking their designs past the 'layman' stages.

That said, I am attempting to find a happy medium between having a great soundstage and keeping my car driver friendly. Having horns up on the dash is quite an eyesore but getting them below the dash also seems to be intrusive for some cars or drivers needing knee room. 

Being a Geddes owner for home speakers, I am not sure how you would call them wide dispersion as they are actually quite the opposite compared to typical designs. We all know that reflections are going to be the devil in a car. Keeping a controlled directivity should be exactly what you are looking for.

My thoughts still go back to getting a Summa in a car. I look at the kickpanel area and keep thinking that this would be a great and simple way to place a waveguide into your car. The compression driver can be placed into the corner if you are willing to cut a hole for recess. Proper termination into the firewall, floor and kickpanel areas should be easy enough.


----------



## Eric Stevens

western47 said:


> Eric,
> 
> I for one find your inputs quite valuable. Like many others, I also find Patrick's posts very intriguing. On the flip side, having industry experts whom have dedicated their lives to such said designs and installs will have a wealth of beneficial information to provide. I would love to see more two sided communications about certain aspects of designs similar to those that have been happening over at diyaudio as of late. It would further the knowledge of a comparatively small group of enthusiasts that may be taking their designs past the 'layman' stages.
> 
> That said, I am attempting to find a happy medium between having a great soundstage and keeping my car driver friendly. Having horns up on the dash is quite an eyesore but getting them below the dash also seems to be intrusive for some cars or drivers needing knee room.
> 
> Being a Geddes owner for home speakers, I am not sure how you would call them wide dispersion as they are actually quite the opposite compared to typical designs. We all know that reflections are going to be the devil in a car. Keeping a controlled directivity should be exactly what you are looking for.
> 
> My thoughts still go back to getting a Summa in a car. I look at the kickpanel area and keep thinking that this would be a great and simple way to place a waveguide into your car. The compression driver can be placed into the corner if you are willing to cut a hole for recess. Proper termination into the firewall, floor and kickpanel areas should be easy enough.


I love sharing the contents of my gray matter. Sometimes its hard to balance time available with everything that needs to get done so I probably dont do this as much as I could.

If you operate a horn within its intended frequency range and have an appropriate mouth area say at least 1/4 sized the termination becomes unimportant. If you are trying to reduce the size of the horn by reducing the mouth are to say 1/8th then termination will help you extend the low frequency response and other aspects making it very important. There is also a significant roll of flare frequency to mouth size you must not ignore.

A round horn by nature is a wide dispersion device as in equal in vertical and horizontal. The summa in the car would suffer from early reflection problems just like a direct radiator. Not a huge issue if trying to get great imaging is not high on your list of priorities.

I prefer the sound of a Tratrix horn over even the waveguide designs of Dr Geddes but have chosen to use a modified exponential because I can achieve much better pattern control with added loading at lower frequencies extending the low frequency cutoff for a given mouth size. 

Horns under the dash in most cars is less intrusive than you would think, some cars are impossible though.

Eric 
Image Dynamics


----------



## Patrick Bateman

Eric Stevens said:


> Patrick I really enjoy your enthusiasm. You are tireless in your search to improve things and that is very commendable.
> 
> That being said your understanding of horn theory and the physics at work is limited and you are drawing some strong conclusions based upon flawed theories and tests.
> 
> The most and I STRESS "the most" important factor in any horn is the horn design itself this consists of throat, flare and mouth. The termination of said horn when designed properly will have its largest effect on diffraction at a given frequency range and the diffraction effects amplitude will be well below the pass band if crossed over and used properly.
> 
> If you understood horn theory you probably placed the USD horn in the receptacle most suited for it long ago. Read up on the basics and then review the USD's throat, flare and mouth as I previously mentioned.
> 
> To say our Horns sound anything like the USD is absurd and only discredits you and your efforts.


Eric, if I followed your advice, I'd "read up on the basics", then try to cram a horn into a car. In fact, that's exactly how I got my start, many many years ago.

Here's the problem with the advice you've given me:







This is a properly sized horn. The "horns" sold by USD and Image Dynamics are massively under-sized. That's why I put "horn" in quotation marks.

In my opinion, horns have very limited usefullness in a car. Horns are designed to increase the efficiency of a loudspeaker. But a pair of my compression drivers can hit 130dB with ten watts each! So why would I bother using a horn?



Eric Stevens said:


> You can take the TAD TD2001 a $1500 ea compression driver and what is the best 1" compression driver IMHO and listen to it on a crappy horn and guess what it WILL SOUND CRAPPY, take a mediocre compression driver on a well designed horn and compare it to the TAD 2001 on a crappy horn and you will choose the sound quality hands down of the mediocre driver on the good horn over the best compression driver on a crappy horn.








Hmmm, I've heard the TD2001s a few times...



Eric Stevens said:


> To use an analogy like you use often, to say that all horns are alike is the same as saying all 15" speakers sound alike. bottom line is it just aint so.
> 
> A horn needs to be designed for the frequency range in which you intend to play it with a proper throat, flare and mouth area, when these this are done right you will find that you dont need the termination to get it to work correctly. I am not saying the termination does not have an effect I am just saying it is not as important as you state in your comments. A large part of this working correctly in the car is you need to design the horn for proper dispersion.


I agree, termination is less important if the horn is properly sized. Unfortunately we don't have the space in the car for a properly sized horn. (see my first pic.)




Eric Stevens said:


> If you want a better understanding of creating a good sound stage in a car start measuring amplitude of the first reflection versus the direct sound, do this using a impulse response and look at the initial arrival of the direct sound and then look at the 1 st reflection. Wide dispersion and some of what Geddes suggests are actually counter productive in the car because of the early reflection that is generated. Geddes is a brilliant theorist but hasnt done enough practical testing to prove all of his theories.
> 
> Stepping off the soap box for now.
> 
> Eric
> Image Dynamics


Eric, I have a question for you:

*Why are you bothering with horns?*

I know that Image Dynamics works with one of the world's experts on horns - Dr Bruce Edgar. Horn theory is great if you're designing giant loudspeakers powered by single ended triodes. That's Bruce's market.

Here in the car audio world, 95% of us are running solid state, and we simply don't *need* horns. That's why I spend a lot more time obsessing over directivity and diffraction, and Geddes is clearly the person to study when it comes to that. (I've met both Geddes and Edgar, but I've studied Geddes quite a bit more. My reference for my car audio projects is a Gedlee Summa, the same speakers that he uses.)







Here's the polar response of an under-dash horn. When you dramatically reduce the size of a horn, it creates ripples in the frequency response. This measurement illustrates this - note the ripples.

The bigger problem with horns under the dash is their terrible directivity. When the diameter of a duct exceeds the diameter of a wavelength, the duct controls the directivity of the wave. For instance, if your loudspeaker is radiating a 4khz sound wave, the directivity of the wave will be constrained when the duct exceeds 3.375". (speed of sound/wavelength.)

That last paragraph is critical to understand. I'm sure you already know that, but for the others reading this, wrapping your brain around the directivity problem will go a long ways towards helping you create a believable sound stage.

As you noted, _"A horn needs to be designed for the frequency range in which you intend to play it with a proper throat, flare and mouth area._ The USD horn, in the measurement above, is about 3.5" tall, with a throat that's 1" in diameter. A 4khz sound wave is about 3.5" long. A 13.5khz sound wave is about 1" long.

_Now check out my measurement - and note what's going on between 4000hz and 13500hz._

Would anyone care to comment on what's happening in the under dash horn between 4000hz and 13500hz? Take a look at the polar response, you'll see what I mean.








Here's the polar response of a waveguide, mounted in the kick panel of the exact same car. Everything else is the same as the last measurement, except we're using a waveguide instead of a horn. I measured them back-to-back. But what do you see in the polar response of the waveguide?

Now the reason that I obsess over directivity is that I can fix frequency response with an EQ. But EQ and DSP can't fix directivity.

So it's a chicken and an egg problem. A horn increases efficiency, but I already have plenty of efficiency. A waveguide fixes directivity. So I use waveguides, and I have efficiency to burn. Which makes my EQ very effective.


----------



## Patrick Bateman

western47 said:


> That said, I am attempting to find a happy medium between having a great soundstage and keeping my car driver friendly. Having horns up on the dash is quite an eyesore but getting them below the dash also seems to be intrusive for some cars or drivers needing knee room.


The "horn vs waveguide" argument hasn't come up very much in car audio, but it should be fairly obvious which camp I belong to 

Back in the day people would use large format compression drivers and big horns to get a low F3. For instance, the horns in Mark Eldridge's 4Runner* have a pathlength of 24". For a quarter-length horn, that's 140hz. That's how Mark was able to cross his Altecs over so low.

What I am doing with the Unity horns is different, and even the name is misleading. It's really a _waveguide_ not a horn. Instead of using a giant horn to load down to 140hz, I am using a brute force approach. While the midranges on my waveguide don't have the efficiency of the Altec, and the horn doesn't load down to 140hz, the mids on my waveguide have more excursion than the Altec.

Does that make sense? It's the same idea as using a small sealed box with a big amplifier instead of a big vented box with a small amplifier. I don't have the efficiency of the Altec, but I make up for it via higher excursion.























To give you an idea of how this "brute force" approach works, here's a picture and a frequency response measurement of a Unity horn which fits under the dash of the car. The first few inches of the horn is tractrix. In the frequency response measurement, you can see that the tractrix shape has flattened out the response, and raises the upper limit of the compression driver. The compression driver has a 3" diaphragm, and real output to 400hz. (That's the red curve.) But excursion becomes a problem at low frequencies, and it creates distortion. (Remember that when the horn unloads, excursion goes through the roof. This horn is about 9", and will completely unload at 375hz.)
The orange curve is our puny Peerless midbass. Without a horn, it's efficiency is just 83dB. But mount it on a horn, and it rockets into the high 90s.
The purple curve is the response of both. At 400hz, one midbass has added just 1dB. But at 300hz the efficiency has gone up by TWELVE dB. That's a huge bump.

Things REALLY get interesting when you use FOUR midbasses instead of just one. That raises our efficiency by ANOTHER twelve dB. And that brings our F3 down to the mid 100s.

And these aren't even in car measurements! (That's why they're so flat.) Factor in cabin gain and this gets even sillier. Best of all, with four midbasses, we have excursion to burn. So we can EQ it to our hearts content, potentially even dropping the F3 into the double digits.

Try doing THAT with an Altec 

And again, this is a total "brute force" approach, because _the horn is way too small._



western47 said:


> Being a Geddes owner for home speakers, I am not sure how you would call them wide dispersion as they are actually quite the opposite compared to typical designs. We all know that reflections are going to be the devil in a car. Keeping a controlled directivity should be exactly what you are looking for.
> 
> My thoughts still go back to getting a Summa in a car. I look at the kickpanel area and keep thinking that this would be a great and simple way to place a waveguide into your car. The compression driver can be placed into the corner if you are willing to cut a hole for recess. Proper termination into the firewall, floor and kickpanel areas should be easy enough.









You know that you don't have to drive a horn or waveguide at the throat right? 

I'm getting 20khz off my waveguides, and they're driven at the edge, not the throat. In the pic above, you can see that the driver enters the waveguide at an angle. (Ignore the cat  ) That's how you could get a 90 degree waveguide into the kick panels - don't mount the compression driver at the throat. Mount it at the edge. The tricky part is that you'll get a null in the response that gets deeper as the angle gets bigger. So if it's 30 degrees off axis, the null will be mild and correctable, but if it's 90 degrees, you're gonna have problems. The USD has a 90 degree bend, and you can see the null in the response. You can calculate the null by measuring the distance from the diaphragm to the bend. (Yes, this means that smaller compression drivers work better in this respect. This one from 18Sound would be ideal for a "bent waveguide." It's $49.









* Mark Eldridge: Do The Evolution (Jan/Feb 2001)


----------



## Eric Stevens

Patrick Bateman said:


> Eric, if I followed your advice, I'd "read up on the basics", then try to cram a horn into a car. In fact, that's exactly how I got my start, many many years ago.
> 
> Here's the problem with the advice you've given me:
> 
> 
> 
> 
> 
> 
> 
> This is a properly sized horn. The "horns" sold by USD and Image Dynamics are massively under-sized. That's why I put "horn" in quotation marks.




While that is quite a horn system that has little or no bearing on your observations of a horn in a car. A horn does not need to have a full size or even 1/2 size mouth. A horn can have a 1/8th sized mouth and still function but I believe 1/4 is really the limit. 



Patrick Bateman said:


> In my opinion, horns have very limited usefullness in a car. Horns are designed to increase the efficiency of a loudspeaker. But a pair of my compression drivers can hit 130dB with ten watts each! So why would I bother using a horn?


But you are using a horn. The Geddes waveguide is a horn by definition and function although I agree they are not identical.




Patrick Bateman said:


> I agree, termination is less important if the horn is properly sized. Unfortunately we don't have the space in the car for a properly sized horn. (see my first pic.)


We have plenty of room for a horn used above 500 to 800 Hz. Your original photo has no merits on which to base a conclusion on a proper sized horn for use in a car.




Patrick Bateman said:


> Eric, I have a question for you:
> 
> *Why are you bothering with horns?*
> 
> I know that Image Dynamics works with one of the world's experts on horns - Dr Bruce Edgar. Horn theory is great if you're designing giant loudspeakers powered by single ended triodes. That's Bruce's market.


I use horns for several reasons, controlled dispersion, reduced distortion and improved dynamics range, and wide bandwidth. All of these things separately are a strong reason to consider using them together they make a strong argument for their use.



Patrick Bateman said:


> Here in the car audio world, 95% of us are running solid state, and we simply don't *need* horns. That's why I spend a lot more time obsessing over directivity and diffraction, and Geddes is clearly the person to study when it comes to that. (I've met both Geddes and Edgar, but I've studied Geddes quite a bit more. My reference for my car audio projects is a Gedlee Summa, the same speakers that he uses.)


Geddes Waveguide is just a different type of horn, wider dispersion and less efficient than other types of horns but still a horn.




Patrick Bateman said:


> Here's the polar response of an under-dash horn.  When you dramatically reduce the size of a horn, it creates ripples in the frequency response. This measurement illustrates this - note the ripples.


I wouldnt recommend you try and understand anything about horn response or directional characteristics/polar response using a USD horn, they are that bad in my opinion. 



Patrick Bateman said:


> The bigger problem with horns under the dash is their terrible directivity. When the diameter of a duct exceeds the diameter of a wavelength, the duct controls the directivity of the wave. For instance, if your loudspeaker is radiating a 4khz sound wave, the directivity of the wave will be constrained when the duct exceeds 3.375". (speed of sound/wavelength.)


Horns under the dash can have good dispersion. You understand a lot of the physics at work but dont completely understand how they all interact and how they can be controlled. You are then basing your conclusions on measurements made with a very poor horn design and assuming that any horn that is even similar at all will have the same characteristics. 




Patrick Bateman said:


> That last paragraph is critical to understand. I'm sure you already know that, but for the others reading this, wrapping your brain around the directivity problem will go a long ways towards helping you create a believable sound stage.


I have been preaching controlled dispersion since 1992 



Patrick Bateman said:


> As you noted, _"A horn needs to be designed for the frequency range in which you intend to play it with a proper throat, flare and mouth area._ The USD horn, in the measurement above, is about 3.5" tall, with a throat that's 1" in diameter.


Just because it has those dimensions does not mean it is a proper well executed design. The USD horn measures and perform poorly in every way.



Patrick Bateman said:


> A 4khz sound wave is about 3.5" long. A 13.5khz sound wave is about 1" long._Now check out my measurement - and note what's going on between 4000hz and 13500hz._
> 
> Would anyone care to comment on what's happening in the under dash horn between 4000hz and 13500hz? Take a look at the polar response, you'll see what I mean.
> 
> 
> 
> 
> 
> 
> 
> 
> Here's the polar response of a waveguide, mounted in the kick panel of the exact same car. Everything else is the same as the last measurement, except we're using a waveguide instead of a horn. I measured them back-to-back. But what do you see in the polar response of the waveguide?


Great work and effort put into measuring an inferior product. I will say this again drawing conclusions based upon measurements made using the USD horn is only going to be wrong because you drawing those conclusions on a very poor design.


----------



## Patrick Bateman

Eric Stevens said:


> A round horn by nature is a wide dispersion device as in equal in vertical and horizontal. The summa in the car would suffer from early reflection problems just like a direct radiator. Not a huge issue if trying to get great imaging is not high on your list of priorities.
> 
> I prefer the sound of a Tratrix horn over even the waveguide designs of Dr Geddes but have chosen to use a modified exponential because I can achieve much better pattern control with added loading at lower frequencies extending the low frequency cutoff for a given mouth size.
> 
> Eric
> Image Dynamics












When you look at a horn like the USD or Image Dynamics, you would expect that it would have wide dispersion horizontally, and narrow dispersion vertically. This is only obvious, because the horn is very wide, and very short.

*Ironically, it's the complete opposite.*

Directivity is dictated by the width of the duct. Going back to other example, a duct with a height or width of 3.375" will control directivity down to 4000hz.

So as odd as this sounds, the Image Dynamics horns have narrower directivity in the horizontal axis than in the vertical!

Now anyone who's listened to an Image Dynamics horn will say that's silly, because they're sensitive to the vertical angle. How can I say that they have wide vertical directivity?

_The catch is that the directivity is frequency dependent._

At high frequencies, the Image Dynamics horn will limit vertical directivity, because the walls of the horn are greater than the wavelength. For instance, at 5khz the sound will be constrained by the horn.

But below a certain frequency, *poof*, the horn loses directivity.

This is why horns under the dash sound more extended when you tilt them up a bit; the high frequencies are focused at our knee caps. Tilting them improves that.

You can see this effect in my measurements - at some angles the response is the same on axis and off. And at others the horn has directivity, and the sound is focused on-axis.

As strange as this sounds, the solution isn't a taller horn; it's a _shorter horn._ Theoretically, a 0.675" tall horn wouldn't need to be tilted up, because it wouldn't have any directivity control below 20khz!

As usual, I learned this one from someone else:

High Efficiency Speaker Asylum: Re: best horn dispersion angles for home listening by tomservo

_"I’ve been off line for a while and just saw your question, I’ll take a shot at an answer that I hope makes sense. 

In general, the more asymmetric the horns coverage pattern is, the more it is liable to suffer from a problem called “pattern flip” at / near the frequency range the horn losses its pattern control (which to the first approximation is set by the mouth dimension and horn wall angle). 
Here, the problem is that the narrow vertical angle and wide horizontal coverage angle actually flip temporarily. If the H angle were say twice the V angle, then to avoid pattern flip, the height of the horn exit must be twice the width (which is the opposite of what you get with most horn geometry’s).. 

So far as this issue, more similar the H and V angles are, the less this is a problem there is with pattern flip with normal horn shapes. 
If you define an acceptable mouth size for your room, you have not yet defined the directivity. In theory, if one wanted the least room interaction, then the most directivity / narrowest coverage angle is desired. In fact, if it were possible and you wanted a minimum room situation, one would confine the direct sound path to the listening positions only which means a narrow dispersion angle (like many curved wall horns are at the very top end of there response). 
Because there is very rarely a free lunch in the universe, one faces the problem that for a given mouth size, halving the horns coverage angle also raises the frequency you loose pattern control by about an octave. 
As a result, a small narrow angle horn on a baffle board acts more like a point source on a baffle board over most of its range. 

Personally, I would suggest more towards a larger and wider angle mouth like 60X60 or greater conical horn. The large size / wide angle means you loose directivity lower in frequency and even with a fairly wide angle horn, positioned about halfway between floor and ceiling won’t have strong reflections until the bounce quite some distance (time) from the source. 
“Close to the speaker” reflections are probably the worst thing about wide angle speakers in most rooms. 
I suggest a conical horn because they can be built by a DIY’r on a table saw, they can have constant or nearly constant directivity. 
This means that else where in the room or house, the sound will have more like the same tonal balance as in the listening position. 
The down side is they need to be equalized to have flat response, this is mostly to make up for the fact that the compression driver actually does not have flat acoustic power response. 
Horns / speakers which have highly frequency dependant directivity generally sound fine on axis but the sound is murky and dark elsewhere in the room or house. 
Hope this provides some food for thought. 
Tom Danley "_


----------



## Eric Stevens

Patrick,

I really do admire what you do and the enthusiasm you have. 

Please never stop trying to make things better!!

Horns including wave guides are not for everyone but for those that experience what they are capable of can usually never go back to direct radiators.

The problem with controlled dispersion is the forces at work that control directivity vary by frequency range and it requires a good understanding of the physics and deciding where to make your trade offs and compromises.


Eric
Image Dynamics


----------



## Horsemanwill

so you have some ID horns now my question is have u listened to them properly installed yet?


----------



## Eric Stevens

Patrick Bateman said:


> When you look at a horn like the USD or Image Dynamics, you would expect that it would have wide dispersion horizontally, and narrow dispersion vertically. This is only obvious, because the horn is very wide, and very short.
> 
> *Ironically, it's the complete opposite.*
> 
> Directivity is dictated by the width of the duct. Going back to other example, a duct with a height or width of 3.375" will control directivity down to 4000hz.
> 
> So as odd as this sounds, the Image Dynamics horns have narrower directivity in the horizontal axis than in the vertical!
> 
> Now anyone who's listened to an Image Dynamics horn will say that's silly, because they're sensitive to the vertical angle. How can I say that they have wide vertical directivity?
> 
> _The catch is that the directivity is frequency dependent._
> 
> At high frequencies, the Image Dynamics horn will limit vertical directivity, because the walls of the horn are greater than the wavelength. For instance, at 5khz the sound will be constrained by the horn.
> 
> But below a certain frequency, *poof*, the horn loses directivity.
> 
> This is why horns under the dash sound more extended when you tilt them up a bit; the high frequencies are focused at our knee caps. Tilting them improves that.
> 
> You can see this effect in my measurements - at some angles the response is the same on axis and off. And at others the horn has directivity, and the sound is focused on-axis.
> 
> As strange as this sounds, the solution isn't a taller horn; it's a _shorter horn._ Theoretically, a 0.675" tall horn wouldn't need to be tilted up, because it wouldn't have any directivity control below 20khz!


You are exactly correct they have very wide vertical dispersion and and limited horizontal dispersion.

Our horn was designed for off axis listening and not intended to be angled upward in most cases. If you look at our horn carefully with your understanding you will see that we addressed as best we could the dispersion of different frequencies. our horn for the nearest and most off axis listener is closer to 1" tall in function. We have not problem measuring very well at 45 degrees off axis vertically in fact that is what the horn was designed for 

A simplified explanation of pattern control in a horn is that the high frequencies are controlled by the flare and the low frequencies are controlled by the mouth. 

Eric 
Image Dynamics


----------



## SSSnake

Eric,

Can you recommend an authoritative text that discusses pattern control in horns/waveguides? The online synopses of the AES papers are a bit to succinct to provide much insight as to whether or not the paper offers much insight into general pattern control.

Thanks

Charles


----------



## Patrick Bateman

The AES papers and the books are unnecessarily complex IMHO. Once you get past the math, waveguides are incredibly simple.

Basically, you have to worry about three things:


The height and the width of the waveguide will determine your coverage angle. For instance, if your waveguide is 60 degrees by 40 degrees, the energy from your loudspeaker will be concentrated into that beamwidth.
The diameter of the mouth will determine how low directivity is controlled. For instance, if your mouth is 15" wide, you'll have directivity control down to 900hz. (speed of sound/diameter.)
The diameter of the throat will determine how high directivity is controlled. For instance, if your throat is 1" wide, you'll have directivity control up to 13500hz. (13500 inches per second / 1".) BTW, the phase plug of the compression driver can extend this above it's theoretical limit. That's one of the reasons a $1500 TAD can sound better than a $50 Selenium. I'll post some pics of phase plugs if anyone's curious.
Proper termination improves the off axis response.






 The easiest way to see why this happens is to look at this simulation above. The top pic is an unterminated waveguide. Can you see how the sound "wraps around" the edge, and then goes *backwards?* When you look at a waveguide, it looks like it would direct all the sound towards you, but this isn't the case. The sound waves are more than happy to wrap around, due to their length.
Now look at the pic at the bottom. This is a Le'Cleach horn, which has a big fat roundover. See how the sound *doesn't* wrap around? That's because of the roundover.






These are BIG devices though... In the car it's a lot easier to use the dash itself. A sound wave doesn't care if it's reflecting off a dash or a perfectly sculpted horn, which is why it's so important to terminate the horn or waveguide properly. Use boundaries to your advantage.

Also, these concepts apply to direct radiators too. That's the reason that guys are getting good results when they stick their tweeters in spheres. The spec sheets from manufacturers use a baffle that's about ten feet tall!* That's one of the reasons that spheres work so well. Instead of one strong early reflection off a small edge, you get an infinite number of reflections, delayed in time, and "sprayed" in every direction.

* FRD Consortium tools guide


----------



## Patrick Bateman

Forgot to mention - the software to simulate this is free. Google "hornresp."


----------



## Eric Stevens

SSSnake said:


> Eric,
> 
> Can you recommend an authoritative text that discusses pattern control in horns/waveguides? The online synopses of the AES papers are a bit to succinct to provide much insight as to whether or not the paper offers much insight into general pattern control.
> 
> Thanks
> 
> Charles


Well what I have learned is a combination of AES papers, Text books on acoustics and talking with various people. 

Let me see what I can dig up if I get some time.

Eric


----------



## DaleCarter

I know they sound great, but these horns look like they were designed by TheodorGeisel.


----------



## SSSnake

Patrick,

Thanks for the reply! I am particularly interested in non circular cross-section waveguides and the underlying physics. Intuitively I have never been able to understand why a waveguide which is small in the vertical dimension has a large dispersion pattern in that dimension (underdash waveguides are a good example). 

Does horn length (and therefore associated flare rate) not have an effect on directivity? Again intuitively it would seem to have an effect...

I do have a copy of hornresp. I will have to dust it off and investigate all of its capabilities.

Eric,

Thanks and I appreciate any information that you can provide.

Charles


----------



## Patrick Bateman

SSSnake said:


> Patrick,
> 
> Thanks for the reply! I am particularly interested in non circular cross-section waveguides and the underlying physics. Intuitively I have never been able to understand why a waveguide which is small in the vertical dimension has a large dispersion pattern in that dimension (underdash waveguides are a good example).


The key to understanding this is to realize that the device has *no* directivity whatsoever when the duct is less than the wavelength. The sound is basically radiating in all directions.








For instance, when I first saw a closed back midrange, it just seemed really *wrong.* The whole idea of having the cone a half an inch from a big hunk of metal just seemed like a really bad idea. I mean, you're going to get a huge reflection right?

But it's actually the opposite - reflections don't occur at all in the passband, because the length of the wave dwarfs the distance between the diaphragm and the reflective surface.







I'm willing to bet that's the same reason that the throat of the ID horn is so short. If it was tall, there *would* be directivity, and the high frequencies would beam at your kneecaps. I think I need to officially admit that the USD is bound to sound different than the ID, because the *vertical* coverage of the horn will have a big effect on the height of the soundstage. In the car it's easy to get wrapped up in how things behave horizontally, when the soundstage size is defined by vertical coverage as well. (IE, wide vertical coverage gives you a bigger stage, and masks the fact that the speakers are at your kneecaps.)




SSSnake said:


> Does horn length (and therefore associated flare rate) not have an effect on directivity? Again intuitively it would seem to have an effect...
> 
> I do have a copy of hornresp. I will have to dust it off and investigate all of its capabilities.
> 
> Eric,
> 
> Thanks and I appreciate any information that you can provide.
> 
> Charles


The horn's length, and it's affect on directivity, goes back to my post from this morning. The angle of the walls determines the coverage angle.








In an oblate spheroidal waveguide, the walls are flat. The coverage angle is constant. So the angle won't vary one bit; lengthening the waveguide will simply lower how low it controls directivity.

The downside with the OS waveguide is that it gets ridiculously big in a hurry. The waveguide in my Summas is about two cubic feet in volume and it has a cutoff of 900hz!

As far as directivity goes, horns and waveguide follow the same rules. The difference is that a horn's directivity narrows at high frequencies because the angle of the walls is narrower.

There are some ways to cheat; for instance a diffraction slot will change how the device behaves.


HTH


----------



## Horsemanwill

Patrick Bateman said:


> When you look at a horn like the USD or Image Dynamics, you would expect that it would have wide dispersion horizontally, and narrow dispersion vertically. This is only obvious, because the horn is very wide, and very short.
> [/i]





Horsemanwill said:


> so you have some ID horns now my question is have u listened to them properly installed yet?



i ask again you show urself having some ID horns now have u listened to them properly installed yet?


----------



## Mic10is

Horsemanwill said:


> i ask again you show urself having some ID horns now have u listened to them properly installed yet?


those are old 1E motors, which are piezo drivers. they arent terrible but by no means representative of what a real compression driver on a horn sounds like


----------



## Patrick Bateman

Horsemanwill said:


> i ask again you show urself having some ID horns now have u listened to them properly installed yet?


Those aren't mine. Just took the pic off the web for the sake of illustration.







The ID horns are too small for what I'm doing. To get down low, you need a big mouth.


----------



## western47

PB,

Are you willing to provide a couple copies off of your molds for the unity?

I am wanting to start this project but would rather not have to build my own molds since you have already done the work involved. If not, please just let me know.

Thanks.


----------



## Patrick Bateman

western47 said:


> PB,
> 
> Are you willing to provide a couple copies off of your molds for the unity?
> 
> I am wanting to start this project but would rather not have to build my own molds since you have already done the work involved. If not, please just let me know.
> 
> Thanks.


I *could*, but I personally think there is a better option. Here's why:

To get a waveguide up on your dash, you want a few things:


By far the most important thing is a smooth transition from the throat of the compression driver to the windshield itself. By doing this, _the windshield becomes the waveguide._ This is critical, and getting it right gives you the best pattern control, the best polar response, and it just sounds better.
I have personally found that the first few inches of the waveguide are very important. For instance, in 2008 I invested a lot of work in an asymmetrical waveguide, and it didn't work. I believe this is because the waveguide needs to by symmetrical for good polar response.
If the volume of the horn is too small, the response gets really peaky. In 2009 I made a "shark fin" waveguide with very broad vertical coverage, and it really didn't sound good. Too many peaks, I simply made it too small for the driver. (It might work with a much smaller driver though, so I'm not throwing it away just yet.)

To make a long story short, I have personally built a ton of horns and waveguides over the past decade, and my waveguide from 2006 works the best of all of them. It has excellent polar, power, and frequency response. It is an oblate spheroidal waveguide with a vertical coverage of 108 degrees, horizontal of 72 degrees, and an average of 90 degrees. (The Summa is 90 degrees btw.)

















The coverage angles on QSC's 2009 waveguide, and my 2006 waveguide are virtually the same. _(Hoo hoo! They're ripping me off Robin!*_)​
So basically, I could spend a few hours making a waveguide for you off my mold. Or you could just spend six bucks on the QSC, and get better results. It will look a lot better too. Of course you're still going to have to chop it down like crazy to fit it on the dash, but remember, the mouth and the throat are the most important parts of the waveguide IMHO. You're free to chop the thing down, as long as you baffle it properly on the dash.







The original waveguide for this project, from six months ago, is a clone of the 18Sound xt90. The problem with the 18Sound is that the throat is too long, which makes it very difficult to fit the compression driver on the dash. While it's no big deal to reduce the mouth of a horn, chopping up the throat is very dangerous. Errors at the throat are a much bigger deal than errors at the mouth. So if you're going to bust out the table saw, reduce the mouth, not the throat. (Having said that, I *did* reduce the throat on my waveguide, by a fraction of an inch, so that the compression driver mounts at a thirty degree angle.)















For comparisons sake, here's the ill-fated waveguide from 2008, the shark fin waveguide from a few months ago, and the 2006 waveguide which works the best. Note that horns are flared, while waveguides have a constant coverage angle. (IE, the walls are flat for the most part; the walls define the coverage angle.)






* 10 points to anyone that gets that reference


----------



## KP

Batman


----------



## western47

I'll go a completely different route and say Stern.

Can you post a link to the proper QSC device? The one that I have is the shallow horn which has consistent coverage angles. 

In the first two pics, I am guessing that the plug shown was not made from the rectangular horn?


----------



## SSSnake

OK, but I'm still fuzzy on a few things...

Let's take an example of the Pyle PH612










The dimensions are given above as 6.4"h x 11.9"w x 4.4"d

The coverage pattern is 90 degrees horizontal and 40 degrees vertical.

The problem is the horizontal dimension (w) is around two times that of the vertical (h). Yet the coverage angle shows the maximum coverage in the horizontal dimension (which seems to be in disagreement with the previous directivity statements -


> When you look at a horn like the USD or Image Dynamics, you would expect that it would have wide dispersion horizontally, and narrow dispersion vertically. This is only obvious, because the horn is very wide, and very short. Ironically, it's the complete opposite.
> 
> Directivity is dictated by the width of the duct. Going back to other example, a duct with a height or width of 3.375" will control directivity down to 4000hz.
> 
> So as odd as this sounds, the Image Dynamics horns have narrower directivity in the horizontal axis than in the vertical!


Can we use the diamter rule to assume that vertical dispersion is controlled at 40 degrees above 2600hz (speed of sound/vertical diameter) and becomes omni below?

Then the horizontal dispersion would be 90 degrees above 1100hz (speed of sound/horizontal diameter).

I assume these angles are provided by the contour angles of the waveguide.

But in the case of the ID horn the vertical dimension is so small it only has directivity above 13200hz?

If all this is true then where does the horn depth enter into the directivity discussion?


----------



## Patrick Bateman

SSSnake said:


> OK, but I'm still fuzzy on a few things...
> 
> Let's take an example of the Pyle PH612
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> The dimensions are given above as 6.4"h x 11.9"w x 4.4"d
> 
> The coverage pattern is 90 degrees horizontal and 40 degrees vertical.
> 
> The problem is the horizontal dimension (w) is around two times that of the vertical (h). Yet the coverage angle shows the maximum coverage in the horizontal dimension (which seems to be in disagreement with the previous directivity statements -
> 
> Can we use the diamter rule to assume that vertical dispersion is controlled at 40 degrees above 2600hz (speed of sound/vertical diameter) and becomes omni below?
> 
> Then the horizontal dispersion would be 90 degrees above 1100hz (speed of sound/horizontal diameter).
> 
> I assume these angles are provided by the contour angles of the waveguide.
> 
> But in the case of the ID horn the vertical dimension is so small it only has directivity above 13200hz?
> 
> If all this is true then where does the horn depth enter into the directivity discussion?


I've abandoned this set of waveguides, and started a new set. I'll answer your directivity question, and document the new project, here:

http://www.diymobileaudio.com/forum...forum/71993-unity-v-midbass-strikes-back.html


----------



## Patrick Bateman

I received an email this afternoon inquiring about listening to a set of conventional tweeters off axis. Because it might be of interest to others on the forum, I thought I'd post the answer here.







Here is a pic of a ring radiator. Similar tweeters are offered for sale by Scan Speak, Alpine, and Polk. They aren't all identical, but their performance is similar. The phase plug in the center of the dome acts as a high frequency waveguide. It prevents a cancellation at the apex. By preventing that cancellation, on-axis frequency response extends well beyond 20khz, which is unusual for such a large diaphragm. Because the energy is focused into the forward lobe, off-axis energy is greatly attenuated. Some might thing that's a bad thing. In the car, I believe it's A Very Good Thing. (I am personally using ring radiators, albeit in a compression driver.)







The person who emailed me wrote _"I have been futzing around with some speakers in my basement and the Alpine Scan F1 Ring Radiators sound great on axis but drop off terribly off axis. So are they unusuitable in a car?"_

*So let's figure this out - is this tweeter suitable for listening to off-axis?*

In the pic above, we see the on-axis response, 30 degrees off axis (green) and 60 degrees off axis.

*Scenario 1 - both tweeters on-axis*
In Scenario 1, the driver's tweeter is pointed at the driver, and the passenger's tweeter is pointed at the passenger. With no EQ, the driver's tweeters is going to seem about 6dB too "hot", because it's too close to the driver. The passenger's tweeter is going to be virtually inaudible above 5khz, because once you're off axis the output has fallen by 6-12dB.

Here's what the driver is hearing:
Left tweeter : 91dB @ 2.5khz, 91dB @ 5khz, 91dB @ 10khz, 91dB at 20khz
Right tweeter : 85dB @ 2.5khz, 83dB @ 5khz, 76dB @ 10khz, 69dB at 20khz
_We arrive at these numbers by looking at the graph. The driver's tweeter is the on-axis response. The passenger's tweeter is 45 degrees off axis, and attenuated by 6dB because it's twice as far away._

Have you even wondered why the tweeters in your car sound like crap, and tweaking the balance knob only makes a small improvement? Check out the graph and the numbers above, and you can see why.

*Scenario 2 - both tweeters are steeply cross-fired*
In Scenario 2, BOTH tweeters are steeply cross fired. So the driver's side tweeter is aimed at a point in front of the passenger, and vice versa. In this scenario, the driver is listening to his tweeter at sixty degrees off-axis.

With a steep crossfire, here is what the driver hears (before EQ.)
Left tweeter : 90dB @ 2.5khz, 89dB @ 5khz, 80dB @ 10khz, 73dB at 20khz
Right tweeter : 84dB @ 2.5khz, 84dB @ 5khz, 81dB @ 10khz, 70dB at 20khz
_We arrive at these numbers by looking at the graph from Vifa. The driver is listening to his tweeter at sixty degrees off-axis. He's listening to the other one at 30 degrees off-axis. *Note that above 10khz the left and right are virtually identical.*_

Now let's apply some EQ. [email protected], and 12dB @20khz. That gives you:
Left tweeter : 90dB @ 2.5khz, 89dB @ 5khz, 84dB @ 10khz, 85dB at 20khz
Right tweeter : 84dB @ 2.5khz, 84dB @ 5khz, 85dB @ 10khz, 82dB at 20khz

See the difference? If we listen off-axis, and apply EQ, the ring radiator is now flat for driver *and* passenger from 10 to 20khz. Below 10khz, the response starts to shift from left to right. This is exactly why I use waveguides - they fix this.

But even WITHOUT any waveguide at all, the Vifa ring radiator makes a fine supertweeter, once you apply EQ. And that bullet in the center of the diaphragm is the reason why.

Used as a supertweeter, the Vifa would be an excellent companion for a small woofer in the kick panels. The long path length of kick panels equalize pathlengths. As you can see from the numbers above, one of the main problems with mounting tweeters in the A-Pillars is that one is much louder than the other because it's much closer. Combining kick panels with a super tweeter gives you the best of both worlds. A wide deep stage thanks to kick panels, and treble at ear level thanks to the super tweeters.

Also, if you've ever listened to a car stereo where the soundstage extended beyond the confines of the car, this is the easiest way to do it. When you combine a steep crossfire with a very directional driver, you basically annihilate all early reflections off the windshield and the side windows. Because if these same tweeters fired forward, you'd get a mess of reflections off the windows.

The thing that makes the soundstage ultra-wide is that you get a *delayed* reflection off the *opposite* window. It's this delayed reflection that widens the stage. (early reflections *BAD* delayed reflections *GOOD*)


----------



## thehatedguy

I've had the Scan Ring Revelators...and EQ didn't really fix the off axis performance.


----------



## Patrick Bateman

thehatedguy said:


> I've had the Scan Ring Revelators...and EQ didn't really fix the off axis performance.


Well you have the same problem that I have. I have two of the Vifas, and for two or three years my home speakers were Polks (which use the ring radiator.)

The Vifas are very nice, but they can't compare to a compression driver and a good horn or waveguide.

It's like comparing a Ferrari to a VW GTI. I'd rather drive the Ferrari, but I'd happily recommend the GTI to people who are driving Camrys.

Some people actually have to DRIVE their cars, and don't want a stereo that's under construction all the time


----------



## thehatedguy

On axis they were the best direct radiating tweeter I've heard. Get off axis...eh, they were "ok" at best. Even after EQing the magic wasn't there like on axis. In fact, the Hiquphon OW2 was better off axis than the Ring Rev.

If they had better dispersion then they would have been an excellent super tweeter. Putting a "real" super tweeter- something 105-110 dB up high in the car would be hard. But the benefits with horns might be worth it. The wider dispersion pattern could really add some "air" and "spaciousness" to the topend. Could bring them in at 18-20k on a shallowish slope passive with the horns.


----------



## katodevin

Thanks for detailing the 2 scenarios. What about a 3rd scenario where both tweeters are aimed at the driver? I understand that the left channel would be too loud, but what would it do for the frequency response?


----------



## Patrick Bateman

katodevin said:


> Thanks for detailing the 2 scenarios. What about a 3rd scenario where both tweeters are aimed at the driver? I understand that the left channel would be too loud, but what would it do for the frequency response?


In other words, the drivers side tweeter is pointed at you, and the passengers side tweeter is pointed at you?

That would work (kinda) if you were listening outside.

In the car you run into two problems:

#1 - there's a ton of early reflections, and using asymmetric angles makes the power response asymmetric
#2 - our HRTF changes depending on angle.

Not a lot you can do about the second one, but cross firing solves the first one. It also makes the soundstage wider.

The speakers in my car are cross fired, and it's interesting how different they sound with the windows down. The stage narrows quite a bit.

Then again, I personally prefer it with the windows down, because it's more intelligible.

But I'm really obsessive about this stuff. I've toyed with the idea of buying a convertible because it would have superior imaging! (The best room is no room at all.)


----------



## storm

A quick question: For a 3-way setup, will having the midbass in the doors + midrange in the kicks, and tweeters in the pillars work as well to minimise early reflections? 

Assumption is independent TA and EQ are available. Will there be any potential problems with the above proposed positions? e.g stage hieght?


----------



## sqnut

I have the rings on my sr's. Assuming that the aim is perfection for drivers side and given TA and l/r eq ability; How about if far side tweet was dead on axis and the near side one being a little more on axis to driver than than normal xfiring mode?

I feel there's a very narrow angle band within which these tweets sound sweet and wholesome and natural. Anything outside this and the highs get hollow real fast and imaging gets pulled one way or the other. Once this happens it becomes almost impossible to maintain tonality and image stability, even with the eq.


----------



## Lars Ulriched

storm said:


> A quick question: For a 3-way setup, will having the midbass in the doors + midrange in the kicks, and tweeters in the pillars work as well to minimise early reflections?
> 
> Assumption is independent TA and EQ are available. Will there be any potential problems with the above proposed positions? e.g stage hieght?


Hi Mr. Bateman....I need answer for this questions too....the tweeter is on the dash (touching the windscreen) and steeply cross-firing....as the mid will and the mid bass on the stock door panel is this the best location for xt25, PL11 and PL18?

Is it a good idea having both mid and tweeter on the A pillar both the mid left and right on axis and and the tweeter cross fired?


----------



## Patrick Bateman

sqnut said:


> I have the rings on my sr's. Assuming that the aim is perfection for drivers side and given TA and l/r eq ability; How about if far side tweet was dead on axis and the near side one being a little more on axis to driver than than normal xfiring mode?
> 
> I feel there's a very narrow angle band within which these tweets sound sweet and wholesome and natural. Anything outside this and the highs get hollow real fast and imaging gets pulled one way or the other. Once this happens it becomes almost impossible to maintain tonality and image stability, even with the eq.



What can I say, I went down that road for years. Tried all kinds of byzantine combinations of angle and location, nothing sounded correct.

I never tried listening off axis until a few years ago, and there's no way I'm going back. It just sounds better. The soundstage is wider, articulation is better, and the soundstage is deeper. Of course, equalization is an absolute requirement. This simply *will not work* without EQ. You have to bring up the top end to compensate for listening off-axis. The good news is that we have tons of headroom in the top octave. It's the bottom end of a tweeter's response where we run out of steam.

I think that people take for granted how much the windows screw up the soundstage.

There are only two choices that I can see:

Use the windshield as part of the design. (See my waveguides.)
Aim the tweeters so the frontal lobe is as far away from the windows as possible. (IE, cross fire them.)

The conventional solution is to move the tweeters away from the window. *This only makes things worse.* It makes things worse because it increases the delay between the original sound and the reflection. For instance, if you move your tweeters seven inches from the windshield, you've only delayed that reflection by *one half of a millisecond*.

Taken to the extreme, you would simply buy a convertible... Which I've seriously considered. The windows are THAT big of a problem.


----------



## Se7en

Patrick Bateman said:


> Taken to the extreme, you would simply buy a convertible... Which I've seriously considered. The windows are THAT big of a problem.












Problem solved!


----------



## Patrick Bateman

storm said:


> A quick question: For a 3-way setup, will having the midbass in the doors + midrange in the kicks, and tweeters in the pillars work as well to minimise early reflections?
> 
> Assumption is independent TA and EQ are available. Will there be any potential problems with the above proposed positions? e.g stage hieght?


In my opinion you have to approach everything below 1khz differently. Above 1khz we're uber-sensitive to frequency response for our localization cues. That's why I'm such a freak about directivity control. You could use the most expensive unobtanium tweeters and amplifiers in the world, and those reflections off the window are still gonna get ya'.









Here's the polar plot from another Vifa tweeter. Note that above 5khz, the off-axis energy is reduced by a *minimum* of 3dB. Now I know some of you guys are thinking "3dB, big deal, why bother?"

Here's where the Haas effect comes into play. The Haas effect says *"when two identical sounds (i.e., identical sound waves of the same perceived intensity) originate from two sources at different distances from the listener, the sound created at the closest location is heard (arrives) first."**

Now what do you think happens when you mount a tweeter and it's facing forward? Do you think there's going to be a reflection off the window, and do you think that reflection is going to create a secondary imaging cue? And due to the Haas Effect, do you think that cue may override your perception of the original sound itself? The reason that even a modest reduction in off-axis energy makes a quantum improvement to the soundstage in a car is due to something called "intensity trading" (Google "intesity trading precedence effect", I really gotta get off the computer  )

Is it starting to make sense why my soundstage is deep and wide?

As for midbasses, you have to use a whole different approach to those. 500hz is 28 inches long. At these lengths, our entire hearing mechanism behaves differently. Check out the Natural Bass thread for more. Werewolf is getting to me; I am starting to think that my midbasses belong in the kick panel or even the door.

* Haas effect - Wikipedia, the free encyclopedia


----------



## Se7en

All joking aside, this is a major concern for me because the majority of my roof is glass. I'm starting to suspect that windshield and side glass reflections are the least of my worries.

The surface area is 32X36". I'm almost considering building a custom diffuser.


----------



## Patrick Bateman

Se7en said:


> Problem solved!




I've been know to build furniture on occasion, and thought it would be fun to build a unity horn into a Retreat Pod. (google it.)







Here's a pic of my wife in one, back in happier days.







You can get a better idea of what the pod looks like here







Your humble narrator. Don't let the typewriter fool you - that's actually a very powerful personal computer.












* My jokes make a lot more sense if you're an Opie and Anthony fan btw


----------



## TREETOP

Patrick Bateman said:


> I've been know to build furniture on occasion, and thought it would be fun to build a unity horn into a Retreat Pod. (google it.)
> 
> 
> 
> 
> 
> 
> 
> Here's a pic of my wife in one, back in happier days.
> 
> 
> 
> 
> 
> 
> 
> You can get a better idea of what the pod looks like here
> 
> 
> 
> 
> 
> 
> 
> Your humble narrator. Don't let the typewriter fool you - that's actually a very powerful personal computer.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> * My jokes make a lot more sense if you're an Opie and Anthony fan btw


The first two pics gave me visions of ultraviolence, the third confirmed. Well played.


----------



## Se7en

I have a question regarding staging tweeters based on some of the other comments made previously in this thread.

Although certainly not a "perfect" sound stage, it has been well documented that staging tweeters do in fact help the perception of an elevated stage height.

Lycan, you previously made the statement that our sensitivity to stage height can begin as low as 2.4k. In most systems I've heard with staging tweeters, the effect is generally very slight (but effective) and generally employ a very high XO point. What this suggest to me is that to establish the perception of an elevated stage, drivers playing for 2.4k up are not required in a physically elevated location (perhaps an ideal but not required). 

Patrick, you've suggested that all of these reflections are potentially very destructive unless we find either a way to use these reflections to our advantage and or find an effective way of controlling their dispersion characteristics so to minimize the reflections entirely. The downside to this is the physical size required to create a wave guide effective enough for the desired frequency range.

Can either of you speak to the psycho-acoustic effect that staging tweeters actually have. Clearly their ability to augment certain frequencies is enough to distract our attention away from a physically lower mounted tweeter (kick panel). In your opinion is this the effect of the actual frequencies being played, their arrival time in relation to the other tweeter playing the same or similar frequencies, their dispersion pattern in relation to reflective surfaces? 

Given an install utilizing staging tweeters, would a wave guide help the efficacy of a staging tweeter, given better overall directivity within it's operating range. I can only imagine that given their very narrow operating range, a much smaller wave guide could be developed to optimize their role in the system.

I ask because earlier in this thread I posted an image of my roof (mostly made of glass) and all of this talk of reflections has now given me the fear. Almost to the point of considering not installing in this car at all. My current thinking is that I may be much better off installing my tweeters in the kicks and look to some sort of staging configuration to ensure reasonable stage height. 

Thanks for your input.


----------



## lycan

Se7en said:


> I have a question regarding staging tweeters based on some of the other comments made previously in this thread.
> 
> Although certainly not a "perfect" sound stage, it has been well documented that staging tweeters do in fact help the perception of an elevated stage height.
> 
> Lycan, you previously made the statement that our sensitivity to stage height can begin as low as 2.4k. In most systems I've heard with staging tweeters, the effect is generally very slight (but effective) and generally employ a very high XO point. What this suggest to me is that to establish the perception of an elevated stage, drivers playing for 2.4k up are not required in a physically elevated location (perhaps an ideal but not required).
> 
> Patrick, you've suggested that all of these reflections are potentially very destructive unless we find either a way to use these reflections to our advantage and or find an effective way of controlling their dispersion characteristics so to minimize the reflections entirely. The downside to this is the physical size required to create a wave guide effective enough for the desired frequency range.
> 
> Can either of you speak to the psycho-acoustic effect that staging tweeters actually have. Clearly their ability to augment certain frequencies is enough to distract our attention away from a physically lower mounted tweeter (kick panel). In your opinion is this the effect of the actual frequencies being played, their arrival time in relation to the other tweeter playing the same or similar frequencies, their dispersion pattern in relation to reflective surfaces?
> 
> Given an install utilizing staging tweeters, would a wave guide help the efficacy of a staging tweeter, given better overall directivity within it's operating range. I can only imagine that given their very narrow operating range, a much smaller wave guide could be developed to optimize their role in the system.
> 
> I ask because earlier in this thread I posted an image of my roof (mostly made of glass) and all of this talk of reflections has now given me the fear. Almost to the point of considering not installing in this car at all. My current thinking is that I may be much better off installing my tweeters in the kicks and look to some sort of staging configuration to ensure reasonable stage height.
> 
> Thanks for your input.


First, i didn't mean 2.4kHz ... i meant 2 --> 4 kHz 

We simply can't recognize any height cues below this frequency range, given the dimensions of our outer ears ... which are the only means by which we can determine _height_.

So, mounting tweets up high makes some sense. I _still_ maintain that vertical separation from the midrange is no big deal, to first order, assuming arrival times remain equal (the ear just has no way to perceive that the midrange is "lower" than the tweet). What IS a big deal, however, is that raising the tweets does put them in a more "treble reflective" environment. There's always tradeoffs ...

Careful aiming may help. Waveguides, to minimize reflections and combat side bias, may help. What can I say? Experimentation is your best friend 

Fortunately, tweets are small. Unless they're engulfed with PB waveguides, that is


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## sqnut

Hi Patrick,

I just wanted to thank you for your advise on angling the RR tweets. Its highly topical for me. I upgraded to the Polk Sr's about 3 weeks back. The mids are securely mounted on the door, the tweets are still in temp mode. When I got the sr's installed, I figured that I would play around with the angles first to try and understand what works best. I'm was sure (still am) that I want them mounted on the A-pillars, but at what angle? The entire exercise from day 1 has been about keeping the tweets as on axis as possible.

This flew in the face of everything I had been aiming for, over the last few weeks. But I really liked the simplicty of your assumptions and what you said was logical. Since my tweets were in temp mount, I tried it just to see what happens. Here's what I found:

1. I reset the angles so that the far tweet was about 30deg off axis and the near one about 60deg. These are approximations. I'm not a measuring, numbers guy. Next I checked if I needed to change any TA values, no I didn't. Told myself, 'Well Duh!!'. You havent changed the mids, the TA for tweets only changes, if you need to change the mids TA. I guess I was just following a routine. 

2. From the frequency chart I used the general trand for 30deg and 60deg off axis to re-adjust from 5khz upwards. I didn't use the exact numbers on the chart just followed the general idea to the point where the sound was right. I brought the tweet gains up some. The highs get really dead when you hear them off axis. So you have to breathe some life back into them. In a nutshell above 5khz everything changed, some of it drastically. I have also attached a copy of my settings from earlier and those after the change in tweet angles.

3. *Subjective:*The first thing I noticed was that the image had moved back, deep over the dash. Near the windshield. The next realisation was, that I had been seeing an image that was kinda in my face. Hence certain parts of the image were much larger than they should have been and as a result, the scale of the picture as a whole, was lost. Hold a photograph at an arms length, then bring it up to like 4" from your face. Do you see the same photo differently? Kinda the same thing with the image.

The proportions of the image are so much better and realistic. The aural and visual balance between the frequency ranges is so much better now. So I guess I'm saying, the tweet mounting will have to wait till I get the angles right in this setup. :blush: I'm still oing to play for awhile on this. Thats the fun part for me. 

I'm still working on this and it will be a while before I have it dialed in properly, but staright off the bat its night and day. Thanks a ton. 

I have attached a copy of my tuning sheet for before and after. This is for a vehicle where the wheel is on the right side. Oh, one more thing, you mentioned in one of your posts that the rings struggle at the lower end. You're spot on. I noticed this a few days back. My solution here was to let the mid run full range at the top. The SR mid rolls off around 6khz. So it gives the tweet good support in the 4-6khz range. 

You have a lovely house and I love your 'computer'. I have an IBM daisy wheel some where in storage.


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## lycan

just thought i'd toss this into the mix, hell might not even be the right thread but why not ...

Reflections are nicely described by "image theory". Let's say you have a speaker playing near a reflective surface, like a windshield or side window. See that visual "reflection" of the driver in the glass? Imagine putting a _real_ driver where you see that visual reflection. This is a second "phantom" driver, playing in addition to the first one that caused the reflection. Then remove the glass. What you hear inside the car will, to first order, be the same 

It's a quick way to demonstrate that reflections are identical to a second "phantom" source playing _behind_ the reflective surface. The acoustic field on the listener's side of the reflective surface will be quite the same  And it allows us to apply first-order comb filter relationships.

This can be demonstrated by applying wave theory, and establishing the correct "boundary conditions" at the reflective surface. Or, we can immediately appreciate that it works for EM waves (eg, visible light), because we all observe mirrors at work everyday 

Works the same for sound. Now the reflective surface may not have the same reflectivity for _all_ wavelengths of sound, which disrupts the simple version of "image theory". But it's a good approximation nonetheless


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## savagebee

so with the visually reflected driver being situated to being perpendicular to the reflective surface?

for example, my windshield is very steep, and Ive been considering placing some widebanders on the dash, right next to the windshield, firing up. Will the reflected sound be directed perpendicular to the windshield? 

Or to put it this way, will the visual image you see on the windshield act as though there is a driver mounted directly to its surface? Or will it simply go off of basic physics and fire at an angle from the windshield, based upon the angles of the dash and windshield.


Nevermind, I think I answered my own question.


----------



## lycan

savagebee said:


> so with the visually reflected driver being situated to being perpendicular to the reflective surface?
> 
> for example, my windshield is very steep, and Ive been considering placing some widebanders on the dash, right next to the windshield, firing up. Will the reflected sound be directed perpendicular to the windshield?
> 
> Or to put it this way, will the visual image you see on the windshield act as though there is a driver mounted directly to its surface? Or will it simply go off of basic physics and fire at an angle from the windshield, based upon the angles of the dash and windshield.
> 
> 
> Nevermind, I think I answered my own question.


The phantom driver is placed just where you see the reflection, when observing from the listening position. It will be "behind" the glass, pointing the same way the reflection is pointing. You simply put the phantom driver _exactly_ where the image appears, then remove the glass 

Of course, we are only "conceptually" removing the glass, and "conceptually" replacing the reflection with a phantom driver operating behind the glass, to create the _same_ acoustic field inside the car. We can then analyze the situation with our two drivers operating : the real, first driver, along with the phantom driver ... and no reflecting surface anywhere in sight 

It's a cute ... but accurate ... way to conceptualize, and simplify, this whole 'reflection mess".


----------



## savagebee

so if i place a widebander directly against the windshield the point source will be fairly similar?

I have a dash pad on my car, so the tertiary immediate reflections should be minimized, correct?

Im going to play with these as soon as I get some test mule pvc enclosures built.


----------



## CobraVin

sqnut said:


> You have a lovely house and I love your 'computer'. I have an IBM daisy wheel some where in storage.


psst...thats not him or his house, wife, or IBM, fortunately


----------



## Patrick Bateman

CobraVin said:


> psst...thats not him or his house, wife, or IBM, fortunately


YouTube - A Clockwork Orange - Break-in Scene (Warning: Graphic)

Did anyone else think of this scene when they saw Children of Men?


----------



## CobraVin

savagebee said:


> so if i place a widebander directly against the windshield the point source will be fairly similar?
> 
> I have a dash pad on my car, so the tertiary immediate reflections should be minimized, correct?
> 
> Im going to play with these as soon as I get some test mule pvc enclosures built.


the measurements and math were in another thread, but thats what im going to do with my on dash mids, im just not sure where to put my tweets, deciding between real close to glass firing up next to mid, or in a crude waveguide in the corners


----------



## Fast1one

lycan said:


> just thought i'd toss this into the mix, hell might not even be the right thread but why not ...
> 
> Reflections are nicely described by "image theory". Let's say you have a speaker playing near a reflective surface, like a windshield or side window. See that visual "reflection" of the driver in the glass? Imagine putting a _real_ driver where you see that visual reflection. This is a second "phantom" driver, playing in addition to the first one that caused the reflection. Then remove the glass. What you hear inside the car will, to first order, be the same
> 
> It's a quick way to demonstrate that reflections are identical to a second "phantom" source playing _behind_ the reflective surface. The acoustic field on the listener's side of the reflective surface will be quite the same  And it allows us to apply first-order comb filter relationships.
> 
> This can be demonstrated by applying wave theory, and establishing the correct "boundary conditions" at the reflective surface. Or, we can immediately appreciate that it works for EM waves (eg, visible light), because we all observe mirrors at work everyday
> 
> Works the same for sound. Now the reflective surface may not have the same reflectivity for _all_ wavelengths of sound, which disrupts the simple version of "image theory". But it's a good approximation nonetheless


Using this logic, if we could approximate the center-to-center distance between the real driver and the phantom driver, we can thereby predict where comb filtering will take effect. This depends on the geometry of the windshield itself.

Moreover, if we operate the driver in a bandwidth well below the comb filtering critical frequency point, the reflections due to the windshield can be considered as minimal. Obviously, there will still be minor interference due to a slight difference in phase with the direct vs. reflected sound, but it will be minor compared to the large wavelengths in effect. In addition, the closer we can the driver to the reflective boundary the better.

Doesn't really help us much though. Wavelengths become small very quick. All it pretty much tells us is that we can mount a midbass driver on the dash without issues


----------



## lycan

Fast1one said:


> Using this logic, if we could approximate the center-to-center distance between the real driver and the phantom driver, we can thereby predict where comb filtering will take effect. This depends on the geometry of the windshield itself.
> 
> Moreover, if we operate the driver in a bandwidth well below the comb filtering critical frequency point, the reflections due to the windshield can be considered as minimal. Obviously, there will still be minor interference due to a slight difference in phase with the direct vs. reflected sound, but it will be minor compared to the large wavelengths in effect. In addition, the closer we can the driver to the reflective boundary the better.
> 
> Doesn't really help us much though. Wavelengths become small very quick. All it pretty much tells us is that we can mount a midbass driver on the dash without issues


Bingo 

The closer the driver is to it's phantom ... which lives "through the looking glass"  ... the farther out in frequency the first comb null will be. Might even be able to avoid problems with midrange drivers close to the glass, but tweeters, not so much.

Damn the girl in that new SciFi series "Alice" was hot :surprised:


----------



## sqnut

CobraVin said:


> psst...thats not him or his house, wife, or IBM, fortunately


Yeah I should have figured with this line of his:

* My jokes make a lot more sense if you're an Opie and Anthony fan btw*

His idea though works really well.


----------



## Fast1one

lycan said:


> Bingo
> 
> The closer the driver is to it's phantom ... which lives "through the looking glass"  ... the farther out in frequency the first comb null will be. Might even be able to avoid problems with midrange drivers close to the glass, but tweeters, not so much.


It's going to be difficult with midrange drivers as well. Figure complete destructive interference happens at 1/2 wavelength separation, correct? Some say a full wavelength is a more real world applicable figure IIRC. Let's take best case. 

So if you can get the c-t-c spacing to be roughly 5 inches (3-4 inch midrange shoved in the very corner of the dash): 13,575/5= 2,700 Hz. Not exactly ideal if you are trying to run a dedicated midrange since the crossover point is right in the vocal range. 

What's more, you don't want to run the tweeter that close to a windshield. Moving the tweeter away from the midrange will make the power response at the crossover point unpredictable.


----------



## lycan

Fast1one said:


> It's going to be difficult with midrange drivers as well. Figure complete destructive interference happens at 1/2 wavelength separation, correct? Some say a full wavelength is a more real world applicable figure IIRC. Let's take best case.
> 
> So if you can get the c-t-c spacing to be roughly 5 inches (3-4 inch midrange shoved in the very corner of the dash): 13,575/5= 2,700 Hz. Not exactly ideal if you are trying to run a dedicated midrange since the crossover point is right in the vocal range.
> 
> What's more, you don't want to run the tweeter that close to a windshield. Moving the tweeter away from the midrange will make the power response at the crossover point unpredictable.


All true, the first null occurs when the distance corresponds to 1/2 wavelength.

But, the situation is not quite as bad as it seems because the primary driver, if flat-ish on the dash, is probably starting to beam, meaning it's off-axis response is starting to attenuate. The phantom in the windshield is not beaming yet (the phantom is more "on-axis" than the real primary driver), which simply means that the cancellation null may not be terribly "deep". 

I'm not strongly arguing in favor of dash-mounted midrange drivers, just offering an explanation as to why they might work decently well in some situations close to the glass.


----------



## Fast1one

lycan said:


> All true, the first null occurs when the distance corresponds to 1/2 wavelength.
> 
> But, the situation is not quite as bad as it seems because the primary driver, if flat-ish on the dash, is probably starting to beam, meaning it's off-axis response is starting to attenuate. The phantom in the windshield is not beaming yet (the phantom is more "on-axis" than the real primary driver), which simply means that the cancellation null may not be terribly "deep".
> 
> *I'm not strongly arguing in favor of dash-mounted midrange drivers, just offering an explanation as to why they might work decently well in some situations close to the glass.*


And I completely agree with this statement. 

The beaming is actually a very good observation. We are obviously simplifying the case greatly, but a midrange driver mounted flush with the dash at the very corner may actually operate ok beyond first null. Never thought of it that way. Kudos!


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## CobraVin

how would angling the mid on the dash affect things?


----------



## k-ink

So if you wanted to use one of the 3" wide range point source drivers (without an additional tweeter), would you say an optimum position might be mounting:

- right in the corner of the windshield & dash 
- angled upwards to clear the instrument housing
- angled crossed over inwards, so that:
- the driver hears the near side at 60 degrees off axis and the far one at 30 degrees?


----------



## BigRed

an observation I have noticed recently is that most of the dls demo vehicles all use a mid flat on the dash, and a tweeter on the pillar or sail panel angled in approximately pointed toward a phantom center seat person. they seem to think they work


----------



## stills

are those xlarge defroster vents calling you Savage?
i've got some old rockford audiophile 4in. i may play with soon myself.


----------



## sqnut

heres a pic of Scott Selvidge's 300M from 2006. He has mounted 4, 5" scans, running 2 as mid-bass and 2 as mid drivers. 

http://www.cardomain.com/ride/803525

*source polk audio forum*


----------



## ryan s

lycan said:


> All true, the first null occurs when the distance corresponds to 1/2 wavelength.
> 
> But, the situation is not quite as bad as it seems because the primary driver, if flat-ish on the dash, is probably starting to beam, meaning it's off-axis response is starting to attenuate. The phantom in the windshield is not beaming yet (the phantom is more "on-axis" than the real primary driver), which simply means that the cancellation null may not be terribly "deep".
> 
> *I'm not strongly arguing in favor of dash-mounted midrange drivers, just offering an explanation as to why they might work decently well in some situations close to the glass.*


The last part was something that I inferred from one of Patrick's other posts...correct me if I'm wrong...

It kind of came down to:
-Relatively large-ish waveguide for a relatively small speaker (tweeter)
-Small waveguide for a large (relatively) midrange

That's one of the reasons I gravitated towards a 3" mid playing full range, up in the corners of the dash...it produces a more "narrow beam" of sound vs a tweeter...and needs less "guidance" as the waves are produced.

I probably simplified it too much :blush:


k-ink said:


> So if you wanted to use one of the 3" wide range point source drivers (without an additional tweeter), would you say an optimum position might be mounting:
> 
> - right in the corner of the windshield & dash
> - angled upwards to clear the instrument housing
> - angled crossed over inwards, so that:
> - the driver hears the near side at 60 degrees off axis and the far one at 30 degrees?


That's what I'm going to be experimenting with once it's warm outside. Your conclusions seem correct, but I'm sure you'd rather have Patrick or lycan answer :blush:


----------



## lycan

The mids-on-dash model is a bit more complicated, naturally, than a classical mid+mid in a 2-D line array (for example). Allow me to splain 

The simplest model (while still being useful) looks something like this :

A 3" midrange (for example) on a _horizontal_ surface. Right at the edge of the driver, we have a _reflective_ surface extending (for example) 45 degrees up from the horizontal. I've argued that this situation is essentially identical to removing the reflective surface, and placing a "phantom" driver where the reflected "image" is. In other words, we can remove the reflective surface and place a second driver on the _vertical_ plane "adjacent" to the first driver.

What does the "radiation" pattern look like for this 3-D driver placement (one horizontal, one vertical, necessarily playing the exact same range of frequencies)? Where, in frequency and space, will the first destructive null be? Please note that this is essentially a problem in geometry (and probably calculus), rather than a problem in acoustics. And typical c-t-c spacing rules developed from drivers placed on the same 2-D plane don't really apply, except as general guidelines. Our 2-driver "array" has been "folded" into a 90 degree L-shape 

What still applies, of course, is that waves add constructively or destructively depending on phase (or arrival time) relationships at the measurement point in space. We could "restrict" the spatial concern by just focusing on where the listener will be (one fixed listening position), and just worry about where the first null will be in frequency ...

I gotta think about this smore ...

EDIT : superposition still applies (naturally) 

EDIT II : a simple approximation is that this placement of two 3" drivers in 3-D (one horizontal, one vertical, ends touching) resembles a _single_ driver, of diameter sqrt(2)*3", with a 90 degree cone. Know what I mean?


----------



## k-ink

Can some of these complex reflective issues simply be eliminated by covering up the window in an absorbing material? It would only need to be a patch or strip of material a few inches high, right behind the driver (assuming the driver is mounted right next to the glass)


----------



## Fast1one

k-ink said:


> Can some of these complex reflective issues simply be eliminated by covering up the window in an absorbing material? It would only need to be a patch or strip of material a few inches high, right behind the driver (assuming the driver is mounted right next to the glass)


That wouldn't work well because the effectiveness of the material is wavelength dependent. A small piece of foam for example will only be effective in the upper treble because you are limited by its thickness (<1 inch). 

A dense, diffusive surface with randomly placed peaks and valleys would be more effective. Think of a city skyline with random height skyscrapers.


----------



## thehatedguy

Jeff, a dome mid would work better in that scenario than a cone...corect?


----------



## lycan

thehatedguy said:


> Jeff, a dome mid would work better in that scenario than a cone...corect?


maybe 

howz that for a definitive answer ?


----------



## k-ink

Fast1one, good point. I may have a play with some studio foam I have (flat one side, with triangles on the other). It could be hidden in a small pod right behind the driver, covered with a soft grill to hide the mad looks.


----------



## savagebee

stills said:


> are those xlarge defroster vents calling you Savage?
> i've got some old rockford audiophile 4in. i may play with soon myself.


theyre screaming at me.

I got lucky, and am off work this friday
Im hoping to get my spl tiles installed and get some pvc tubes made up for test enclosures
Im going to try and mock up some positioning in the corners


----------



## Fast1one

k-ink said:


> Fast1one, good point. I may have a play with some studio foam I have (flat one side, with triangles on the other). It could be hidden in a small pod right behind the driver, covered with a soft grill to hide the mad looks.


You need to experiment with something denser and/or more reflective. Reason being is you want to promote reflections and not absorption. However, you want to the reflections to be highly randomized or "diffused" 

I don't think a simple "Checker Board" like diffuser is going to work quite as well as a highly randomized pattern over three dimensions. Take a look at the lower right example:










THAT is what you want.

Edit: I forgot to mention some of the more simple diffusers simply use curved surfaces to diffuse the sound...










You can buy single plys of wood that easily bend into the shape you want. Might be a little more difficult to replicate in miniature form, but it should be doable.


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## Patrick Bateman

CobraVin said:


> how would angling the mid on the dash affect things?


Let's find out!

In this exercise I intend to prove two things:

#1 - In car audio, we often choose speaker locations based on intution. For instance, putting speakers in your A-Pillar _seems_ like a superior location. But is it? Before we rip our cars to pieces, we can use an SPL calculator and the polar response of a speaker to figure out the best location. Keep in mind that the goal _is not flat frequency response._ The goal is _equal frequency response, for both speakers._ This is why we need to do the math, instead of listening to the speakers. If you simply put the speakers in the car and listen to them, _your ears will fool you._ Remember, _we can fix frequency response electronically, but getting the speakers to the same level on both sides can only be done mechanically._ I don't have anything against listening to speakers, but this entire scheme hinges on using EQ to "fix" the off-axis response. So doing this exercise with your ears is like evaluating a filet mignon before you've bothered to cook it. The EQ is fundamental here.

If you don't want to wade through the data, the conclusions are at the bottom of this post.







Here's a pic of a typical dash. The numbers indicate the various schemes we'll explore.















Here's the polar response of a fairly typical 3" midrange from Tymphany. IIRC, Hybrid Audio and Focal don't publish polar curves, but they're all fairly similar as long as there isn't a phase plug. A diaphragm will begin to beam at one wavelength. In the case of a 3" driver, one wavelength is 4500hz. _In the graph above, you can see it's behaving exactly as we'd expect it to._ So you can do the same exercise with any woofer you'd like really.

*Location 1 - midrange mounted in A-Pillar*
In the first scenario, the midrange is pointed at the passenger seat. We're listening 45 degrees off axis. In an Accord, the A-Pillar near the driver is 36" away, and the opposite is 48" away. Based on the chart above, and these distances, here's what we get:

_(note that the goal isn't FLAT response. The goal is EQUAL response. We can fix frequency response electronically, but directivity can only be manipulated mechanically.)_



*Frequency / SPL (left) / SPL (right) / Where's our stage?*
1250hz / 84.72dB* / 82.2dB** / shifted 2.42dB to the _left_
2500hz / 87.72dB* / 85.2dB / shifted 2.52dB to the _left_
5000hz / 78.72dB* / 83.2dB / shifted 4.48dB to the _right_

*Location 2 - midrange mounted at top of door*
In the second scenario, the midrange is pointed at the passenger seat. We're listening 90 degrees off axis. In an Accord, the top of the door near the driver is 34" away, and the opposite is 50" away. Based on the chart above, and these distances, here's what we get:

_(note that the goal isn't FLAT response. The goal is EQUAL response. We can fix frequency response electronically, but directivity can only be manipulated mechanically.)_



*Frequency / SPL (left) / SPL (right) / Where's our stage?*
1250hz / 85.2dB*** / 81.9dB / shifted 3.3dB to the _left_
2500hz / 88.2dB*** / 84.9dB / shifted 3.3dB to the _left_
5000hz / 77.2dB*** / 82.9dB / shifted 5.7dB to the _right_

*Location 3 - midrange mounted in extreme corner of dash, all the way to the windshield*
In the third scenario, the midrange is pointed at the passenger seat. We're listening 45 degrees off axis to our side, and ON axis to the other. This is the stock location for a 2" driver in an Accord. The distance to the left is 45", and to the right is 54". _Note that these pathlengths are about 50" plus or minus 10%. So this location will have the deepest stage, and the closest pathlength match of all._ The difference between location 3 and 4 is that the midrange is pointed AT us, not up. Based on the chart above, and these distances, here's what we get:

_(note that the goal isn't FLAT response. The goal is EQUAL response. We can fix frequency response electronically, but directivity can only be manipulated mechanically.)_



*Frequency / SPL (left) / SPL (right) / Where's our stage?*
1250hz / 82.8dB* / 81.2dB** / shifted 1.6dB to the _left_
2500hz / 85.8dB* / 84.2dB / shifted 1.6dB to the _left_
5000hz / 76.8dB* / 82.2dB / shifted 5.4dB to the _right_

* to get the values for 45 degrees off-axis, I averaged 30 and 60 from the chart.
** To figure out the left and right numbers, I plugged the distances into a calculator which will give you SPL vs distance. You can use it here: Damping of sound level with distance - decibel dB damping calculation calculator distance versus sound reduction free field - decrease in sound over distance microphone distance versus dB sound at different distances - sengpielaudio Sengpiel Berlin
*** We don't have any measurements for 90 degrees off axis, so I used 60. It's all we got. It should be "in the ballpark."

*Conclusions*​Now the good part. The conclusions. Based on the data above, you'd be inclined to choose the extreme corner of the dash as the best location for your midrange or tweeter. At high frequencies we're strongly affected by frequency response, so we want the left and the right speaker to be as close as possible. And below 5khz, this location has the closest match of all. The left speaker is just 1.6dB "hotter" than the right.

But if you chose that location, you would be wrong 








Here's the last part of the puzzle. This is something called "intensity trading." This is something we're all familiar with; basically if you're too close to one speaker you can reduce it's volume to counteract it's proximity. *This is exactly what you're doing when you turn the balance knob.*

I've taken the liberty of marking the curve for our three locations. Location 3 and 4 require the least intensity trading, while location 2 requires the most.

The intensity trading curve shows us something that we already know -
*In order to get the image on the center of the dash, we need a strong bias to the right*

As the numbers above demonstrate, the best way to achieve that bias is by using the speakers in a range where they're beaming.







Please re-read that conclusion above about ten times, seriously 

Because of intensity trading, we need a bias of about three to six dB *to the right*. And NONE of the three locations will give you that bias, UNTIL THE SPEAKER IS BEAMING.

Seriously, I know this flies in the face of what everyone recommends. In home audio, you typically listen on axis, and you cross your drivers over at a frequency where they're NOT beaming.

In car audio, we basicaly want the opposite, *because we're listening off axis*

If you don't believe me, just look at the numbers. Or crunch them yourselves. Once you do, you'll realize that *the intuitive locations are not necessarily the best, and you can use directivity to create a wide and centered stage for BOTH listeners.*


----------



## Patrick Bateman

One thing I wanted to add - I'd like to thank you guys for encouraging me to do this. Honestly, even with years of experience with horns and waveguides, I'd never realized how much directivity changes the puzzle. For instance, I would normally dismiss putting a tweeter in the top of the door, because it's WAY too close to the driver. For instance, the pathlength differential between that location and the extreme corner of the dash is almost DOUBLE.

But directivity changes EVERYTHING, because the _pathlength difference is 3dB but the directivity difference can be 3-10dB._ (In other words, the door is way too close, but we can direct the output AWAY from us to counteract it's proximity. The key to this is that *we must listen to the driver when it's beaming.*

Therefore, I believe it's possible to create a wide centered stage with tweeters in the doors. And I wouldn't have agreed with that statement even one day ago.

To me, this is really exciting stuff. It seems like it might be possible to create a real soundstage with woofers in the kicks and tweeters on the door. (Yes, I know this is what people have been doing for the past twenty years  ) The key is that you absolutely positively need a tweeter that's beaming, and it will work best if the off axis response is very VERY good. (Not flat, just smooth. We can fix the response with EQ.)















To give you an idea of what I mean, here's a picture and the frequency response of a SEAS tweeter that fits the bill nicely. See how the on-axis and the off-axis curves look very similar? _That's what we want._ Yes, it uses a waveguide.


----------



## Hernan

I think that two more issues must be considered.

Reflexions from the windows and the phantom images from the opposite side drivers.

The very different angles between the drivers and the eardrums. If we don't sit equidistant from the source, the HRTF is playing a huge role in the perception. This is one of the reasons that mic measurments doesn't correlate to subjetive evaluation...
The mic is omni, our hearing system is not.


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## lycan

ahhh ... Patrick is seeing the light 

At first glance, we would like to follow home audio mentality : listen on axis!
Then we find out that may not be the best way to go in a small, reflective environment. What does "on-axis" even mean, in such a near-field reflective environment ... ???

Then we think a little more, and realize that, no matter what, we're going to be listening to drivers "off-axis", especially if we care about _both_ front seat listeners. So ... we must want drivers with GREAT off-axis response, right?

Well, not so fast. How can we attenuate sound _intensity_, in the frequency range where inter-aural _intensity_ dominates, for the near-side listener ... when _both_ front seat listeners are near-side to their own speakers? Sure can't do that electronically  

ALSO ... how can we maybe control some directivity to help mitigate reflections? The answer is : take advantage of off-axis attenuation of drivers, maybe even using waveguides (still intriguing to me, by the way) in some innovative ways 

Off-axis attenuation can be more friendly to you in car, than in a home  And it's one reason (of many) that keeps me interested in this hobby. The car environment is _not_ just some bastard stepchild of the "great realm" we know and respect as home audio  The car is a fascinating environment, all to itself, with some unique constraints that force us to learn lots more about audio than we might ever experience in a home.


----------



## stills

i'ma mount a fake ficus tree to my dashboard.


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## katodevin

Patrick Bateman said:


> But directivity changes EVERYTHING, because the _pathlength difference is 3dB but the directivity difference can be 3-10dB._ (In other words, the door is way too close, but we can direct the output AWAY from us to counteract it's proximity. The key to this is that *we must listen to the driver when it's beaming.*
> 
> Therefore, I believe it's possible to create a wide centered stage with tweeters in the doors. And I wouldn't have agreed with that statement even one day ago.



Forcing the driver's side tweeter into a beaming posistion is not difficult, but a tweeter on the passenger side in the same orientation would nearly be on axis, unless it is a tweeter with very narrow disperson. Do you feel that an asymmetrical tweeter orientation forcing both tweeters into off axis would be the solution?


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## falkenbd

katodevin said:


> Forcing the driver's side tweeter into a beaming posistion is not difficult, but a tweeter on the passenger side in the same orientation would nearly be on axis, unless it is a tweeter with very narrow disperson. Do you feel that an asymmetrical tweeter orientation forcing both tweeters into off axis would be the solution?


I think the point is that the tweeter closer to YOU (in either seat) is off axis and the other is closer to or on axis.

The reason being: this is what will create the equal intensity (between L and R tweeter) at both seating/listening positions. Giving you a better chance at a 2 seat sound stage.

The closer speaker being off axis and the further speaker being farther away (and closer on axis) putting them closer in level.


----------



## Patrick Bateman

lycan said:


> Off-axis attenuation can be more friendly to you in car, than in a home  And it's one reason (of many) that keeps me interested in this hobby. The car environment is _not_ just some bastard stepchild of the "great realm" we know and respect as home audio  The car is a fascinating environment, all to itself, with some unique constraints that force us to learn lots more about audio than we might ever experience in a home.


Car audio is also a "communal environment." I have Gedlee Summas at home, but it's rare when other people get an opportunity to listen to them. OTOH, I have other people in my car all the time. My girlfriend's car has an excellent soundstage, as good as I've heard, but it uses DSP to get there. (stock Bose system.) DSP makes the passenger side unlistenable.

Also, generally when I *do* have an opportunity to use the Summas with other folks around, it's for a movie, and in that situation the excellent sound is masked by the picture.

Last but not least, it's not practical to listen at really crazy SPLs at most house. 120dB will get you evicted in a hurry.


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## Patrick Bateman

katodevin said:


> Forcing the driver's side tweeter into a beaming posistion is not difficult, but a tweeter on the passenger side in the same orientation would nearly be on axis, unless it is a tweeter with very narrow disperson. Do you feel that an asymmetrical tweeter orientation forcing both tweeters into off axis would be the solution?


Asymmetry sucks because it screws up the power response. You want things symmetrical.

Check out the numbers in this post:
http://www.diymobileaudio.com/forum...creating-perfect-soundstage-8.html#post930489

If the numbers are correct, then it means that the directivity of the tweeter influences how "solid" the soundstage is more than the location of the tweeter itself. This correlates nicely with what people notice subjectively, which is that aiming their tweeters has a huge effect on the size and stability of the stage.

Rather than futz around with aiming, I'd argue that we should figure out the directivity problem first. Aiming is too much trial and error.







The numbers also imply that even locations like the upper door aren't as crappy as they once seemed. Due to the way that we perceive high frequencies, we really don't have to obsess about getting them as far or wide as possible. _By juggling the directivity of the near and far tweeter, we can use a less-than optimal location. Of course the tweeters MUST have very smooth off-axis response. (Not necessarily flat, but smooth; we can use EQ to flatten things.)_ Pathlengths are much important form midranges and midbasses.


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## rugdnit

stills said:


> i'ma mount a fake ficus tree to my dashboard.


Finch! You stay the ____ away from that ficus!

Lengthy read.... but thanx for the info guys!


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## katodevin

Ah, that makes sense. Which I now understand why you stressed having a tweeter who's off axis curve is similar, albiet lower, than the on-axis curve. 

Thanks so much, this topic could not be more timely in terms of what I'm going to be experimenting with in the upcoming few weeks.


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## lycan

katodevin said:


> Ah, that makes sense. Which I now understand why you stressed having a tweeter who's off axis curve is similar, albiet lower, than the on-axis curve.


That's what a waveguide does  Can't get a frequency-independent, off-axis attenuation without it (as far as i know).


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## Se7en

I'm really not trying to be lame but I have a question sort of regarding the PLDs but for this question I'll call "relative" distance versus the "actual" distance to the drivers and how the actual space contributes to the perception of stage depth & width. 

Really, the question is if all other elements were equal except seating distance (plds, reflections/managed directivity, speaker location in the kicks, let's even say that the physical geometry of the car is the same but one is the size of a Buick 225 and the other the size of a Civic, ) how important psycho-acoustically is relative far field listening vs near field? What would give us the perception that we were in a smaller or larger space? Would our perception of width or depth be compromised by the smaller environment?


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## thehatedguy

That is a good question, a great one infact.

The effect can be dramatic. Gary Biggs did this in his Regal. His seats were extended backwards and at the same time relocated closer to the center of the car. Then with his dash rebuild, he took probably 8" of depth off of the dash. What this did was create a bay window effect. It looked and felt more spacious, bigger than it actually was. And I think the car scored better after the rebuild because of this.

I know if my old car when I had the dash out of it, it felt like you were a mile away from the windshield and everything was so much bigger. I think if I would have finished the shallow dash rebuild the psychoacoustical benefits would have been there too...in addition to opening of a better path for the floor mounted speakers.

And I haven't forgotten about your PM...


----------



## Se7en

Thanks for your reply.

My take away from your references were that the majority of spacial benefit were visual one and less so audible, _perhaps it's just the wording_. But this effect could ultimately be extended across more than one sense of spacial awareness.

Also, although having a shorter dash would be of acoustical benefit (for acoustics sake), you're also saying that the "perceptual" benefit as it applies to staging boundaries is really informed on a visual level (perhaps others as well). You're not actually saying that the sense of width/depth is being driven by any acoustical differences of those spaces.

One last question. It also occurred to me that even given these perfectly similar, yet different vehicle scenarios, all things could not actually be equal given the varying wavelengths at distance. Or is this not the case?




thehatedguy said:


> That is a good question, a great one infact.
> 
> The effect can be dramatic. Gary Biggs did this in his Regal. His seats were extended backwards and at the same time relocated closer to the center of the car. Then with his dash rebuild, he took probably 8" of depth off of the dash. What this did was create a bay window effect. It looked and felt more spacious, bigger than it actually was. And I think the car scored better after the rebuild because of this.
> 
> I know if my old car when I had the dash out of it, it felt like you were a mile away from the windshield and everything was so much bigger. I think if I would have finished the shallow dash rebuild the psychoacoustical benefits would have been there too...in addition to opening of a better path for the floor mounted speakers.
> 
> And I haven't forgotten about your PM...


----------



## Se7en

Patrick Bateman said:


> My girlfriend's car has an excellent soundstage, as good as I've heard, but it uses DSP to get there. (stock Bose system.) DSP makes the passenger side unlistenable.


Do you mind sharing some details about the GFs car and the Bose system? Do you have a sense of what type of 2 channel processing they're doing? I only ask because my currently has a Bose factory unit and it is surprisingly good, but stage width is pretty narrow and almost all of the imaging is centered around the driver.

thx!


----------



## k-ink

Can you uber guru's suggest the ideal placement for my comps that are about to be installed. I now have 3 ways passive's: 6.5" will be in the lower usual place in the doors. I then have a 3" mid and a 1" tweeter to locate somewhere...

I have factory tweeter grilles in the sail panels (of my Alfa hatchback). Or I don't mind using the pillars (bit of a pain, but I'll do it if required), or the dash tops are fine (although the dash isn't quite as deep as some modern cars). Or the kicks are fine too. If it was down to me I'd be tempted to keep tweets in the sails or dash corners, then put the 3" deep in the kicks as far forward as possible. The only down side is the dash extends very low down, so it's a bit cramped under the glove box / foot well pedal areas. I don't know if this would be an issue or not though.

But I know jack compared to you guys. Not my car, but it shows the space...


----------



## stills

fwiw. i mention the ficus only partially in jest.
i own Magnepan home speakers which are dipole. so i've got sound reflecting pretty much all over.
i have been thinking more about reflections lately. after living in a home w/ carpet and sheetrock for @ 10yrs, i moved to a place w/ all hardwood. my maggies now sound very diffrent.
a common temp. fix is to place a ficus tree or two in your corners. a poor mans diffuser.
widely discussed here:
The Planar Speaker Asylum

not much help in a car, unless you want a topiary in dash.

this weekend i think i may cover my side windows w/ towels and tape. just to see how it will sound.


----------



## k-ink

Maybe those girls with a dash full of fluffy toy animals are on to something!


----------



## Patrick Bateman

stills said:


> fwiw. i mention the ficus only partially in jest.
> i own Magnepan home speakers which are dipole. so i've got sound reflecting pretty much all over.
> i have been thinking more about reflections lately. after living in a home w/ carpet and sheetrock for @ 10yrs, i moved to a place w/ all hardwood. my maggies now sound very diffrent.
> a common temp. fix is to place a ficus tree or two in your corners. a poor mans diffuser.
> widely discussed here:
> The Planar Speaker Asylum
> 
> not much help in a car, unless you want a topiary in dash.
> 
> this weekend i think i may cover my side windows w/ towels and tape. just to see how it will sound.


With my tweeters in the center of the dash, I noticed the soundstage gets bigger when I move the passenger seat all the way back :O

I guess it's because the beam is aimed right down the center of the car, so anything in the beam's path can screw with things.

The difference wasn't huge, but it was noticeable.


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## mosconiac

PB: Thanks for reporting your finding WRT single-tweeter. Did you use the higher XO frequency (octave above 1,600Hz) you mentioned earlier? What takes up the slack from there down (size/location)?


----------



## Andy Slater

Mr. Bateman,
You posted up a ridiculous home made horn pic in a thread I ran a while back when I was selling some old horn stuff. Not having a clue who you are I just blew it off as a whackjob guy. I have done nothing to even find out what your about. I stumbled on this thread and I had no Idea what kind of things your doing. I would love probably more than anything on earth to come over to your house and just play toys for a afternoon. Wow I am blown away on what you are doing in audio in a car. I envy you and your talent I wish so much I had the resources and time to experiment like you are doing. I am not kidding, But can I come over and play sometime before we die. After reading this thread I feel utterly humbled like a total rookie. I would truly love to come visit you sometime. Please PM me if that would ever be possible
Sincerely,
A.slay


----------



## sqnut

Anyone who tweaks and tunes will tell you, that after a while your mind starts playing tricks on your ears. Perhaps because it gets overloaded with all the, 'is it better now?', kind of processing. So you could be going downhill and your minds telling you, 'yeah thats better'. Cause its shut down and you're going on auto pilot. You come back the next day and you know its a dog. 

Sometimes you jump to the next level and the mind gets so focused on the gain and its benefits that it forgets to evaluate is the 'whole' sound better, not just the part you're working on. 

The morning after the last post, the benefits of the off axis tweets were still there, everything was better proportioned, the image was plastered to the windscreen, but something was missing. I had taken the image from like 10" in front of my face and put it on the windshield, but I had lost stage depth. Good sound in 2D. 

The objective of the off axis tweets, is to have the front edge of the sound stage at your windshield and its depth to extend out beyond the windshield, onto the hood. To achieve this, with the right balance, you need two things. You need to mount your mids as low and wide apart and as far forward as possible, kicks deep in your floor-well would be one option. You also need to control 7-8 frequencies from your eq over the 4-20khz range.

You need to pull up the 4-20khz range a fair bit (depending on how off axis you set the tweets). This range is like 2 and a bit octaves. You need to tune over 7-8 frequencies over these two octaves to maintain the balance. I control 4 frequencies in this range from my p-880. A processor would sure be handy. 

So for one issue I need to change my mindset and for the other I need to start saving. For now I've settled on a compromise. I've brought the image a bit forward to the edge of the dash by bringing both drivers a bit more on axis, I don't have to raise the 4-20khz range as much and I can thus maintain the balance. As a concept, it works. 

A couple of points if you're going to try this. The tweets on the sr's are ring radiators and while these have great extension at the very top and don't break up, they are also highly directional. So there is a very narrow angle range in which the left and right tweets would snap into place to give you that seamless sound. Anything out of this range and the top end would fall apart.

One other advantage of running the tweets off axis is that 3.25khz and 5 khz are better managed. Assuming a normal xover point between 4-5khz for mids/tweets (active), both drivers would be playing these frequencies, loud enough for it to impact your sound. The average 6.5" driver beams at around 3-3.5khz. At this frequency, your off axis mid would be much weaker than your on axis one. On my eq the on axis mid is -6 and the off axis one is -2 Even though the on axis one is further away. Your tweets are not beaming at this frequency. So it would just make one side brighter than the other. Sure the tweet would be playing the 3.25khz lower than the mid (approx 5-6db's in my case) But still enough to leave an impact. 

5khz is an other example where the sound is 5-6db's louder from the right. Here, the impact of the tweet would be more pronounced. Aiming the tweets off axis would attenuate all the frequencies they play so now you can set 3.5 and 5khz according to mids and have a lesser impact from the tweets.


----------



## sqnut

Pat,

I agree 100% that running the tweets off axis is great. But I would contest your point on not futzing over the tweet angles. Over the last 7-8 days the one thing I have found is that the tweet angle is critical. The angle and the inclination (dash mounted tweets). This defines where the centre stage (vocalist ). I like the centre stage just below my rear view mirror, about the centre of the windshield. It is impossible to get this focus with getting the tweet angles right. L/R eq is secondary. Would be interested in hearing your opinion.

Rgds
Arun


----------



## Patrick Bateman

Andy Slater said:


> Mr. Bateman,
> You posted up a ridiculous home made horn pic in a thread I ran a while back when I was selling some old horn stuff. Not having a clue who you are I just blew it off as a whackjob guy. I have done nothing to even find out what your about. I stumbled on this thread and I had no Idea what kind of things your doing. I would love probably more than anything on earth to come over to your house and just play toys for a afternoon. Wow I am blown away on what you are doing in audio in a car. I envy you and your talent I wish so much I had the resources and time to experiment like you are doing. I am not kidding, But can I come over and play sometime before we die. After reading this thread I feel utterly humbled like a total rookie. I would truly love to come visit you sometime. Please PM me if that would ever be possible
> Sincerely,
> A.slay


I've had people over on occasion, but I'm also having a lot of fun posting videos on Youtube. Even a crummy iPhone does quite a good job of demonstrating how a loudspeaker sounds in a room!

I'm wish I'd started doing this ten or fifteen years ago. I have so many projects that I never took pics of, much less video.

Here's my latest (and very crummy) Unity horn:

deadmau5 on unity horn.mp4 - YouTube

It needs a lot of work, but even with an extremely basic crossover (just one capacitor) you can hear that awesome Unity coherency.

Here's the original track, for comparison's sake. To hear what the Unity is doing right, I'd recommend listening over headphones, or a single driver speaker. The magic is in the midrange, and most two-way speakers will obscure what the Unity is doing there.

Deadmau5 FT. Kaskade - I Remember - YouTube

This Unity horn plays two octaves lower than anything USD Audio, Illusion, or Image Dynamics ever sold.

Plus I give the design away for free


----------



## thehatedguy

I wish I could get one small enough to use l/r/c in my car.

I just realized how nice that little Celestion compression driver Zilch was using in the Econolines was...I think you messed with it as well.


----------



## Patrick Bateman

thehatedguy said:


> I wish I could get one small enough to use l/r/c in my car.
> 
> I just realized how nice that little Celestion compression driver Zilch was using in the Econolines was...I think you messed with it as well.


I'm hoping these ribbons are even sweeter 

The entire horn on my new design is designed to optimize the wavefront coming off a Fountek ribbon.

I'm certain it will be more fragile than the Celestion used in the video above, but the very narrow width of the Fountek allows me to get a wider vertical coverage, which should 'fix' some of the problems with underdash horns. (IE, raise the soundstage)


----------



## SSSnake

Patrick (I forget your real name),

I have always loved the unitys but in a car I'm a little skeptical (for many of the reasons you have previously noted). I would assume the placement of the horn in the video was by design and adds a bit of low freq loading for the horn. Have you taken a look at the response in free field (no boundary loading) conditions? If so, what is the cut off freq?


----------



## Patrick Bateman

SSSnake said:


> Patrick (I forget your real name),
> 
> I have always loved the unitys but in a car I'm a little skeptical (for many of the reasons you have previously noted). I would assume the placement of the horn in the video was by design and adds a bit of low freq loading for the horn. Have you taken a look at the response in free field (no boundary loading) conditions? If so, what is the cut off freq?


The 4pi flare rate on the horn is 600hz. But that number is fairly irrelevant; in a car you can extend the horn on two, three, or even four sides quite easily. *And once you do that, your flare rate is much lower, possibly in the double digits.*

I don't think the flare rate is much of an issue in the car. As long as you find a good spot to continue the horn curve, the flare rate will be far lower than you'll need.

The big problem is the horn mouth. If you use a mouth that's too small, high order modes become very audible, and the horn is audibly colored by peaks in the frequency response.

At this point, I think the solution to these colorations is to get the woofers as close to the mouth as possible. This probably sounds very counter-intuitive; what's the point of horn loading a woofer if it's practically hanging outside of the horn?

But the reason that this works is that woofers and tweeters need two types of horns. Tweeters need a horn with a very small throat, a horn which is short. For instance, an Image Dynamics horn has a throat with an area of 5.07cm^2. *But woofers need a much larger throat.* For instance, a woofer needs a throat that's about 50cm^2, or larger.

So we have two completely different requirements.

The trick here then is that we basically have a tweeter horn perched atop a woofer horn.

Now one might think the dash won't do much to horn load the woofers, but it really does. I've posted some graphs of a B&C 8" woofer located in the kicks, and you can clearly see it's getting horn loaded. Even though there is a cap at the bottom of the horn body, that gap isn't very large at low frequencies. For instance, in my Accord, the gap from the bottom of the horn to the floor is about 25cm. 300hz is 115cm long, so that gap doesn't mean much at low frequency.

Obviously, the key is to push that horn into a spot where we can continue the curves as perfectly as possible.


----------



## Jaze63ford

Ok..Kind of a newbie here... But A veteran of the early days of car audio.. I was a whore for any company that would give me free gear..Autotek, Lanzar, Phoenix Gold, Soundstream, Mtx, and Kicker in that order.. Had a 63 Ford Galaxie that I ended active IASCA and USAC competition in 1998 when my daughter was born.. Got as high as 2nd in USAC pro class behind Todd Crowder and 4th in IASCA Expert 1-600 class.. The car was featured in June 1996 Car Audio magazine..... But this is about Soundstage right? I sat in the Richard Clark GN the first time I heard Horns and it floored me!!! "Money" by Pink Floyd has never been the same for me.. I became a dealer for Speaker Works based on the function of HLCD's I believe I was one of the first to use front midbass in my Buick in 94?.. Not saying that I will never use conventional drivers in my newest install but the fact that the drivers are against the firewall (1967 Fairlane) and as far away from me as the mid/high frequencies can reasonably be has more to do with good soundstage than any other factor.. I also design runners to the dash edge to help with path length.... Yes.. they require an experienced non damaged ear to tune,but the well set up pair will kill most anything out there for 3 dimensional stage proportion and realism.. not to mention sheer amplitude if that's your thing.. at the moment I have some Veritas VD 1.75s and also a pair of TAD 4003s that will fit those horns if I choose to.. I do like Image Dynamics older molded units as well.. and I did cut my teeth on The Speaker Works stuff..(Yeah.. I am a whore) but working with many types of products gives you expanded experience too. Science in car audio is interesting to read but getting your hands dirty and discovering new ways to apply gear is far more fun .. Thanks for letting me run on.. Jay Bacon


----------



## thehatedguy

Did you bring the car to Greenville, Sc for any IASCA Finals?


----------



## stills

i think i remember your car. i had a later model galaxy('68) at the time


----------



## Jaze63ford

Yeah.. I was at Greenville.. Fun weekend... I always loved driving that beast..It was fun blasting past the trailer queens on the way to the show.. I do remember seeing another Galaxie there too... Back when it truly was fun huh?


----------



## thehatedguy

I think I went on Saturday and saw your car, and drove another hour and half back on Sunday to take a look at it again.


----------



## Jaze63ford

Thanks so much man!! I never quite got the whole package working on that car all at one time.. So...no world champ status for me I guess.. I did enjoy helping my midwest installer friends out though.. I met some truly great friends competing back then.. And won my fair share of big shows too.. I am finally interested in Car audio again so.. The Fairlane ragtop I am working on right now is truly fun and not work.. My approach to integration and design is real simple... optimum speaker location first, then make it look like it is and extension of the car... not something that was imposed on it.. Besides.. I got tired of looking at all this old stereo stuff laying around anyway...Gonna utilize new tech for the head unit for convenience and flexibility though. Too bad us sound Q guys don't have a place to hang out any more huh?


----------



## thehatedguy

Gonna have to dig through my pictures and see if I have any of the car...being that they are real pictures, hard to tell if I still have them all from back in the day.

I was just lucky enough to be sort of local to all of the Finals in Greenville and into stereos to see what some called the heyday of car audio at it's finest. Lord knows it was different when I started competing in 01...and 02 wasn't as good as 01.


----------



## Hardtofathom

Don't mean to bother you but what is your take on the TS-S062PRS from pioneer? Could it replace a tweeter and midrange setup on the dash? Anything you could tell me would be appreciated thanx.


----------



## damonryoung

Great info!


----------



## Patrick Bateman

The 'spiritual successor' to this thread is a project located here: 

http://www.diymobileaudio.com/forum/1600497-post38.html

Basically a similar horn, but will play higher *and* lower. Instead of a compression driver it uses a ribbon. It's also easier to build and doesn't look quite as ugly.


----------



## Patrick Bateman

Patrick Bateman said:


> The 'spiritual successor' to this thread is a project located here:
> 
> http://www.diymobileaudio.com/forum/1600497-post38.html
> 
> Basically a similar horn, but will play higher *and* lower. Instead of a compression driver it uses a ribbon. It's also easier to build and doesn't look quite as ugly.


The project above didn't work out so great. The enclosure size got out of control in a hurry. Sounded pretty good, but the ribbon definitely can't take the abuse that a compression driver can. And whether the ribbon sounds more 'transparent' is arguable.

It's definitely a promising project - one of my better ones - but I'd still say that the set of Unity horns documented in this thread are the best front stage I've ever come up with.


----------



## Patrick Bateman

_nobody does it better
Though sometimes I wish someone could
Nobody does it quite the way you do
Why'd you have to be so good?_

Well it's been over three years since I worked on this project, and I'd say it's the best front stage I've ever had. I've been messing around with a bunch of different solutions in the past few years, but they just didn't work as well as this one did.

So I thought I'd take another stab at this one, this time around using some things I've learned, particularly from the Paraline project. (see my 'biggs poppa' thread on diyma, and my 'square pegs' and 'sunshine' threads on diyaudio for details on those two.)


----------



## Patrick Bateman

I know this thread meanders all over the place -

but if you want to build the second interation of this device -

*the plans begin on this post*

I am not organized enough to put them all in one place, like I should, but I definitely intend to make the effort to post all the information necessary to build this yourself.


























The waveguide will look like a cross between the Image Dynamics HLCDs, and my oblate spheroidal waveguides which were used in my Unity projects in 2006 and 2009.

So basically, very very very small footprint, Unity summation on the midranges and the compression driver.

The big change for 2012 is that the vertical height of the waveguide is going to be very very very small. This is one of the things I'm stealing from the Paraline. I never realized that such a small horn could load a midrange. (The Paraline horn is only 0.20" or 0.25" tall.

I've attached a PDF of the new waveguide. If you want to build one at home, just print the PDF, and follow along with the pictures that I'll post over the next few weeks.


----------



## thehatedguy

Wouldn't a conical horn be easier for the unity loading? Or are you doing that on the paraline?


----------



## electro

I didn't read all the post. I mainly looked at pictures. I noticed this thread started back in 2009. Are you still building your soundstage? This is a pretty cool set up btw!!


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## Patrick Bateman

thehatedguy said:


> Wouldn't a conical horn be easier for the unity loading? Or are you doing that on the paraline?


Basically conical has advantages, and oblate spheroidal has advantages:

- conical horns are easy to build, their expansion rate works well with a Unity/Synergy horn, and conical horns offer the ability to 'hide' the midrange ports from the compression driver.

- oblate spheroidal horns are more difficult to build, their expansion rate is virtually identical to a conical horn, so they work well with a Unity/Synergy horn. The main advantage that I see is that oblate spheroidal reduces diffraction. This was an aspect of the Synergy horn that I didn't 'get' for a couple years. Basically, diffraction occurs when the exit angle changes. For instance, if the exit angle of your compression driver is ten degrees, and the coverage angle of your horn is 135 degrees, you're going to get a lot of diffraction as the angle changes sharply at the throat. For instance, if the change in angle in this horn was abrupt, you get diffraction:










Basically oblate spheroidal is designed so that the transition from one curve to the other is as gradual as possible. We can see that here:










One of the things about the Synergy Horn, which I didn't realize for a couple years, is that the narrower coverage angle (compared to the Unity horn) means that the Synergy horn should have lower diffraction than the Unity horn. And that any effort to reduce the coverage angle of the horn should reduce diffraction.

I *do* think that's one of the reasons that the Paraline sounds good. Considering all the reflectors in the Paraline, you'd think that it would sound nasty, but it doesn't. And a big part of that is likely due to the fact that sound waves can't diffract inside of the Paraline, because the dimensions are so small. (Well, technically they CAN, but only at very high frequencies.)


----------



## Patrick Bateman

Here's a pic of me starting the horn from post #238. If you want to build this, just print out the PDF









The frustums for the midranges. One thing that I learned from the Paraline is that *a big heavy plywood enclosure improves bass output and dynamics.* If you look at all my other waveguides and horns, you'll notice that I typically use fiberglass. But I noticed with my Paralines that the plywood construction is really a big improvement over fiberglass.

The frustums are also very important for these horns. It basically acts like a crude phase plug. So chances are good that the frustum will improve the frequency response.









Here's what the frustum looks from the other side.









this is one small horn!

















My goal was to make the horn as small as a soda can.


Note that this it's CRITICAL that the horn is close to a boundary; this thing will simply not work properly if it's out in the middle of a room. I put a lot of work into jamming this as close to the windshield and dash as possible.


----------



## Patrick Bateman

Gorilla Glue is drying on the driver's side horn.

Some observations:

- The construction is much much much beefier than my 2009 project. I'm avoiding fiberglass wherever possible, and focusing on building the horn out of good ol' plywood. I'll likely use some fiberglass or carbon fiber for cosmetic reasons, but I want this horn to be ROCK SOLID first. I've found that midrange clarity and bass reproduction is much much better with solid construction, even with 5cm drivers!
- The vertical coverage is basically zero degrees. This is much narrower than the 2009 project.
- The horizontal coverage is ninety degrees. Basically the same as 2009. (My 2009 horn had a coverage angle of 72 by 108 degrees IIRC, for an average coverage of 90 degrees. This horn is zero by 90, for an average of 45 degrees.)










Trying to make this as small as humanly possible.


----------



## keep_hope_alive

i applaud your tenacity.


----------



## subwoofery

keep_hope_alive said:


> i applaud your tenacity.


x2 

Kelvin


----------



## Patrick Bateman

Thanks for the support!

Here's some new pics of the horn as it comes along.









I put a decent amount of time into smoothing out any rough edges. Basically get a container of wood filler, apply liberally, then sand it down.









In this view you'll notice that I had to use a bit of a spacer for the inverted midranges. Basically I want the horn to be as small as humanly possible, so I ended up spacing it out a quarter of an inch just to get the basket to fit. If you look at the volume of air for the midranges, it's barely enough to contain the basket.







There's a couple of innovations here which are worth discussing. If any of you are planning to build a Synergy horn like this one, you'll want to copy what I did here.

Basically, there is a plexiglass mount for the compression driver, which allows you to line up the mounting plate, horn, and compression driver perfectly.

Second, I used bamboo chopsticks to form the curve at the throat.









If you look at the curve close to the throat, you'll notice that the angle gently changes in the last couple inches. This is an important thing; it reduces diffraction. *But the way that I built the horn, it's tough to fill in that curve.* So what I did was to cut a pile of chopsticks, then gorrila glue them into the curve.

There are a couple of other ways to do this, if you want to build this horn:


You could fiberglass it. I didn't go that route because I want this horn to be solid as a rock. I really believe that's essential to get down to 200 or 300hz.
You could modify the plans I posted on page nine, so that there's room for a nice smooth plywood curve. That would work fine. Would probably look better too. Basically my plans didn't take into account how to get that smooth curve in there.


----------



## Patrick Bateman

​
Here's some pics comparing the new horn, with the previous version.


old horn (top) has a coverage angle of 108 x 72 degrees (90 degrees average), with a BMS compression driver at the apex. ($150)
new horn has a coverage angle of 90 degrees x 0 degrees (45 degrees average) with a Celestion CDX1-1525 at the apex ($100)























Some thoughts on my new horns:

#1 - By making the vertical height very short, I can get the Synergy Horn nearly as far back as the wussy stock tweeters are. (pictured above)
#2 - The Synergy Horn is basically in the same spot as the stock tweeters in a Aston Martin (pictured above)
#2 - The very short height allows you to get the synergy horn further back on the dash than my 2006 and 2009 projects. I think it looks better too.


----------



## Patrick Bateman

http://www.youtube.com/watch?v=6959m_r60gg&feature=plcp

Here's a video of the new Synergy horn.

I was WAY impatient with this one. In the video it really sounds like crap, but I'm actually quite happy with it. (And I generally hate my projects five minutes after I finish them, which is why I make so many. So the fact that I actually like this one is a good sign!)

The mpeg compression is very noticeable to me in this video. Also, this is the first video that I shot outside - you really notice that the low frequency output just disappears when you record outside.

I'd shoot a video of it playing in the car, if only I had an amp hooked up.


----------



## Patrick Bateman

Here's the response of the woofers and tweeters. Yeah this is darn nice, especially with no xover. *(don't hate the player, hate the game)*









45 degrees off axis. *this is killer*
If you go back to page one of this thread, you'll read that *the whole point of these horns is to get the image in the center of the car.* And if you look at this measurement, you'll see it basically looks like the on-axis response, *it's just lower.* That's exactly what we want for good imaging. No weird off-axis blips, no suckouts,









45 degrees off-axis vertically. Not too bad really. Not as good as the horizontals, but not so bad that it wouldn't work in a door or under the dash. One idea I had for this design was to put it in the location where a 6.5" woofer would go in a car door.









Output with the tweeter only. Right now I'm running crossover-less, so you can see that the tweeter is playing about an octave lower than I intend to have it play once everything is finished.









Output of the woofers only. *Note that I only have two woofers wired up at the moment* Despite this, we see that the woofers are nearly as efficient as the compression driver; at 800hz they're only 3dB down from the compression driver. *Horn loading adds a ton of gain in the woofers passband (about one octave on either side of 800hz. IE, 400hz to 1600hz.)*


----------



## trumpet

This is fascinating. Great thread.


----------



## Patrick Bateman

This is a bit random, but if any of you are playing along at home, there's a potential improvment to this horn.









Unity and Synergy horns are 'fractal' in nature. By 'fractal', I mean that all of the math, and the formulas do not change no matter how big or small the horn is. *All that changes is the bandwidth.* For instance, the way that I am able to get away with such a small midrange is because I shift the xover frequency UP, and I also move everything closer to the throat. IE, you can't just swap out those 2" mids for 4" or 5" mids; if you did that you'd have to make the compression driver larger, and you'd also have to move the midrange entry holes further from the throat.









The new Synergy uses four midranges. This basically gives us the same output as a single 4" horn-loaded midrange. (Four 2" drivers have the same surface area as one 4" woofer.)










But one interesting improvement might be to go to six midranges. Like Paul Spencer did.

Common sense would dictate that two 4" midranges, or perhaps a pair of 3" midranges would outperform six 2" midranges. But, again, it's a fractal thing. *As the midranges get bigger our compression driver has to get bigger too.* So if our compression driver is basically fixed in size, then using a crapload of small midranges starts to look like the way to go. Literally as many midranges as you can squeeze onto the horn.

Don't worry, I'm not going to scrap this project, I'm very happy with how it's going. But if you're following along at home, and you got the space, you might go for six.









The Genesis horns are a good example of this 'fractal' thing. Two compression drivers, eight midranges, and eight woofers.


----------



## fuji6

Hi Patrick,
Every time I see one of your posts it makes me want to experiment with it myself. Your progress looks fantastic.

I had a few questions for you if you don't mind.
You plan on placing your horns on top of your dash. It appears the nearside would be 45 degrees off axis and the far side on axis. Your RTA graphs seem to show that this would work out well for imaging. (Your off axis graph appeared to be an attenuated version of the on axis graph). 
For somebody who wants to go under the dash would you need similar aiming? What about vertical aiming?

I'm also intrigued with what you mentioned about putting a horn like that where the stock door speaker would normally be. What do you think you would have to do to make that work?


----------



## zener

The best soundstage I have experienced was in a car with 4" MB Quarts, using the supplied crossovers, JBL titanium tweets, on the same, but with an added cap added, all in the dash, reflected off the windshield back towards you. 
The 8" profile subs were under the dash aimed at the floor, were in odd-shaped sealed boxes, using coils to lo-pass.
All powered by a mere 30wX2 Profile amp, factory Delco HU. There were some small speakers for rear fill, ran off the deck.
Truly gave the effect of a very large space, was amazing.

I love to see stuff like those horns, makes me want to get out the fiberglass and try and package that up into some A/C ducts or something!


----------



## Patrick Bateman

fuji6 said:


> Hi Patrick,
> Every time I see one of your posts it makes me want to experiment with it myself. Your progress looks fantastic.
> 
> I had a few questions for you if you don't mind.
> You plan on placing your horns on top of your dash. It appears the nearside would be 45 degrees off axis and the far side on axis. Your RTA graphs seem to show that this would work out well for imaging. (Your off axis graph appeared to be an attenuated version of the on axis graph).
> For somebody who wants to go under the dash would you need similar aiming? What about vertical aiming?
> 
> I'm also intrigued with what you mentioned about putting a horn like that where the stock door speaker would normally be. What do you think you would have to do to make that work?


Putting them under the dash seems to work pretty darn well. I gave it a try this morning:

Gento Synergy under dash - YouTube

It's funny how well this works, because 'theoretically' the dash is a much better location. First off, on the dash, the speakers are at ear level. Second, on the dash the mouth mates up with the windshield almost perfectly. Also, the windshield is very rigid and strong, which are excellent properties for a horn. (Try hitting a windshield and see how much it 'gives'. Next, try hitting your fender. I'll bet you'll find that the windshield is more rigid than the steel fender.)

But despite all the 'theoretical' advantages of the dash, I gotta admit I think this thing sounds better UNDER the dash. Just guessing, I think this is why:


You can't see the drivers. I think that your eyes play a big role in speaker imaging. When you can see where the speakers are, you mentally expect that's where the sound is coming from.
Under the dash, the location seems more 'diffuse.' This is likely due to sound absorption by the carpet.
Under the dash you can get the speakers back about another 15-30cm.


Anyways, watch the video, decide for yourself. As usual, the video was shot with an iPad and it's hosted on Youtube, so you're going to hear compression artifacts. Also, the bass seems a lot louder in my car than it seems in this video. Not sure if that's the mic or something psychoacoustic.

All I really care about is midrange, and the midrange quality of the video is consistent with what I'm hearing in the car.

Credit where credit's due, here's the original track. If anyone from the Portland / Seattle area is going to the show, hit me up!

DATSIK - Firepower (Live) - YouTube


----------



## subwoofery

I know you just installed those quickly for the video but if you ever decide to keep them underneath the dash, it would be a good thing to add some sort of cardboard above your horn in order to have a better transition with the dash... 

In the past, when I was experimenting with duck tape for a smooth transition, I found out that it was cleaning up the midrange... a lot - likely due to some peaks in the response due to diffraction 
Also, helps in extending the horn which also help in going slightly lower

Sounds like you have a keeper here - well at least until you read about something else 

Kelvin


----------



## Patrick Bateman

subwoofery said:


> I know you just installed those quickly for the video but if you ever decide to keep them underneath the dash, it would be a good thing to add some sort of cardboard above your horn in order to have a better transition with the dash...
> 
> In the past, when I was experimenting with duck tape for a smooth transition, I found out that it was cleaning up the midrange... a lot - likely due to some peaks in the response due to diffraction
> Also, helps in extending the horn which also help in going slightly lower
> 
> Sounds like you have a keeper here - well at least until you read about something else
> 
> Kelvin


Yeah it's pretty bizarre to have a project that's actually a 'keeper'.
Most of my projects tend to be pretty bizarre and a lot them simply don't work.
But this one is coming along nicely.

I'm basically taking the most successful front stage I've had, and improving it. There's nothing too radical here, except for the push-pull mounting of the midranges. (Surprised no one noticed that!)


----------



## bigguy2010

So I've been following this recent build and I have some general questions. 

What model are the mid-range and compression drivers? Did you already have them or did you seek out specific drivers?

Is there 4 mid ranges per horn? If so, what orientation are they mounted? (Push-pull)

How did you cut the dish-like spheres out of the plywood? Router? Or drill press? 

How are the mid-ranges wired up? All in phase with each other?


----------



## fuji6

Not to get too far off topic, but in thinking about trying this out I couldn't help but want to find a "higher quality" mid... I know I know... it might be all in my head but those parts-express closeout mids just look like they might not last long. 
How do these look as a substitute? (Aside from being an ass load more expensive to get 8 of)

Tang Band W2-1811S 2" Neodymium Poly Full Range Driver
Specifications: • Power handling: 10 watts RMS/20 watts max • VCdia: 1" • Impedance: 4 ohms • Re: 3.6 ohms • Frequency response: 140-20,000 Hz • Fs: 140 Hz• SPL: 82 dB 1W/1m • Vas: 0.008 cu. ft. • Qms: 2.15 • Qes: 0.52 • Qts: 0.42 • Xmax: 0.5 mm • Dimensions: Overall diameter: 2.25", Cutout diameter: 2.05", Depth: 1.5".
I think FB would be around 540.

Also thinking about a B&C CD (maybe the 250) over the Celestion, any thoughts on that?

Not going to run and try this right away, but just thought I'd ask while I had the opportunity.


----------



## Patrick Bateman

bigguy2010 said:


> So I've been following this recent build and I have some general questions.
> 
> What model are the mid-range and compression drivers? Did you already have them or did you seek out specific drivers?
> 
> Is there 4 mid ranges per horn? If so, what orientation are they mounted? (Push-pull)
> 
> How did you cut the dish-like spheres out of the plywood? Router? Or drill press?
> 
> How are the mid-ranges wired up? All in phase with each other?


The midrange is part number 289-127, you can get it from Parts Express, it's $2
The compression driver is a Celestion CDX1-1425, you can get if from PE, it's $95

























There are four midranges per horn.
Half of the midranges are mounted so that their face is firing into the horn. The other half are mounted so that the rear side is firing into the horn.

I just realized I don't have any pictures at all that show the midranges on the horn and fully closed off. (In the pic above the rear chamber is missing; the midranges are basically encased in very small bandpass enclosures.)










I use this chamfer bit so much, it's ridiculous. $37 and gets used constantly when you're making synergy horns. The frustum in front of the midranges is cut using this bit. Available at any Lowe's or Home Depot: Diablo 5/8 in. Carbide Chamfer Router Bit DR40114 at The Home Depot


*** please be careful with this bit ***

You really have to be gentle with this thing, because the router bit has so much surface area.

A Dremel might be safer, but it would probably be slower.






In regards to the midranges, they all move in phase. Half of them are wired out-of-phase, because they're upside-down. Basically the ones that fire INTO the horn are wired in phase, and the ones that are mounted upside-down are wired out of phase.

Art Welter at Diyaudio did some measurements that showed a reduction in 2nd harmonic of something like 20-30dB from push-pull mounting. These midranges are kinda grungy; they ARE two bucks after all. So the push-pull mounting cleans that up.



The choice of midrange is really something that I obsessed over for a while. (For six years and sixty three pages, to be honest : Suitable midrange cone, for bandpass mid in Unity horn. - diyAudio )
There are definitely midranges which are cleaner than this two-buck driver. For instance, the Peerles 831970 sounds cleaner. The problem with the 'clean' drivers is that they crap out at 1000hz or so. If you look at a lot of the other people that have build Unity and Synergy horns, they've run into the same problem.

*Basically, we have to use a driver with an ultra-light cone, or else we run out of output at 1000hz, or even lower.*

For the most part, that means we have to use a paper cone.

So once we realize that, it really only leaves us five or ten options, at any price. So I went with these woofers because they're 80% as good as the Tangband W2, but at one-tenth the price.









The Dayton RS75 and the Peerless 831970 are probably my other two favorite choices. Although the RS75 has an aluminum cone, it's surface area is ridiculously small because the whole center of the cone is absent, due to that phase plug. PLUS, that phase plug is a great match for the frustum. (And it looks cool too!)

To be honest, the main reason I didn't use the RS75 is that the horn gets pretty big pretty fast; the two buck buyout drivers are less than half the size, as far as volume goes. They're tiny.

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## thehatedguy

What about a pair of the goldwood cone tweeters? Is the fr better w the 2s?


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## Patrick Bateman

thehatedguy said:


> What about a pair of the goldwood cone tweeters? Is the fr better w the 2s?


Yes, the Goldwoods are undoubtedly the hot ticket if you don't want to waste a lot of time building tiny little loudspeaker enclosures.

For instance, if you go with the 2" buyout drivers, you have to build EIGHT enclosures. True, they're simply hunks of PVC, but it's still a lot of work. You have to cut twelve pieces of PVC, you have to cut eight end caps, you have to drill eight holes for the wiring, etc etc etc

Going with the Goldwoods cuts out all that crap.

On the downside, you can't get the Goldwoods as tight as you can get the 2" drivers, because the Goldwood cones are much larger. Plus, the 2" drivers have a real suspension, so they'll likely move more air.


I honestly can't say if that means they're inferior though; they really sound surprisingly good, at least when they're on a horn. (The Goldwood tweeters are pretty low-rent as tweeters, but they have some specific features which make then work well on a horn. Basically an ultra-light cone which is a good match for horn-loading.)



If one wanted to try this project and didn't want to futz around with building eight loudspeaker enclosures, yeah I'd try the Goldwoods


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## thehatedguy

A benefit of the underdash alternative is the number of mids can be increased. Which does all kinds of good things for you. Can do 6 of the 2s or maybe 4 of the goldwoods or miscos per horn.


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## nubz69

Patrick I enjoy reading your posts, and I always see the parallels with the work I have done on my own and from others on diyaudio.com I just have one problem. I have yet to see you post up a finished, installed design. It's always test rigs and we all know that the finished product can perform differently then a proof of concept. I hope one day you try posting the final product and then explain how you got there.

considering the nearfield installation, limited space and complexity of the build, I am not sure synergy horns are necessarily the answer. It may be a very good one but there might be other, more simpler options. Have you ever looked to see if there are any production cars where the angle of the windshield to the dash would allow you to use both as the walls of a larger wave guide? Rather then build waveguides that fit in front of the A-Pillars, mold the whole dash and A-pillar into one large waveguide. You would not be able to achieve a 100% oblate spheroid shape due to the boundry constraints but you could possibly get really close with the right car. 

Synergy horns are great in the home and concert environments but generally those locations do not use time alignment. In the car environment TA is relatively cheap and easy to use. Because of this I think that you should consider focusing on the midrange and not the tweet/compression driver. If you have a mid setup that can play up to 10khz and down to 300hz while using a wave guide to control directivity and reflections, you have a real winner. This would free up more space for you to work with and cost you little to nothing in SQ and imaging. 

Keep up the great work, I am curious to see where it ends.


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## nubz69

Hey patrick

I was wondering if you have any experience with 3d modeling. I don't but I can see that your designs could be further improved by taking an oblate spheroid and constraining it by the dimensions of your cars interior. From there you could modify it's shape and angle to optimally form in it's space and function with the fixed parts of your car. Then you would just need to build it, cnc it out of something or 3d print it.


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## thehatedguy

A unity or synergy horn is perfect for the car because you get the output and dynamics only found in horns but with a phase response of a single driver.

When you start to put horns up on the dash like you are talking about, you start to get to a physically narrow part of the interior and doesn't work really well. Plus I don't know how many dashes you have built...


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## thehatedguy

What strikes me about this project is that it is looking more similar to the current car horns on the market...abit these are symmetrical in design whereas the others as asymmetrical. Which makes me wonder how well this design can be retrofitted to the current horns...I have an idea, but no way to model it at the moment.

Now I wonder how well you could apply the 4 push pull mids on a horn loaded paraline under the dash.


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## fuji6

Patrick Bateman said:


> Putting them under the dash seems to work pretty darn well. I gave it a try this morning:
> 
> Gento Synergy under dash - YouTube


Awesome!! Thanks for the reply. 
I'm going to try out something very similar. I contemplated the de250 but decided I might miss the top end. I liked the idea of the de250 because it looked as if it would reach down lower than the cdx-1425. I'll just have to be careful to get my mids to play up high enough so that I don't have to play the cdx1425 too low (put in an order last night). 

1 change I will definitely try out is using the W2 mids since I already had a few, so I ordered a few more to try one horn as well as some of the $2 buy outs just in case they don't work out (hey they are cheap enough). 

Although I'm a total noob on this stuff by far, I'm going to take a stab and guess the W2 mid might have trouble getting high enough with the cone material I ASSUME is heavier than the cheapo drivers. 

I'd be interesting in seeing your plans for crossover design etc.


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## Mr.M

intresting
sub'd


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## thehatedguy

The crossovers are pretty easy once you keep in mind the acoustical nature of the roll off of the drivers in their enclosures. You need to get the acoustical slopes equal from the use of the electrical slopes...and keep in mind the phrasing from the mids.


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## left channel

Could you use a 4" on top and a 4" on the bottom or would there be an issue with them firing in to the horn from opposite planes?


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## thehatedguy

You can do that. The trick is finding a 4 that would work. The goldwood tweeters we mentioned are 4s.


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## oilman

I love these kind of threads. So much to learn.


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## Patrick Bateman

thehatedguy said:


> What strikes me about this project is that it is looking more similar to the current car horns on the market...abit these are symmetrical in design whereas the others as asymmetrical. Which makes me wonder how well this design can be retrofitted to the current horns...I have an idea, but no way to model it at the moment.
> 
> Now I wonder how well you could apply the 4 push pull mids on a horn loaded paraline under the dash.


The biggest challenge with using 'conventional' car audio HLCDs for a Unity horn is that there's a correlation between the volume of air in the horn, and the mass of the driver that's ON the horn.

IE, the smaller the volume of air in the horn, the smaller the mass of the driver that's ON the horn needs to be.

I've posted some projects which used one or two 5" woofers on an underdash horn. One of those projects can be seen on my Youtube channel. *IMHO, a single 5" woofer is about all you can cram on an underdash horn before it starts to sound pretty crappy.*

That's one of the reasons I went with 2" drivers for my project. The 5" drivers start to sound 'shouty' on these undersized horns.


The Goldwoods allows us to 'cheat' a bit. This is because the cone is SO light. If you look at it, it's literally just paper, and nothing else. It doesn't have a big heavy foam surround like the Pyle. It doesn't have much of a suspension even.

We can only guess what it's parameters are. I attempted to measure it using a WT2, with no luck.




Long story short, if one wanted to use a HLCD like the Image Dynamics for one of these projects, I would recommend using an array of drivers with a cone that is as light as you can find, to keep it from getting 'shouty.' Candidates would be the Tang Band W2-854SH, the $2 buyouts from PE that I'm using, the Goldwood cone tweeters, and the BG NEO 8. (It might seem odd to put a NEO8 in a bandpass, but I can't think of a reason that it wouldn't work.)


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## Patrick Bateman

left channel said:


> Could you use a 4" on top and a 4" on the bottom or would there be an issue with them firing in to the horn from opposite planes?


No issue at all. I only put the midranges on the bottom of the horn because I was trying to keep the height to a minimum.

If you arrange them carefully, you can go pretty crazy with the number of drivers. One of the Danley designs has ninety six drivers.


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## bigguy2010

Any other compression driver you'd recommend? The CDX1-1425 isn't available at PE for a few months.


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## Patrick Bateman

bigguy2010 said:


> Any other compression driver you'd recommend? The CDX1-1425 isn't available at PE for a few months.


If you have the room, this is probably the best choice:

BMS 4550 1" High frequency Compression Driver - BMS 4550 - BMS 4550 1" high frequency compression driver. BMS neodymium 4550 high frequency compression drivers are available here.

IIRC, that's what Danley uses in nearly all of his designs. It plays lower than the Celestion that I use, though it *is* bigger. Now that I have my Synergy horns under the dash there's a little more flexibility as far as space goes.

In fact, the size of the midrange enclosures is the thing that's bugging me now. It almost makes me want to rebuild the thing, using a Pyle PDMR5 ($15) and a BMS 4550 ($148)


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## Patrick Bateman

bigguy2010 said:


> Any other compression driver you'd recommend? The CDX1-1425 isn't available at PE for a few months.





























Here's a nice collection of various options:

Index of DIY Synergy and Unity Horns

Danley used to use the B&C DE25 before switching to BMS. Although I think the BMS is a better option than the B&C, there are clones of the newer B&C drivers available for half of what the BMS costs:

Denovo DNA-360 Compression Driver DIY Sound Group


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## Wesayso

Thanks Patrick for Posting that... Due to your post I stubled over this video that answered all my audio questions:





 

The description of the sound of a snare drum was an eye opener for me...


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## thehatedguy

With them under the dash, you could probably do 4 of the goldwoods per horn. Might create a better topend roll off compared to a pair of 6s.


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## Patrick Bateman

thehatedguy said:


> With them under the dash, you could probably do 4 of the goldwoods per horn. Might create a better topend roll off compared to a pair of 6s.


Honestly, this is the most successful projects I've done in years.

BUT...

I'm not happy with a few things (I never am.)

1) I'd designed it for the dash, so it's taller than I'd prefer. On my dash I have room for something that's about 15cm tall, while under the dash, I'd like to keep it under 7.5cm tall.

2) It would be pretty easy to reduce the height. The midrange enclosures are quite tall. As Jason noted, the Goldwood or Misco drivers would reduce the height easily.

3) I could also reduce the height by using something beefier than plywood for the horn. I'm REALLY happy with my decision to use plywood - I've found that using a sturdy material for the horn makes a world of difference. Having said that, if I opted for aluminum or carbon fiber I could likely reduce the height quite a bit.




One idea I've been toying with is using planar drivers for the midranges. I can't see any reason that a BG Neo 8 or Neo 10 couldn't be used. Then again, it's a bit of a splurge since the Goldwood tweeters are hella cheaper and probably work just as well.


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## thehatedguy

I would be cautious using materials with low internal damping. The veritas horns rang like bells if not treated right. The aluminum was so resonant that the mouths rang because of it. Illusion made their horns out of aluminum, but they added a brace/vane to fight that.

Next I would be cautious with the planars. They are planars so they are thin. They are resistive so getting t/s parameters is next to impossible...but the ones I have seen suggest the qts is over 2. Not .2 but whole number 2. I have owned the neon 8s and had them about an inch from the rear wall and it sounded decent, but it wasn't until they were true IB that they sounded the best...no rear wave reflecting back. So IME they would need a deepish enclosure or no rear enclosure to sound the best.

Some people might be wondering why the need for more than a single 6 for the midrange. It would be plenty loud enough for the car especially in the bandpass. What happens with these things is that in the bandpass on the horn there is a notch in the output and it comes back up...and down...and up. The more mids you have in addition to the obvious increase in output and lowend, it makes the notch deeper and more suppressed ...which is good.


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## Jaze63ford

This thread is fun!!.... WOW!! amazing unity project too!! 
Since my own audio project is my driver I am limited by space and cosmetics.. it is a 1967 Ford Fairlane with a high rounded under dash and wide open front.. My midbass are actually flush with my kick panels and deep as my feet with enclosures outside built into the fenders.. I use Veritas horns and a hand built throat adapter that is straight instead of 90 degrees.. The TAD 2003 drivers are decent enough.  and it helps that all six speakers in the car have 31 bands each and delay with variable crossover slope for flexibility too.. I pick my cars with audio in mind mostly.. I was lucky this one is one of my all time faves and it is so receptive to what I wanted to do to it..


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## Jaze63ford

Oh yeah... For the Veritas horn.. I mount a brace in the center of the horn top to bottom and dynamat it well.. also smooth the manifold areas too..thanks.


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## bigguy2010

Finally took the plunge on some CDX1-1425's. Got a pair for $70! Just need to get some 2" mids and I'm in business!


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## Patrick Bateman

Patrick Bateman said:


> Here's some more speaker porn.
> 
> From left to right, we have a Misco KCN5FD, a Misco JC5RTF-B, a Tang Band W2-852SH that I sealed, a Seas L11RCY/P, and a Parts Express 5" professional midrange.
> 
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> According to Tom Danley, the midranges for the original Lambda Unity were made to his spec by Misco. I looked through their catalog, and the 2nd woofer in the picture above seemed to be the same woofer. The first one is a newer model, and appears to be an excellent candidate if you can live with a higher crossover to the subwoofers.
> 
> Here's the link:
> 
> diyAudio Forums - Another Unity Horn - Page 9


My collection of drivers is getting a bit ridiculous, and I intend to move into a new house in the next few months. I have posted an eBay add for my set of Misco JC5RTF-Bs. I believe it violates forum rules to post the link, but anyone can find my add easily. (Hint : it's the only set of JC5RTF-Bs on eBay, in fact it's the only set of Misco woofers on eBay.)

The lead time to have these built is a bit lengthy, and I'd be willing to bet they cost more nowadays, due to the rise in neodymium.

Long story short: get 'em while you can!

If you seal the back off on these they should work for a Unity. But you can also do some interesting things with these in a back loaded horn.


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