# Smoke and Mirrors



## Patrick Bateman (Sep 11, 2006)

In this thread I'll show half a dozen different ways to bend sound.
This is handy in a car, because we frequently can't put our speakers in the ideal location.

Before I get into how to do that, it's useful to illustrate how sound radiates.










Sound radiates in a series of concentric rings. Basically sound expands in a sphere, but there are 'rings' of high and low pressure. These peaks and dips correspond to the phase of the sound.


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## Patrick Bateman (Sep 11, 2006)

Underdash horns, like the HLCDs from Image Dynamics, take a small fraction of that sphere and 'constrain' it. Constraining all the energy into a fraction of it's original shape does a couple things. It increases the output, and it increases the efficiency. (The diaphragm is basically 'pushing' on the air in your car; and now it's 'pushing' on a smaller volume of air.)










Here's my feeble attempt to illustrate how the Image Dynamics HLCDs work. See how the shape of the HLCD is designed to take a 'slice' out of that pulsating sphere that was described in the first post?

And in particular, notice how the height of the HLCD grows taller and taller as it gets further from the apex of the sphere. This is by design; the further away you get from the apex, the larger the width and height needs to be.

Next up - how to bend sound!


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## req (Aug 4, 2007)

In for the info! Excite!


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## Patrick Bateman (Sep 11, 2006)

If you've read the first two posts, you've seen that sound radiates in a sphere, and that underdash HLCDs basically take a segment of that sphere and 'constrain it' to raise the efficiency and output level.










In the picture above, I've shown what it would look like if you took a larger chunk of that sphere. The driver at the bottom is about the size of an Image Dynamics HLCD; the driver at the top takes a full ninety degree segment of that sphere.

(I hope all of this makes sense; if it doesn't just ask!)

The problem with that big ol' ninety degree chunk of sphere is that it's too darn big. If you put that in your car it would extend all of the way to your lap. Your car would be undrivable.

So - *how can we make that thing smaller?*

Simple: *We fold it.*










^^^ I hope the pic above illustrates how the waveguide is folded. Basically we slice it down the middle, then fold it over.

It might not be immediately obvious - but that fold needs to be perpendicular to the axis of the waveguide. And the shape of the fold makes a difference too.

(I'll explain both of these things in an upcoming post.)









^^^ here's the same waveguide, but that segment has been folded over along the cut line.









^^^ aaaand here's the final result. The waveguide has been folded over and I've added a proper mouth to mate it with the dash of a car.


In summary, we have four steps here:

1) Take a segment of a sphere
2) slice it right down the middle
3) fold it over
4) make a mouth that fits the car


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## Patrick Bateman (Sep 11, 2006)

OK, with me so far?

Because things are about to get confusing.

In post #4, I showed how we could take a waveguide, slice it in half, and reflect the output. This youtube video gives a good example of how reflection works:

Physics 11.1.1b - The Law of Reflection - YouTube

In a car, we can do some interesting things if that reflector *isn't* straight. For instance, we can make that wavefront curve one way or the other, or we can even flatten it out.

But first off, *why go to all this trouble?* Why not buy a $20 Vifa dome tweeter, stick it in the A-Pillar, and be done with it?

There's a number of reasons to do this:

1) We can create a believable soundstage by directing the sound towards the passengers, instead of all over the car. (Remember, sound radiates in a sphere, it reflects off of everything. Unless we constrain it.)
2) We can raise the output level and the efficiency

But any ol' waveguide can do that. Even a $20 waveguide from Parts Express does a fairly good job. But I want to go above and beyond here.

My manager at work would call these 'stretch goals.' As I see it, here are some 'stretch goals' for our waveguide:









1) A waveguide that faces one direction, but fires another. The Image Dynamics HLCDs are a good example of this. The driver points one direction, but the sound radiates another.








2) There's a reason that hifi horns are big... everything else being equal, big horns generally have smoother response and are better behaved in the time domain than small horns. So if we can use a reflector to maximize the space that's available to us, let's do it!








3) One of the weirder things that we can do is bend the wavefront, so that the sound coming off the speaker diverges, or converges, or is simply flat.


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## Patrick Bateman (Sep 11, 2006)

As noted in the last post, *there are a number of ways to reflect sound.* (and light, and radar, and radio waves, etc..)

In Danley's Paraline patent*, the reflector is called a "correction slot." And we can use that reflector, or correction slot, to change the shape of the wavefront.

Here's some pics showing how this works.









^^^ This pic shows a straight reflector. With a straight reflector, the reflection is a mirror image of the origin. If the origin is 45 degrees off axis, then the reflection is rotated 90 degrees (like a mirror.) If the origin is zero degrees off axis, then the reflection is rotated zero degrees... *like a mirror.*

A straight reflector allows us to take a waveguide, slice it in half, and preserve the shape of the wavefront.









^^^ This pic shows a circular reflector. A circular reflector basically reflects the origin back upon itself. The angle doesn't matter; every single angle is reflected 180 degrees, right back to the origin.

Kinda useless for audio, but helps to illustrate how a curved reflector works.









^^^ Here's something interesting. A blend of the flat reflector and the circular reflector. The flat reflector acts like a mirror; the circular reflector reflects back on the origin. *This blended curve gives us a flat wavefront.*

This 'blended curve' gives us some great options in the car; the ability to put sound where we need it. Or to decide how wide or narrow we want the stage to be.

As always, ask questions if this doesn't make sense. Took me a few years to figure out how this works.


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## req (Aug 4, 2007)

so in practice, what or how do actually build to control this that will fit in the car that is not just a horn lens from eric stevens, USD, or wherever?

looking at what bang and oulfsen - i dont remember who invented the lens they use - this is the same principal, is it not? we were talking about this back then...

http://www.diymobileaudio.com/forum/hlcd/113901-bang-olufsen-tweeter-lens-idea.html

just using horrible off-axis as a tool to control reflections in-car enviornment. one thing i am using now is ring radiator tweeters, because they inherently have bad off axis specs.


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## Patrick Bateman (Sep 11, 2006)

Yep, the reflector in the Sausalito Audio Works lens, and the Danley Paraline works on the same principle. It was the Paraline that inspired me to figure out how to get this stuff to work, and which helped me to understand how hard/important it is to keep the pathlength consistent at all angles.









Here's an example of what I mean. This pic is an overhead view of what I believe would be the "ideal" radiation for an underdash horn in a car. Basically it has the following features:

1) The sound radiates in ninety degrees
2) The wavefront is curved. The reason that we want a curved wavefront is so that the sound gets bigger and bigger as you get further away. (Remember, the ideal sound source is a pulsating sphere.) So this wavefront is basically a segment of that pulsating sphere.

In a car, one of the problems with underdash horns is that you can't crossfire them HARD, due to the center console. (For instance, if you point them 45 degrees off axis about 30% of your output will reflect off the center console.)









Hopefully this illustrates the problem a little better; see how the center axis of the HLCD is about 25 degrees off axis, when I want it 45 degrees off axis?


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## BigAl205 (May 20, 2009)

You could just take the reflector off a large flashlight and mount a tweeter behind the bulb opening.


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## Patrick Bateman (Sep 11, 2006)

cajunner said:


> doesn't the increased expansion rate towards the inside of the car, "bend" the wave to the center?
> 
> (on an ES full body)


Jason knows these horns better than I do, so correct me if I'm wrong:









^^^ these are ID full bodies









^^^ these are ID mini bodies

Both horns are conical. I know that they were advertised as tractrix, right? But look at that curve; it's conical. (A conical horn has flat sides, like a cone.) And the edges of these horns are definitely flat.

The interesting difference in these two horns isn't the size of the horns; *it's the reflector in the horns.* Both horns have a reflector, but in the full body horns the reflector is vertical, and in the minihorn the reflector is horizontal. Since the reflector bends sound waves 90 degrees, the reflector in the full body horn will reflect sound from UP to FORWARD. The reflector in the mini horn will reflect sound from RIGHT to FORWARD. (or LEFT, if it's on the passenger side.)

This probably accounts for a lot of the differences in imaging between the two horn bodies, because you also have to take into account the exit angle of the compression driver.









For instance, a small compression driver like the Celestion CDX1-1445 has a much larger exit angle than a LARGE compression driver like a B&C DE250:










IIRC, the exit angle on the B&C is something like six degrees. It's very small.

Everything else being equal, I'd be willing to bet that the full body horns are less sensitive to exit angle than the mini horns, because the reflector on the full bodies is much smaller.


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## quietfly (Mar 23, 2011)

sub'd cause knowing is have the battle!!!


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## thehatedguy (May 4, 2007)

The big horns are exponential.

Eric was wanting to do tractrix at one time but never got around to it.


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## Patrick Bateman (Sep 11, 2006)

Here's some plans for an underdash horn that uses some of these 'sound bending' ideas.










Here's a layered view of the horn. Yes, I know this doesn't look much like a horn 

I've attached PDF files which are drawn to scale. You literally print them on your printer, tape the printouts to a piece of wood, and cut! That's it. No weird angles, no routing, you could even cut these with a hand saw. I nearly tried to make them cut-able with a scissors, but that required too many layers 

If you're going to build this horn, you'll probably want to print up the PDFs, it'll make more sense that way.

With that out of the way, here's how this horn works:

1) There are five layers to the horn. The first layer is the bottom layer. The compression driver bolts to the bottom layer. That's where the sound enters the horn.

2) The second layer has our reflector in it. Basically the sound comes through layer 1, then expands in a circle, then hits that reflector.

3) Layer three is very simple - it's just a slot that connects layer two to layer four. So layer three is mostly solid, except for that slot.

4) Most of our horn is in layer four. The sound travels through the correct slot from layer three, then goes through the horn layer in layer four.

5. Layer five is just the top of our horn. It's just a plain ol piece of wood, with no cuts in it at all.

Ideally, I'd use 5mm plywood for the layers. If you want to get high tech, you could use clear Lexan. Both options are available at Home Depot. I use Luan, the same stuff that's used for door skins, which runs about $20. A single 4'x8' sheet of Luan is enough to make three or four horns.

Questions?


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## Patrick Bateman (Sep 11, 2006)

All of my tools are packed up (I'm moving) so I haven't built this yet.
The general idea of it is very similar to my 'stargate' horn from a few months back.
Here's what that looked like:


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## oilman (Feb 21, 2012)

Thanks and appreciated.


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## thehatedguy (May 4, 2007)

JLH built a paraline last year that's shown in his youtube channel that ended up in a car. He added a horn to the whole thing...paraline firing down into an asymmetric conical horn- looks sort of like a cross between the big ID horn but with conical expansion and your shark fin horn.

I think he said over on DIYA it would go 300-20k with a pair of Misco 3s and a Selenium D220Ti at about 105dB. The video shows it running full range with no electrical crossovers on any of the drivers. Said had to EQ the very top end a lot...probably due to the air load of the horn and the reflector.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> JLH built a paraline last year that's shown in his youtube channel that ended up in a car. He added a horn to the whole thing...paraline firing down into an asymmetric conical horn- looks sort of like a cross between the big ID horn but with conical expansion and your shark fin horn.
> 
> I think he said over on DIYA it would go 300-20k with a pair of Misco 3s and a Selenium D220Ti at about 105dB. The video shows it running full range with no electrical crossovers on any of the drivers. Said had to EQ the very top end a lot...probably due to the air load of the horn and the reflector.


There's a couple things about the Paraline that have really mystified me for about a year:

1) why is the high frequency rolloff so bad?
and
2) why are there peaks and dips in the response?

I don't think it's the air load - I think it's the geometry. And the geometry problem affects all of the car horns, everything from Image Dynamics to Veritas to USD.

If I'm correct (and I'm not 100% sure that I am), *here's what's happening:*


First off, conventional horns and conventional tweeters are 'hotter' on axis. We've all experienced this; when you point the driver at your face, it sounds louder. Point it away, and it gets quieter.

The reason that this happens is directivity. Basically there's a transition where the driver starts to beam, and when that happens, the energy is focused into the forward lobe. *BOOM, it sounds louder.*

Having said that, *a constant directivity conical horn shouldn't be hotter on axis.* Basically, *if it was perfect, it's output level would be completely even as long as you were on axis.*









Ideally, the sound would be like a flashlight beam. Basically if you're in the beam, the coverage is even. Step out of the beam, and it drops like a rock.









In the real world, constant directivity horns have a coverage pattern which looks more like the pic above. Hot in the middles, and then it 'fades' as you get close to the edges.









Here's a sonogram of a CD waveguide; see how it 'fades' at the edges? The dropoff is not abrupt, it's gradual?

So...

We KNOW this happens, but WHY does it happen?

I think the answer is "higher order modes." Basically, a higher order mode is a sound wave which doesn't travel axially down the horn. For instance, if some of the energy travels down the horn, but is off by a few degrees.

I think what's happening is that these higher order modes hit the edges of the waveguide, get reflected 90 degrees, and cross over to the other side.









^^^ this sim from hornresp illustrates this a bit. See how there are five 'beams' that extend from the throat? And in those 'beams' the interference level is higher?

That's higher order modes - and I think that's what's causing the two problems in the Paraline. (The dips in the response, and the loss of high frequency output.)

And higher order modes are also the thing that's increasing the ON axis output on a conventional conical horn. Basically the reflected energy will tend to accumulate at the center, not the edges. (Because it's reflected off of the horn's sides, and the reflectios "cross over" along the axis.)

But - and this is a BIG BUT -

*The higher order modes are delayed.* And these delays create comb filtering, because the initial wave and the HOM are no longer in phase. (They ARE in phase at the throat, but they get further and further out of phase as the wave travels along the waveguide path.)



I know all of that sounds long and meandering. Hope it makes sense. Geddes was talking about wavefront shapes and higher order modes and eigenvalues for close to a decade...

It just didn't make sense until I started studying the Paraline, and tried to figure out why it did the things it did.


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## thehatedguy (May 4, 2007)

Have you built a paraline that had 1/4" reticulated foam in the openings? Maybe if you added foam to all of the places it were cut out, it could do something...maybe not. Might would have to use different densities of foam to trap the offending waves- JBL uses 20 ppi foam in one of their devices, and Geddes uses 30 ppi.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> Have you built a paraline that had 1/4" reticulated foam in the openings? Maybe if you added foam to all of the places it were cut out, it could do something...maybe not. Might would have to use different densities of foam to trap the offending waves- JBL uses 20 ppi foam in one of their devices, and Geddes uses 30 ppi.


Of all the horns I've build, no horn saw a greater improvement with the foam than the USD horn. So I'd bet these Paraline and reflector devices would benefit too, since a reflector is bound to disturb the motion of the wave.

There's another thing that might make an improvement too. Simply polishing the surfaces. If you think about it, we need to keep the air flowing at the speed of sound. Anything that impedes that is going to screw up the wavefront. For instance, if there's something in the horn that causes the airflow to slow down by ten percent, then that's going to have the same effect as making the pathlength ten percent longer. (Since all of our calculations depend on the speed of sound.)

So that might explain a couple things:

1) it explains why guys like Mic Wallace saw an improvement from polishing the inside of their Image Dynamics horns

2) it explains why Danley went from Plywood in the early paralines, to aluminum in the later ones. Plastic would probably work well too; basically it just needs to be super smooth, so that the airflow isn't reduced at any point in the path.

Obviously, simply making it bigger would increase airflow too, but then that opens up a whole new can of worms by reducing high frequency output due to comb filtering.

The reticulated foam might seem like it's at odds with maximizing air flow. But at least the foam is very consistent. If it slows the airflow, *it will slow it equally at all angles.* Whereas problems with turbulence or going to be angle dependent, since the pathlength to the mouth of the horn varies depending on the angle.

Basically the last thing we want is for certain angles to be delayed by a few fractions of a second, because that will create dips and peaks in the response and it'll cause the phase to vary by angle.


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## [email protected] (Nov 7, 2010)

Way back in the day a shop I worked at sold USD, Eric H. said that the horns would benefit from smoothing the inside. (that's all I have to offer on this conversation.. lol)


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## fcarpio (Apr 29, 2008)

Subbed.


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## Golden Ears (Jul 18, 2010)

Hmm... very interesting.

I used to work for Bang and Olufsen when they introduced the Acoustic lens (licensed the tech from S.A.W.) . Our showroom was an odd space- a 11 foot wide room that was over 70 feet long. 

I could play the Beolab 3 speakers - perhaps a meter apart from each other and walk way down the corridor and the highs - nor overall volume...did not roll off to any appreciable amount. 

I could also separate them more than 10 feet and the imaging was not destroyed either.

However, IMHO I am not impressed by the use of an acoustic lens in the Audi A8 cars. Before they introduced the concept of using them in a car I had wanted to do it. But the poor implementation made me think it was the wrong idea for a car application.

My concern was that the acoustic lens has too wide dispersion for a car and should be restricted for better sound.

I aslo think that there is a fight of direct and reflected sound in a car...that severely damages SQ and causes your brain signal processing to go into overdrive to cancel out a tsunami of <5ms reflections (or actually IMHO I think the brain is detecting the louder of the two sounds...what it sees as the reflected and time delayed reflections and being fooled into thinking it could be the PRIMARY sound.) This gives your brain a headache not from noise but from trying to discard "noise in the perceived signal"

So my LOW TECH solution was to try and reduce the amount of direct HF-MF signal and turn it all immediately into reflected signal of similar time domain. Sounds pretty good sonically to me (not at all fatiguing) but needs precise (parametric) EQ. Also- the angles of the dashboard and windshield seems to play a large part in the success of this strategy


P.B.'s description of how the USD and other horns works is really clear.. nice. For cars without complementary windshield and dash angles its probably the best bet and best strategy for an off centered listening position.

I work for a loudspeaker company that uses its midrange ports directivity to enhance center fill and its tweeters directivity to enhance stage height. Rawdawg heard our direct radiating T-7 speaker at the Newport Show, but I think our T-8MKII concept would be cooler in the car. Our midrange ports to the middle of the sound stage. 

Never thought about this until I read this post.

SO PB... why not work backwards? Figure out the optimal slice of the Sphere pie for the car and then fold a horn to fit that directivity? Make a couple of varients and listen . 

Literally block some of the wave front (with panels in a a car or a mock up of a car interior -( which you could make in the corner of a room) and see which blocked parts least detrimentally affect the sound and then fold those parts of the horn to "lose" those sections (this will reduce unnecessary (ie...unhelpful) reflections ..your goal right?)

I am sure my description is not as clear as yours.. just trying to toss out an idea, no offense taken if you think its totally wrong.


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## Patrick Bateman (Sep 11, 2006)

I'll definitely give that some thought. I think the Paraline and the SAW lens are basically two approaches to the same problem. One is designed to control the entire wavefront; the other one is designed to control the part of the wavefront that's beaming.

Lots of good reading in both patents, and I really like Manny LaCarrubba's work.


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## sonikaccord (Jun 15, 2008)

I was reading the "Apparatus for the Redistribution of Acoustic Energy"

It's actually pretty easy to build. I'm confused on these relationships:
Frequency, directivity, ellipse 1, ellipse 2, driver angle

The two ellipses must share a focal point:
How do you determine the focal point for your desired response?

They must share a point on an imaginary axis, L.
How do the size/shape of the ellipses affect the sound?

The focal point must be between the inverse arc and the base of the lens
How is the distance from the shared focal point to the inverse arc chosen?

The two ellipses can be rotated through an angle
Does this affect horizontal dispersion?

Just brainstorming here...


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## akdingo (May 19, 2011)

Okay, stick with me - I'm fairly new to alternate loading techniques, and researching this has prompted a thought. It's either useless and assanine, or worth experimenting with. Either way, I'll demonstrate my ignorance...

If I understand the principle correctly, a secondary effect of loading a driver in a paraline increases efficiency and controlling directivity. While it seems primarily aimed at compression drivers and minimizing horn size, there is the variant with small midranges loaded quasi- Unity-style.

Could this design be adapted to one midrange with a low efficiency and sub-optimally mounted to overcome both disadvantages? If the woofer were mounted in the lower door, couldn't the throat theoretically be turned at any angle (i.e., pointing 1 & 7 on a clock face) to improve imaging by controlling the coverage angle while at the same time raising the efficiency and allowing for closer matching to more efficient drivers?

I'm pretty sure this has nothing to do with the intended purpose, but I just thought that these side-effects could be used beneficially in other ways. If I am way off target, let me know. I am by no means educated on this type of thing, so feel free to tell me if and why this thought is better suited to this discussion: http://www.diymobileaudio.com/forum/general-car-audio-discussion/135721-%2A%2Astupidest-thing-anyone-has-said-you-audio-wise-%2A%2A.html


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## Patrick Bateman (Sep 11, 2006)

As noted earlier in this thread, both the Paraline and the SAW Lens bend the sound wave. Basically the Paraline is two dimensional and the SAW Lens is three dimensional. (IE, if you look at a cross section of the SAW lens, it's the same shape as the Paraline. They're both parabolic reflectors.)

I've been screwing around with both devices for over a year now, and both do things that I like, but both have their drawbacks.

The SAW Lens sounds really nice, but the size can get rather large if you want it to play low.

The Paraline is insanely small, but it has a tendency to sound 'honky.'

I've owned Gedlee Summas for over five years now, and I'm really tuned in to horn honk. Geddes knows how to fix it - you basically avoid sharp edges and reflections.

Unfortunately, bot the SAW lens and the Paraline are *based* on reflectors 

But I've noticed that the SAW lens is in a whole 'nother class when it comes to sound quality, compared to the Paraline. (Seriously, anyone thinking about building one, GO DO IT.)

So my 'hunch' is that the SAW lens sounds better than the Paraline because the sound wave expands a lot faster than the Paraline.

So here's something I wanted to explore today:

*Can we use the windshield as a reflector?*









By using the windshield, we can basically reduce the foot print of our device by at least 50%. Because in the SAW speakers, those big cymbal shaped things aren't just for looks. They're functional reflectors.
And the problem I'm having in my car is that I can't get the reflectors on the dash along with the speakers. (In the Audis and the Aston Martins the reflectors are smaller because only the tweeters are up there. I want a lot wider bandwidth, at least 500hz-20khz.)


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## Patrick Bateman (Sep 11, 2006)

Here's a simulation of using the car's windshield as an acoustic reflector.

The first pic shows the dash of a car, and the windshield.
That little spec is our speaker. I used a 'point source' because it's the most accurate at high frequncies. (Ideally you'd simulate the radiator at it's actual size, but let's not get crazy here.)

The second pic in the first row shows the speaker radiating off of the dash and reflecting off the windshield. When the sound radiates into the corner of the car, it's reflected and delayed. This causes comb filtering in the speakers frequency response. (peaks and dips.) At the same time, the reflected energy can make the soundstage more 'spacious' and I kinda like that effect.

In the first pic in the second row I've added a waveguide. Basically the waveguide is there to minimize the energy that's going into that corner that forms between the dash of the car and the windshield of the car. That corner causes a lot of issues. If I could just fill that corner with sound absorbing foam I would, but that would look so ugly. (Same reason people use a dash mat.)

In the last pic, I've shown one effect that the waveguide is having. The waveguid is making the sound more directional, and now we have 'lobes'. See how there's more sound going DOWN then there was before?

So what we can do is STEER that lobe, and aim it right at ya face.

The trick is to get the right combination of waveguide angle, windshield angle, waveguide width, and depth.

Neat huh?

One could also use a parabolic reflector like the SAW lens, and I'm going to look into that too. Basically figure out if we could use the SAW lens but omit the cymbal looking things at the top and the bottom, but use the windshield and dash instead.

One last thing -

All of us have heard systems where the tweeter was on the dash, and the sound was harsh. Note that with the waveguide, the shape of the wavefront is more consistent. *See how without the waveguide the wave shape is almost random?*








This operates the same way as waves in a pool do. If you disturb that wave, you get a random interference pattern. The waveguide doesn't just control directivity, it also controls the shape of the wavefront. This is something that's really REALLY hard to visualize without actually watching the wavefronts. You can tinker with the wavefront simulator in hornresp to get a good understanding on how this works. But *the pics above clearly show that the wavefront with the waveguide is closer to perfect than without.* (The perfect wavefront would be spherical or flat, depending on what you're trying to do. For my purposes, it would be spherical.)

Also, if you've noticed that tweeters on the dash sound 'harsh', this may well be the sound of higher order modes. Perhaps there's something in our hearing system that prefers wavefronts that aren't distorted. For more on HOMs, check out 'Geddes on Waveguides' at diyaudio.


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## Patrick Bateman (Sep 11, 2006)

akdingo said:


> Okay, stick with me - I'm fairly new to alternate loading techniques, and researching this has prompted a thought. It's either useless and assanine, or worth experimenting with. Either way, I'll demonstrate my ignorance...
> 
> If I understand the principle correctly, a secondary effect of loading a driver in a paraline increases efficiency and controlling directivity. While it seems primarily aimed at compression drivers and minimizing horn size, there is the variant with small midranges loaded quasi- Unity-style.
> 
> ...



Could a Paraline be used to raise the efficiency of a low efficiency driver?

YES.

It works exactly like a horn does. It is a radial horn, like the old 'Smith Horns' from the 50s, but it's folded.

As far as the directivity goes, that is mostly determined by the shape of the mouth. IE, a Paraline with a mouth that's 1" x 8" will have directivity that's similar to a ribbon that measures 1" x 8".

The advantage over a ribbon is power handling, durability, cost, etc. For instance, a 1" x 8" ribbon costs something like $300; I can make a 1" x 8" Paraline with a $50 compression driver. And the compression driver will have higher power handling and more output for less cost.

If one did not like the sound of compression drivers you could easily substitute a ribbon for a Paraline. They'll behave fairly similarly. One caveat though - I've noticed that the directivity of the Paraline is better behaved than ribbons are. For instance, I have a B&G NEO8 here and a Paraline that's about the same size, and the Paraline directivity is more consistent.


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## Patrick Bateman (Sep 11, 2006)

thehatedguy said:


> JLH built a paraline last year that's shown in his youtube channel that ended up in a car. He added a horn to the whole thing...paraline firing down into an asymmetric conical horn- looks sort of like a cross between the big ID horn but with conical expansion and your shark fin horn.
> 
> I think he said over on DIYA it would go 300-20k with a pair of Misco 3s and a Selenium D220Ti at about 105dB. The video shows it running full range with no electrical crossovers on any of the drivers. Said had to EQ the very top end a lot...probably due to the air load of the horn and the reflector.


when I search youtube for JLH I get a lot of this:










But here's the video that Jason is referring to:

Paraline build - YouTube


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## 69Voltage (Jul 30, 2013)

Thanks for the research. Great thread, and useful considering I'll be utilizing waveguides in my build.


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## Patrick Bateman (Sep 11, 2006)

Thanks! Glad people find this useful.


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## Patrick Bateman (Sep 11, 2006)

Here's some sims of the dash with lower frequencies.

Things actually get easier as the frequencies get lower; basically as the wavelengths get longer diffraction and reflection and comb filtering is less of an issue.

If you look at the picture that's in the bottom right corner, see how the wave shape is now spherical? *That's the wave shape we want.* We basically want the waves to radiate in such a way that the sound isn't going to change if we move our head two inches.

The pic in the top right shows what the radiation is like without any waveguides. Basically with the woofer placed face up on top of the dash, in a sealed enclosure.

Here's a few things you might notice without the waveguide:

1) There some vertical nulls. Those are the black 'rays' that radiate outwards from the dash. In those nulls, the sound will change dramatically and that change will be frequency dependent. (IE, if the null was pointed at your head the sound would be very bad.)

2) One thing that's kind of odd is that the waves are spherical, *but the phase inverts at some angles.* Kinda trippy; I'm not sure what the effect of this would be. You can see the change in phase where some bands are red, but then you move your head down by four inches vertically and the phase is 180 degrees different. (green instead of red)


If you look at the pic that's in the bottom left, you'll notice that the waves are closer to spherical. That sim is WITH the waveguide. So the waveguide is definitely improving the response, *even though we're listening a full 90 degrees off axis!*

Kind of interesting stuff, no? I always knew that waveguides improved the off-axis response, but I didn't realize that you could combine a waveguide with a reflector.


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## Patrick Bateman (Sep 11, 2006)

Here's a funny story that inspired this idea of bouncing the sound off the windshield:

A few weeks back I was doing some measurements on some speakers. I was rotating the speaker, measuring it, and then rotating it some more. I was doing these measurements in my living room.

I did one measurement 180 degrees off axis; IE the speaker was aimed AWAY from me.

When I measure a speaker, I 'gate' the response. The 'gate' is used to eliminate the 'sound' of the room. Basically I capture a few milliseconds of sound, before the room reflects it.

With me so far?

Here's the odd part:

I noticed that when the speaker was pointed AWAY from me, it sounded like the soundstage was coming from the wall behind the speaker, instead of the speaker itself.

What was happening was that the speaker had a waveguide, and it was SO DIRECTIONAL, *the reflection off of the back wall was louder than the sound emanating from the speaker!* (Because it was pointed AWAY from me.)

Out of curiosity, I measured the *reflection* instead of the speaker, and I found that the frequency response of the *reflection* was actually quite good. It was basically like the speaker, but the treble was rolled off a bit.

But there weren't any big peaks or dips; the reflection off of the wall was basically the same as what the speaker sounded like, *but it was delayed by a few milliseconds and the treble was rolled off.*

So it occured to me that you might be able to use this to your advantage. Basically *make the windshield of your car appear to be the speaker.*


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## Regus (Feb 1, 2011)

I'm intrigued... Sub'd.


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## 69Voltage (Jul 30, 2013)

Patrick Bateman said:


> Here's a funny story that inspired this idea of bouncing the sound off the windshield:
> 
> A few weeks back I was doing some measurements on some speakers. I was rotating the speaker, measuring it, and then rotating it some more. I was doing these measurements in my living room.
> 
> ...



That is interesting and cool.


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## Hanatsu (Nov 9, 2010)

Very interesting thread, love reading your posts, Patrick!


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## Yankeesound (Jul 11, 2009)

I came in and left, its like Chinese to me lmaooo. I am out of here, I am way over my head, lol


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## Patrick Bateman (Sep 11, 2006)

Yankeesound said:


> I came in and left, its like Chinese to me lmaooo. I am out of here, I am way over my head, lol


I appreciate that, so let me back up a little bit.

This thread is about bending sound.
Bending sound is something that I've been interested in for a few years, but I really didn't know how to do it properly until about a year ago.

*Bending sound is really important in the car, because we typically can't put our drivers exactly where we want them to be.* Even worse, sometimes when we chop up our cars and put our drivers *exactly* where they should sound best, THEY DON'T. It sucks.

For instance, I've heard a lot of cars that put the midranges and the tweeters up high, and the stage is high, *but it's not wide.* And I've also heard cars that had a wide and deep stage where the tweeters were in kick panels. If you follow this thread, I'll explain why that is.

Going with a kick panel solution might be the best way for me to go, but I likt to do things a little differently. And while I've heard cars with kick panels that had a wide and deep soundstage, I've never heard one with that config that had a HIGH sound stage.

Horns under the dash get pretty close; the stage is definitely taller, but it also tends to be narrower in my experience.










All waves are subject to diffraction, reflection, etc.

It's easiest to visualize it with water. In this pic, you can see that the outcropping is creating an 'eddy' in the water. And outcroppings do the same thing to a sound wave.

Sound waves are quite long, so these 'eddies' caused by diffraction make an audible difference to the music we're listening to. For instance, when a sound wave hits an object and diffracts, a delay of just a fraction of a millisecond is enough to create a dip in the frequency response.


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## Jepalan (Jun 27, 2013)

I'm down with the concepts in this thread, but I have difficulty imagining that the direct path plus the reflected waves can be directed in a way that produces favorable constructive happiness across a band of frequencies. One frequency, yes, but a finite band of frequencies seems a challenge. Anything involving reflected wave and a mechanical structure can only be optimized at one frequency. How is this dealt with?????


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## Patrick Bateman (Sep 11, 2006)

OK, so I tried half a dozen different shapes on the dash, and I only found one shape that worked well:

A waveguide with a big fat roundover.









A 'roundover' is what's on the horn in the top left. Basically at the termination of the horn the lip of the horn 'rounds over.'









^^ this is my car










Here's a sim of how sound radiates on the dash of my car.

1) The top left and top right sim is our loudspeaker in a waveguide that's 6" deep with a 1.25" roundover
2) The bottom left and bottmo right sim is the same loudspeaker, same waveguide, *but no roundover.*
3) The left column is 6000hz and the right column is 3000hz



If you look at the sims, they seem similar. *But there's a dramatic different in two respects.* First, the wavefront shape of the waveguide with roundover is much better. *See how the waveguide on the bottom left, without roundover, has ripples in the wavefront?* These ripples will add dips and peaks to the frequency response; the wavefront we want is perfectly spherical.

The second difference, and it's a big one, is in the corners. See how the waveguide without a roundover radiates a lot of sound into the corners of our dash? This is a big problem, because that energy will hit the corner and reflect back into the cabin. That will muddy our imaging, create comb filtering, etc.

Note that these waveguides are *very* small; just 6" deep.


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## Patrick Bateman (Sep 11, 2006)

Jepalan said:


> I'm down with the concepts in this thread, but I have difficulty imagining that the direct path plus the reflected waves can be directed in a way that produces favorable constructive happiness across a band of frequencies. One frequency, yes, but a finite band of frequencies seems a challenge. Anything involving reflected wave and a mechanical structure can only be optimized at one frequency. How is this dealt with?????


Yeah I found the same problem when trying to make a reflector for the windshield. I tried literally a dozen shapes. Here's a list of problems I saw:










1) The most shocking thing I noticed was that tweeters in the A-Pillar were basically The Worst Case Scenario. In the wavefront simulator, you could see that the energy radiates in 180 degrees, hits the window, then gets reflected back into the on-axis response. *The reflected energy takes a longer path, which inserts a delay, which completely trashes the wavefront coming off of the tweeter.*

A very small waveguide would make a huuuuuuuge improvement for a pillar tweeters apparently.

2) I also screwed around with a LOT of different waveguide widths, depths, and angles, all of them reflecting off of the windshield. *The problem with that setup was vertical nulls.*









Basically you get vertical nulls, similar to the dark areas in the top right of the picture above.

Vertical nulls were only an issue at frequencies above 3000hz or so; below that the wavefronts looked pretty good.



I tried to figure out some way to fire the loudspeaker UP and bounce the sound to the LEFT, towards the cabin. But I couldn't find anything that would work. Waveguides helped, but there was still a lot of energy that was radiating into the corner of the dash.

It's like you need a waveguide that basically radiates UP and INTO the cabin, but not into that corner.

Unless, obviously, you're willing to stick a big ol' dash mat into the corner of the dash.


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## Justin Zazzi (May 28, 2012)

You are so close to an idea I've wanted to try, but didn't have the knowledge or parts to attempt. What if you use the windshield and the dash as the surfaces of your horn's mouth, hide the compression driver under the dash, and connect the two with the throat of your horn? The "horn" would become the interior geometry of the car and thus, be invisible. The horn would also mate perfectly with the edge of the dashboard because it would _be_ the dashboard. Here is a crude illustration using one of your images.










Instead of trying to get sound to radiate _away from_ that corner of the dash that is so problematic, why not have sound _come from_ that corner? Seems like a win-win, no?


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## Brian Steele (Jun 1, 2007)

A paraline has wide horizontal and very narrow vertical output. How about upward-facing paralines on the dash, angled so that its narrow angle output is aimed towards where the windscreen meets the dashboard?


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## Patrick Bateman (Sep 11, 2006)

Jazzi said:


> You are so close to an idea I've wanted to try, but didn't have the knowledge or parts to attempt. What if you use the windshield and the dash as the surfaces of your horn's mouth, hide the compression driver under the dash, and connect the two with the throat of your horn? The "horn" would become the interior geometry of the car and thus, be invisible. The horn would also mate perfectly with the edge of the dashboard because it would _be_ the dashboard. Here is a crude illustration using one of your images.
> 
> 
> 
> ...


I am too lazy too find the quote on a Friday night, but Andy Wehmeyer wrote a post where he described Mark Eldridges 4Runner. And he mentioned that it basically sounded like a giant pair of headphones, and really dynamic. But Andy also noted that it was a 'sound' that he couldn't live with; he preferred a system with more ambiance. 

I think that's the problem with using the entire windshield as part of the horn mouth. You get two issues:

1) The only ambiance is what's in the recording. Basically the limits of the soundstage are defined by the dimensions of the windshield.

2) I've been building horns for years and years and years, and I've begun to realize that horns with a slow expansion rate don't sound as good as horns with a fast expansion rate. There's an AES paper on this.

















Basicallly the AES paper found that rapid expansions, like in the second horn, sound better than slow expansions, like in the first horn.

That's a problem for horns in a car, because we often use very slow expansions. Possibly the only exception to this rule is the Image Dynamics mini-horns, and maybe that's why a lot of people think they sound great.



The jury is still out, but I'm thinking that getting that wavefront correct is pretty important. And if you can get a fraction of the energy to radiate to the back, that will probably add some 'ambience.' The trick is probably to get that wave to radiate *mostly* forward, but not 100%.


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## squeak9798 (Apr 20, 2005)

Patrick Bateman said:


> Here's a funny story that inspired this idea of bouncing the sound off the windshield:
> 
> A few weeks back I was doing some measurements on some speakers. I was rotating the speaker, measuring it, and then rotating it some more. I was doing these measurements in my living room.
> 
> ...


Werewolf had a huge thread probably 7 years ago on ECA about reflecting the midrange off of the windshield to turn the windshield into a phantom source to improve/raise the soundstage. I don't know how much he dealt with waveguides in that thread. 

Believe this was the thread: Elite Car Audio : Car Audio Forum - Dashboard Domes & Reflection Combs


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## Hanatsu (Nov 9, 2010)

This might not belong in this thread but I have a few comments on hard edges and waveguides.

This is old measurements of my tweeter pods. The tweeters are currently mounted in small waveguide/"anti-diffraction" pods aimed on-axis in front of the pillars. The driver I'm using is a Vifa XT25. 








If you compare the two plots you'll see that the second one has a more controlled off-axis response with less peaks and dips. After comparing the old pods (used the OEM flange) with the new I noticed some interesting things. The new pods made the sound harder to locate, they improved focus and it sounded "smoother" in the upper midrange, even the highs felt "richer" somehow. If I just laid the driver on the dash, the stage was ruined but just a few inches up it sounded great again. I had the best result actually facing the drivers slightly towards the side windows (left driver -> left window). The sound was overall more "spacious". My point is that controlling the sound power is always necessary even if go the horn route or trying to "spead the chaos" around with a wide dispersion. My new pods didn't change the on-axis response that much really but it had a greater impact in shaping the off-axis response. I concluded that the off-axis response was really important even with the speaker pointed directly on-axis, both tonality and staging was affected. No matter how you deal with the install, I think 'getting the wavefront' right is paramount for a great stage in any install. 

I don't have much experience with horns but it would be really interesting to try out the waveguide - window reflection thing. The windshield has been discussed as a reflector but how about side windows? Point a horn into the far corner of the side window, so only the reflected sound can be heard. I wonder if this can give some illusion of better stage width...


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## Orion525iT (Mar 6, 2011)

Maybe the issue is, in part, trying to use the windshield, side windows, ect as reflective surfaces in the respective vehicle. Maybe a better approach is to find a wave guide, horn, reflecting surface that works and then make the thing out of clear acrylic. That way you are not restricted in as many variables. The approach to problem solving is to eliminate the variables where possible. Obstruction of vision in a vehicle is a huge variable.


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## Broshi (Jun 9, 2012)

Keep it up Patrick you're bloody onto something here! I seriously wish I had the resources and knowledgeable background to understand wavelength manipulation. I think I'll be making the investment to add a acoustics lab to the shop in the next few years. Perhaps I can actually contribute to your ideas. Until then, I am patiently waiting for the next step in your project. Just contemplating and trying to comprehend. Cheers!


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## robtr8 (Dec 6, 2011)

I don't mean to highjack the thread, just trying to understand it as it relates to my current build.

1998 S70 w/ L3SE which I think has a more upright windscreen than your model.



What I think you said was, this works well in the lower frequencies, which is hand in hand with using a "full" range driver like this. Just wish my 80PRS would allow a lower cross over point. As it is, I've got the slope as low as it can go.

Imaging in this system is great. I've had some problems with sum-gain at certain frequencies which I was able to EQ out. I also played with the time alignment. Which brings up a question: you've modeled a single driver. What happens when you add the second driver to the dash and B) how does time alignment effect the wave patterns? It would seem that a large delta would be a bennefit. Of course I pitty the fool who gets to ride *****.

Placing the driver on top of a column resulted in almost no direct radiation. Does your analysis suggest that the sound would be improved by adding a wave guide around the column? Should I try filling in the space between the dash and the windscreen? Somebody needs to buy a microscribe and 3D printer and offer a wave guide/custom pod service.


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## win1 (Sep 27, 2008)

Sub'd


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## NateZ28 (Oct 2, 2013)

I'm extremely interested in this. I may want to do something like this in my Genesis Coupe. How big is the horn you're building and would it be possible to fit it practically in a smaller vehicle?


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## Patrick Bateman (Sep 11, 2006)

NateZ28 said:


> I'm extremely interested in this. I may want to do something like this in my Genesis Coupe. How big is the horn you're building and would it be possible to fit it practically in a smaller vehicle?


I pretty much gave up on putting a stereo in my Genesis. The Lexicon system does so much well, and bypassing it would disable a lot of the tech gadgets I like in the car. 

What I was trying to do with the horn is bounce the highs off the windshield at a 45 degree angle. (This is for my Mazda6)

The waveguide seems to improve things. The problem is that it gets big in a hurry and we don't have a lot of space up there. 

I'm beginning to wonder if a simple cardioid is a better solution. 
A cardioid would nuke about ten decibels of sound that would normally radiate back towards the windshield.


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## Patrick Bateman (Sep 11, 2006)

robtr8 said:


> I don't mean to highjack the thread, just trying to understand it as it relates to my current build.
> 
> 1998 S70 w/ L3SE which I think has a more upright windscreen than your model.
> 
> ...


I'd start with the aiming. You want the reflected sound to end up at ear level. 
For instance, if your windshield is 45 degrees than the speaker would be at zero degrees. (Flat and facing UP)

The reason that the angle is important is the nulls. At certain angles there will be nulls; you want to 'steer' them into the ceiling and the floor. 

The worst case scenario is that the sound reflects in such a way that the listening axis is at chest level, and those nulls are at ear level!

I would get out the digital camera and take a profile shot of the windshield. And then figure out what the angle is between the speaker and the windshield. 

As far as those pods, GET RID OF ALL sharp edges. Check out Hanatsus pods, that's what it should look like, totally smooth. Even the mounting screws create diffraction and the surround does too.


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## NateZ28 (Oct 2, 2013)

Patrick Bateman said:


> I pretty much gave up on putting a stereo in my Genesis. The Lexicon system does so much well, and bypassing it would disable a lot of the tech gadgets I like in the car.
> 
> What I was trying to do with the horn is bounce the highs off the windshield at a 45 degree angle. (This is for my Mazda6)
> 
> ...


You must have the Genesis sedan. In my 2010 coupe the computer system is retarded. The only feature I like is the hands free microphone, which I can get with pretty much any aftermarket head unit.
Right now I'm trying to figure out the best aftermarket head unit/DSP solution for playing music via my iPhone. It seems all of the aftermarket head units are terrible as far as "audiophile" sound goes.


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## rton20s (Feb 14, 2011)

Let me preface this by saying I am probably in *WAY* over my head, but I would love to learn and understand what it is you are presenting. 

A very interesting read indeed. Judging by some of the illustrations you created, it would appear that a steeper windshield would/could be advantageous?

I ask because I have an xB and my plan is put my tweeters in the stock dash location firing up. There is plenty of room to adjust angle, and probably enough room to even add an extremely small wave guide that would stop on the plane of the dash. How effective could a small wave guide like this be, say less than 3" deep and no more than 4" diameter/square? 



















To simplify your examples even further and so I understand correctly what you are looking to do in using the windshield for reflection...

You will use the angle of the windshield and the relative ear height of the listener to determine at what angle the driver should be placed for a given location and waveguide design. For instance, a windshield with a slope shallower than 45 degrees would likely need to be angled back toward the driver, otherwise the reflection from the waveguide would be focused too far below horizontal. (Assuming we are mirroring about a line perpendicular to the windshield?) 

A windshield at exactly 45 degrees could make use of a driver with waveguide at exactly 90 degrees from horizontal *if* the reflection point was approximately at ear level? Above or below ear level would have to be compensated for through positioning and angle? 

And finally a windshield steeper than 45 would actually need to be *more* than 90 from horizontal pointing back toward the windshield a bit to prevent the sound from being directed toward the headliner. 

Lastly, this is just general aiming and location that doesn't take into enough account the affects of a given wave guide. It could be that one of these options geometrically calculates correctly but the wave guide could create a null right at a given listening level. Is this correct? Or am I way off base?


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## Patrick Bateman (Sep 11, 2006)

NateZ28 said:


> You must have the Genesis sedan. In my 2010 coupe the computer system is retarded. The only feature I like is the hands free microphone, which I can get with pretty much any aftermarket head unit.
> Right now I'm trying to figure out the best aftermarket head unit/DSP solution for playing music via my iPhone. It seems all of the aftermarket head units are terrible as far as "audiophile" sound goes.


Yep! Seven channel Lexicon sound. First time I've heard a car with a center channel that I thought sounded better than stereo.


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## Patrick Bateman (Sep 11, 2006)

rton20s said:


> Let me preface this by saying I am probably in *WAY* over my head, but I would love to learn and understand what it is you are presenting.
> 
> A very interesting read indeed. Judging by some of the illustrations you created, it would appear that a steeper windshield would/could be advantageous?
> 
> ...


Here's what you might try:

1) Take a side shot of the car like this:










Now figure out what angle on the *dash* will reflect the sound at eye level.
If the windshield is a perfect 45 degrees, than the answer is easy. *Aim the tweeters straight up.*









In a lot of cars like mine, aiming the tweeters straight up will actually send the energy into your chest!
Even worse, you get really nasty nulls and peaks off axis. So the sound that is at your ear level is basically a worst case scenario.

If you juggle everything nicely it looks like it may be possible to 'aim' the nulls at the ceiling and at the chest.









Here's an example of these lobes. See how if you move your head 30 degrees above the listening axis there is a hole?

more info here:

Off-Axis Response | Beat Stamm


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## Golden Ears (Jul 18, 2010)

My car is a w124 Mercedes E500 the windshield is not so raked. I decidedi wanted reflected sound to overwhelm the direct sound so I shoot straight up into the glass and position the drivers seat for the best height. I took a small flashlight and some " earth quake museum putty" to afix it into my empty speaker hole. I then took some honey and smeared it on the inside of my windshield and took aluminum foil and stuck the shiny side facing inwards.

I turned on the flashlight ( single bulb small Surefire with tight corona on beam) and pretty much just sat in my seat with sunglasses on maneuvering my chair until I was maximally blinded. And then lowered the chair because my pupils are higher than my ear holes

The bulb of the light was put where the imaginary internal center of my Scan Soeak 12m 4.5" mids are.... ( they sorta work like partial domes anyhow.

I moved my seat fire and aft to try to minimize the path length differences between my dash and door midbass Jehnert drivers and to keep my distance from my subs to be greater because of crossover delay.

I jam the tweeters as close to the boundary of windshield and dash as possible to eliminate more direct sound.

Sure it requires EQ but I am very happy with the result. I used the museum putty to seal the drivers and will also smooth the drivers baffle into the drivers with more putty to reduce diffraction and tune. I'm not sure what to do about the stock grills because the metal grills ruin the sound. I was thinking about making acoustic foam grills ..... Or maybe cutting away the metal and stretching speaker grill cloth or perhaps panty hose over cutaway metal grill sections.

I've had good sound this way for 2 years but never finished my amp rack so driving it is not possible yet.

I think comb filtering affects the highs a lot because if the short wave length so eliminating the direct sound seems to help. Also the natural quasi done shape of the 12m seems to help too


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## sqnut (Dec 24, 2009)

The torch example is fine for the 4.5" driver above ~3khz. Below 3khz where dispersion is omni directional, you will get a large band pass where you are hearing direct and reflected sound, no way around that.


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## Patrick Bateman (Sep 11, 2006)

I'll probably change my mind in a week, but here's where I'm at right now:

1) If you look at the sims on this page, you'll notice that it's not just the waveguide that's important; basically there's a frequency where the music just wraps right around the enclosure.

2) Since the music wraps around the enclosure, one way to address that is to put the speakers into the car. You can do that by putting them in the doors, or jamming them all the way into the corners like I did here: 









3) The thing I don't like about option two is that it tends to make the car sound like a big set of headphones. No "air" around the soundstage. I think a moderate amount of early reflections can make the soundstage better.









So I'm thinking something along the lines of the Genelec monitors would work well. It has the following advantages:
1) That low diffraction enclosure will allow the sound to simply wrap right around the enclosure
2) After living with my Summas for a few years now, regular tweeters just sound really weird. So I basically have to have a waveguide.

I'll fire up Design 3D and see what I can come up with.

I am going to continue this on the thread "28 Days Later", which is basically my current build documentation:

http://www.diyaudio.com/forums/multi-way/239808-28-days-later-4.html


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## robtr8 (Dec 6, 2011)

Waveguides from the plumbing isle.





Just ordered the L3 grills. I think they will look OK now that the base is bigger plus hopefully cut down on the UV damage. Barn door, I'd like you to meet horse. I played around with re-aiming the drivers but I feel they're pretty good right where they are. I noticed the sound stage seems broader now. A little less one positional.


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## Patrick Bateman (Sep 11, 2006)

robtr8 said:


> Waveguides from the plumbing isle.
> 
> 
> 
> ...


That's awesome!

One thing you might try, particulary if you're going to have grills, is to use modeling clay to smooth the lip from the woofer to the enclosure.
It makes a small measurable difference, and everything counts.
Plus, it's basically free; clay is cheap cheap cheap










B&W is a good example of this; even the screws have been eliminated to reduce diffraction.


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