# In Depth Explanation of different horn designs



## ncv6coupe

So we all know that horns are the easiest thing to use for controlled dispersion which is influenced by the width, height and angle of the horn's interior walls.

I would like us to discuss the design philosophies of the throat to mouth transition and how it affects freq. response, tonality and acoustic gain for any given design. Then let that carry on into horizontal-vertical dispersion characteristics that effect the outcome of strong center imaging, wide soundstaging and focus "IN CAR"

Horns of particular interest are in the likes of the classic straight thru design, the USD labeled waveguides, the 90 deg. bend at the throat Image dynamics full body, the older image dynamics mini body(closer to 90 deg horizontal bend) compared to the newer image dynamics mini body.(rounder transition which looks like a 225 deg circle bend in the throat)

I know and believe in the quarter wave theory so I understand little bits and pieces but would love to get the engineer low down. I'm also not just limiting the choices to the above mentioned horn frames but those are the more off the shelf options that most people settle for it seems.

Thanks for contributing the information in advance...


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## ncv6coupe

cajunner said:


> well, I've read that the phase plug/collector part of a compression driver is based on Western Electric's 190 hz horn bend, and all modern and not so modern drivers use this same topology when making that first expansion in the mouth.


I'll have to look more into this as I've never read much about the original Bell horns.



cajunner said:


> So, even though most horns won't be operated below 800 hz, and the ability of a horn to produce the sub-harmonic of 400 hz still leaves a lot of room between that and the 190 hz mouth flare, then it would maybe make sense to use a compression driver suited for a bit higher flare ratio?
> 
> Is this what you're talking about?


I doubt these small car horns can utilize a 190hz mouth flare, they just aren't deep enough. I will try to measure up the mouth area and throat area best I can on a set that I have and see what I can tally up(cant promise any accuracy whatsoever):laugh: I am facinated by that new 2" BMS coaxial driver. Really want to try one out but hot damn where's it gonna go? I drive a manual.



cajunner said:


> it gets kinda complicated, I don't really understand it except that it's like if you could use a bunch of colors to shade out the response, you'd see that the end result that is coming off the edges of the horn body's exit has been acted upon by several different mechanisms, not the least of which is the initial 190 hz to whatever flare the body employs in it's design.


I know exactly what you mean here. There is a web program that has the actual visual graphics of the waveform, I played with it a couple months ago and you could see all the diffraction effects, DRAW in vanes, straight walls or literally anything you wanted and see how it affected the wavefront in real time. It was cool as hell. I never saved the link but It would be great if you were a diy oriented jock with a little fiberglass and woodwork skills to build some custom horizontal kick panel waveguides. hmm which gets me to thinking..................


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## Patrick Bateman

ncv6coupe said:


> So we all know that horns are the easiest thing to use for controlled dispersion which is influenced by the width, height and angle of the horn's interior walls.


I'd argue that's what waveguides are for



ncv6coupe said:


> I would like us to discuss the design philosophies of the throat to mouth transition and how it affects freq. response, tonality and acoustic gain for any given design.


A narrow horn creates more energy on axis than a wide horn, just as a car headlight with a narrow beam does the same.

The main problem with horns is that they get very VERY long to get gain down low. For instance, to play down to 100hz, it needs to be 33.75" long.

Another problem is that a horn is a high pass filter. And the longer it gets, that high pass filter goes lower and lower and lower.

As far as tonality goes, IMHO good termination at the throat and the mouth makes a world of difference. Google "homster diyaudio" for my thread on that.



ncv6coupe said:


> Then let that carry on into horizontal-vertical dispersion characteristics that effect the outcome of strong center imaging, wide soundstaging and focus "IN CAR"


It's really hard to get a wide soundstage, due to reflections off the doors. Getting a strong center image is fairly straightforward, and equalizing pathlengths goes a long way.

At this point I'm starting to think that a wide soundstage is easier to achieve with tweeters which are very close together, like the ambiophonics guys use.

See video here:

3D audio report



ncv6coupe said:


> Horns of particular interest are in the likes of the classic straight thru design, the USD labeled waveguides, the 90 deg. bend at the throat Image dynamics full body, the older image dynamics mini body(closer to 90 deg horizontal bend) compared to the newer image dynamics mini body.(rounder transition which looks like a 225 deg circle bend in the throat)
> 
> I know and believe in the quarter wave theory so I understand little bits and pieces but would love to get the engineer low down. I'm also not just limiting the choices to the above mentioned horn frames but those are the more off the shelf options that most people settle for it seems.
> 
> Thanks for contributing the information in advance...


I have never measured a waveguide which could outperform this:










They're like eight bucks, and they work incredibly well.









There seems to be a tendency for people to think that "bigger is better" when it comes to horns. But big horns are really only good for one thing - GAIN.

But amps are cheap cheap cheap, and drivers take a lot more abuse than they did twenty years ago. That's the reason that I use very small woofers and compression drivers, compared to what most people run. YES, I lose some efficiency, but again, power is cheap.

Genelec and JBL are on the right path IMHO, and these small shallow waveguides sound more natural and image better than the horns of old.


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## fish

Patrick,

Do you plan on using those round waveguides in your car?


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## Patrick Bateman

fish said:


> Patrick,
> 
> Do you plan on using those round waveguides in your car?


Nah. I like to listen at fairly extreme SPLs, and the Genelec and JBL solutions are SPL limited due to their use of a conventional tweeter.

Compression drivers are a p.i.t.a. to work with, but there's no better solution if you want to keep distortion to a minimum.


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## ncv6coupe

Patrick Bateman said:


> I'd argue that's what waveguides are for
> 
> A narrow horn creates more energy on axis than a wide horn, just as a car headlight with a narrow beam does the same.


Ahhaaa, I was using the term a bit loosely about the horns and waveguides as the same thing since I was referring to conical straight horns but now since you brought this up and posted the picture of the MCM the distinction should be much more apparent by virtue of the waveguides rapid expansion design. I've never seen manufacturer posted polar response graphs. Is it possible to get some in this thread? *cough*





Patrick Bateman said:


> The main problem with horns is that they get very VERY long to get gain down low. For instance, to play down to 100hz, it needs to be 33.75" long.
> 
> Another problem is that a horn is a high pass filter. And the longer it gets, that high pass filter goes lower and lower and lower.


Yeah I know about horn lengths and underdash car horns can't even come close to even 20 inches in depth but the new access to tiny neo compression drivers open up some oppurtunities that werent available before. Is there any general formula for the high pass filter frequency or do you know this offhand from hornresp simulation modeling after all these years of building them?



Patrick Bateman said:


> As far as tonality goes, IMHO good termination at the throat and the mouth makes a world of difference. Google "homster diyaudio" for my thread on that.
> 
> Genelec and JBL are on the right path IMHO, and these small shallow waveguides sound more natural and image better than the horns of old.



Is it safe to assume that less diffraction and the smooth waveguide wall contours is the reason for less distortion(not THD) but actual tone distortion? 

EDIT: waveshape distortion is what I specifically mean but through design I think the image dynamics underdash horns re-align the wavefront spherically at the very edge of the mouth. Saw that on here in a old thread a while back.



Patrick Bateman said:


> It's really hard to get a wide soundstage, due to reflections off the doors. Getting a strong center image is fairly straightforward, and equalizing pathlengths goes a long way.


Every loudspeaker type reflects off the door which is still a challenge across the board, horns with straight crossfiring walls are definately the buisness for strong center imaging. When you talk about equalizing pathlengths would you consider T/A as a good alternative? I don't want to assume too much so do you mind commenting on maximizing horn pathlengths too? Some cars you can push wayyy back to the firewall*see mic10is* some cars you can only go as far as the front edge of the dash since it is nice flat and even on both sides but the blower motor is in the way on the passenger side and fuse box on the driver side*7th gen accord* Another thing is when you push the horns way back if your car has a huge center console, It is quite possible to introduce early reflections off the console which we are trying to avoid in the first place.



Patrick Bateman said:


> At this point I'm starting to think that a wide soundstage is easier to achieve with tweeters which are very close together, like the ambiophonics guys use.


This is a toughie to think about. I was looking at some of those older USD waveguide installs and some of them look like they did not even care about mounting them as wide as possible, I'm seeing inches of clearance between the doors and outer edges of the waveguides. 9 out of 10 times people say to put underdash horns as wide as possible...... Possible to mimic ambiophonics with the underdash horns mounted more towards the console? There would be a midrange death ray shooting down the middle of both front seats though.:laugh: Thoughts?



Patrick Bateman said:


> There seems to be a tendency for people to think that "bigger is better" when it comes to horns. *But big horns are really only good for one thing - GAIN.*
> 
> But amps are cheap cheap cheap, and drivers take a lot more abuse than they did twenty years ago. That's the reason that I use very small woofers and compression drivers, compared to what most people run. YES, I lose some efficiency, but again, power is cheap.


Well you know the bigger the horn mouth area the lower it should be able to play or this is how the car horns are designed and manipulated by going very wide horizontally and keeping the height to the best compromise. We still have to get our feet under there to drive right

My interest in the design theory peaks here because say someone is crazy enough to want to cut 1.5" off the bottom edge of their dash to be able to "flare" the off the shelf underdash horn bodies itself what else in the design would have to be adjusted and how far down the horn should be adjusted also. Is it worth it or does the generic statement of the dash would extend the mouth give the same performance frequency response wise and tone wise?


I just saw some little waveguides on my sister's entertainment center surround sound speakers which point upward towards the roof with 360 deg dispersion patters. I'm about to jack them when she's not home and make a mold for some sail pillar or door mounted dome tweeters just to see how they will sound. They aren't as shallow as that genelec waveguide so I figure they will load the tweeter at a lower frequency but they appear to be 2" fullrange speakers in the sealed enclosure underneat. I didn't get to measure or check them out because she caught me with them in my hands and shouted at me.


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## fredswain

Typically I see people who understand horn design try to understand how it applies to in car horns and then they end up getting frustrated that the numbers don't look good or work right. You need to understand that the main design consideration for horns in a car is to achieve good imaging. Sound quality comes second. That may sound strange but I have yet to hear a set of horns mounted in a car that sound good with no eq, stuffing, damping, etc. I have heard many that sounded fantastic though but all had "help". In home audio where we have a greater control over our surroundings and less limitation on size, we can design a very nice sounding horn that needs no eq help. We have countless numbers of surfaces in a vehicle that lead to diffraction and even if you designed the perfect horn for a particular car (as perfect as it can get in a car), it wouldn't work in another car. As a result, the whole design issue around a car horn is to get good imaging through image dynamics. No the name is not a coincidence. It is assumed that you are going to eq it heavily, play with crossover points, level match, amplifier match, etc...

Stuffing the mouths of the horns, adding vanes inside the mouth, rounding off the mouth, etc have all been done in car horns. In free space this will definitely improve things. No question about it. This tactic may improve them in a car or they may not simply due to the amount of reflections off of all of the other nearby surfaces, including your legs which will typically affect the top 2 octaves the most heavily. Some horns need it more than others. There are really 2 different camps in regards to adding foam and other techniques to horns. There are those that say a good horn doesn't need it and there are those that say they do. Who is right? The simple answer (in my opinion) is that a good horn doesn't need it and that the better the horn design, the less of an effect these things have. In competition or to sensitive ears every little bit counts though! A bad horn absolutely needs help in this area and can potentially be unlistenable without them. If you are looking at a car audio horn, it may need it to some extent. It really depends how bad the car you are putting them is and which horns you have. The smoother you can get the response through these treatments, the easier they are to eq. The main goal is to dampen as many secondary vibrations as possible so as much of the primary wave reaches the listener as possible. We actually never stuffed the mouths of ID horns but with the USD horns you almost had to. One trick that we did when I was at Audio Designs with Matt Borgardt was to not stuff the body of the horn but to play with dampening inside the motor both in front of the diaphragm and rear, and play with the phase plug. We had great competition results with our cars but we never told anyone that we modified the motors a bit. Even the piezo motors could be improved quite a bit although were still terrible. Keep in mind I'm not talking about anything drastic. For the most part it was cleaning out any metal shavings from the voice coil and smoothing any rough edges around the phase plug.


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## thehatedguy

<- took phase plugs out of some old CD2 drivers with a large socket...Matt told me that's how he used to do it. Sanded rough edges etc before putting them back in.


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## Mic10is

<--------Had Matt do all the work bc Im lazy and it makes him feel special to be needed


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## thehatedguy

<- wanted it done before that decade was out...lol


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## Mic10is

<------------had it done when Matt 1st went to ID, so as the new guy i think he wanted to actually show he can get work done on time....


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## Horsemanwill

now it's a pray and wait thing with matt


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## Patrick Bateman

ncv6coupe said:


> Ahhaaa, I was using the term a bit loosely about the horns and waveguides as the same thing since I was referring to conical straight horns but now since you brought this up and posted the picture of the MCM the distinction should be much more apparent by virtue of the waveguides rapid expansion design. I've never seen manufacturer posted polar response graphs. Is it possible to get some in this thread? *cough*
> 
> 
> 
> 
> 
> Yeah I know about horn lengths and underdash car horns can't even come close to even 20 inches in depth but the new access to tiny neo compression drivers open up some oppurtunities that werent available before. Is there any general formula for the high pass filter frequency or do you know this offhand from hornresp simulation modeling after all these years of building them?
> 
> 
> 
> 
> Is it safe to assume that less diffraction and the smooth waveguide wall contours is the reason for less distortion(not THD) but actual tone distortion?
> 
> EDIT: waveshape distortion is what I specifically mean but through design I think the image dynamics underdash horns re-align the wavefront spherically at the very edge of the mouth. Saw that on here in a old thread a while back.
> 
> 
> 
> Every loudspeaker type reflects off the door which is still a challenge across the board, horns with straight crossfiring walls are definately the buisness for strong center imaging. When you talk about equalizing pathlengths would you consider T/A as a good alternative? I don't want to assume too much so do you mind commenting on maximizing horn pathlengths too? Some cars you can push wayyy back to the firewall*see mic10is* some cars you can only go as far as the front edge of the dash since it is nice flat and even on both sides but the blower motor is in the way on the passenger side and fuse box on the driver side*7th gen accord* Another thing is when you push the horns way back if your car has a huge center console, It is quite possible to introduce early reflections off the console which we are trying to avoid in the first place.
> 
> 
> 
> This is a toughie to think about. I was looking at some of those older USD waveguide installs and some of them look like they did not even care about mounting them as wide as possible, I'm seeing inches of clearance between the doors and outer edges of the waveguides. 9 out of 10 times people say to put underdash horns as wide as possible...... Possible to mimic ambiophonics with the underdash horns mounted more towards the console? There would be a midrange death ray shooting down the middle of both front seats though.:laugh: Thoughts?
> 
> 
> 
> Well you know the bigger the horn mouth area the lower it should be able to play or this is how the car horns are designed and manipulated by going very wide horizontally and keeping the height to the best compromise. We still have to get our feet under there to drive right
> 
> My interest in the design theory peaks here because say someone is crazy enough to want to cut 1.5" off the bottom edge of their dash to be able to "flare" the off the shelf underdash horn bodies itself what else in the design would have to be adjusted and how far down the horn should be adjusted also. Is it worth it or does the generic statement of the dash would extend the mouth give the same performance frequency response wise and tone wise?
> 
> 
> I just saw some little waveguides on my sister's entertainment center surround sound speakers which point upward towards the roof with 360 deg dispersion patters. I'm about to jack them when she's not home and make a mold for some sail pillar or door mounted dome tweeters just to see how they will sound. They aren't as shallow as that genelec waveguide so I figure they will load the tweeter at a lower frequency but they appear to be 2" fullrange speakers in the sealed enclosure underneat. I didn't get to measure or check them out because she caught me with them in my hands and shouted at me.


My precious car had big ol' horns in it and I could never get it to sound great. OTOH, I have had a lot of luck using boundaries to extend the waveguide. For instance, my Unity horns used the entire dash and the windshield. They went down to 300hz. A 300hz waveguide is 45" across, so the entire dash was the obvious choice.

When you use really good termination on a waveguide, it seems to "disappear.". If you've seen pics of my car where I had towels around the unfinished waveguide, that was to improve the termination.

Basically, you can fight the car by trying to avoid reflections off the dash or the center console. But I'd rather recruit them and make them part of the waveguide. Honda itself is doing this - if u look in the corners of your dash you'll see a small set of full range drivers, all the way in the corner.

As far as putting waveguides closer together, check out the soundstage thread on my forum. I've been messing around with this, and getting some really unexpected results. For instance, I used the locations from the Opsodis paper and was able to get a WIDER stage by moving my mid basses CLOSER together.

This is some crazy stuff, and we're all going to owe choueiri a debt because he's done some SERIOUS research into soundstaging over at Princeton. 3D3A Lab at Princeton University


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## CraigMBA

Patrick Bateman said:


> For instance, I used the locations from the Opsodis paper and was able to get a WIDER stage by moving my mid basses CLOSER together.


Don't you mean mid _range_?


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## CraigMBA

I think that this thread can be surmised with one word:

Packaging.

Speakerworks gets all the credit for innovating the use of horns in cars, but IMO it’s not exactly correct. Speakerworks should get credit for making horns with packaging you could put in a normal car. There were others using horns (namely Don Vitrees and Sam Zamora) and G&S Designs (who was selling a lot of rebadged ElectroVoice 1834, often coupled with T-35 or an OD-KD tweeter). The common method of installing them was to mount the 1934’s under the seats and fire them at the front bumper.

There is no doubt in my mind the $8 horn that Pat posted is dynamite and all that, but where the heck are you gonna put it?

Minor hijack: Eric Holdaway told me some time ago that the first time Don ever heard the Grand National he got out, looked at Eric deadpan and said “Horns, huh?” Don totally knew. That would have been about 1985.


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## Patrick Bateman

CraigMBA said:


> Don't you mean mid _range_?


yes. My mids will cover 600hz to 3500hz, just like the opsodis paper specifies. I may tweak it a bit once I have the crossover and waveguides sorted.


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## Patrick Bateman

CraigMBA said:


> There is no doubt in my mind the $8 horn that Pat posted is dynamite and all that, but where the heck are you gonna put it?


It's kind of amazing how much you can hack off if you get the termination right 

In my Unity horn project I kept hacking and hacking and hacking bits and pieces off the waveguide. It reached a point where about 75% of the waveguide was gone, and it still worked, because it was carefully terminated to the dash.

In fact the hacked up waveguide worked *better*, because the full size waveguide wasn't well terminated at the left and at the right.









Here's a pic of the mold, I'm not sure if I have any pics of how much I hacked up the final version. It was much MUCH smaller than this.

I wouldn't be surprised if I hack the QSCs down from a diameter of 12" to 4". Even a 4" waveguide will control directivity down to 3375hz, and I intend to use a crossover of 3200hz.

In a nutshell, a hacked up waveguide gives you the sound of a dome tweeter in a footprint that isn't much larger, but with directivity control and about 10dB more headroom.


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## Patrick Bateman

cajunner said:


> here's perhaps a stupid observation:
> 
> the USD horn, operates on the principle of liquid propagation, and the waveguide has that contour that is primarily designed to "throw" the sound into the middle of the car, if not across the car to the other side. That's why you see the inner curve flaring to the inside of the horn instead of opening to the near-boundary of the car interior. This design concept seems to create the worst listening experience without "help" due to considerable effects of HOM within the guide.


The USDs sound surprising good if you tweak them. I know Holdaway doesn't post much on here, but he makes a good product. I think it was designed long before everyone grasped how important termination is.

Check out the polar response that I posted of the USD. If you aim them carefully, it's possible to get the left and the right to have roughly the same frequency response.

And that's 90% of the battle isn't it? If you can get the left and the right to measure the same, you're going to get real imaging.

I still see tons of loudspeakers with square edges, which are basically the worst way to terminate. JBL has got it right - you won't see any sharp edges on their speakers.



cajunner said:


> The ID full bodies, have a narrow aperture until the "liquid" portion of the wave energy is acted upon more by reflections due to the area of the horn, and thus causes the waveguide interior to look something like a 'baby cheeks' flare, or whatever that's called, constant directivity or controlled dispersion, I don't know... but the issue is the change within the horn that occurs about 2/3 way from the mouth termination. This is also about the same distance that the horn takes on a more radical "gain stage" due to expansion in area at an increasing rate.


Sound like a diffraction horn? I'd have to see the throat. The USD has a diffraction slit. I hate diffraction - and I would never run a waveguide or a horn with a diffraction slot. There are better solutions.



cajunner said:


> The Veritas, holds on to the liquid part of the program until near the very end, where it then terminates into a very high flare, as if the designer felt like it was necessary to continue the vertically narrow aperture in order to benefit, and a more even response comes at the width of the guide's response, and I'm not sure whether that panned out or not as my own listening tests have been with clones and without any foam at all.


Is there a diffraction slot in the Veritas? If not, it sounds like it might be a "real" waveguide. Basically a very narrow angle waveguide with a big flare at the end to improve termination. If so, that's aligns nicely with how I like to design things.



cajunner said:


> So, three schools of thought, the USD chooses to view wave propagation as liquid until the mouth, the ID changes about 2/3 way out, and the Veritas has it about 7/8th of the way from the end, with a double ended expansion that diffuses the outer edges of the guide's response towards both the center of the car and the door side.
> 
> From what has been recently posted, the liquid portion of the wave does indeed give way to a change in the wave propagation, and my observation is that you could simply terminate a horn at this juncture without ill effects, and that juncture seems to be when the horn's mouth area is about 4 times the initial 1" exit at the phase plug.
> 
> If someone can definitively say "yes, this is the case" that would be cool, and maybe give a ratio where we could create a compact horn that fits more easily into the car interior?
> 
> or, if it's not correct... throw the red card...


My vote is still for QSC. It's cheap, it works. It's not a complicated design - it's just a really simple and well terminated waveguide. If you can figure out where to mount them I think you'll like them. If not, you're out twelve bucks, no big loss.


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## CraigMBA

cajunner said:


> Okay. I saw this one coming for a while now, check this out:
> 
> You take a power-pac hydraulic ram, and affix it from underneath the car to the floorboard of the car.
> 
> push an oval ring about 10 inches wide on the long axis, forward in the area of transition between the firewall and floor corner, stopping when you see a raised oval in the sheet metal about 1.5 inches, and you use a mallet with a big punch to drive the middle of the oval to the right shape. thread the hole in the center made by the punch to fit a 1" compression driver. Straight through design, mostly EOS shape, and in a vehicle with no center console. Probably work?


Definate fail. Not with the horn (I have almost zero opinion there) but your method for forming the firewall. I do a lot of sheetmetal work, what you are trying to do is certain to fail because the material won't work that way.


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## Patrick Bateman

cajunner said:


> it's hard for me to describe, I'm using words like throat, mouth, angle, flare, etc. without really knowing whether they are correct.
> 
> when I say a narrow aperture, I mean the area of the horn where in the USD, you have a common chamber that coincides with the outside, as it should because it's a constant thickness mold design. The casting model that the ID horn uses, is variable thickness material and truncates the wave in the acoustic path/center of the horn, controlling the output so that most of the wave energy is evenly distributed across a wider plane, and you get a more even wavefront near the termination where it widens quickly, perhaps for less diffraction, or....?
> 
> I've seen those huge waveguides that look like 9 foot tall butterfly wings,
















Jadis Eurythmie? Have always wanted to hear those. Definitely a case of form over function, but they're stil gorgeous.



cajunner said:


> and I understand the concept of that Le'Clea'ch model, (hahah, put an apostrophe wherever....) you posted, in reducing diffraction much better as a result.








Le'Cleach and oblate spheroidal both have a monster roundover at the termination, to reduce diffraction. But the curves in the body of the horn differ - the walls of an OS waveguide are basically flat. The walls of a Le'Cleach horn narrow. They narrow for the same reason that an exponential or a tractrix horn do, which is to flatten the on-axis frequency response. The response of a waveguide falls at high frequencies, by design.


cajunner said:


> You're bent on cutting down OS waveguides to fit the car interior, is this right?
> 
> and Dr. Geddes said he was going to attempt it, but has not of yet, correct?
> 
> Okay. I saw this one coming for a while now, check this out:
> 
> You take a power-pac hydraulic ram, and affix it from underneath the car to the floorboard of the car.
> 
> push an oval ring about 10 inches wide on the long axis, forward in the area of transition between the firewall and floor corner, stopping when you see a raised oval in the sheet metal about 1.5 inches, and you use a mallet with a big punch to drive the middle of the oval to the right shape. thread the hole in the center made by the punch to fit a 1" compression driver. Straight through design, mostly EOS shape, and in a vehicle with no center console. Probably work?
> 
> here, you have a waveguide with Le'Clea'ch terminus, formed in the steel of the firewall. Mount and weatherize the driver as it sits below the brake booster, and under the AC drier on the passenger side, you'd have the deepest mount possible, and you'd be as far away from the kick panel/transmission hump/dash underside/floorboard as feasibly possible....
> 
> anyways...
> 
> always thought that would be plain simple, forming the sheet metal and making a threaded insert from the same hole used to form the curve.
> 
> and adding:
> 
> it would probably be easy to see whether it would work or not using the JBL waveguide on their 660 component set, it just wouldn't drop nearly as low with a flare less than 5 inches across, and maybe that would be a good form to try and attach a compression driver to the back of?


There's really no need to hack up the car, just find a spot where you can terminate the waveguide. Kinda like Biggs did in his Regal.

The JBL waveguide and the QSC waveguide are virtually identical. I would use the QSC because it's $12 and there's a $65 compression driver that mounts to it with 30 seconds of work. I know a lot of my solutions are byzantine but this is not one of them 









Here's the JBL, as used in Biggs' Regal. Picture at bottom left.








Here's the QSC, and it's compression driver. Yes, it's twelve inches across but you can hack it down to size. Once you do the depth will be about five inches, which isn't any worse than the typical under dash horn. And NO that's not how I'm going to mount it in my car lol

The tweeter in the JBL is crossed over at 2500hz. The waveguide in the JBL measures six inches across. That means that it works down to 2250hz. See the connection?*

*We don't need to use giant horns and waveguides in the car if we move the xover point up.*

I'm not saying that there's anything fundamentally incorrect about using the giant HLCDs that most people do, but if you're crossing over at 2 or 3khz, they're waaaaaaaay larger than necessary.

OTOH, you can also see how people have difficulty using a very low crossover point, because the minimum crossover point of a horn or waveguide is influenced by it's size.

* the jbl manual: http://www.jbl.com/resources/Brands...-US/OwnersManual/560GTi660GTiOMrev3_20_07.pdf


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## Jscoyne2

CraigMBA said:


> Definate fail. Not with the horn (I have almost zero opinion there) but your method for forming the firewall. I do a lot of sheetmetal work, what you are trying to do is certain to fail because the material won't work that way.


5 years of reading and this is the greatest thing i've ever seen on this website. 

9 years too late.


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## Eric Stevens

This is a very deep rabbit hole.... meaning complex. There are many factors at work and typical of complex systems, every engineer will provide a different solution after choosing different trade offs. 

I am going to just throw a few things out because I dont have hours to spend at the moment.

What affects dispersion or "directivity" in certain octaves is different than in other octaves.

The horn has far more impact on the tonality and sound quality than the compression driver.


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## Jscoyne2

Eric Stevens said:


> This is a very deep rabbit hole.... meaning complex. There are many factors at work and typical of complex systems, every engineer will provide a different solution after choosing different trade offs.
> 
> 
> 
> I am going to just throw a few things out because I dont have hours to spend at the moment.
> 
> 
> 
> What affects dispersion or "directivity" in certain octaves is different than in other octaves.
> 
> 
> 
> The horn has far more impact on the tonality and sound quality than the compression driver.


Im thinking about switching to horns so ill be looking thru the hlcd section for awhile. You'll probably be hearing from me in the not too distant future

Sent from my XT1710-02 using Tapatalk


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## Eric Stevens

ncv6coupe said:


> So we all know that horns are the easiest thing to use for controlled dispersion which is influenced by the width, height and angle of the horn's interior walls.
> 
> I would like us to discuss the design philosophies of the throat to mouth transition and how it affects freq. response, tonality and acoustic gain for any given design. Then let that carry on into horizontal-vertical dispersion characteristics that effect the outcome of strong center imaging, wide soundstaging and focus "IN CAR"
> 
> Horns of particular interest are in the likes of the classic straight thru design, the USD labeled waveguides, the 90 deg. bend at the throat Image dynamics full body, the older image dynamics mini body(closer to 90 deg horizontal bend) compared to the newer image dynamics mini body.(rounder transition which looks like a 225 deg circle bend in the throat)
> 
> I know and believe in the quarter wave theory so I understand little bits and pieces but would love to get the engineer low down. I'm also not just limiting the choices to the above mentioned horn frames but those are the more off the shelf options that most people settle for it seems.
> 
> Thanks for contributing the information in advance...


The difference between straight entry like an illusion and 90 degree angle such as Stevens Audio / ID and others is mainly one of packaging to fit the environment and space available. A proper reflector at a 45 degree angle will reconstruct the wavefront traveling 90 degrees in another direction with very little to no effect at all. It only has a small effect above 15000 hz when using a reflector at the entry as done with Stevens horns. The curved 90 degree entry as used in the USD has a noticeable and easily measured effect on the FR. The MH body is still only a 90 degree entry, it just folds in a different direction.

I will share the basic design criteria and goals I was trying to achieve. A sound stage, and the images produced within that sound stage, by a stereo pair of speakers is a product of the sounds time, phase, and amplitude, relative to the two channels. The dispersion of the Stevens HLCD is designed to direct more energy towards the opposite listener to help overcome the early arrival of the near side. Additionally having less reflected energy so that the direct sound arrival is significantly higher in amplitude than the reflected energy as would happen in a conventional audio environment. 

I would love to have some of the testing done many years ago looking at amplitude of direct versus reflected energy of different speaker locations and different speaker types to share. Dash / pillar locations are the worst with reflections at the same level as the direct sound and poor decay when looking at response in the time domain.


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