# Project GNIB - Grand National in a Box



## Patrick Bateman (Sep 11, 2006)

I've been studying horns for over a decade now, and the Grand National was a big inspiration for car audio projects. A few years ago I built a system which was largely based on the GN.

Since it worked quite well, I thought I would document a comparable system, for anyone else on the forum that's interested in a dynamic and affordable system.

Before I get into the details on the components, it's worth discussing why you might want to build it. In car audio, it's very easy to generate bass. Due to the small dimensions of a car, generating lots of low frequency output is almost effortless. The problem is that it's difficult to engineer a midbass that can keep up with the subs. This is why many people find the bass in their systems overpowering and sluggish. It's not the sub that's the problem - it's the midbass.

Even more difficult is generating a convincing image. In a typical car, the left speaker is mounted in the door. Speaker Works, the designers of the original Grand National solved this problem by using extraordinarily long path lengths. The way that they accomplished this was by placing horn loaded compression drivers *under* the dash.

In "Project GNIB" I will demonstrate how to build a similar system, but at a much lower cost. More importantly, this system will be within reach of anyone. Many of my projects require fabrication, measurements, and tools. This project will require none of that. It uses readily available components in a format that's rarely seen in car audio.


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## donkeypunch22 (Nov 5, 2008)

Nice! Always appreciate your posts, Patrick.


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## Patrick Bateman (Sep 11, 2006)

Even before Clark purchased the Grand National, it was well known for it's impressive image. The key to this image are the waveguides that are located underneath the dash.







Here's a pic of the waveguides in the Speaker Works Grand National. According to their website, these were the first set. If you look at the compression driver, you'll notice that it uses a "two bolt" pattern. Only one compression driver uses that pattern these days, a company named Radian. (It's possibly an Emilar, but Emilar is no longer around.)







If you've seen some of my other projects, you may be familiar with the horns and waveguides that I've fabricated. I know that horn fabrication is anything but easy. USD Audio sells an excellent set of waveguides, and for this project, I am going to use them. Here is a pic of my set. If you'd like to build the Grand National in a Box, you can get a set of USD Waveguides here:

USD Audio WaveGuide BC-300







Here's a pic of the waveguides in the Grand National. In my car I've found that waveguides under the dash are a lot less obtrusive than kick panels. And there isn't a kick panel in the world that will keep up with the GN (or the GNIB.)







Clark retired from competition undefeated. Some might argue that his success is due to a combination of solid engineering by Speaker Works, along with a series of upgrades. The most noticeable upgrade was the replacement of original compression drivers with more expensive units. Radian compression drivers retail for about $150 new, about $50 used. The compression drivers in the picture above, likely Altec 288C, are worth about $2500. IF you can find a good used pair. In addition to that, it was reported in CA&E that the Altec compression drivers were modified.







While the Altec is a fine driver, it is also very old, and sought out by many audiophiles. Due to the relative scarcity of clean used units, expect to pay top dollar for one. I wasn't interested in spending $2500 on a set of compression drivers, so I personally chose a competing model from JBL. _(fun fact - JBL stands for "James B Lansing", as in "Altec Lansing.")_

The model that I chose was the JBL 2470. It's readily available - on any given day there are at least two or three sets on Ebay.

It's affordable - about $300 to $400 for a working pair. Better yet, get one with a blown diaphragm, because we're going to replace it anyways.

As I see it, the main advantage of the JBL is that it has a smaller voice coil than the Altec used by Clark, but it's bigger than the Radian used by SpeakerWorks. A small voice coil increases high frequency response at the cost of power handling, and the use of a large compression driver allows us to play lower than the Radian.

Of course this is all just theory...

Let's find out how this will work in the real world.


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## Patrick Bateman (Sep 11, 2006)

According to Car Audio and Electronics, Richard Clark made a number of improvements to the waveguides in the Grand National.







Even with a set of $2500 compression drivers, the Grand National still required a narrow band EQ. The reason is that the horns have a series of peaks and dips. The EQ is used to fix that.

The reason that I named this thread "Grand National in a Box" is that I want to demonstrate a solution that's within reach of people who don't have years of experience tuning horns.

Before I demonstrate how to do this, I'd like to discuss *why* the GN needed a narrow band EQ.

Even though the horns in the GN are hyoooge, they're not as big as they need to be. Ideally, the horns should be about *four* times as big. Because the horns are too small, peaks and dips will appear in the frequency response. I will demonstrate this shortly.

Even with an ideal horn, *diffraction* occurs at the throat and at the mouth. I won't bore you with a technical discussion of diffraction. If you are interested in learning about it, this interview is a good start:
http://www.audioxpress.com/magsdirx/voxcoil/addenda/media/mowry1008.pdf

Have you ever listened to a horn loaded loudspeaker at the club, and noticed that the midrange has a "screechy" and "raspy" coloration in the midrange? Ever noticed that it's particularly offensive at high volume? _That's diffraction you're hearing._

Anyways, diffraction is A Bad Thing.

In a moment I will show you how the GN's EQ is used to deal with the symptoms of diffraction. The EQ is used to cut the peaks and fill in the dips.

I have another solution - *let's fix the cause, not the symptoms.* The cause of the peaks and dips is diffraction and reflections, so let's treat that. You can't eliminate it completely, but you can treat it with about five bucks worth of PVC pipe and open cell foam. Sure beats using a thousand dollars worth of studio EQs 

Here's a full writeup on the diffraction treatment: 
The HOMster! (or How I Learned How to Fix a Horn) - diyAudio

Kudos to Dr Earl Geddes - these treatments were inspired by his extensive studies on diffraction and psychoacoustics.







Here's a close up of the diffraction treatment on the USD horn. There are additional pictures in the diyaudio thread.


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## Patrick Bateman (Sep 11, 2006)

Let's get to the measurements.







Here's a distortion measurements of the "stock" USD waveguide, along with the modified waveguide.

Most manufacturers don't publish distortion measurements; even high profile manufacturers like Morel, Scanspeak and Dynaudio don't offer them.

John Krutke and Brandon (aka Augerpro) have generously published distortion specs of popular tweeters.* In their measurements, you'll see that a good dome tweeter has distortion that's 20-30db below the fundamental. Now look at the graph above. Even the _unmodified_ horn has distortion that's about 30db below the fundamental, at least above 2khz.

The performance of the Radian is good, but the performance of the USD waveguide with the JBL driver is even better. Above 3khz the distortion is virtually unmeasurable.

The Radian is still very good though. Though the JBL can play lower, it's over twice the size, and the Radian can play higher. It also has an efficiency advantage.

Personally, I prefer the JBL. It has more efficiency than we'll ever need, the response of the modified horn is smoother, and the JBL plays lower with finesse, thanks to it's very low distortion. Note that the 2nd harmonic distortion is very low - this is due to the silver shorting ring in the motor. Even the Altec doesn't offer this feature.

* Zaph|Audio
* Home (drivervault)


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## DanMan (Jul 18, 2008)

OMG! I never realized how big those horns were.

Now I get why my ID Mini's don't have the bonecrushing dynamics I have heard about in the GN.

I do like them though and small format tweeters don't do it for me much anymore.

Great thread, PB. You are the man!


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## trebor (Jun 30, 2008)

How is that big horn motor mounted to the horn body? I can't tell by looking at the picture.

In that same pic it looks like Clark is wearing a fishing shirt, must be an avid fisherman. Wonder what the biggest he ever hooked was.....


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## Patrick Bateman (Sep 11, 2006)

DanMan said:


> OMG! I never realized how big those horns were.
> 
> Now I get why my ID Mini's don't have the bonecrushing dynamics I have heard about in the GN.
> 
> ...


The horn in the Grand National was half of the puzzle. The treatment of the car played an important part in the car's imaging and dynamics. But we can do even better 

(If anyone wants me to clarify anything in the next paragraph, please let me know. What I am about to say is a big part of the reason that "conventional" horns sound so bad.)

Imagine that you have a speaker, mounted underneath your dash. When sound is emitted from the diaphragm, it's moving at 13.5 inches in a millisecond. Reflections and diffraction are bad, *but they're exceptionally obnoxious in the first five milliseconds.*

OK, hold onto that though for a second.

In the CA&E article*, Clark said the following:

"Absorption material was added to almost all the upholstered interior surfaces. Unlike mass damping, which only prevents resonance, the absorbtion material that I chose also *reduces unwanted reflections inside the car. These reflections can cause unwanted secondary imaging cues.*

Now if we agree that reflections in the car are unwanted, why treat the car alone? Why not go waaaaaaay back to the driver itself, all the way to the actual diaphragm? Which is exactly what I've done.







In this pic, you can see that there's sound absorbing foam in the waveguide. But why stop there? There's polyfill inside of the compression driver throat, in fact there's sound absorbing foam INSIDE the compression driver's chamber.

Clark had the right idea, he's just going about it a different way than I am. In the Grand National, Clark is absorbing reflections in the cabin. What I'm suggesting is to absorb the reflections AS SOON AS POSSIBLE. As in, right at the diaphragm.







I know it seems absurd to put a bunch of sound absorbing foam in front of your speaker, but it works. The graph above compares how the USD horn performs with and without treatment. The difference between this one, and the one I posted yesterday is that it uses the same compression driver. This helps illustrate that it's not the compression driver that's creating all those nasty reflections - it's the horn. In particular, *it's the horn's mouth*


The graph at the top is untreated. The graph at the bottom is the treated horn. I shifted the bottom graph by 10db, to make it easy to compare.
See that big peak at 2800hz in the untreated horn? But see how it's NINE db lower in the treated horn? What that means is that over FIFTY percent of the sound we are hearing in the untreated horn is due to reflections! How awful is that? With reflections like that, it's guaranteed to audibly color the sound, and create "false imaging cues" as Clark alluded to.
Sometimes it's hard to determine what's causing a peak. But the dip at 1400hz confirms that the two are related.
In the *treated* horn, we see the peak is reduced by half. The dip is virtually gone.
Notice that the treated horn doesn't have a lot of the weird "squiggles" in the response.
Most important of all, note that the response of the treated horn doesn't jump around as much... In other words, the soundstage isn't going to change if you move your head two inches. Accomplishing that goes a long way towards creating an authentic acoustic environment.
This diffraction treatment has been discussed extensively at diyaudio, and is inspired by the Gedlee Summa speakers. Good stuff, and highly recommended for the home, theater, or studio.

At this point, you're probably wondering, what does all of this have to do with the _dynamics_ of the Grand National?

Here's how this works. According to the research from Geddes**, the _sound_ of diffraction is exceptionally obnoxious. Clark freely admitted that the foam in his car played a big part in it's sound. I'm suggesting an alternative which is even more effective (and very cheap to implement.)

If you're still on the fence as to whether this is audible, try this experiment:

Get a small efficient speaker, and listen to it outside, where there are no reflections. Literally hold it up in the air, at least a few feet away from anything. Now take the same speaker, and play it near a very hard reflective surface. For instance, a kitchen countertop. And don't just set it on the counter, press it right into a corner, where there are a ton of reflections.

What you'll notice is that the sound on the kitchen counter is raspy and congested, and intelligibility is very poor. And the same might be said about an _untreated_ horn.

* the CA&E article has been posted here: http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/69060-natural-bass-6.html#post883102
** http://www.audioxpress.com/magsdirx/voxcoil/addenda/media/mowry1008.pdf(check out the AES papers too, if this piques your curiosity.)


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## mosconiac (Nov 12, 2009)

I am very intrigued by this project, Patrick. Can't wait to see what you lay out before us.


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## western47 (Nov 17, 2008)

Does this mean that the unity based WG to be placed on top of the dash is now defunct?

Fine by me as it was going to be quite an eyesore. I am quite tall so under the dash is not going to be easy but much more of an achievable task.

Keep it coming as the other solutions involve the midbass which can keep up with the top end and the low side which should be the easiest of all solutions.


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## TREETOP (Feb 11, 2009)

Patrick Bateman said:


> ...If you look at the compression driver, you'll notice that it uses a "two bolt" pattern. Only one compression driver uses that pattern these days, a company named Radian...


So do B&C, Pyle, Selenium, and Eminence. 
Buuuut, you can get adapters either direction to use regular threaded drivers with 2 or 3 bolt horns, or 2 or 3 bolt drivers with threaded horns.

I had the same USD waveguides you've got, but I used some (relatively) large piezo drivers with a standard 1.375"-18 thread and made ABS adapters to the waveguides. I'll see if I can find pics.

[edit] Can't find pics, and my eBay auction where I sold them is too old to access. I think I used Motorola KSN1188A piezo drivers, they supposedly had a frequency range of 800hz-20khz.


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## thehatedguy (May 4, 2007)

I have a feeling the original driver in the picture was a large format driver. Most use a 4 bolt pattern mounting attachment...they probably just used 2 of the 4 holes.

Well, looking at it closely, you can see the 2 bolts in the picture are moreorless parallel with the mouth meaning it would look like the 3 bolt triangle like the JBLs pictured.

How big is the driver? Think of a Folger's coffee can.

And also the horns in the GN were a bad design. That bend has no deflector to align the wavefront back...and the bend is pretty far down the throat. Both will cause serious nulling in the FR of the horn.


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## thehatedguy (May 4, 2007)

The 288s were 7.1" around and 5.8" deep. And weighed 28 pounds.


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## Oliver (Jun 25, 2007)

That'll make you stand out in a pack ^^^^

I have subwoofers that weigh 13 pounds


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## sqshoestring (Jun 19, 2007)

So you are saying if you curled the horn up more to use a larger one, one would have more reflections?


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## Patrick Bateman (Sep 11, 2006)

western47 said:


> Does this mean that the unity based WG to be placed on top of the dash is now defunct?
> 
> Fine by me as it was going to be quite an eyesore. I am quite tall so under the dash is not going to be easy but much more of an achievable task.
> 
> Keep it coming as the other solutions involve the midbass which can keep up with the top end and the low side which should be the easiest of all solutions.


No, the Unity horn is the ultimate solution. The whole reason that I named this thread "Grand National in a Box" is a riff on "home theater in a box."

This is an accessible solution, that's relatively affordable. Most importantly, the midbass and the tweeter are so well behaved, you won't need an equalizer and a microphone to get this to sound good.

When I finish mapping this one out, it's going to be the kind of system where you can literally put the pieces together, hook them up to an active crossover, adjust the levels, and **boom**, you're done.

The Unity is waaaaaaaaaaaaaaaaaaaay more complex. But if you have the time and the patience, it's the ultimate.


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## mosconiac (Nov 12, 2009)

Hopefully this isn't an OT question, but does anyone know how Mark Eldridge tackled these issues? Surely his implementation was successful given his winning record. He must have done something different.

It seems to me that he improved the length of the horns by extending them into the engine compartment, but did they have any bends? It appears that the horns enter the interior at the base of the windshield.

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


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## TREETOP (Feb 11, 2009)

mosconiac said:


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


Funny that I have that February 2001 Car Sound magazine in the bathroom.


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## Patrick Bateman (Sep 11, 2006)

mosconiac said:


> Hopefully this isn't an OT question, but does anyone know how Mark Eldridge tackled these issues? Surely his implementation was successful given his winning record. He must have done something different.
> 
> It seems to me that he improved the length of the horns by extending them into the engine compartment, but did they have any bends? It appears that the horns enter the interior at the base of the windshield.
> 
> Mark Eldridge: Do The Evolution (Jan/Feb 2001)


Both Geddes and Clark are addressing the same problem, but in different ways. How about an analogy?







Richard Clark's solution is like making coffee with a coffee press. You make the coffee, and then you filter out the grounds by pressing down on the plunger. In Clark's solution, the vehicle is treated with foam to absorb reflections *after they're generated*

Here's a quote from Clark:

_Absorption material was added to almost all the upholstered interior surfaces. Unlike mass damping, which only prevents resonance, the absorbtion material that I chose also reduces unwanted reflections inside the car. These reflections can cause unwanted secondary imaging cues."_

Here's a quote from Eldridge, who worked closely with Clark:

_"The horns critically control the dispersion pattern of the 300 Hz to 7 kHz frequency range. *One of the biggest advantages of this design is that the dispersion pattern is controlled to the point that early reflections from the windshield, side windows, and dash are either eliminated completely, or are directed towards an area where they are absorbed. No image and/or stage degrading early reflections are allowed to proceed directly to the listeners' ears.* The angle of the horn throat axis, the physical dimensions and flare characteristics of the horn itself, the ability to control potential reflections off the windshield, and the dash design all play critical roles here. As before, the windshield and dash are integral parts of the design. Rather than fight them as enemies of good sound, they are used as allies (so to speak) and actually contribute to the cause."_

It is clear from interviews that Clark and Eldridge both recognized that combating reflections was important.








Geddes' solution is like running coffee through a filter. Instead of making the coffee, then removing the grounds, you filter out the grounds as the coffee is being made. In other words, instead of mopping up the reflections in the car's cabin with sound absorbing foam, you mop up the reflections inside the horn itself. The foam acts like a "sponge" for reflections. The roundover at the mouth basically takes the reflected energy and diffuses it in every direction.

Does that make sense? Mop up the reflections right at the source. And if there are any left (and there will be) diffuse them all over the place, so that the carpet and the seats of the car "mop up" what's left of them.







Again, if this sounds like it wouldn't work, just look at the treated and untreated horn. The treated horn is much much smoother. See that six DB peak at 2800hz? A six db peak is equivalent to a SECOND speaker playing, at 3khz, _delayed in time._

That's why a lot of horns sound so nasty - delayed reflections are obnoxious. It makes it difficult to understand song lyrics, it messes up the sound of guitar strings, and basically robs music of the "texture" that's so rewarding. It's not just that there's a peak. It's the delay that makes everything sound so miserable, and why absorbing (or diffusing) it is one of the secrets of the Grand National's success.


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## western47 (Nov 17, 2008)

Patrick Bateman said:


> No, the Unity horn is the ultimate solution. The whole reason that I named this thread "Grand National in a Box" is a riff on "home theater in a box."
> Yeah, unfortunately the HTIB market controls the mass of the known home audio world.
> 
> 
> ...


I would love to look at the Unity solution as a possibility. What intrigues me even more is the fact that you have the same car as I do. Not only do I have the car but I also have measuring equipment. Oh, I am also willing to fabricate certain items. The WG itself seems to be the most difficult thing which is definitely a doable thing.


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## jbholsters (Jun 17, 2009)

You know Patrick, looking at the pics again of the horn bodies, I'm more convinced than ever that RC didn't put those Altec's in the GN. In a 1000 post thread on another site there was a big discussion as to how exactly he fit those under the dash (this was a back and forth between RC and Eric Holdaway). RC said that he cut the throats of the horns, shortening them, to fit them under the dash. I call shananigans.... Take a look at the pic you posted of the original horns from the USD site and the one he is holding. The length is the same, although a little deceiving due to the angle it was photographed at. If you look on the site and the bungs in the dash, you can see the original driver. The throat ends at the top of the glove box, and is angled toward the firewall and A pillar. Even if you gutted the inside of the dash on a T body, there is no way that Altec would fit. It would be sticking through the firewall and the top of the dash.

Cool thread by the way. Can't wait to see what what you have for us next.


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## hybridspl (May 9, 2008)

Another great thread Patrick, you should have your own audio blog!


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## Hiace200 (Apr 26, 2009)

hybridspl said:


> Another great thread Patrick, you should have your own audio blog!


X 2.

A real good Man.


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## thehatedguy (May 4, 2007)

If he shortened them, then he really f.cked things up...or made new horns. This is if the original drivers were 2" drivers. If anything to get the area progression of the flare correct, going from a 2" driver to a 1.4" driver, the horn would have to be longer.

Yes, if the horn was bent it would cause more nulls and reflections in the throat. The null points can be calculated though. Also, without the use of a deflector the wavefront is going all to hell at and past the bend. But this was probably not well understood when the horns were built.


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## audio+civic (Apr 16, 2009)

I am a horn idiot. I know nothing about the subject. Would linning the horn with an absorbant material (acoustic foam) do the same thing as stuffing it with polyfill. This is a fantastic write up for those of us that are not horn inclined.


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## rawdawg (Apr 27, 2007)

If you do a search on Patrick Bateman, he discusses foam to control HOM's. I once met a blind dude who suggested I line the horn's throat with those baby blankets that have a funny name.


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## ECM (Dec 23, 2007)

Patrick, will the horn driver be supplemented with a set of tweeters considering their output is between 500Hz to 12kHz?

Or is that why the diaphragm will be replaced?


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## jbholsters (Jun 17, 2009)

PB is recommending stuffing with reticulated foam and polyfill, along with poly in the compression drivers chamber.

Winslow, exactly. I would love to see a pic of the passenger side horn from the SW install book. There are lots of wrapping marks that would determine if the horns were cut. I put enough equipment in those body styles to know there is no room for what he is holding in that pic. Here is a pic from the USD site where you can see the mounting ring and bolts. Hard to see if the driver is mounted, but look at the angle the horn takes. LINK


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## jbholsters (Jun 17, 2009)

ECM said:


> Patrick, will the horn driver be supplemented with a set of tweeters considering their output is between 500Hz to 12kHz?
> 
> Or is that why the diaphragm will be replaced?


Read the thread he linked to at the beginning. here is the link: The HOMster! (or How I Learned How to Fix a Horn) - diyAudio


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## jbholsters (Jun 17, 2009)

Hopefully this is relevant to PB's thread. Here is a photo, in which I combined a shot of the entire dash height of the GN with a shot of the plugs. I photoshoped the perspective of the plug shot to match up to the other shot and combined them. I painted part of the closed glove box back in so you can kind of get an X-ray view behind the dash. Next will be the same shot with the Altec attached


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## Patrick Bateman (Sep 11, 2006)

According to the CA&E article, Clark improved upon the Grand National by replacing the compression drivers with a set of Altecs.

I am leaving this one up to you, but I am measuring all the options, and discussing the pros and the cons.







Here are some measurements of the distortion performance of a "stock" USD Audio waveguide, and the same waveguide where I've replaced the compression driver, filled the horn with foam, and added a roundover to reduce diffraction at the mouth.

In the distortion measurement, you can see an improvement in harmonic distortion with the large format compression driver, and a much lower F3. You may note that the diffraction treatment is having a significant effect on the driver's efficiency.

Some might think that any reduction in efficiency is A Bad Thing, but I disagree. At low frequencies I want all the efficiency I can get, which is why I use tapped horns in my own car. But at high frequencies I'm interested in low distortion and good polar response. I wouldn't care if my tweeters had an efficiency of 85db, as long as they had excellent polar response, could take a lot of power, and had low distortion. As I see it, that's what's important at high frequencies.

Note that Clark treated reflections in the car, and we're treating them inside of the horn itself.

Note that distortion in the 2nd horn is over 40db below the fundamental above 2khz. Check out the distortion figures at zaphaudio if you're curious to see how a dome tweeter behaves. Note that my distortion figures are skewed higher because they're done in a car too.







Here's the polar response of both horns. Ideally we'd like to see these lines fit in a "window" of about six db. In the untreated horn you'll notice that the polar response is particularly abysmal in the octave between 1250 and 2500hz. This is bad for a number of reasons:

Our ear's sensitivity is extremely high between 1 and 2khz - any problem is very audible
These horns are typically crossed over between 1 and 2khz - the crossover will exacerbate the polar response problems
The problems with the USD horn between 1 and 2khz cannot be fixed with EQ, because they vary with angle. In other words, fix it at one spot in the car, and you make it worse at another.







This measurements shows an average of all the polar response measurements, for both horns. It's basically the "power response." In the power response it's easier to see the issues that the stock setup has between 1 and 2khz, and how the treated horn has improved things.

If any of this post doesn't make sense, let me know.


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## Patrick Bateman (Sep 11, 2006)

The JBL compression drivers that I'm suggesting as an alternative to Clark's Altecs run about $300 a pair on Ebay. I would not recommend using the "stock" diaphragm - it won't play high enough. If you can find a set with bad diaphragms, you'll save a few bucks.

Parts-Express.com:Radian 1225-16 Diaphragm Fits Most JBL 1" 16 Ohm | replacement mid hf high frequency
This is the diaphragm that I'm using with my JBLs. It's a 16ohm model. I prefer passive crossovers, and it's easier to crossover a 16ohm driver. We have efficiency to burn, so that's why I go with 16ohm.

Also, those old alnico compression drivers can't take a lot of power. IIRC, the 2470 is good for 50 watts at 8ohms. With the 16ohm diaphragms, you're basically lowering the compression drivers efficiency intentionally.

It's the same idea as using a 2ohm sub with a 4ohm midbass, but in reverse.


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## Patrick Bateman (Sep 11, 2006)

ECM said:


> Patrick, will the horn driver be supplemented with a set of tweeters considering their output is between 500Hz to 12kHz?
> 
> Or is that why the diaphragm will be replaced?









The jury is still out on this one. This afternoon I measure a tiny Celestion compression driver, hoping that it would be good for 25khz. But it's not.

The price is right - under $60. And it's tiny, which makes it easy to use in a car. It's actually smaller than a dome tweeter. But it doesn't have enough motor strength to get to 25khz, or even 20.

The BMS 4540ND can do it.

Anyways, I haven't decided what to do about the last octave. EQ will get the JBL up to 16khz, I'm not entirely sure I care about the last 4khz. My home speakers hit a wall at 18khz, using a B&C DE250.

If you used the BMS, it would really limit your xover point, since the JBL will play at least an octave deeper.

Maybe a ribbon tweeter?


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## chauss (Sep 20, 2009)

I am a fan of electrostatic speakers! Hard to beat the airy lifelike quality of voice on a ribbon!


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## Patrick Bateman (Sep 11, 2006)

chauss said:


> I am a fan of electrostatic speakers! Hard to beat the airy lifelike quality of voice on a ribbon!


I sit in front of a computer and write software all day long, and I have a pair of Summas that I listen to while I do it. After work yesterday I headed down to a local pub to have dinner. The pub has brick walls, concrete floors, and a typical PA system with horn loaded compression drivers.

Immediately I noticed that all the "texture" and "detail" was absent from the music. For instance, the bass guitar almost sounded synthetic, as if all detail had been smeared in time. And keep in mind, this wasn't a recording, there was a band playing!

Anyways, the reason that I bring this up is that ribbons are very well behaved in the time domain. Because the diaphragm barely moves, the spectral delay is very clean.

Conventional horns can't do that, and listening to that band at the pub made that obvious. All those early reflections, exacerbated by the concrete floors and brick walls, made the music sound like a muddled mess.

And getting back to the thread, we have two ways to treat that. Treat the horn, treat the room, or both.


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## ECM (Dec 23, 2007)

Patrick Bateman said:


> The jury is still out on this one. This afternoon I measure a tiny Celestion compression driver, hoping that it would be good for 25khz. But it's not.
> 
> The price is right - under $60. And it's tiny, which makes it easy to use in a car. It's actually smaller than a dome tweeter. But it doesn't have enough motor strength to get to 25khz, or even 20.
> 
> ...


Agreed. I'd rather have the JBL go lower and eq the top end or even supplement it before using a CD with an x-over point of 1.2kHz.


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## tronik (Sep 1, 2009)

Very interesting stuff. Look forward to reading more from you Patrick!


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## Patrick Bateman (Sep 11, 2006)

Not to go off on a tangent, but someone emailed me about doing this project for $500. That price is a bit low, but we can do a "variant" on it for about three hundred. Here's what I would use if cost was a big factor:


*








Parts-Express.comeerless 830987 3" Full Range Woofer | Peerless 830987 3" Full Range Driver bass mid midbass mtm 2-way vline logic line array lat tymphany09
Midbass and midrange - Peerless 830987*​For midbass and midrange, I'd buy six of the Peerless 830987. This is a computer speaker, but it has all the distortion-killing components that make the B&C so special, and more. It has an underhung motor, a copper cap, and lots of xmax. I've measured a comparable model, and it is superior to the AuraSound. The main reason I am using the AuraSound is that it has a displacement advantage (ie, will go louder.)

To keep it simple, I would put two of these UNDER the dash on each side, in VERY small sealed boxes, as far back as they will fit, and as wide as possible. The cones of the two woofers should be within five inches of each other, to improve the response. It doesn't really matter if they're firing forward, backwards, downwards, whatever. At these frequencies sound is omnidirectional. That's why we can put them UNDER the dash.

The other two woofers would be mounted in the quarter panel or on the rear deck. Basically wherever you can hide them.

As noted in the "natural bass" thread, I believe the GN used "the Haas effect" to "trick" the listener into thinking that two midbasses were playing, when there were actually four. So we're going to do the same thing.

Nine years ago, Richard Clark said the following:
"_When radiating as single sources it is extremely easy to localize a midrange or high frequency speaker. Only when a similarly matched pair of speakers radiating similar frequencies with similar path lengths does our localization ability become fooled._"*

Because the Haas effect is level dependent, my recommendation is to increase the level of the front midbasses by six db. This is accomplished by wiring all three midbasses in parallel, which yields a 2ohm load.

The cost for the midbasses is $115.68.









8'' High Excursion Woofer | MCM Audio Select | 55-2421 (552421)
*Bass - Triple8*​
A few years back I built a clone of Bill Fitzmaurice's "AutoTuba", and found that it's an SPL monster that's very clean too. The Triple8 is my attempt to increase the power handling and reduce the box size. I think it works quite well. The box is much smaller, and power handling is easily tripled, via the use of three woofers instead of one, along with excursion that's much lower. All the information that you need to build one is in my tapped horn thread on this forum.

Because this is a tapped horn, you can't sell the box, it's patented by Danley. But you *can* build it for your own use.

The cost for the three woofers is $104.97.









Compression Driver, 1.4", Alum., Neodymium
*Treble - Celestion CDX1-1425*​
The Celestion CDX1-1425 is a great find. Brandon (Augerpro) on Diyaudio clued me into this one. (Celestion | Professional Loudspeakers) It has a diameter of about two inches, which makes it one of the very VERY few compression drivers that you can use in a kick panel (or on the dash.)

While I personally prefer to have my tweeters on the dash, mounting them in the kick panel is easier and has a lot of cosmetic benefits.







To mount the Celestion in your kick panel, you're going to need a waveguide. This is the Celestion SP_000106_GP. It's depth and width is just about perfect for mounting in the kick panels. *Be sure to build a baffle - without a baffle these will sound AWFUL. If you don't terminate a horn/waveguide properly, THEY SOUND ATROCIOUS. Just use some plywood, and "blend the baffle into the corners of your car.*







These are my measurements of the Celestion's frequency response and distortion *in car.* On the Celestion waveguide, the distortion is lower than you're going to get with a dome tweeter, and the efficiency is well over 100db. The top graph is without the Geddes foam; the bottom graph is with it. You'll note that the USD horns take a big efficiency hit from the foam, and these do not. I believe this is because the QSC waveguides have lower reflections and diffraction than the USC models. Check out my "Homster" thread on Diyaudio for a deeper discussion of horn diffraction.







This is the polar response of the QSC horn, mounted in my kick panels. You might notice that this is *the best polar response I've ever measured in a car.* It's even better than my Unity horns, up on the dash. The QSC is very VERY good. Did I mention it's six dollars?







For comparison's sake, this is a "stock" USD horn and compression driver. Note the dip in the midrange. I believe that's due to the 90 degree bend in the horn. Notice how the QSC's polar response above 10khz is almost perfect. Ignore the SPL levels - I don't have an SPL meter and can't calibrate my levels. The wattage in both measurements is virtually identical. (1 watt at 8ohms.)

_The important thing about the QSC waveguide isn't that the response is flat, it's that the response is consistent. If you look at the polar curves, they fit in a VERY tight window. About +/- 3db across the entire range. From 3000hz to 15000hz its a ONE DECIBEL window!_ This kind of performance is completely unheard of in car. Check out my other measurements to see how "real" speakers behave in a car. _Because the polar response is SO good, and the distortion is SO low, and the efficiency is SO high, you can basically EQ this thing to *any target curve you want.*_*

You want it flat? EQ it flat. You want a falling response? You can do that. Whatever curve you want, you can have it with the QSC and Celestion. You can't do that with any other speaker that I've seen, because they don't have a polar response that's this good. In other words, if you add EQ, the off-axis response won't match. The reason that USD and Image Dynamics horns require narrow band EQ is that they have narrow-band peaks and dips. The QSC does not.

You better get out your checkbooks for this one. State-of-the-art tweeters don't come cheap. The QSC waveguides are $6.55, and the compression driver is $44.26. That's $101.62 for both sides.

The grand total for my "cheap" variation on The Grand National in a Box is $322.27.​
That leaves $177.73 for plywood, glue, nuts, bolts, wiring, etc...

The electronics for this project will set you back a few hundred though - I'm not sure if the person who emailed me expected the $500 budget to include amplifiers, crossovers, and EQ.

* AutoSound 2000 tech brief #2447. $3.50 here : DavidNavone.com - Tech Briefs
*


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## fury (Dec 12, 2007)

Hi Patrick,

Thanks for your immense contribution to this forum, and other audio forums you visit.
Will the small BMS driver (4540 i think?) you've mentioned in the past marry up with this waveguide?
Does it give better response in the top octave (10khz+), and is it physically much larger?
Do you have a link to this wave guide?

Giving me lots of ideas


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## JayinMI (Oct 18, 2008)

Has anyone else noticed that GNIB is "Bing" backwards? 

Jay


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## Patrick Bateman (Sep 11, 2006)

fury said:


> Hi Patrick,
> 
> Thanks for your immense contribution to this forum, and other audio forums you visit.
> Will the small BMS driver (4540 i think?) you've mentioned in the past marry up with this waveguide?
> ...


With any loudspeaker, there are three things you can do to extend the high frequency response:


Use a smaller diaphragm
lower the inductance in the motor
use a lighter diaphragm

Each one of the compression drivers in my "arsenal" does this to one extent or the other. The Celestion has a smaller diaphragm than the JBL. The JBL has silver shorting rings. (silver!!!) The BMS has the smallest diaphragm of all, and a bigger motor than the Celestion.

Here's some data on these:

Welcome to Assistance Audio

http://www.bmspro.info/fileadmin/bm...ssion_drivers/neodymium/bms_4540nd_t.data.pdf

Frequency Response (drivervault)

You can see that in the frequency response and distortion measurements of the various compression drivers. The BMS will indeed go the highest, but it costs 3X as much as the Celestion.

About the only way to go higher than the BMS would be to use a lighter diaphragm, like the beryllium diaphragms used by Tad. But those are about *twenty four times* as much as the Celestion.

Law of diminishing returns...


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## fury (Dec 12, 2007)

I guess my question is, can you get away without a tweeter if using the celestion compression driver?

The BMS drivers (4540nd and 4552nd) do look interesting, but most of their top end appears to be caused by 2nd order harmonics...reflections off the phase plug?
Adding Geddes style foam will no doubt help to reduce these, but it will also roll off the top end... I understand he doesn't place much emphasis on 10khz or above, but it certainly makes a difference to the music i listen to.


Also I found the info about that QSC waveguide - looks like it uses a 1.4" throat? which would mean either a 1.4" CD, or are 1" to 1.4" adaptors easily available?


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## danssoslow (Nov 28, 2006)

Alright. I believe my juices are now flowing enough to actually get out and do something to my truck. I do have a couple questions first; and I figured I'd ask them here in case others had the same questions.

First question is about a mid variant. I have two sets of Peerless 830986's. Would these work in place of the Vifas above?

Second is about the compression drivers. Are we looking to get these on axis as much as possible? Will simply firing at each other work? I've never messed with horns before, please pardon my ignorance. I was also thinking about the possibility of grafting the horns into the stock grills on the dash of my Blazer, and was wondering the effects of possibly manipulating the outer edged of the horn to make such a modification possible.

Third, if room will allow for it, would there be a problem with mounting the third midbasses with the other two under the dash? You say a very small enclosure for the mids, how small are we talking here?

Thanks a big bunch!
Dan


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## Patrick Bateman (Sep 11, 2006)

danssoslow said:


> Alright. I believe my juices are now flowing enough to actually get out and do something to my truck. I do have a couple questions first; and I figured I'd ask them here in case others had the same questions.
> 
> First question is about a mid variant. I have two sets of Peerless 830986's. Would these work in place of the Vifas above?


The speaker in recommended to those on a budget is a Peerless, and appears to be virtually identical to the one I listed. The model number is off by one digit.

Keep in mind that's a budget recommendation. The 8NDL51, JBL 2204/6, or any good large prosound midbass will work better. But if you want to save a few bucks, the Peerless is hard to beat at the price.

Over the weekend I did some "high power" measurements for the first time ever, and it was pretty amazing how loud 10 watts is with the B&C. I think I scared the neighbors. The AuraSound enclosure sounded like it was about to explode at 10 watts, I really need to brace the poor thing.



danssoslow said:


> Second is about the compression drivers. Are we looking to get these on axis as much as possible? Will simply firing at each other work? I've never messed with horns before, please pardon my ignorance.


The answer to that is in the polar plot. See how the response of the QSC is virtually identical at all angles?

That's how guys like Gary Biggs can put their tweeters under the dash, and pointed off axis. Biggs uses a waveguide on the tweeter to improve the off-axis response.

The QSC does the same thing.

I would personally recommend "cross firing" the waveguides. But aiming isn't very important, the response is all but identical at all angles. That's the idea.

If you have the ability to sink the waveguides into the kick panels, that is how I measured them, and how I would set them up personally. To keep it from looking like hell, fill the waveguide with 30ppi reticulated foam. That will keep dirt and moisture out, as well as reducing higher order modes in the waveguide. You can even use nylon carpet to cover it, just don't use anything that's *too* thick.



danssoslow said:


> I was also thinking about the possibility of grafting the horns into the stock grills on the dash of my Blazer, and was wondering the effects of possibly manipulating the outer edged of the horn to make such a modification possible.


When I saw how good the QSC's response is, I started daydreaming about mounting them vertically too. I don't know how it would work - I haven't tested them that way. You'd want to keep it away from the apex of the windshield, since there will be a reflection there.



danssoslow said:


> Third, if room will allow for it, would there be a problem with mounting the third midbasses with the other two under the dash? You say a very small enclosure for the mids, how small are we talking here?
> 
> Thanks a big bunch!
> Dan


For the midbasses, you basically want to make the smallest enclosure humanly possible. I actually used a grinder to shave an eighth of an inch of my AuraSounds, just to get them in the box!

We're talking literally the smallest box you can construct. Take a look at the enclosures I made for my TangBands - I literally sealed off the basket.

In the car you can get away with really REALLY small sealed enclosures, because of cabin gain.

This has been something that's always mystified me. You see guys put twelve inch woofers into boxes that are the size of a shoebox, and then they put their midbasses into boxes that are eight times as big, leaky, and just generally ****ty enclosures. (ie, the car door.)

A small sealed box increases the power handling, and a leaky enclosure like a door is very inefficient at low frequencies. (IE, a small sealed box has more bass in the real world, despite what WinISD says. WinISD doesn't factor in big ol' leaks.)

As for putting all three in one spot, that kinda defeats the idea of using three. If you're not going to use multiple midbass locations to smooth the response, you might as well get one woofer that can take some power, and works in a small sealed box.


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## KP (Nov 13, 2005)

Speaker Works did a car with the horns firing out of the top of the dash. They claimed the windshield acted as an extension of the horn. I belive it was an RX7? Silver? It was in a Mag or two back in the day.

Kirk


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## Mic10is (Aug 20, 2007)

AcuraTLSQ said:


> Speaker Works did a car with the horns firing out of the top of the dash. They claimed the windshield acted as an extension of the horn. I belive it was an RX7? Silver? It was in a Mag or two back in the day.
> 
> Kirk


Jerry Zeigler also had CRX with ID horns in top of dasg. Randal Holdman did a 90 civic w similar set up.
There was an S-10 as well back in the day that did it.

its been done several times


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## thehatedguy (May 4, 2007)

And none of them worked well either. None.


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## bradwood (Feb 14, 2009)

Patrick, this is awesome work you're doing!

Re the Peerless 830987 array, I assume you recommend bandpass filters - if so what settings? Also, you say "wire all three midbasses in parallel, which yields a 2ohm load", how does this work with 2 pairs of 2 in the front and a single pair in the back?

Apologies if this has been answered previously, keeping up with the thread is challenging ;-) Cheers


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## jbholsters (Jun 17, 2009)

thehatedguy said:


> And none of them worked well either. None.


amen to that. I could never understand the point of the horns firing up through the top of the dash. Kind of defeats getting the pathlengths close. I remember judging a Corvette back in the early 90's at a regional (in Kentucky I think) that had that setup.


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## bassfromspace (Jun 28, 2016)

Keep up the good work PBateman.


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## qikazel (Aug 9, 2009)

We're talking literally the smallest box you can construct. Take a look at the enclosures I made for my TangBands - I literally sealed off the basket.

Where can this pic be found?

Thanks.


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## qikazel (Aug 9, 2009)

Also, I followed the general way of doing things and put a set of PPI 356 6.5 in mids in the doors with the dome tweets on the pillars. I love midbass and want that really hard hit. So without sounding too ignorant, 4 of the 3" speakers you recommended in sealed boxes under the dash and 2 more in the back will be louder and hit harder. What wattage would be recommended? I am currently sending 250 watts to each of the mids in the doors. I am really intrigued by your posts and am trying to grasp as much as possible.


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## bayvanman (Nov 22, 2009)

As this is my first post, can I just say PB thank you for re-lighting my enthusiasm for car audio again.
(Sitting back and enjoying your posts)


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## danssoslow (Nov 28, 2006)

Another question if I could. Where did those prices for the compression driver and the waveguide come from?


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## slvrtsunami (Apr 18, 2008)

AcuraTLSQ said:


> Speaker Works did a car with the horns firing out of the top of the dash. They claimed the windshield acted as an extension of the horn. I belive it was an RX7? Silver? It was in a Mag or two back in the day.
> 
> Kirk


 
It was an F body Camaro...


Also, from what I recall....Clark never did put those monsters in the Buick. When he bought the car from the Holdaways, he simply modified them a little ( i think something as simple as a voice coil change). To me, in my opinion, Clark had a tendency for the dramatic and wow factor...kind of reminds me of BOSE marketing department.


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## Patrick Bateman (Sep 11, 2006)

danssoslow said:


> Another question if I could. Where did those prices for the compression driver and the waveguide come from?


Compression Driver, 1.4", Alum., Neodymium

The part numbers are in my post on page 2.

Also, the prices that they charged me are lower than what is listed. Very fast service too - I had mine in less than three days, with standard shipping.


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## Patrick Bateman (Sep 11, 2006)

qikazel said:


> Also, I followed the general way of doing things and put a set of PPI 356 6.5 in mids in the doors with the dome tweets on the pillars. I love midbass and want that really hard hit. So without sounding too ignorant, 4 of the 3" speakers you recommended in sealed boxes under the dash and 2 more in the back will be louder and hit harder. What wattage would be recommended? I am currently sending 250 watts to each of the mids in the doors. I am really intrigued by your posts and am trying to grasp as much as possible.


In order to achieve "natural bass" in the car, I believe it's important to use drivers with low distortion, and to pay attention to the power response.

You can reduce distortion with a driver that has shorting rings, an underhung motor, or both. The Peerless has two of those features, the AuraSound and the B&C have one.

The Peerless woofers are an inexpensive option, but the B&C will offer much higher performance. Then again, the B&C costs three times as much!

Basically, if you want something with a lot of dynamics and low distortion, the 8NDL51 is a small sealed box is tough to beat. If you have the space for a pair of twelves, the 2206 woofers appear to be amazing, but they're even more expensive, and I haven't personally used them.

If you're on a limited budget, but you'd like a solution that offers low distortion and good power response, the Peerless woofers are a viable solution.

Of course there's a limit to how much SPL you're going to get out of an array of computer speakers.

I am personally using the AuraSound NS4s because soundstaging is exceptionally important to me, and the small woofers offer mounting options which are impossible with the 8NDL51.


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## Patrick Bateman (Sep 11, 2006)

fury said:


> I guess my question is, can you get away without a tweeter if using the celestion compression driver?
> 
> The BMS drivers (4540nd and 4552nd) do look interesting, but most of their top end appears to be caused by 2nd order harmonics...reflections off the phase plug?
> Adding Geddes style foam will no doubt help to reduce these, but it will also roll off the top end... I understand he doesn't place much emphasis on 10khz or above, but it certainly makes a difference to the music i listen to.
> ...


The *diaphragm* is 1.4", not the throat. For a compression driver, this is extraordinarily small. The throat is an inch in diameter.


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## Patrick Bateman (Sep 11, 2006)

Patrick Bateman said:


> Not to go off on a tangent, but someone emailed me about doing this project for $500. That price is a bit low, but we can do a "variant" on it for about three hundred. Here's what I would use if cost was a big factor:
> 
> 
> *
> ...


*

A few people asked me if the Peerless woofers will be competitive with larger options, like a seven or a twelve.

They won't - they're an inexpensive alternative. All of the parts in the post from above are inexpensive substitutions.

Here's why I went this route:

In car audio, we typically evaluate equipment at various price points. For instance, if we are going to purchase a midbass, we might consider a Morel at $200, a Vifa at $80 and a Dayton at $40.

If you compared the three woofers, you would probably find that the expensive options include a well damped cone, lots of excursion, shorting rings to lower inductance and high power handling.

As you lower the budget, distortion goes up, and excursion goes down. Inexpensive drivers typically have low excursion, high distortion, and high inductance.

The reason why I recommended the Peerless is that an array of the woofers have low inductance, low distortion, wide response, and surprising high excursion.

Basically, I would rather have low power handling and low distortion than high power handling and high distortion. The Peerless woofers won't get as loud as one big woofer, but they'll sound a heck of a lot cleaner doing it, because they excel at the things that are important to me.

The next step up would be an 8NDL51 or a JBL 2206. In the "natural bass" thread I am also exploring the possibility of using computer speakers in a tapped horn to get their efficiency up to the level of the B&C.

*


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## western47 (Nov 17, 2008)

I have gone back and re-read this thread and I have certainly missed a couple of things. I have never seen that WG from the QSC store. I have gone ahead and ordered one to see how that might fit.

The main problems I am running into is where to put the goods. My car is an 7 gen Accord and is a manual. Being a tall guy with a manual transmission means that the kickpanel area as well as the area below the dash are often used for general space and operating the vehicle. I really wanted to put an 8" B&C unit below the dash towards the firewall but I have the clutch on one side and my cabin fan on the other. Neither of these items can be moved at all to provide any sort of access for a large driver.

I remembered seeing this post about those little Peerless drivers. Now I can definitely stuff a couple of those into some spots on both sides below the dash. Made my cardboard replicas and fit them in well. Went back into the house as I remember the statement that these will not keep up with a 7". Sure enough, Sd alone on 3 of these drivers only comes up with 93cm^2. Compare this to a 6.5' at 130 and an 8" at 220 before the excursion limitation and we are getting into some trouble. I don't need a ton of head room but I want to be able and turn it up a little 

So, what I am hoping for right now is that this WG will not intrude on my footwell enough to make my car undriveable. The question then becomes one of hoping that the work on placing some of the 3's in a tapped horn on the rear package deck works OR the possibility of placing a larger 8" in the door and possibly supplementing the image with an addition 3" below the dash towards the firewall.

Any thoughts?


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## Patrick Bateman (Sep 11, 2006)

western47 said:


> I have gone back and re-read this thread and I have certainly missed a couple of things. I have never seen that WG from the QSC store. I have gone ahead and ordered one to see how that might fit.
> 
> The main problems I am running into is where to put the goods. My car is an 7 gen Accord and is a manual. Being a tall guy with a manual transmission means that the kickpanel area as well as the area below the dash are often used for general space and operating the vehicle. I really wanted to put an 8" B&C unit below the dash towards the firewall but I have the clutch on one side and my cabin fan on the other. Neither of these items can be moved at all to provide any sort of access for a large driver.
> 
> ...


With a narrow bandwidth alignment (bandpass, tapped horn, etc) we can get the efficiency of a pair of fours up to where the 8NDL51 is. Basically we're trading bandwidth for efficiency.

I built a couple prototypes, and the results were promising, but too damn bulky. I'll post some pics soon.

At this point, I'm leaning towards doing what I recommended earlier in this thread - an array of small woofers distributed throughout the cabin. While it won't offer the same output as Clark's twelves, it *should* have a level of distortion which is competitive. That may sound a bit absurd, considering the low efficiency, but the performance of the Peerless and Aurasound is *very* good.

At the moment I've been simulating various array options, all of them _horizontal._

Normally horizontal arrays are frowned on, because they beam like crazy, but in a car, *that's a good thing!* Basically we can take advantage of the beaming to reduce reflections, and improve the polar response.

So that's where I'm at now. Trying to sacrifice maximum SPL for improved power response and low distortion.

Of course, the B&C is still a good solution, but I have the same problem you do. There is no where to put them. And if I put them against the firewall I wind up with a soundstage that's three feet wide


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## KP (Nov 13, 2005)

I remember a couple cars back in the late 80's, early 90's that had midbass enclosures built into the bottom of the dash with the midbass pointing down towards the floor board. I wonder how something like that would work in a car/truck that it is possible in?

K


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## jbholsters (Jun 17, 2009)

There were also some cars during that time that had enclosures floor mounted in from of the drive and passenger seats, firing at the windshield. Greg Cassis' Typhone from PJ's comes to mind. His previous vehicle (Regal) sounded better.


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## western47 (Nov 17, 2008)

I will wait to see what you come up with as I am intrigued and a little skeptical. 

Upon doing more looking last night, I do think that the 8" B&C driver will fit. Removing the cover underneath the glove box exposes the cabin fan. Towards the corner and firewall is a little hole which should fit an 8" rather nicely.

The driver side is a little trickier for me as I have a manual and this is where the clutch mechanism attaches. I think with a bit of cable rerouting that I would be able to fit an 8" close to the steering column. 

If you can get a small driver solution to work then that will be easy as pie to locate and install. I might just order a couple of those Peerless drivers and see just how much output will happen once their backsides are sealed. From the numbers alone, it doesn't look like they have enough surface area or excursion to produce as much as a 6.5" driver unless I am missing something. Granted, dispersing these throughout the cabin will help in smoothing response which may help more than you would think.

The positive thing for me is that I think the shallow QSC waveguide might work for me. I have placed one on order as I can't find the actual dimensions anywhere. If the depth isn't too great then I would likely try to mate these with a B&C DE250 as we know that these are good drivers. Playing lower vs top end extension is an easy decision for me.


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## jbholsters (Jun 17, 2009)

^keep those mid mass as far to the sides as you can. It will affect stage width.


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## bassfromspace (Jun 28, 2016)

I took a bit of a different take on the GNIB.

I'm doing dual Tang Band fullranges in the kicks with 6 Lat 250's. I plan to place the Lat's like Patrick suggested with 4 under the dash and 2 on the rear deck. The Lat's seem to be a midbass alternative to the Peerless.

Only time will tell.


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## cubdenno (Nov 10, 2007)

bassfromspace said:


> I took a bit of a different take on the GNIB.
> 
> I'm doing dual Tang Band fullranges in the kicks with 6 Lat 250's. I plan to place the Lat's like Patrick suggested with 4 under the dash and 2 on the rear deck. The Lat's seem to be a midbass alternative to the Peerless.
> 
> Only time will tell.


Interesting idea....


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## otis857 (Feb 12, 2008)

Hey JB, I'm curious about the mids in the floor. I posted about this on PB's other thread about natural bass and got no replies. Before I got the bug for car audio and was strictly a home Hifi nut, I worked on a hifi salesman buddy's 66 LeMans. He had mid bass speakers mounted in the floor just under the edge of the seats facing the windshield on a 3 way active front stage and it imaged very well. Dont know what he was running, but I do remember the pods gave me fits removing the cross member.

Im definitely curious where PB goes with this thread. Thanks Pat for the DIY research.


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## rawdawg (Apr 27, 2007)

otis857,

I have my Mids/midranges in floor mounted enclosures. They work well enough to stage on the dash and occasionally above it. I do get the feeling that things could be wider but I still have lots of tuning to do. The cool part of this design is that I get a solid enclosure with no rattles and no deadening other than the polyfill inside. Also, I can uninstall the enclosures, replace the carpet and go back to stock. Eric Holdaway, of Speakerworks fame, once said that if he back knew then what he knows now, he would have put the GN's Midbasses up front in the floors.

Here is a pic of my front stage done by Speakerworks several years ago. Originally they had Kicker RMB8's but were replaced with Dynaudio MW170's. USD Audio BC-300's are up under the dash.










Here is my front stage as it stands now. The enclosures are underneath the carpet and the big black thing is to protect stuff from a 300 lb. wrecking machine of an old salty man. I can't feel them there while shifting. Same Dyns' and waveguides but no PVC pipes or foam yet...


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## funkalicious (Oct 8, 2007)

Thanks for the excellent thread, Patrick! Since the Peerless speakers you recommend are so small and easily placed would increasing the number of them per side to say 6 (4 underdash and two rear quarter panel per side) provide enough of an output improvement to compete with 6" or 8" drivers? Will increasing the number of drivers create unmanageable problems?


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## Fast1one (Apr 6, 2007)

bassfromspace said:


> I took a bit of a different take on the GNIB.
> 
> I'm doing dual Tang Band fullranges in the kicks with 6 Lat 250's. I plan to place the Lat's like Patrick suggested with 4 under the dash and 2 on the rear deck. The Lat's seem to be a midbass alternative to the Peerless.
> 
> Only time will tell.


I almost pulled the trigger on the LATs, but with no concrete T/S parameters (FS was way off and there isn't a measurement on VAS), it was difficult to determine whether they would work well in small enclosures or not. In addition, distortion performance is questionable below 90hz.Scroll down for John Krutke's impression: Zaph|Audio

I also found a project at the parts express forums, being used as a midbass/low midrange. Impressions at Dayton were that the LAT-250 was the weak point, but I have no idea in what regard.

In other words, it wasn't worth the $150 dollar risk to buy six for me personally. So I opted for something more proven. The Dayton ND90 aluminum cone 3.5 inch driver was measured by zaph to be the same as the Aura NS3-194 from what I hear. For good reason, it looks damn near the same. These driver's are well known for their distortion performance (John uses the NS4, for example). I opted for its bigger brother, the ND140. Four up front, two in the back.

On another note: Got my CD-1E mini bodies in. Pretty exited about that


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## bassfromspace (Jun 28, 2016)

Fast1one said:


> I almost pulled the trigger on the LATs, but with no concrete T/S parameters (FS was way off and there isn't a measurement on VAS), it was difficult to determine whether they would work well in small enclosures or not. In addition, distortion performance is questionable below 90hz.Scroll down for John Krutke's impression: Zaph|Audio
> 
> I also found a project at the parts express forums, being used as a midbass/low midrange. Impressions at Dayton were that the LAT-250 was the weak point, but I have no idea in what regard.
> 
> ...


Yeah, I read Zaph's review on these drivers prior to purchasing the Lat's. I gathered from the review, that he had unrealistic expectations of them. They seem to be designed for the average,non-critical, listener. It's not a subwoofer, but a woofer.

Hopefully cabin gain will befriend me. I'm sure that 6 of these with 100 watts apiece will make for an interesting experiment.


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## Patrick Bateman (Sep 11, 2006)

bassfromspace said:


> I took a bit of a different take on the GNIB.
> 
> I'm doing dual Tang Band fullranges in the kicks with 6 Lat 250's. I plan to place the Lat's like Patrick suggested with 4 under the dash and 2 on the rear deck. The Lat's seem to be a midbass alternative to the Peerless.
> 
> Only time will tell.


Here's something I've been messing around with.







This is a simulation of three ND90 midbasses in a _horizontal_ array. This is a bit unusual - horizontal arrays are normally frowned upon because they "beam" as the frequencies get higher.

The idea I had is that we can use this to our advantage, by using the narrowing directivity of a horizontal array to reduce reflections.

The idea is that you would put three midbasses in a simple sealed box under the dash. Instead of using a waveguide to narrow the directivity, we're using an array. Andy from JBL clued me in to this on this forum.

Anyways, the red line in this simulation is the off-axis response. You can see that it narrows to ninety degrees at 1400hz. So basically reflections would be reduced by about half from 1400hz and up.

I'm not 100% ready to "pull the trigger" on new woofers, but I'll probably try building one of these with a few woofers I have laying around.

Also, the response is falling on purpose, I'm using two different low pass frequencies to increase output at low frequencies.








Here's the simulated response of a Vifa LAT250. For $25, this is a screaming deal. Because the LAT is basically an array of small woofers, it's damn near ideal for our application. It's a bummer I haven't tried these earlier.

If I were using it, I'd mount it horizontally, because that arrangement will narrow response to ninety degrees around 1700hz.

If you mount it vertically, you'll get the opposite result. (wide response from left to right, but not much output from top to bottom.)


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## donkeypunch22 (Nov 5, 2008)

How do you interpret the frequency lobing graph in your picture, Patrick?


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## bassfromspace (Jun 28, 2016)

Patrick Bateman said:


> Here's something I've been messing around with.
> 
> 
> 
> ...


I planned to use the LAT'S strictly as a midbass.

Patrick, are you recommending they be used up to 1700hz?


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## cubdenno (Nov 10, 2007)

I was looking to get another set of Dayton Rs225's and mount firing down under the dash in a small sealed enclosure. 

Now, I am thinking the LAT 250 similar to what BFS is considering.

Would you seal it or port? A small 1"ID tuned to say 90-100 hertz.

Dammit!! BFS!! You have started my hand traveling to my wallet!!


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## bassfromspace (Jun 28, 2016)

.


cubdenno said:


> I was looking to get another set of Dayton Rs225's and mount firing down under the dash in a small sealed enclosure.
> 
> Now, I am thinking the LAT 250 similar to what BFS is considering.
> 
> ...


Sorry Cub. Our hobby is not our friend

Tymphany has several different enclosure options on it's site. I'm taking Patrick's advice and throwing them in sealed enclosures just big enough for the driver. I'm hoping cabin gain will take care of the rest.


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## cubdenno (Nov 10, 2007)

bassfromspace said:


> .
> 
> *Sorry Cub. Our hobby is not our friend*
> 
> Tymphany has several different enclosure options on it's site. I'm taking Patrick's advice and throwing them in sealed enclosures just big enough for the driver. I'm hoping cabin gain will take care of the rest.


Amen brother!


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## thehatedguy (May 4, 2007)

What is the 250 equivalent to in traditional speaker size?


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## Fast1one (Apr 6, 2007)

thehatedguy said:


> What is the 250 equivalent to in traditional speaker size?


They say 8 inch, but more like 6.5 with small X-max. The outside diameter is 2.70 inches. Essentially its an array of five ~2.5 inch woofers with an xmax of 3mm.

5*PI*(1.25in.)^2 = 24.5 in^2

Compared to the average cutout of a 6.5 inch woofer, which is about 5.5 inches:

PI * (2.75in.)^2 = 23.8 in^2

But the X-max is only ~3mm. So any 6.5 inch woofer with >6mm of x-max will beat two LAT-250s in displacement advantage. The attraction is the form factor, which is much easier to hide or tuck away.

The LAT-250s have a linear displacement advantage of 7% compared to the ND140s. But the 20mm P-P of mechanical excursion of the ND140s is comforting


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## thehatedguy (May 4, 2007)

They might be fun to try out. The price is certainly right.


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## bassfromspace (Jun 28, 2016)

I wonder if the 3mm rating is 1-way and should be doubled to get the true xmax. The reason I ask is because this driver works in a horizontally oriented push-pull configuration and I'm assuming each complete left and right movement creates displacement. Tymphany also lists the max xmax at 7 mm.


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## Fast1one (Apr 6, 2007)

bassfromspace said:


> I wonder if the 3mm rating is 1-way and should be doubled to get the true xmax. The reason I ask is because this driver works in a horizontally oriented push-pull configuration and I'm assuming each complete left and right movement creates displacement. Tymphany also lists the max xmax at 7 mm.


I doubt it. It most closely resembles an isobaric configuration from what I can tell.. As the one set of drivers pushes from inside the box, the other set pulls out, just like two woofers mounted in an isobaric alignment would act. 

As a result you get better distortion performance and smaller box requirements, but you still have the same linear displacement. 

Refer to the first figure in the following document: http://www.madisound.com/catalog/PDF/LAT250-004.pdf


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## western47 (Nov 17, 2008)

I am going to order a bunch of the Peerless 830987 drivers and start messing with placing two of them, motor structure to motor structure, in a 3" piece of PVC keeping the volume as small as possible. This will allow the piece to be small for location as far and wide as possible. If more output is needed then just keep adding small units under the dash.

You could easily configure such a setup so that a horizontal array could be arranged underneath the dash. A cheap, easy solution which could easily be configured for additional output if needed. A completed unit would be 3"x4" in length. Attractive, no?

Thoughts?


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## SSSnake (Mar 8, 2007)

The LATs are NOT isobaric. Each pair does fire at each other (great for cancelling vibrations). This however does not double Xmax. You are still only creating the displacement of the cone area multiplied by stroke. Get the SD spec and multiple by Xmax (one way).


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## Fast1one (Apr 6, 2007)

SSSnake said:


> The LATs are NOT isobaric. Each pair does fire at each other (great for cancelling vibrations). This however does not double Xmax. You are still only creating the displacement of the cone area multiplied by stroke. Get the SD spec and multiple by Xmax (one way).


You're right, this would give the displacement potential of an 8 inch with 3mm of xmax.


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## Patrick Bateman (Sep 11, 2006)

western47 said:


> I am going to order a bunch of the Peerless 830987 drivers and start messing with placing two of them, motor structure to motor structure, in a 3" piece of PVC keeping the volume as small as possible. This will allow the piece to be small for location as far and wide as possible. If more output is needed then just keep adding small units under the dash.
> 
> You could easily configure such a setup so that a horizontal array could be arranged underneath the dash. A cheap, easy solution which could easily be configured for additional output if needed. A completed unit would be 3"x4" in length. Attractive, no?
> 
> Thoughts?


I would have answered sooner, but I've been in Manhattan all week*. My team just got our very own supercomputer so I'll probably be spending more time thinking about high speed network interconnects than loudspeakers in 2010.

Anyways, some thoughts:

The LAT250s that bassfromspace found are tough to beat. The eights in my trunk have an SD of 220, and the LAT250 has an SD of 196. So a pair of these can move more air than a twelve. That's quite a feat for such a small foot print.

Also, the efficiency of a woofer is tied to it's free air resonance. So the LATs, with a relatively high FS, will have higher efficiency than an eight with an FS of 30-40hz.

All in all, I am a lot more impressed with the LATs than Zaph was. As a subwoofer, they're useless, the distortion is too high below 100hz. But as a midbass? They're VERY nice.

For a $100, they would be a good buy, but at $25, they're a steal. This HAS to be a closeout or something - there's no way that Vifa is making any money at these prices.







One of the most intruguing things about the LATs is this distortion graph. About seven years ago, there was a thread on one of the subwoofer forums where Tom Danley from Sound Physics Labs was discussing the use of XBL woofers with Dan Wiggins from Adire Audio. Nothing came of it, and I was always curious why that was. Years later, Danley mentioned offhand that push-pull arrangements were more effective at reducing distortion at low frequencies than motor topologies. Anyways, if you look at the distortion performance of the LAT250, you'll see what Danley is talking about. Do you see how 2nd harmonic distortion is lower than 3rd harmonic distortion from 20hz to 400hz? I *believe* that's due to the push-pull arrangement.















For comparison's sake, here's a diagram and a distortion measurement on a push-pull design that I built. Do you see how 2nd harmonic distortion is about 10dB lower than 3rd harmonic distortion from 500hz and down? (2nd harmonic is the yellow line, 3rd harmonic is the grey line.)







Now compare the two graphs above to this one, which uses a conventional motor. The 2nd harmonic (yellow) is about 5-8dB higher than 3rd harmonic (grey.) You can see that the push-pull designs have dramatically lower 2nd harmonic distortion. The 2nd box uses an underhung motor, which plays a factor too. I don't know if the LAT250 is underhung, I'd bet that it is.















Here's the distortion measurement of a B&C 8NDL51 in a very small sealed box. The B&C has very good distortion performance. It uses shorting rings. But look at the 2nd harmonic distortion - note that it's about 2-5dB lower than the 3rd. This appears to confirm what Tom Danley mentioned - the push-pull is more effective than the shorting rings.

If Danley is correct (and I think the graphs show that he is), then a simple push-pull mounting arrangement is more effective at reducing distortion at low frequencies than shorting rings. It *might* be more effective than XBL, but we'd have to get Dan Wiggins involved in the discussion.

I wish I owned a sub box with dual woofers, it might be fun to see how effective this is at reducing distortion at low frequencies. It's not like there's a lot of work involved - all you have to do is invert one of the two woofers, and invert the phase so that both cones are moving the same direction.

The reason that it's so effective at very low frequencies is that the frequencies are insanely long. An 80hz wavelength is about the length of a car, fourteen feet. The reason why we see the distortion reduction in the LATs all the way up to 500hz is that they're so tightly coupled.

To tell the truth, the main reason I haven't *bought* a pair of LAT250s is that they lack some things I want in a midbass. It appears they have an underhung motor, but I'm not certain. It does not appear that they have shorting rings. (If they did, you'd expect that 2nd harmonic distortion would be cleaner at high frequencies.)

It would be interesting to build a LAT250 type of enclosure, but using woofers with more xmax, shorting rings, and an underhung motor. I have the 830987 at home, but I'm starting to lean towards the 830985. A lot of manufacturers use the same motor on different drivers, and the 830985 appears to have the motor of the 830987 but with a smaller cone. (I'll have to dig into the spec sheet to be sure.) The advantage of the smaller cone is higher efficiency and lower QTS, due to the lower moving mass (mms.)

Here's the 830985:
Parts-Express.comeerless 830985 2-1/2" Full Range Woofer | Peerless 830985 2-1/2" Full Range Driver bass mid midbass mtm 2-way vline logic line array lat tymphany09

Anyways, an array of these in a LAT250 style array could be pretty amazing.


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## Patrick Bateman (Sep 11, 2006)

donkeypunch22 said:


> How do you interpret the frequency lobing graph in your picture, Patrick?








In the car, the frequency response of a loudspeaker is atrocious, due to all the reflections. The pic above shows the response of an eight inch midbass, measured in the car. The jagged lines are taking at ten degree increments from one side of the car to the other. The bold line is an average, which shows that the average response is good. But the response varies wildly as you move even an inch or two. A waveguide can control directivity, but the size of the waveguide gets ridiculous as the frequency gets lower. For instance, a 500hz waveguide is 27" wide!!!







This is a simulation of a loudspeaker array. Besides increasing SPL and reducing distortion, arrays can also be used to control directivity. In the simulation above, I am using three woofers with various filters to narrow the directivity above 1khz. In the graph, you can see that at 2khz the off axis response is down by 6db. Basically the energy is getting "steered" in one direction, reducing reflections in the process.

The tool is neat - you can get it from the FRD Consortium. Note that it was designed for *vertical* arrays. Which means that you have to flip the axis to model horizontal arrays. (IE, x is y, y is x.)

Durwood did a horizontal array in his Mazda3, and seemed to have good results. I know that the home audio guys haaaaaate horizontal arrays, but keep in mind they want different things than we do. In home audio you want wide horizontal response, and narrow vertical response. That reduces reflections off the floor and ceiling. In the car, I'm more concerned about the doors and the windows. Reflections off the floor aren't a huge issue because we're much closer to it than in the home.

Basically, we can use the directivity of an array to our advantage, with a bit of tinkering.


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## bassfromspace (Jun 28, 2016)

Patrick Bateman said:


> I would have answered sooner, but I've been in Manhattan all week*. My team just got our very own supercomputer so I'll probably be spending more time thinking about high speed network interconnects than loudspeakers in 2010.
> 
> Anyways, some thoughts:
> 
> ...


How would the lat's mate with your waveguide, Patrick?


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## savagebee (Sep 12, 2006)

this is a little behind the discussion, but I have some questions that have been discussed previously.

On my full size image dynamics horn bodys the motor is mounted at a 90 degree angle to the main body, is this something to be concerned about? Is the fact that the bend is so close to the diaphragm minimize the reflections?

Also, on the floor mounted midbass...
Ive been trying to fins a way to do a floor mounted MB in my caprice, but I was looking in area under the dash, for better PLDs, since the piezo drivers Im using now only play to about 800 cleanly. But it seems like people are sugegsting using a mounting location thats pretty much between and beneath the drivers/passengers legs. Would the fact that my MB are going to be playing a lot of localizable material be an impediment to this spot?

I dont want to use my doors, and I cant fit them under the dash due to so many reflections from the underdash and horn bodies as well as lack of space (Im shooting for 10" midbass or more), so is on the floor in front of the seat the best compromise?

I want to get some beffier drivers for the horns, but i have other, more pressing needs for my car audio than that right now.

Thanks for the thread PB, very informative


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## Blake Rateliff (Jul 12, 2008)

I'm interested in this as well. After seeing the pictures of floor mounted midbass enclosures posted earlier in the thread, I think I'd like to try floor mounted 8's (maybe rs225's) and then 2 of the small peerless drivers (per side) for midrange duty,along with the celestion horn's in the kicks. Sounds like a decent idea to me as I'm SO SICK of messing around with my doors trying to kill rattles and resonances (I drive a saturn, which is comparable to a tupperware container on wheels with a bunch of loose pieces rattling around inside). What kind of crossover points would I be looking at on the midbass drivers to keep the soundstage from being all jacked up (the midbasses would be 1.5-2 feet closer to me that the tweeters if I used floor mounted encloures right up next to my seat.)


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## thehatedguy (May 4, 2007)

My question is, do the LATs sound like a lot of smaller drivers together or do they sound like one large driver?


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## Fast1one (Apr 6, 2007)

thehatedguy said:


> My question is, do the LATs sound like a lot of smaller drivers together or do they sound like one large driver?


That's a good question. Traditional line arrays have a maximum listening distance that is a function of their height (transition from near field to far field), where some benefits diminish*. This can be used as an advantage because if you listen in the near field the SPL decreases at a rate of 3db per doubling of distance instead of the traditional 6db. In the far field, they begin to exhibit characheristics of a point source. 

They also have a minimum distance for the drivers to sum properly. This is function of the CtC distance, which appears to be quite small on the LAT-250, and the height of the driver. Driver's will have different path length differences to the listener in the near field. Curved baffles and power tapering are used to reduce this effect. Also, placing the listener just before the near/far transition is vital.

Since they have limited vertical dispersion, placing them in line is the best bet, The near field to far field transition is given by the following equation:

d=1,5fH^2 (where f is frequency in kilohertz and h is the array height in meters)

For our particular pair of LAT-250s, the height is roughly 20 inches (.508 meters) and the intended crossover point is about 1khz. The transition to far field is 0.387 meters or about 15.2 inches. This means that our array is effectively a point source with a spherical wavefront at the listening distance at frequencies BELOW 1khz. The 6db spl decrease in volume applies here. 

Conclusion? I think the distance to the listening position should be far enough for the LAT-250s to sum properly since the transition from near field to far field already occurred for the particular bandwidth in question. To confirm, picture an array of 20 inches with 10 woofers 2 inches apart. Take a listening distance x and compare the path length differences with the center woofers and the outer woofers. For midbass frequencies, this ptd is quite minimal compared to the wavelengths. 

*See attachment for line array theory.


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## Patrick Bateman (Sep 11, 2006)

Fast1one said:


> That's a good question. Traditional line arrays have a maximum listening distance that is a function of their height (transition from near field to far field), where some benefits diminish*. This can be used as an advantage because if you listen in the near field the SPL decreases at a rate of 3db per doubling of distance instead of the traditional 6db. In the far field, they begin to exhibit characheristics of a point source.
> 
> They also have a minimum distance for the drivers to sum properly. This is function of the CtC distance, which appears to be quite small on the LAT-250, and the height of the driver. Driver's will have different path length differences to the listener in the near field. Curved baffles and power tapering are used to reduce this effect. Also, placing the listener just before the near/far transition is vital.
> 
> ...


That's really interesting! I'm kinda bummed that only two people downloaded the PDF 

I really despise line arrays, because all of the commercial ones make my ears bleed. I've heard the $100K Pipe Dreams as well as Jim Griffins arrays, and didn't like those either.

I've always felt that line arrays sound like crap in the nearfield, but never realized the transition from near-field to far-field is frequency dependent. (I always thought it was based purely on the length of the array. Didn't realize frequency was a component.)

The bottom line is that your post is a real eye-opener. It demonstrates why I do not like the sound of line arrays, but also demonstrates how we can make them better. Since the transition is frequency dependent, *you can get away with a much longer array at lower frequencies than at high frequencies.*

For anyone that didn't read the paper, here's an example of what I am talking about:

At the Seattle Seahawks Stadium, they have line arrays that are about 7 meters tall. Everytime I've listened to a show there I feel like blood is going to gush out of my eardrums at any moment  *The treble is atrocious.* I believe that this is due to the line array being far too large for the venue. So lets plug the numbers into the equation, and find out.

To my ears, the treble is especially offensive at 2khz. So let's figure out what the nearfield to farfield transition for a seven meter array:

_transition distance = ((array length ^2)*frequency)/2300
transition distance = ((7 meters ^2)*2000hz)/2300
transition distance = 42.6 meters!!!_​
Is that crazy or what? If you're anywhere inside of FOURTY THREE meters, the arrays at Seahawks Stadium are going to blow your eardrums out. It explains why i HAAAAATE the sound there, and why I hate arrays in general.

The curious thing about arrays is that I *have* heard them sound very good. For instance, Fort Vancouver in Washington has a very nice array set up, and some of the best sound I've ever heard outdoors. Fastone's post really helped me understand why that is, it's because I was listening to that set of arrays from a much further distance.

For future reference, here's a quick list of "maximum array lengths." This list makes the following assumptions:

We *don't* want to be in the nearfield.
The distance from the array to our ears is two meters
I've chosen an arbitrary transition of one meter. The idea is that we want the transition from farfield to nearfield to occur a full meter in front of our ears, for the best possible integration. (In the nearfield, frequency response is completely chaotic.)

Based on that, here's the maximum array lengths*:
*
10khz - 0.265M (0.87ft)
5khz - 0.374M (1.23ft)
2.5khz - 0.53M (1.74ft)
1khz - 0.837M (2.75ft)
500hz - 1.18M (4.2ft)
250hz - 1.67M (5.48ft)
100hz - 2.65M (8.69ft)
*






Here's a pic of the Pipe Dreams that I didn't like - you can see that it has an extraordinarily long tweeter line, much longer than theory would recommend. It may explain why I didn't like them, but also demonstrates that arrays may hold promise in the car.

* If anyone wants the equations, I took them from page 7 of "Line Arrays - Theory and Application." It's by Mark Ureda at JBL, and is freely available online. To generate the table I had to re-arrange Ureda's equation. Here's how I did it:

_nearfield to farfield transition = r
array length in meters = l
radiation frequency = f

r = ((l^2)*f)/700
l^2 * f = r * 700
l^2 = (r * 700)/f
l = sqrt ((r*700)/f)_​


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## fish (Jun 30, 2007)

I gotta ask something that's been on my mind for a while... 

How does one manage time alignment with arrays?


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## Fast1one (Apr 6, 2007)

Patrick Bateman said:


> That's really interesting! I'm kinda bummed that only two people downloaded the PDF
> 
> I really despise line arrays, because all of the commercial ones make my ears bleed. I've heard the $100K Pipe Dreams as well as Jim Griffins arrays, and didn't like those either.
> 
> ...


I'm glad my post was useful; usually you are the one enlightening me on the subject of audio 

I definitely agree with you that most professional line arrays are downright piercing from what I have experienced. I can't comment on home use arrays since I haven't listened to any other than the cheap ones I built (which sounded different, but not particularly horrible).

I suppose that is why I sit far back if I see a line array. If they are short enough, I can get far enough to reduce the effect of screeching highs 

You can make an array that spans from the kick panel to the center console under the dash and still have no issues with summing in the far field. Unfortunately the apparent acoustical center of each array will limit the width of the sound stage, BUT you gain a good amount of efficiency vital for this to work with small woofers.

Let's take it farther. Use the mounting scheme of the LATs (push push, face to face) and replicate it using sealed underhung small woofers. Unfortunately you are limited by the mounting depth of each woofer, but at least the distortion performance is well known  You can mount them all in one direction. In other words, the cone of one woofer will nearly touch the magnet of the other and so on. Two woofers share a common enclosure. The outer enclosures only have one woofer and should be sized accordingly

[]<[]<[]<[]<[]

Where "<" is a magnet and "[]" is the enclosure, lol. That particular example employs eight woofers. Mount them as tight as possible without the cone hitting the magnet at full excursion.


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## Patrick Bateman (Sep 11, 2006)

Fast1one said:


> I'm glad my post was useful; usually you are the one enlightening me on the subject of audio


Collaboration is good!



Fast1one said:


> I definitely agree with you that most professional line arrays are downright piercing from what I have experienced. I can't comment on home use arrays since I haven't listened to any other than the cheap ones I built (which sounded different, but not particularly horrible).


Back in 2004 I built an array, based on the internet hype, but abandoned the project after listening to about ten different "HiFi" arrays. So your post was quite interesting, because it seems to indicate that big tweeter arrays are a bad idea, but woofer arrays are good. Also, due to lobing, it seems like a "mirrored" array is the way to go. (IE, woofer-woofer-tweeter-woofer-woofer is good, T-W-W-W-W is bad.)







OB-7 Plus - OB-7 Plus
Also, my subjective evaluations correlate with the paper. Of all the arrays I listened to, only one was truly impressive, and it uses a single tweeter.



Fast1one said:


> I suppose that is why I sit far back if I see a line array. If they are short enough, I can get far enough to reduce the effect of screeching highs


As Winslow has noted a few times, all speakers behave like arrays. Even a single driver speaker. The cone itself behaves like an array of smaller drivers, bonded into a single unit. So it's good to understand the science behind them. My home speakers have a center-to-center spacing of eighteen inches, and I've definitely noticed that the treble is improved by sitting back as far as possible. And they're a two-way!



Fast1one said:


> You can make an array that spans from the kick panel to the center console under the dash and still have no issues with summing in the far field. Unfortunately the apparent acoustical center of each array will limit the width of the sound stage, BUT you gain a good amount of efficiency vital for this to work with small woofers.
> 
> Let's take it farther. Use the mounting scheme of the LATs (push push, face to face) and replicate it using sealed underhung small woofers. Unfortunately you are limited by the mounting depth of each woofer, but at least the distortion performance is well known  You can mount them all in one direction. In other words, the cone of one woofer will nearly touch the magnet of the other and so on. Two woofers share a common enclosure. The outer enclosures only have one woofer and should be sized accordingly
> 
> ...


I'm actually thinking of a different arrangement. I'll throw together a prototype and take some pictures, but here's the basic idea:

First, you take a couple of small drivers, like the 2.5" Peerless woofers, and you mount them face-to-back in a sealed sphere. 








Picture a sphere like this, but with the woofers face to back, one on each side.







The key to this "trick" is that the woofers have *no directivity whatsoever* at low frequencies. You can see this in the measured response above; it doesn't matter if the sphere faces up, down, left, right, whatever. Makes no difference. In face, the only thing that's going to affect the directivity and the response is:

The spacing between the various woofers
reflections

Because these "woofer modules" don't have directivity on their own, it gives you a lot of mounting options. For instance, I'd probably put one module deep under the dash, above the dead pedal. Then put another one wherever it will fit under the dash, perhaps a bit north of the kick panel. And then a third one wherever there's room...

Basically the push-pull arrangement of the woofers will reduce distortion. And the small size opens up a lot of mounting options. Then you would use simple trial and error to find the best locations.

Of course, I'd recommened doing polar measurements to choose the best combination of locations and crossover points. The "neat" part is that the direction of the spheres won't matter below 2khz or so. Based on some quick sims, here's what WILL matter:


Diffraction off the enclosure screws up the polar response, which is why you want to use a sphere to mount the woofers. The second best option is a cylinder, like the LATs use.
Comb filtering will be an issue, but it's dependent on the crossover point. You can simulate the effect with A.R.P.E., which is available for free from FRD Consortium. A good "rule of thumb" is to keep the modules within one half wavelength at the crossover point. (IE, with a 1400hz crossover, they should be within five inches of each other.)
You can "cheat" on the comb filtering problem by staggering the crossover points. For instance, you can run one module up to 1400hz, and the other two modules up to 700hz. By doing that, you can spread them ten inches apart safely. Again, check out A.R.P.E.

While I like the LATs, I think they'd be difficult to hide in my car. A series of spherical modules potentially offers lower distortion via the use of better woofers, and are easier to mount and hide. I think they look better than the LATs too.


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## jbholsters (Jun 17, 2009)

Any guesses as to why the horns in the GB sounded so go, even though the design was all wrong with the bend? And does that horn mouth in the article I posted look large enough to go down to 500 Hz?


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## Patrick Bateman (Sep 11, 2006)

Patrick Bateman said:


> For future reference, here's a quick list of "maximum array lengths." This list makes the following assumptions:
> 
> We *don't* want to be in the nearfield.
> The distance from the array to our ears is two meters
> ...




Thanks to the tip from Fast1one, it looks like we can get away with a horizontal array in a car. I didn't think this was possible a week ago - I thought the nearfield transition problem would limit us to a listening distance of about five meters or greater 

Apparently not.

I messed around with some sims, but kept coming back to a couple problems. I think I have solutions to them though.

The first problem is where to put the array. A horizontal array is actually better in this application than a vertical array, because a horizontal array has narrower directivity. At home, that's A Bad Thing, but in the car, it's exactly what we want. But putting one down low has a lot of problems. Due to reflections off the steering wheel, the driver, and the passenger, you really don't want to run them much higher than 500-1000hz.

As usual, the dash seems to be a better location. You can run the array full range on the dash, and it's easier to drive the car that way.









The array is a simple MTM, with two of these woofers flanking a tweeter.






My choice of tweeter is a very unusual one. The Tang Band W4-1805S is a "full range" driver, and an odd choice for a tweeter. The reason that HiFi tweeters are small is that large pistons beam, and large pistons roll off at high frequencies. The TB is a bit unique - it has output all the way to 20khz.* And it beams like crazy, but that's exactly why I used it. Because it beams, it reduces reflections off the windshield and the doors, without the use of a waveguide. Neat huh? 







Here's a simulation of the array's polar response. You can see that the directivity narrows above 3khz, and by 8khz the off-axis response is down by 18dB. This is intentional - the idea is to cross-fire the arrays, so that the *farther* array is louder than the nearer array. This centers the stereo image.**







I know that horizontal arrays are known to sound like crap. Here's why that is. This is a simulation of the *exact* same array as above, but I've moved up the crossover point. You can see that the crossover point makes a HUGE impact on the directivity and polar response of an array. The "good" sim is crossed over at 280Hz. We can't do that with a conventional tweeter - that's one of the reasons that TB full-range is so bad-ass.
The simulation above, with the terrible polar response, is crossed over at 2240Hz, like a conventional tweeter.


* Here's the frequency response of the TangBand full range:









** For more information on directivity and cross firing speakers in a car, read this:http://www.diymobileaudio.com/forum/diy-mobile-audio-sq-forum/60146-creating-perfect-soundstage.html
​​


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## Patrick Bateman (Sep 11, 2006)

fish said:


> I gotta ask something that's been on my mind for a while...
> 
> How does one manage time alignment with arrays?


All speakers basically behave like arrays, so the methods of doing time alignment are the same. You measure the impulse response of the tweeter, the impulse response of the midranges, then the woofers.

Then you line up the start of the impulse response as much as possible.

Once that's done you start playing with crossover slopes and phase, since all three items are inter-dependent.

I personally do not use time alignment, because the midrange and treble drivers in my car are less than two inches from each other. (Unity horn.)

Physically aligning drive units will always be superior to time alignment, because physically moving them fixes the problem at every point in the car. Time alignment only fixes it where the microphone is measuring.


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## Patrick Bateman (Sep 11, 2006)

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

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

Details are here:

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

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


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## benny (Apr 7, 2008)

Sounds like a midbass might be in order.


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## Patrick Bateman (Sep 11, 2006)

benny said:


> Sounds like a midbass might be in order.


If only it were that easy. There's a catch-22 in car audio. If you use a single midbass, you get polar response that's atrocious, due to strong reflections.

A midbass array seems to be a promising solution, but it's challenging to install them and keep the car "drivable."

A midbass horn controls early reflections, but you run into the same problem (nowhere to mount all the gear.)

I built a Unity horn last night that gets down to 200hz in a ground plane measurements. In the car I may be able to get it down to 150hz or even 100hz.

Efficiency appears to be about 96dB with a single $15 midbass. So an array of them, on the horn, might get me to 120Db or so with 50 watts per side.

That's not up to Grand National standards, but the integration of a Unity horn is rather amazing. So I'll give up 10dB for that.

Stay tuned - this is still in the early stages. It's literally a day old.


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## 75911 (Jan 27, 2010)

bradwood said:


> Patrick, this is awesome work you're doing!
> 
> Re the Peerless 830987 array, I assume you recommend bandpass filters - if so what settings? *Also, you say "wire all three midbasses in parallel, which yields a 2ohm load", how does this work with 2 pairs of 2 in the front and a single pair in the back?*
> 
> Apologies if this has been answered previously, keeping up with the thread is challenging ;-) Cheers


I'm sorry, I seem to have missed the answer to this,

if I need to read about it elsewhere please be kind enough to send me in the right direction


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## vactor (Oct 27, 2005)

updates??  eagerly awaiting ...


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## GlockandRoll (Oct 2, 2009)

Just got my ID Comp2 HLCD's in.. I cant wait to get started on the grand national!


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## Patrick Bateman (Sep 11, 2006)

75911 said:


> I'm sorry, I seem to have missed the answer to this,
> 
> if I need to read about it elsewhere please be kind enough to send me in the right direction


IIRC, the Peerless woofers have a DCR of 6ohms. So three in parallel yield a 2ohm load, which isn't a big deal for most amplifiers. And I use passive crossovers, so there's typically some resistance in series there, which raises things up another 10-25%.

As far as doing series-parallel loads, the total load is going to be dependent on which are in series and which are in parallel.

Check out some of the calculators from Car Audio 101, they work quite nice.


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## GlockandRoll (Oct 2, 2009)

BTW, what's the biggest mid/woof I can put in the factory concert sound II door pod?

I'm thinking a small basket neodymium 6.5 may fit, but the OEM mids are 5.25".


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## rawdawg (Apr 27, 2007)

I don't no nuthin' bout no Factory Concert Sound II door pod but I've seen 10's and 12's put into doors before. Of course, the doors were completely restructured. If you're lookin' to sort of replicate the GN, you might want to consider drivers bigger than 6.5...


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## GlockandRoll (Oct 2, 2009)

rawdawg said:


> I don't no nuthin' bout no Factory Concert Sound II door pod but I've seen 10's and 12's put into doors before. Of course, the doors were completely restructured. If you're lookin' to sort of replicate the GN, you might want to consider drivers bigger than 6.5...


Wait till you see what my very talented installer friend Garret is doing, I'm amazed at his work. This looks not only identical to the OEM door pods, but it's better and not restrictive of the sound. The buick guys are gonna **** when they see/hear this ride.


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## slvrtsunami (Apr 18, 2008)

good match and stealthy!!


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## LS2Ttype (Feb 13, 2011)

I have a set of boston Pros for the doors of my 87 Turbo T, and i might use a set of the pioneer TS-S062PRS 3" mid range speakers.

for the rear deck i have a set of the Boston 4.5 Pros that i would mount to a 4X6 plate, i also have a set of Infinity 4X9 Kappa plate speakers that i could use instead on the rear deck and try and squeez the Boston 4.5 Pros in the dash,

I like the 15" JBL W15 GTi MkII subs


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## LS2Ttype (Feb 13, 2011)

Glockandroll looks good! and i think your building a similar system that i want to do,, are you installing tweeters in the door?? anything in the dash?


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