# Line Arrays, Dipole And D'Appolito In Car Audio



## asawendo (Nov 22, 2009)

Regarding some great techniques in Home Audio like Line Arrays, Dipole and D'appolito also considering all the obstacles in Car Audio like dispersion, reflection and absorbtion. I wonder if anyone trying these in Car Audio with great success?

For your info I will be using small high quality fullrange 3 inch driver stacked in A-Pillar. The drivers itself are audience A3s from part-express 
Audience A3 3" Full Range Driver 296-220
with specification like these

Premium point source/line array driver
Patented and patent-pending technologies
40 Hz to 22 kHz response
12 mm Xmax
Low power-compression and wide dynamic range
Exceptional resolution and detail

Any input will be appreciated. Thank you and Best regards 

Wendo


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## asawendo (Nov 22, 2009)

Right now I'm using open baffle drivers consisting of Mundorf Tweeter 2440, Accuton Midrange C44 and Accuton Midbass C173-6-191 also B&W Subwoofer


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## miniSQ (Aug 4, 2009)

open baffle in home audio requires 2-3 feet of space behind and above the drivers. in order for the back wave to meld with the front wave...not sure this is a great option for autosound.


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## asawendo (Nov 22, 2009)

The Tweeter above actually is Dipoles design and I have been tweaking for a while in order to have subjectively "optimum" result.


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## asawendo (Nov 22, 2009)

miniSQ said:


> open baffle in home audio requires 2-3 feet of space behind and above the drivers. in order for the back wave to meld with the front wave...not sure this is a great option for autosound.


Yeah that is an obstacle because from my measurement the first reflection from mirror is so wild


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## asawendo (Nov 22, 2009)

But I'm very curious about it because it sound so diffuse and the drivers seems dissapear. From the driver seat image is palpable in the center of the dash.


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## miniSQ (Aug 4, 2009)

asawendo said:


> But I'm very curious about it because it sound so diffuse and the drivers seems dissapear. From the driver seat image is palpable in the center of the dash.


Life is short...go nuts!! I have heard good open baffle and its breath taking. I tried it in my house and was too close to the wall on L+R, and had a TV abov the open CC, and it was "less than breath taking" so i sold them.


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## asawendo (Nov 22, 2009)

miniSQ said:


> Life is short...go nuts!! I have heard good open baffle and its breath taking. I tried it in my house and was too close to the wall on L+R, and had a TV abov the open CC, and it was "less than breath taking" so i sold them.


Yeach The Breath taking experience was overwhelming when you heard properly open baffle design in home audio. Thx Bro.


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## asawendo (Nov 22, 2009)

My best friend told me in D'appolito application we don't just put two midrange and one tweeter in the middle. But in order to overcome lobing error, we must put them on axis. Then measured accurately the distance between driver and also the cutting point and slope of their crossover (usually 3rd order) to get the optimum effect.

It's very interesting for me...


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## miniSQ (Aug 4, 2009)

asawendo said:


> My best friend told me in D'appolito application we don't just put two midrange and one tweeter in the middle. But in order to overcome lobing error, we must put them on axis. Then measured accurately the distance between driver and also the cutting point and slope of their crossover (usually 3rd order) to get the optimum effect.
> 
> It's very interesting for me...


google GR Research and Danny Ritchie....he knows a thing or two about this...


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## asawendo (Nov 22, 2009)

miniSQ said:


> google GR Research and Danny Ritchie....he knows a thing or two about this...


Thx a lot Bro. I will searching for the information you gave.


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## asawendo (Nov 22, 2009)

After searching DIYMA I found interesting statement by Patrick Bateman in his thread http://www.diymobileaudio.com/forum...io-discussion/81244-space-final-frontier.html that said like this: 

"I believe that line arrays and dipoles offer some advantages in the car, and I'd like to explore them further. Kudos to Wehmeyer and Winker from JBL for cluing me in to these."

This is very interesting!


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## asawendo (Nov 22, 2009)

Werewolf also made interesting thread about this http://www.diymobileaudio.com/forum...r-audio-discussion/331-pillar-line-array.html

Quote from that thread

I kinda like line-array speakers ... or I guess more accurate to say I'm very intrigued by the possibilities. Mostly, I think, because they may be the best dynamic approximation to my most beloved Martin Logan CLS electrostats Wide horizontal dispersion, narrow vertical dispersion, rather loud listening levels with little diaghram movement, no crossover near the vocal range, etc.

Well I'm sure I'm not the first to consider building a line array of wide range drivers in the A-Pillars. But i'm thinking that maybe we now have access to the right technology to pull it off. Here's the issues, and possible solutions, as I see them :

1. Driver choice. Why, the Aura NSW2 Whisper of course Hats off to DS-21, and npdang of course, for advocating & pioneering the use of this little marvel in the car. Yes, it has higher-than-expected distortion (given it's large xmax) ... but it's mostly 2nd harmonic and, as suggested by DS-21, that ain't all bad ... at least for an old bottlehead like me. Plus, with enough of these little babies in an array, each driver works less for a given output level, minimizing the distortion. The energy storage near 2kHz, evident in the CSD/waterfall, may be more troublesome. I wonder how much EQ can help ... SL builds a little notch into his Pluto electronics ... not at 2kHz, but closer to 4.5kHz I think to tame a peak observed with the NSW2 mounted in the PVC pipe.

2. Midrange cavity resonance, behind the driver. I've always maintained that what goes on behind the midrange cone/dome is more important than what's in front. May need to drill vents in the A-Pillar, use good damping material, etc. to control that rear-wave from the Aura Whisper.

2. The A-Pillars are not vertical ... the top being much closer to the ear than the bottom. But here's where things can get really interesting We now have access to digital time delay technology ... not delta alignment in this case, but parallel alignment (Delta means different delays for left/right drivers, parallel means same delays for left/right drivers in order to align drivers in the same stereo channel). It's quite possible to give each driver, or, more economically, maybe each pair of drivers, it's own time alignment & amp channel. One can therefore delay the drivers, as you climb up the array, for matched arrival time. In other words, we build an electronic "delay line" into the A-Pillar array to compensate for it's non-vertical angle. Yeah it's possible to do it analog, even passive, but that Quad ESL63 wasn't built overnite, if you know what I mean 

3. Windshield reflections. Perhaps not as bad as one might think. If anyone labored through the ECA clinic thread, you'll remember that image theory tells us that you can model the reflection by placing an "image" or 'phantom" driver where the observed reflection is in the glass, then conceptually "remove" the glass, and get the same radiation pattern. In other words, windshield reflections really mean each side has two line arrays. This may wreak havoc on horizontal dispersion, but might also help attenuate the close array more than the far array ... which ain't all bad for combatting side bias.

Why bother? Simple ... I think we're always looking for ways to create a realistically HIGH stage in a car. No, I haven't heard the best kick panel cars in the world. But I've gotta agree with DS-21 on this one ... tonality & stage height are too often sacrificed at the pathlength altar. It's not a tradeoff to be taken lightly.

Anyway, congratulations npdang on a GREAT forum. Very helpful, informative, happy to be here. And I promise to stay out of any political debates


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## asawendo (Nov 22, 2009)

As my weapon I will be using multiple heavily modified custom digital room correction (build together with my best friend Masswork)


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## Wesayso (Jul 20, 2010)

I'll keep an eye on this thread, I hope you get this to work.
I'm building array speakers for my home but I am curious how they would do in a car. Too bad Lycan (Werewolf) isn't around anymore (as far as I know)


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## asawendo (Nov 22, 2009)

Wesayso said:


> I'll keep an eye on this thread, I hope you get this to work.
> I'm building array speakers for my home but I am curious how they would do in a car. Too bad Lycan (Werewolf) isn't around anymore (as far as I know)


Thanks for your support Bro. It will be difficult task but also very challenging ones


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## asawendo (Nov 22, 2009)

As an alternative for Audience A3s. Maybe I will considering some Visaton Fullrange driver like these one


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## Patrick Bateman (Sep 11, 2006)

asawendo said:


> After searching DIYMA I found interesting statement by Patrick Bateman in his thread http://www.diymobileaudio.com/forum...io-discussion/81244-space-final-frontier.html that said like this:
> 
> "I believe that line arrays and dipoles offer some advantages in the car, and I'd like to explore them further. Kudos to Wehmeyer and Winker from JBL for cluing me in to these."
> 
> This is very interesting!


I've heard some 'open back' speakers which sounded pretty good in the car.

Theoretically, this shouldn't work. As another poster mentioned, the early reflections from the windshield should create imaging cues which will collapse the sound stage. (IE, 'theoretically' the car is a crappy environment for dipoles.)









Here's what I *think* is going on here. Let's say you have a midrange up on the A-Pillar, like a lot of people are doing on this forum. Now you basically have a frequency dependent dipole. Because even though the enclosure is sealed, *it's energy will radiate backwards at the frequency where the sound waves exceed the width of the baffle.* For instance, with a 10cm baffle the sound will radiate backwards below 3400hz.


I can't imagine that a frequency dependent dipole would be a good thing. You basically have a few octaves where the sound radiates forward, and another few octaves where it radiates forwards *and* backwards. And in those latter octaves, you get a reflection off of the windshield.


In this type of scenario, a 'true' dipole may sound better, such as an unboxed midrange. You still have radiation forward and backwards, but the radiation is consistent throughout the entire frequency span. You don't have this strange situation where the reflections are frequency dependent.




Having said all that, I *still* think the best solution is to eliminate the early reflection as much as possible. (By using a waveguide, ideally one that's jammed so far in the corner it becomes an extension of it.)

But if you can't do waveguides, I think there's an argument for open back speakers, because the radiation pattern is more consistent, particularly for midranges.


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## Patrick Bateman (Sep 11, 2006)

asawendo said:


> My best friend told me in D'appolito application we don't just put two midrange and one tweeter in the middle. But in order to overcome lobing error, we must put them on axis. Then measured accurately the distance between driver and also the cutting point and slope of their crossover (usually 3rd order) to get the optimum effect.
> 
> It's very interesting for me...


When you put a midrange and a tweeter on a flat baffle, there is a lobe that's created that points *down*. IIRC, this lobe depends on the crossover slope. Basically, what this means is that a flat baffle with a tweeter and a woofer will have a listening axis that is below the speaker.

There are a few ways to fix this.

1 - slope the baffle backwards, which will take the lobe that points down, and move it up
2 - flip the entire speaker upside down. This will take the lobe that points down, and now it points up. This is why you see a lot of British monitors where the tweeter is below the woofer
3 - put a midrange above *and* below the tweeter. Now you have a lobe above *and* below the loudspeaker. Basically if you're head is in *just* the right place it can sound good. But you also get some directivity in the process; a midrange-tweeter-midrange array has directivity which mimics what a waveguide can do. (Waveguide is still better; it works vertically *and* horizontally, whereas you'd need four midranges and one tweeter to do what a waveguide can, and the waveguide would still have superior directivity.)


By far the easiest way to visualize this is with this program:

Ripple Tank Simulation










A ripple tank simulator lets you visualize the effect of two speakers radiating the same sound simultaneously, which is what happens at the xover point from a midrange to tweeter.


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## asawendo (Nov 22, 2009)

I'm happy you give me some clues for this project Patrick,

I know this is not usual instalation and I must concern about some early reflection and lobing effect. For your info my purpose is for single seater only not dual like yours. 

As for open back speakers, if I tuned in right and also a little bit rise my head I've got exactly center image with deep imaging as if I can see the whole musician from there. (This is exactly like you aforementioned before)

I think I will keep up to continue this project furthermore. Please give your valuable input. Thx a lot!


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## asawendo (Nov 22, 2009)

Here is the picture of Audience A3 Notice this type is dual voice coil and robust design


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## Wesayso (Jul 20, 2010)

Nice drivers, are you going to run an array of them? Or combine 2 of them with a tweeter in the middle...


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## asawendo (Nov 22, 2009)

Wesayso said:


> Nice drivers, are you going to run an array of them? Or combine 2 of them with a tweeter in the middle...


Maybe I will try Midrange Tweeter Midrange configuration first.


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## Woosey (Feb 2, 2011)

asawendo said:


> Right now I'm using open baffle drivers consisting of Mundorf Tweeter 2440, Accuton Midrange C44 and Accuton Midbass C173-6-191 also B&W Subwoofer


Wow what is that port design like on the last pic? Looks interesting...

Sent from my LT15i using Tapatalk


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## asawendo (Nov 22, 2009)

Yeah they are vortex dual ported design enclosure...


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## subwoofery (Nov 9, 2008)

asawendo said:


> Yeah they are vortex dual ported design enclosure...


Did you build the box? Wondering where one could buy those ports... Interesting design 

Kelvin


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## asawendo (Nov 22, 2009)

subwoofery said:


> Did you build the box? Wondering where one could buy those ports... Interesting design
> 
> Kelvin


My very best friend named Koex has made this custom special design just for me. He is maestro in transmission line and bandpass design, including the beautiful vortex port design

Here are another pictures:


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## hippopotamus (Sep 5, 2012)

will the vortex ported box will also sound good in a sedan ?
never see one in a sedan's trunk..


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## subwoofery (Nov 9, 2008)

asawendo said:


> My very best friend named Koex has made this custom special design just for me. He is maestro in transmission line and bandpass design, including the beautiful vortex port design
> 
> Here are another pictures:


Nice 

Kelvin


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## asawendo (Nov 22, 2009)

hippopotamus said:


> will the vortex ported box will also sound good in a sedan ?
> never see one in a sedan's trunk..


Hmm....in order to have optimum effect in small vehicle or typical sedan I believe you can have that vortex ported in your rear deck my friend and your enclosure still in your trunk.


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## asawendo (Nov 22, 2009)

subwoofery said:


> Nice
> 
> Kelvin


Thank you so much Bro...


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## Ultimateherts (Nov 13, 2006)

Can that vortex travel back in time too... Kind of trippy!!!


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## thehatedguy (May 4, 2007)

Kelvin, search for a spiral horn on the net.

Love the mundorf amt tweeters!

Down load a copy of software called "the edge." It will help show peaks and nulls from the open baffle.


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## subwoofery (Nov 9, 2008)

thehatedguy said:


> Kelvin, search for a spiral horn on the net.
> ^ thanks for the info :thumbsup:
> 
> Love the mundorf amt tweeters!
> ...


Kelvin


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## elpulpo (Feb 18, 2010)

B&W ought to make a sub with a port like that to mate with the Nautilus... Get a whole seashell family of speakers going.


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## asawendo (Nov 22, 2009)

elpulpo said:


> B&W ought to make a sub with a port like that to mate with the Nautilus... Get a whole seashell family of speakers going.


Hehehe that will be interesting....


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## Wesayso (Jul 20, 2010)

So how are you doing with these ideas? Any results?


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## asawendo (Nov 22, 2009)

I found that with Dipole configuration I have more ambience and more depth than before (with some trade off in terms of image focusing) But the advantage is I can listen in both seats (driver and co passanger) comfortably enough eventhough I adjust the time alignment solely on driver seats. 

But let me tell you something choosing the driver for dipole application is very very critical, that's why I chose Mundorf AMT and Audience so I can use their late reflection from the glass to my advantage rather than disadvantage. I also put the absorbing material in my dash to tame the nasty early reflection.


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## Patrick Bateman (Sep 11, 2006)

Over on diyaudio, a member posted some measurements of various loudspeakers in his room*. One of them was a mix of dipole and cardioid; the others are conventional design. (Ported, I believe.)

In the graph, notice how the bass from the 'coventional' design becomes very prominent below 200hz? And the dipole does not?

Now, obviously one could simply use EQ to 'cut' the response of the conventional box. And in fact, this is what processors like the JBL MS-8 do.

But here's something to consider:

The REASON that the bass becomes so prominent in the conventional design is because of reflections within the room. For instance, if I take a sealed loudspeaker and I place it 25 centimeters from a wall, then all of the sound below 170hz is going to be reinforced by the wall. The reason that this happens is because *the wavelengths are so long, when they hit the wall they reflect back and they're less than one quarter wave apart.* If the frequencies were higher they wouldn't reinforce; in fact they might even interfere. *But at these low frequencies, the reflection off the back wall does nothing but increase the sound that's already emanating from the woofer itself.* And if you wanted your speaker to sound really boomy, that might be a good thing. But that reflection is ALSO delayed in time. So it's not just making the speaker LOUDER below 170hz, it is also screwing up the transient behavior. (Because of the delay.)

Now the dipole radiation solves all of that pretty nicely; because the radiation from the back cancels out the radiation from the front. And that's why the low frequency response of the dipole, in the measurement above, is flatter than the conventional loudspeaker.

Not necessarily saying that dipoles are a cure-all, but they definitely help in that particular situation.

(* original thread is here: Aino gradient - a collaborative speaker project - Page 28 - diyAudio)


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## 14642 (May 19, 2008)

A super long excursion speaker operating as a dipole, endless amounts of power and plenty of low frequency boost from an EQ and we'd have subwoofers than don't require enclosures and we'd have far less difficulty with room modes...


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## asawendo (Nov 22, 2009)

Patrick Bateman said:


> Over on diyaudio, a member posted some measurements of various loudspeakers in his room*. One of them was a mix of dipole and cardioid; the others are conventional design. (Ported, I believe.)
> 
> In the graph, notice how the bass from the 'coventional' design becomes very prominent below 200hz? And the dipole does not?
> 
> ...


Yes the I have notice cleaner low frequency with dipole design. 

Patrick I also notice the blossoming imaging in dipole design in my car. Which is very good. Unfortunately that is not consistent from one recording to another. You have aforementioned this in your thread about ambiosonic and opsodis arrangement. 

Let's say they have both advantage and disadvantage. So it is very interesting for me to continue the experiment. 

Thank you for sharing your thought


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## asawendo (Nov 22, 2009)

Andy Wehmeyer said:


> A super long excursion speaker operating as a dipole, endless amounts of power and plenty of low frequency boost from an EQ and we'd have subwoofers than don't require enclosures and we'd have far less difficulty with room modes...


Hi Andy Wehmeyer, 

Very Interesting, what kind of subwoofer with super long excursion? Or what specification considered as super long excursion? It woukd be good to have that in my experiment...


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## anton-sa (Nov 24, 2008)

On the topic of subwoofer, i personally hate boom in a car, infact, at the risk of sounding negative, but there are not that many cars ive heard where i can say i like the subbass, to my ears, its often more of re-inforced midbass or lower mid-bass than anything else....

In my last build i by accident build the box (sealed) for the subwoofer, way way too big... i ended up with a subwoofer than was exceptionally strong 40hz---> 16hz. but above 40hz it was useless.

i left it like this as the midbass up front was strong so it worked well to extend the frequency. low-frequency extension and not re-inforcement.

in the time of that last install i did however forever battle with the "time" of the subwoofer, mid-bass / sub-bass cohestion was always a little out of sync...

x-ofer slopes time delay functions etc, and this also changed depending on frequency so finding the compromise setting was difficult.

i guess my point is, sometimes a design or a way of doing things simply just works because of "accident"....


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## Patrick Bateman (Sep 11, 2006)

asawendo said:


> Hi Andy Wehmeyer,
> 
> Very Interesting, what kind of subwoofer with super long excursion? Or what specification considered as super long excursion? It woukd be good to have that in my experiment...


Any subwoofer, or even a subwoofer array, is suitable for experimenting with this.

For instance, let's say you have a 30cm woofer and you just slap it onto a square baffle that measures 91cm x 91cm. The response is going to look like this:










At first glance, this response probably looks terrible. *The bass is rolling off at a furious pace, just as we would expect from a woofer that doesn't have a box.*

But here's another way of looking at it. If you add twelve dB of boost at 30hz, and a 6dB cut at 250hz, *this speaker will be flat.*

Now, obviously 12dB is a lot of boost. But there's no box! So the only thing stopping you from using four subs instead of one is space. And there's a lot of space on a 36" baffle.



















Legacy does it like this ^^ One driver buried in the magnet of another.









The problem with Legacy's approach is that it needs even MORE boost. In this case, you'd need 18dB of boost at 30hz to make it flat. (In the sim above I've made the baffle one quarter the size by reducing it from 91cm by 91cm to 45.5cm x 45.5cm.










For me, the most interesting thing about these BY FAR is that they're directional. I don't have any illusions that dipoles have any magical qualities; but the ability to AIM a subwoofer is pretty neat. For instance, picture having something like this Peerless under the dash of a car. Dipoles don't radiate to the side, so fifty percent of the reflections are basically AWOL. And rotating the subwoofer actually changes the sound.


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## minbari (Mar 3, 2011)

Patrick Bateman said:


> Legacy does it like this ^^ One driver buried in the magnet of another.
> 
> 
> 
> ...


wouldnt something like those legacies get a better bass response from simply making the baffle taller and wider? or would it not make much difference at bass wavelengths?


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## asawendo (Nov 22, 2009)

Now this become really really interesting for me...hmmm got to implement this soon...heheheheh


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## subwoofery (Nov 9, 2008)

Patrick Bateman said:


> Any subwoofer, or even a subwoofer array, is suitable for experimenting with this.
> 
> For instance, let's say you have a 30cm woofer and you just slap it onto a square baffle that measures 91cm x 91cm. The response is going to look like this:
> 
> ...


Wondering how you would manage to install a dipole subwoofer that has the ability to be directional (requires huge baffle) under the dash of a car? 

Kelvin


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