# whispers in the pillar



## Guest (Jan 24, 2006)

no, that's not texas slang for "whispers in the pillow"  

I'm still intrigued by the possibility of putting maybe a pair of Aura whispers in each A-pillar (four total) ... for a high, wide, coherent stage. Two in each pillar, for a little more output (if you know what I mean and I think you do  ). Now, a couple of the "immediate" problems can be quickly addressed. First, the little array can be augmented by a tweeter in the sail panel, to fill out the top octave or two. And time delay can be used to align the two mids in each pillar, for better "point sourcing".

But there's two things that still concern me, and I need some input :

1. The "enclosure" behind the Aura Whispers will probably be less-than-optimal. I can vent into the steel A-Pillar structure itself, to hopefully avoid nasty midrange resonance problems.

2. Any mounting of the whispers up high, augmented (of course) with a door-mounted midbass, may result in a stage that's pulled low in the lower midrange/upper midbass. It's my opinion, based primarily on the wavelengths involved as well as some experience, that separating the midrange and midbass by ~2 feet may be problematic unless the midrange can play down to ~200Hz. And the whispers just won't play that low  It seems that 300Hz might be possible with a real steep xover, but with a resonance of 250Hz, even a pair of whispers won't reach down as far as I'd like.

Thoughts? I know ... A-pillar experiments are pretty easy, maybe that's what I need to do.


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## xencloud (Aug 26, 2005)

I really like that idea! Especially for increased output, but I thought using multiple drivers for the same freq. range was a no-no. How would you go about setting that up properly to sound good?


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## Guest (Jan 24, 2006)

Multiple drivers in the same frequency range _is_ a no-no, if the arrival times from the drivers to your ears are "significantly different" in the frequency range they are playing ... as a general rule.

Consider the D'Appolito MTM array ... the symmetry creates zero lobing error on-axis. If your ear is at tweeter level, it's all good 

Also consider big line array speaker systems ... in fact, the new McIntosh array we just discussed. Sixty-four Aura whispers per side (crossed at 250Hz to the subs btw). The radiation pattern for line arrays is well-studied, and not necessarily problematic if the center-to-center spacing is small enough, distance to the listener is large enough, etc ... again, over the frequency range of interest.

But maybe the simple bottom line in this case is : the drivers will be _very_ close together, with time delay at our side to help  Heck, the whispers can be placed close enough together to create a better off-axis response than a six-inch midrange ... even without time delay


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## Thoraudio (Aug 9, 2005)

I thought I remembered reading something about congestion with line array's in the near field.... 

and which car? 

I experimented with these










in my Grand Am. (2" wide range driver, with proper enclosure). About .75 m on the left side and 1.5 or so on the right. Completely dragged everything to the left... but my TA was only rudimentary at the time... maybe with more playing around...


BTW, there is an active patent application for line arrays with small drivers at the base of the dash and windshield  found that when looking for the RF T15kw


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## Guest (Jan 24, 2006)

Hook me up dude! Send the patent application my way ...

I'm so sick of that damn RF amp discussion


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## racerraul (Jun 8, 2005)

I assume the driver of topic is the 2"...

I am actually considering the Hi-Vi B3N's in a MTM setup using Dayton ND20's. I hope to begin so testing with dash mounted pods & some a-pillar mock ups.

I was planning to begin with no TA... but it seems you are considering TA on each driver in the MTM setup or the tweets & mids. That make sense?

I want to be able to get as close to 250hz as possible and that is why I wasn't considering the Auras to begin with...


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## Guest (Jan 24, 2006)

... regarding path length differences (pld's), midranges in the pillars don't appear to be much worse than low, forward door-mounted midranges ... but, about 2 feet higher of course 

And certainly better than high door-mounted midranges, no?

In any case, I don't mind optimizing for one seat at a time, at the flip of a switch, since I don't compete


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## Thoraudio (Aug 9, 2005)

werewolf said:


> Hook me up dude! Send the patent application my way ...
> 
> I'm so sick of that damn RF amp discussion


now I'll never find it  

but here's one from THX to look at in the meantime. Application # = 20030219137


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## Thoraudio (Aug 9, 2005)

found it.

20050259831


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## Guest (Jan 24, 2006)

racerraul said:


> I assume the driver of topic is the 2"...
> 
> I am actually considering the Hi-Vi B3N's in a MTM setup using Dayton ND20's. I hope to begin so testing with dash mounted pods & some a-pillar mock ups.
> 
> ...


Just keep in mind the main virtues of the MTM array as you try to build one for the car :

1. Zero lobing error on-axis, no matter what crossover order or type is used. This is guaranteed by the vertical symmetry of the array, and it's the reason D'Appolito invented it (I've read his AES papers).

2. Limited vertical dispersion helps to reduce floor & ceiling reflections.

3. Increased midrange output, from two drivers, to help match high-sensitivity tweeters.

These virtues, especially the first, can go quite wrong ... horribly wrong, in my view ... if the array is not executed properly. "Two mids and a tweet do not an MTM make."

A while back we discussed an MTM array that attempted to maintain these virtues : a midrange in the upper/forward door, another identical midrange in the lower A-Pillar, and a tweet in between in the sail panel (behind the side rear-view mirror). The midranges are not precisley equidistant to the ear, but time alignment can help. And the reduced "vertical" dispersion can help with windshield reflections, becuse the "vertical" axis in this case is perpendicular to the windshield.

Might be worth an experiment or two ...


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## rutger j (Aug 1, 2005)

why not mount the midbass on top of the dash?
Firing up into the windshiled... and thus achieve a "corner-loading" affect...!!! 
Or at least get the time delays as close to each other as possible...

Just a thought...
Know it has been done in a car here in Sweden with good SQ result.

Sincerely
Rutger


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## TomT (May 19, 2005)

How would running a pair of Dyn Dome Mids in each kick panel play into this scenario? If I did that I would have to move my tweeters up to dash level (either top of dash or pillars/sail panels). Any guesses as to how it might sound. I have T/A via an Alpine 701.

Tom

Edited to add that the midbasses are in the mid to lower doors.


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## STI<>GTO (Aug 8, 2005)

Is the reasoning behind the MTM really just for more output? In the car environment are you really going to take advantage of this arrangement? I'm not arguing or nocking, I've been considering something similar. However, I cannot get two whispers and a tweeter in the pillars, so an MTM would have to go in the kicks. I could get a single whisper and a tweeter in the pillar though, and I could move my midbass to the kicks (which should allow a slightly higher crossover point on the whispers). Just trying to figure out which option is the best compromise.

Sounds like a fun project!


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## Weightless (May 5, 2005)

Any one have a link or two with any technical papers on MTM arrays? I am interested in this set up in my car. 

I just hooked up my whispers at home for a quick demo and I have to admit, they sound fantastic in the midrange...a lil lacking in the upper frequencies but very nice...I used norah jones' first album and b.f. and the flecktones live art album for listening material, and wow...they captured her voice really well and the banjo plucks on live art just jumped out at ya...these little guys have some good potential...


Justin


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## Guest (Jan 24, 2006)

I think I'll just watch this one all unfold  .

Cheers,

AJ

You with me Pallas?
http://www.zaphaudio.com/commonenclosuretest.html


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## Guest (Jan 24, 2006)

AJinFLA said:


> I think I'll just watch this one all unfold  .
> 
> Cheers,
> 
> ...


Thanks for your input AJ


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## Guest (Jan 24, 2006)

rutger ... I thought about a midbass in the dash to complement the Aura's in the pillars, but it may be difficult to securely enclose a strong midbass to play from, say ~80Hz to ~300Hz in the dash. I suppose one could just put a midbass in the dash to fill in an octave below the whisper cutoff, then allow a door midbass to go lower (until the sub xover) ... but that starts to look pretty complicated.

STI ... I try to be careful with terminology. Even though the little pillar array plus tweet in the sail has 2 midranges and 1 tweeter, I wouldn't call it MTM. Please check my earlier post again about the real virtues of MTM. But to answer your question, yes ... the reason for two whispers in the pillar would be output. Electronic delay would be necessary to help make the arrangement work ... in a way, this is the antithesis of MTM.

Wes ... thanks for the patent application number, I'll do some more research


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## xencloud (Aug 26, 2005)

I don't completely understand what kind of time delay is needed to make this work right. Could you elaborate a little? :blush:


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## Thoraudio (Aug 9, 2005)

If the two mids aren't in the same plane, they'll need to be matched with T/A.


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## xencloud (Aug 26, 2005)

Would this work at all if one is off-axis, and one is on-axis? My idea would put one in the front upper door area, and one in a gauge pod on the A-pillar. The tweet could go in the stock tweet pod right next to the side mirror betwen them.......that would actually be some kind of MTM setup.....


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## Thoraudio (Aug 9, 2005)

then you'll need to address phasing as well....


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## Guest (Jan 24, 2006)

> Thanks for your input AJ


Sorry Werewolf, I just figured myself and Pallas are swimming upstream with our design philosophies. I'll give you my input  . Using 2 auras at the same freq's will lead to massive lobing, even with phase alignment (at what point in space?). If you are determined to do this, a .5 way would be the better approach IMHO. Read that Zaph link I provided.
Using the 2nd aura below 400hz or so would minimize lobing and maintain a somewhat spherical wavefront. Double Sd where you need it the most. An MTM would provide greater SPL, but at the cost of SQ.


> Consider the D'Appolito MTM array ... the symmetry creates zero lobing error on-axis. If your ear is at tweeter level, it's all good


All would be well if our ears functioned as a microphone @ 1m in a tiny fixed point in space. The flat on axis _frequency response_ would be all that was needed. But we don't (or at least I don't  ). What we _hear_ is the _power response_ and its interaction with the environment. So massive lobing off-axis, aka, MTM, is certainly heard by our brains (or lack thereof in my case  ).
Our brains hear the speaker and they hear the room (or cabin in this case).
If the speaker is inherently uniform in its broadcast of power, our brains will still perceive it that way, regardless of the cabins "sound".
There is still lobing when 2 seperate point sources interact, but thats a whole different story for another time. So is minimizing the cabins effect from early reflections.
Basically what I'm saying is that I think the MTM concepts is ok if you are looking for the typical car type setup, screaming loud first, than SQ, what SQ? Unless of course loudness _is_ your foremost criteria for SQ.
BTW, Mcintosh makes some of the poorest sounding speakers I have ever heard, see my previous sentence for their design principles.


> in my Grand Am. (2" wide range driver, with proper enclosure). About .75 m on the left side and 1.5 or so on the right. Completely dragged everything to the left... but my TA was only rudimentary at the time... maybe with more playing around...


Thor has obviously never discovered the "Balance" control.

Raul, if you a going to do something that big on the dash with 2 drivers, why not use a larger single driver (or a coaxial ideally)? Sd increases exponentially with dia. If you must use 2 B3N's, at least consider a .5 way. Unless you enjoy lobing also  .
My lunchtime 5 cents  


Cheers,

AJ


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## xencloud (Aug 26, 2005)

Sorry for another noob question, but what's a .5 way?


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## Guest (Jan 24, 2006)

AJ, now that response is appreciated!

But, 2 Aura's side-by-side will have no more lobing problems than a single 4" midrange. After all, a single driver is nothing more than multiple drivers, very close together, in phase, in the same plane. So if a 4" midrange has "massive" lobing, then I suppose two whispers side-by-side will also  However, with separate drivers, one can use time alignment to "steer the lobe" ... which is not possible with a single radiating surface.

Regarding balance control ... yes, that will help with the treble, where the ear is sensitive to only inter-aural intensity differences (at wavelengths much shorter than the distance between the ears, the ears can _only_ detect intensity differences, rather than phase or time). But in the critical midrange, balance alone will not improve localization ... at least, not very effectively. Time (or phase, if you will) differences as well as intensity differences are significant in the midrange.


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## Guest (Jan 24, 2006)

Oh ... AJ, you asked "what point in space"? Yes, time alignment does offer an optimization for localized points in space. But, given all the sonic nasties in the car, _one_ thing we've got in our favor is pretty rigidly-controlled listening positions. In fact, I don't mind optimizing separately for driver and passenger ... so in my case, I've got a _very_ well defined listening position for optimization. Perhaps some listeners want a stage optimized over a wider audience, but I don't find myself wandering around the listening space very often inside the car


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## Guest (Jan 24, 2006)

More thoughts on MTM ...

It seems to me that , with a true vertically-aligned MTM array, lobing in the horizontal plane is no worse than a single midrange. In the vertical plane, however, "massive" lobing _does_ occur ... you don't have to get too far off-axis vertically before the widely separated midranges conspire destructively. But, that's not all bad ... it _can_ help reduce floor and ceiling reflections ... or, windshield (or other boundary) reflections in the car, if executed wisely 

In my own experience however, I do find my ear highy sensitized to the vertical listening position when enjoying well-exectued MTM arrays. Vertically, even an inch matters when listening to well-executed MTM arrays.

I keep using the phrase "well executed" because I've seen (and heard) plenty of "imposters" ... MTM alignments on floor standing speakers where the tweeter is _far_ displaced (vertically) from any listener's ear (with no electronic refinement for steering the lobe), for example. I suspect there has been a "marketing bandwagon" over the MTM hype, with no recognition of it's true merits and weaknesses.


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## honfatboy (Jul 4, 2005)

Thoraudio said:


> I thought I remembered reading something about congestion with line array's in the near field....
> 
> and which car?
> 
> ...


I have that same set. I like them quite a bit for $40 at Wal-Mart.


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## racerraul (Jun 8, 2005)

Well... having spanish as my 1st language I quickly had to research the definition of lobing & what is meant in the audio world...

Well thanks for the education guys... cause quite frankly I never thought of the potential problems 2 equal drivers side by side playing the same frequencies would have.



AJinFLA said:


> Raul, if you a going to do something that big on the dash with 2 drivers, why not use a larger single driver (or a coaxial ideally)? Sd increases exponentially with dia. If you must use 2 B3N's, at least consider a .5 way. Unless you enjoy lobing also  .
> My lunchtime 5 cents
> 
> 
> ...


AJ...

I was considering the 3" drivers because I wanted smaller drivers to work with. But after some measurements, the dual 3" drivers & tweeters aren't that much easier to fit on my dash than the RS125 & RS28 (without the face plate). I can take pics of the templates for the baffles if anyone is interested.

Just to let you know... I have not completely given up on my Dayton Drivers.

Interestingly enough... the coaxial idea is what I started out with.... but for the mid that I want to use (RS125) I would need NPDANG's tweeter or something with a small footprint that can be xOver around 2khz. (The scan 2904 is too expensive)

Other than that, I have not found coaxials in the raw market that interested me (I want to keep all the drivers xOver active). I am open to coaxial driver sugestions that aren't going to cost an arm and a leg...

Werewolf... considering your last post... I am trying to see what the baffle for the dual 2" whispers + ND20 tweeter would look like. But am a little concerned with the whispers no being able to handle much below 500hz when you take into account road noise.


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## Guest (Jan 24, 2006)

yeah ... it remains my biggest concern, that the whispers just won't play low enough to blend "seemlessly" with a door-mounted (or kick-mounted) midbass.

But I still maintain that two drivers of diameter "x" playing side-by-side will cause no worse lobing problems than a driver of diameter "2x" ... in fact, along one dimension the lobe will be significantly _better_ 

And, as already suggested, you have flexibility to "steer the lobe" with the two "x" drivers ... something that's impossible with the single "2x" driver


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## Thoraudio (Aug 9, 2005)

honfatboy said:


> I have that same set. I like them quite a bit for $40 at Wal-Mart.


I bought them when they first came out for $100 at a comp usa. And up until I bought my WR125's I'd say they were the best $100 I've spent on audio equipment. But the cheap volume pot went bad, and I set them aside for a couple of years, until I figured out that they were 4 ohm satellites, and I started using them as test mules for speaker placement in my car.


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## robert crumbley (May 1, 2005)

can someone explain lobing and axis, please?


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## Guest (Jan 25, 2006)

Wow, not sure where to start here.
Xencloud, you really must follow the links I provide  . In the case of the drivers in question, the Auras, a .5 xo would use one driver fullrange. The second driver would operate strictly below for example 400hz, so it would only add to the spectrum where lobing is a non-issue. _Both_ would operate between 2-400hz, unlike a normal cross over, wher each driver only produces seperate parts of the spectrum. Here is an example of a 2.5 way: http://www.zaphaudio.com/Waveguidetmm.html. The idea of crossing a tweeter to another tweeter (the dayton) seems rather uneccessary to me.

Werewolf


> But, 2 Aura's side-by-side will have no more lobing problems than a single 4" midrange.


This is incorrect! Interference also gets progressively worse as frequencies rise. The Auras are basically large tweeters. Some basics:
http://www.glenbrook.k12.il.us/gbssci/phys/Class/light/u12l3a.html
http://www.walter-fendt.de/ph11e/interference.htm
http://www.logitech.com/index.cfm/products/details/US/EN,CRID=2173,CONTENTID=9066 FDD2 is probably a fancy name for an inductor  .
Two adjacent drivers producing the same frequencies is an awful idea unless its bass, but don't let me or physics stop you if you must experiment.
Same with MTM: http://www.birotechnology.com/articles/VSTWLA.html
Again, dont let me stop you if you are determined to do so.
A small fullrange or better yet, coaxial, 250hz on up with directivity control (mainly as much damping as can be reasonably used to shape the response) would be _much_ better.
Midbass in door below 250. As I said before different strokes for different folks.


> I was considering the 3" drivers because I wanted smaller drivers to work with. But after some measurements, the dual 3" drivers & tweeters aren't that much easier to fit on my dash than the RS125 & RS28


An RS125 on the dash  . Raul, what do you drive, a schoolbus?  .
You are planning to use an enclosure correct? Dipoles might work in a schoolbus actually  .
Seriously, a good 3.5 - 4" coaxial would do. Aesthetics? I'll let you decide your priorities. Unfortunately in that range, the neo drivers (better size) available like the Aura NS3 or TB's are good but not great. KEF makes a nice 80mm coax and the Infinity Kappa 3.5 looks interesting also. I know most here would probably frown on it, but raise your hand if you've heard or better yet measured them. I wouldn't be suprised to find shorting rings in the neo motor or that they were at least as good as the Aura/TBs. Hard to say for sure of course. I'd like something with SEAS Excel or SS type quality, but I have yet to see it.
I'll find something eventually  . FYI, yes, NP's tweeter _is_ slated for a coax project of mine, just not a car one.

Cheers,

AJ

edit: quick addition: http://www.meyersound.com/products/mseries/m3d/line_array_theory.htm


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## Guest (Jan 25, 2006)

AJ, with all due respect, you're missing something very fundamental.

Yes, I understand very well the interference pattern of two point sources, separated in space, playing the same frequency. I've derived ... and taught ... the mathematics on several occasions 

But guess what?

*Any single driver, with non-zero cone area, is nothing but an array of point sources physically separated in space.

The reason any driver presents a lobing pattern as frequency increases is because of the constructive & destructive interference of all the tiny little point sources on the cone playing the same frequency.*

That's why the lobing pattern depends fundamentally on : frequency & cone area 

What do you think is really, _fundamentally_ different about a single 4" driver, and a very compact array of 1", or 2" drivers? Think about it ... as the tiny drivers get closer together, the little array becomes indistinguishable from the larger driver. A big cone area, all moving in phase, playing the same frequencies. NO DIFFERENCE.

Now, it certainly depends on how close the little drivers can get. But the bottom line is this : the lobing can't be any worse than a driver of the same _total_ diameter. But the little drivers present a unique opportunity that a single driver doesn't : lobe steering.

Maybe think about it this way : any driver of , say, 4" diameter can be considered to be an array of 2" (or any size you care to choose) cone pieces in _very close_ proximity ... in fact, right next to each other ... all playing the same frequencies at the same time. Any linear mathematical analysis allows such decomposition!! 

A small Aura array, which allows drivers to be in very close proximity, can be no worse.


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## Guest (Jan 25, 2006)

I know, we tend to think in "rules" like, for example ... 2 tweeters is always a bad idea! 

So here's a quick quiz :

Let's say we're only worried about lobing ... not total output power, linearity, etc. What's worse :

1. A single tweeter, of 1" dimeter.
2. Four tweeters, each 0.4" diameter, spaced so closely together that the maximum diameter in any dimension is 0.9"

Which has the better off-axis lobing pattern as frequency increases?


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## Guest (Jan 25, 2006)

Can you show me an example (paper,etc.) of this single driver (quasi-point source) lobing you are refering to, like the links I provided for multiple driver lobing?
Thanks.

AJ

why are 2 tweeters a bad idea as you say, what reason?


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## Thoraudio (Aug 9, 2005)

AJinFLA said:


> why are 2 tweeters a bad idea as you say, what reason?


comb filtering.


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## Guest (Jan 25, 2006)

AJ, don't you agree that the off-axis response of any driver drops as frequency increases? The fundamental cause of the polar response is the exact same thing as lobing : multiple drivers playing the same frequency  As Wes said, it's variations of the same thing. We might call it polar response for a single driver, and lobing for multiple drivers ... but it's fundamentally the _exact same thing._

Now wait ... why would a _single_ drive exhibit the off-axis response of _mulitple_ drivers, closely spaced? Simple ... a driver of any non-zero area is identical to a tightly-spaced array of smaller drivers. In other words, any _single_ driver already _IS_ an array of smaller drivers 

The fundamental calculus of surface integrals displays this concept wonderfully. Any finite area can be considered the sum of smaller, physically separated areas ... that only stands to reason, based on simple geometry. Calculus of course takes this concept "to the limit" (pun?), allowing each small area element to become vanishingly small.

What ultimately matters, either in polar response or lobing calculations, is the physical separation of the "point sources" involved and the frequency simultaneously being played (and relative amplitudes and phases, if a crossover network is involved). Those point sources may be physically distinct, separate drivers ... playing the same frequency through the crossover (but perhaps different amplitude and phase) ... or, they may be points on the cone of the _same_ driver ... playing the same frequency, at the same amplitude and phase.

Don't know how quickly I can find a link ... doesn't it make sense?


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## Thoraudio (Aug 9, 2005)

interesting... is this why beaming is an issue with larger diameter drivers playing high frequencies?


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## Guest (Jan 25, 2006)

By the way, the quiz answer is of course #2. Four tweeters will exhibit less lobing than one, if the "one" has greater diameter than the combined "four."

The take-away is this : you _never_ have a single driver playing _any_ frequency. What you do have, is a large number of point-sources distributed, and physically separated, over the surface of the cone


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## Guest (Jan 25, 2006)

Thoraudio said:


> interesting... is this why beaming is an issue with larger diameter drivers playing high frequencies?


Of course 

You know, radar science has of course known this for a long time  (Hell, Archimedes knew it too ... you guys know there's now strong evidence that Archimedes invented integral calculus?). Wes mentions a good word : beaming. A large diameter driver will "beam" as frequency increases. However, if you approximate the large diameter as an array of smaller drivers (I say approximate, because you can't get the drivers to a spacing of zero, but close enough for useful purposes), an interesting opportunity arises : "beam forming", and "beam steering" ... by electronically delaying the array elements 

Beaming, lobing, polar response ... all the same stuff, fundamentally : physically separated point sources, playing the same frequency, constructively & destructively interfering at different points in 3-D space.


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## Thoraudio (Aug 9, 2005)

this would have no practical application, and would be uber costly to implement, but you could do some really neat things with * type radiating pattern of small drivers, and a serious DSP to do some steering.... 


but back to practicallity. w/out digging through the windshield thread over at ECA, where's the diameter vs. frequency number where comb filtering becomes an issue?

How high can we play an arrayed pair of whispers?


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## Guest (Jan 25, 2006)

> comb filtering.


Correct. That was my point.

Perhaps Werewolf doesn't consider lobing and comb filtering to be related: http://www.prosoundweb.com/install/cpm/lobes/lobes.php
Please also show me your definition of what you are calling lobing, not _tell_ , _show_ , like my examples.


> By the way, the quiz answer is of course #2. Four tweeters will exhibit less lobing than one, if the "one" has greater diameter than the combined "four."


Again, could we see some evidence for this assertion? Please take your time, no hurry. I would love to see some research papers where this is shown.
Please also provide one that shows that an independent single driver will have comb filtering and lobing like 2 seperate closely space sources. Like the Auras you suggested. Thanks.

Cheers,

AJ


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## Thoraudio (Aug 9, 2005)

did you completely miss the part where he said comb filtering, lobing, and beaming were all related? 

All of those have to do with frequency in relation to the diameter of the driver(s). Get the drivers close enough together, at a low enough frequency, and they act as one. That's the reason alot of large format home speakers have multiple low and mid drivers, but only 1 tweeter. Because the spacing necessary to avoid the combfiltering is increasingly small.

but multiple midrange drivers can be used effectively, because the wavelengths are longer, so the spacing isn't as tight.


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## Guest (Jan 25, 2006)

And did _you_ miss the part where he is saying use 2 Aura TWEETERS side by side?
Did _you_ miss the part where is _ME_ that said that lobing is a non issue at low frequencies.
Did _you_ miss the part about presenting a shred of evidence?
Get a clue what your talkiing about kid and then post.

Cheers,

AJ


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## Guest (Jan 25, 2006)

AJ, please use your brain and think, rather than relying on internet links.

*ALL of these issues are the same fundamental, physical effect : beaming, lobing, polar response. They are are evidence of multiple, physically separated point sources, playing the same frequency, adding constructively & destructively at various points in 3-D space, as the pathlengths (and therefore arrival times) vary.*

The destructive interference is a function of : frequency, and physical separation of the point sources. In one physcial dimension, we call the resulting frequency repsonse "comb filtering", because the frequency response resembles the teeth of a comb.

Physical separation of the point sources can take a couple different "forms". It may be, the separation between physically distinct midrange drivers in an MTM or line array. Or, it may be the physical separation of the points on a single cone. Why would you believe these to be _fundamentally_ different?

Do you really need a link to demonstrate that any finite area may be considered to be a sum of smaller areas? And those smaller areas will give an aggregate acoustic response that is equivalent to the acoustic response of the larger area?

What could possibly be the physical reason why several smaller, physically adjacent areas would NOT behave identically to a larger area, equivalent to the geometric sum of the smaller areas? Assuming, of course, that the smaller areas are are playing the same frequency, at the same amplitude and phase.

In engineering, we call this principle SUPERPOSITION. It's a powerful tool, that simply says (in this context) that the whole will behave as a sum of the parts.

Let's try this : do you agree that it's valid to consider a large cone to be "made up of" several smaller cones, all playing the same frequency, with the same amplitude and phase?

By the way, two 2" whispers side-by-side will, of course, start to beam (along the longer axis) sooner, in frequency, than a single 2" whisper. No doubt about it! But they will not beam (along the long axis) sooner, in frequency, than a 4" midrange. Why would that be hard to believe? Because of the "multiple drivers = bad" rule?


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## PlanetGranite (Apr 12, 2005)

I think the initial goal may have gotten lost in translation. The 2 Auras were to be used as midranges, not tweeters, and the lobing (comb filtering) of the two mids was going to be used to help control reflections from the windshield?

Yes, No?


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## racerraul (Jun 8, 2005)

Thoraudio said:


> How high can we play an arrayed pair of whispers?


I would shoot for 5khz or 6khz to avoid Comb Filtering.


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## geoffire (Oct 21, 2005)

Hmm all this reminds me of the threads I posted about a month ago most people ignored...  

http://www.diymobileaudio.com/forum/showthread.php?t=1867 

My plan was two TB 2"ers and a nd20 in the A pillar. I was hoping to have them all on the same vertical axis from the listeners (same distance from the listener), but after making the baffle I found it was impossible to do without taking up more space and beeing closer to me than a 3" (or even a 4") would have, and therefore was pointless (one b3n has less distortion at 300hz than 2 tb 2"s). 

Think about the distance from each driver center to your ears. If one is farther away than the other, you going to have issues a MTM Does not have.

I agree with AJ, a .5 setup is the way to go if your attempting this. trying to use time allignment IMO would create a "sweet spot" but everwhere else will be in disarray. I don't think its a good idea at all. 

At the time I didn't want to cut the dash, but now that I've hacked the doors all apart I don't really care... My current plan is a b3n on the dash firing up and a nd20 in the A pillar. When the diyma tweeter is released, I think I'll move to it in the A pillars and the rs125 in the dash. Those mated to 10" hf's in the doors will be quite the sound stage


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## Thoraudio (Aug 9, 2005)

AJinFLA said:


> And did _you_ miss the part where he is saying use 2 Aura TWEETERS side by side?
> Did _you_ miss the part where is _ME_ that said that lobing is a non issue at low frequencies.
> Did _you_ miss the part about presenting a shred of evidence?
> Get a clue what your talkiing about kid and then post.
> ...


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## xencloud (Aug 26, 2005)

Can someone explain or give me a link as to what a .5 system is?


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## Thoraudio (Aug 9, 2005)

I _think_ its a shortening of 2.5 way, which is another term for MTM or D'appolito or a system with 2 mids and a tweet (even if they're not in MTM alignment).


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## geoffire (Oct 21, 2005)

a .5 is the term when one of the mids only plays the lower frequencies. Ever heard of baffle step compensation? Its kind of the same idea, with the added benifit of higher efficiency and more output, but your having two woofers instead of one, so thats to be expected...

In this case I'm advocating its use because the 2"ers (at least the TB's I tested) are plenty loud and distortion free 1K up, but below that they could use the help of having two. But having two in the higher frequencies will (possibly) result in negative effects.

So the .5 setup is having one driver full range(between the crossover points at least), and the other playing only the lower frequencies (maybe 1K down) - this could be accomplished with a single capacitor and some equalization, so I don't see the big issue...

Edit - look at page 4 for AJ's post, he explains it much better than I do and has good links...


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## xencloud (Aug 26, 2005)

^^so say I have an 8" woofer in the door, 2 mids, and one tweet......on one of those mids you have it crossed from say, 400hz to 6khz, and the other you'd have crossed say, 400hz to 1.5khz? 

Do I have that concept correct? Isn't that kinda like a 4way system? I thought having less crossover points in a speaker system is better overall for SQ?


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## geoffire (Oct 21, 2005)

you have the idea. I would probably run the two mids off the same amp with one having a capacitor (passive 1st order [email protected] or even lower) in line to it, and use your normal active crossover with [email protected] and [email protected] they are 8ohm drivers, so I think that would work fine with a little bit of eq work.

That way you won't need another active crossover, just the added capacitor.


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## 300Z (Mar 20, 2005)

With all this talking it got me thinking... using the Whispers and that JBL processor?  sounds like a plan? now the question is, would the power from the processor be enough to power the whispers?

Leo


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## Guest (Jan 26, 2006)

I can see this is going nowhere.
Werewolf, by all means, use 2 Auras in a "little array" crossed to a tweeter in the top octave. Please do. Should sound great to your ears.
Try the same drivers in a MTM too. I'm sure you will like it. Do post some polar response measurements if you get a chance.



> I would shoot for 5khz or 6khz to avoid Comb Filtering.


Raul, try exactly that and see what happens.

Xencloud. You have two 8's and one tweeter that you want to cross at 1.5k.
You use one 8 crossed at 1.5k with the tweeter. You cross the other 8 _below_ 400hz, so _both_ 8's are playing below 400hz. Thats a 2.5 way. Got it?

300Z. What JBL?

Cheers,

AJ


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## Guest (Jan 26, 2006)

No thanks AJ ... I'll pick the *other* option from my un-edited first post in this thread, and use 2 Aura Whispers right next to each other, as *midrange* drivers, crossed over to a *tweeter* for the last *two* octaves. Given the physical orientation flexibility of the array ... namely, ears _not_ along the long axis ... plus electronic lobe steering (also mentioned in my first post), I doubt I'll have much difficulty running it to ~4kHz 

I llike to use my ears _and_ my brain


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## 300Z (Mar 20, 2005)

AJinFLA said:


> 300Z. What JBL?
> 
> Cheers,
> 
> AJ


JBL processor thread at CarSound  

Leo


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## rutger j (Aug 1, 2005)

werewolf:

two ideas 

1.
why not test two Trius´s on top of the dash out in the corners, firing up into the windshield?
*edit - That´s four in total...
This was a set up I was thinking about...and complement them with 10" in the kickpanels...
Trius´s would be hp @ ~140-160hz/24db
Subs/midbass would be bp @ ~0hz-140-160hz/12 or 24db
No tweeters.
And the car would be a BMW 535 -92 (E34)

2.
the midbass (6,5"?) that is on top of the dash, firing upwards, could be mounted in an aperiodic membrane.
Another Swedish car (built by tha same Team as the other car I mentioned) put the Sony XES 6,5" midbass/woofers like this, in an ap membrane on top of the dash firing up into the windshield with good results.

It CAN be done my friend, all it takes is som effort and time  

IF You try the first suggestion, please let me know the results...unlike some other happy fellas I only own one pair 

Sincerely
Rutger


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## Guest (Jan 26, 2006)

Rutger ... good ideas, and I appreciate they've been done with success. But holy cow, that's a lot of custom dash work! Especially for someone "fiberglass challenged" like myself !

By the way, it occurs to me that I haven't acknowledged AJ's good idea, about crossing over to fewer (like one) midranage drivers in the array as frequency increases through the upper midrange. It IS smart AJ, and any decent processor that allows time alignment of the separate drivers in the array, should also offer such crossover flexibility. My apologies ...


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## racerraul (Jun 8, 2005)

AJinFLA said:


> Raul, try exactly that and see what happens.


AJ,

At $65 for the 4 whispers it is a rather inexpensive experiment. With all the info available from this thread, I will put it all to the test when I begin. If it works great... if not then I am back to waiting for the DIY tweet to be released for my coax setup using an RS125...


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## Guest (Jan 26, 2006)

*D*o *I*t *Y*ourself should be full of experimentation. All part of the learning experience. I've been at it for 15+ yrs and still have much, much to learn.

300Z ,LOL Logic 7. I've been using that at home with my HK since back when SL recommended it








just for rears of course. No center.

Car version sounds interesting. Everything that I have been recommending has been for driver seat only style imaging. With that sort of processing, if you can use a center, should be quite good. I'd like to here it.

Cheers,

AJ


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## 300Z (Mar 20, 2005)

That processor seems like it will be exactly what i need... But i'm not sure about the Logic 7... i only have room for a front stage, maybe some rear speakers powered by the processor, but i'm not sure i want to go that route... i have never heard a setup using Logic 7 before, so i may change my mind once i try it with that processor...


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## Guest (Jan 27, 2006)

Sorry 300Z,

I probably wasn't clear. Thats SL's setup. In my home, I only used the rears, no sides.
Right now I use no rears in my car. Just fronts. The JBL might change that  . You should be able to get away with using only 4 in a car also. You don't "hear" the rear or side channels. It just adds dimension to your front stage. You really only "hear" them when you turn them off  .
SL explains what the requirments of the surrounds are http://www.linkwitzlab.com/surround_system.htm Basically 2 decent midbasses in your rear deck should work well. They really _need_ to have decent bass, no problem in the rear deck, but the sides? I'd love to see how JBL does it.

Cheers,

AJ


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## 300Z (Mar 20, 2005)

AJ, thanks for the link... good reading material... 

Regards
Leo


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## Guest (Jan 27, 2006)

So ... those with Aura whisper experience, what have you done _behind_ them for use in the midrange (above Fs, of course)? Enclosure, stuffing, deadening, etc?


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## imlikinthebass (Feb 8, 2006)

werewolf said:


> So ... those with Aura whisper experience, what have you done _behind_ them for use in the midrange (above Fs, of course)? Enclosure, stuffing, deadening, etc?


just got my whispers and id like to know this too. thanks.

RJ


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## kappa546 (Apr 11, 2005)

i'll be working on my install this weekend. we'll see how a pair to each pillar with an lpg 26na turns out


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## dwk (Feb 3, 2006)

werewolf said:


> So ... those with Aura whisper experience, what have you done _behind_ them for use in the midrange (above Fs, of course)? Enclosure, stuffing, deadening, etc?


I haven't played with them too extensively, but on the Madisound or PE boards a bit of a stir was caused by Zaph's test showing the problem at ~1.5kHz. Someone from Aura posted and suggested one or two layers of 1/8" felt carefully attached to the back of the driver to damp the cavity resonance.
I'm not sure about enclosure though.


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## Guest (Feb 9, 2006)

thanks dwk ... gotta link? i'm lazy


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## dwk (Feb 3, 2006)

Start here and you can trace the thread from there.
http://www.madisound.com/cgi-bin/archive_discuss.cgi?read=358467

'Donald North' is the aura guy, his initial recommendation is here
http://www.madisound.com/cgi-bin/archive_discuss.cgi?read=358492


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## npdang (Jul 29, 2005)

I'm somewhat skeptical that it's a cavity resonance, since there is really no cavity to speak of. The back of the driver is fully unenclosed. 

I'd love to see a link too


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## npdang (Jul 29, 2005)

Ok, N/M


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## Guest (Feb 9, 2006)

Hi NP,

I recall the discussion on Mad about this. I'd tend to believe Donald North on this one. I've corresponded with him before about one of his designs http://www.dnaudio.com/DNA Speaker.html. Good guy. Likes dipoles  . If you look at Zaphs data you can see it clearly. Right around (1.8-2.8k ish) where you would expect to see a 1/4 wavelength resonance given the depth of the cavity.










Now look at SL's measurement with the backwave damped










You can see the ripple has been nicely suppressed. Could still be a cone mode but it looks benign in SL's implementation.

Cheers,

AJ


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## kappa546 (Apr 11, 2005)

good to know


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## DS-21 (Apr 16, 2005)

werewolf said:


> So ... those with Aura whisper experience, what have you done _behind_ them for use in the midrange (above Fs, of course)? Enclosure, stuffing, deadening, etc?


I cut out the wire screen on mine and stuffed a pillow of fiberfil wrapped in cheesecloth behind the diaphragm. Not enough to impair the movement of the dome, but probably pretty close. Basically, it's Larry Van Wormer's old Vifa D27 mod on a bigger scale. 

No enclosure, though the factory did a great job of keeping the drivers separate. Mounting location uses a modified stock (Bose) bracket and lots of modeling clay.


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## npdang (Jul 29, 2005)

AJinFLA said:


> Hi NP,
> 
> I recall the discussion on Mad about this. I'd tend to believe Donald North on this one. I've corresponded with him before about one of his designs http://www.dnaudio.com/DNA Speaker.html. Good guy. Likes dipoles  . If you look at Zaphs data you can see it clearly. Right around (1.8-2.8k ish) where you would expect to see a 1/4 wavelength resonance given the depth of the cavity.
> 
> ...


I just realized that after I posted 

Usually my first thought when I see cavity resonance for a small tweeter-like driver is not a port, but a poorly dampened rear chamber.


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## Oliver (Jun 25, 2007)

......


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## Babs (Jul 6, 2007)

Ataboy!!!! hehehe  I love thread resurrection. 2006 too.. awesome!
What's funny is I actually read this one yesterday reading up on the small aura's.
I guess small FR drivers are getting some attention these days.


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## Fast1one (Apr 6, 2007)

a$$hole said:


> ......


You always resurrect the greats man, cheers!


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## TXwrxWagon (Sep 26, 2008)

STI<>GTO said:


> Is the reasoning behind the MTM really just for more output? In the car environment are you really going to take advantage of this arrangement? I'm not arguing or nocking, I've been considering something similar. However, I cannot get two whispers and a tweeter in the pillars, so an MTM would have to go in the kicks. I could get a single whisper and a tweeter in the pillar though, and I could move my midbass to the kicks (which should allow a slightly higher crossover point on the whispers). Just trying to figure out which option is the best compromise.
> 
> Sounds like a fun project!



Edit: totally missed the start date.. lol... 

STI, weren't you the one who did the Pair in the outer edges of the WRX dash?

I would think that as long as the midbass can safely play up to say 300-350 (roughly a 1/2 octave above the whispers low point of 250) minimal tweaking should make this work very well.

Werewolf, I assume you are talking vertical array & directly (or as much as possible) on axis to the nearest passenger correct?

Rob


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## dkm201 (Nov 29, 2007)

TXwrxWagon said:


> Werewolf, I assume you are talking vertical array & directly (or as much as possible) on axis to the nearest passenger correct?
> 
> Rob


Werewolf has been permanently gone for some time.


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## Oliver (Jun 25, 2007)

bump


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## SummerGuy (Nov 8, 2009)

he's dead


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