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Discussion Starter #1
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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now thats a first post!!!!!

glad to see you around these parts :)

I too have been considering this

I bought 4 aura ns3's to model just this possibility (two in each pillar)

not sure theyll fit so I bought some backup vifa 4-1/2"

I do think ideally the ns2 would be easier to mount , but the response of the ns3 seems more attractive

now if I could only find a way to mount them withou the flange :)
 

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Excellent post!

Have you by chance heard any of the M-design (Monster Cable) line array speakers using the Aura drivers? I managed to sneak an audition over at the local Best Buy (lol) and unfortunately they had it setup in the worst possible condition.
 

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the wolfman - always full of wonderful information and class. i think we're all lucky to be involved in car audio with this guy posting. great post mr werewolf.
 
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Discussion Starter #5
Thanks for the kind words guys ... but the credit here goes to npdang for sharing his time, knowledge & resources :D

Haven't heard the M-design array yet ... but I did listen to a McIntosh array at CES 04. Not sure what drivers, but I wasn't very impressed with the tonality. Stage was decent, however.

More than a few DIY'ers seem to have had some success with Jordan line arrays ...
 

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muahahah mr wolf i knew it was only a matter of time before you ended up here.

i was also considering a mini-line array of 2 NSWs per channel, dash mounted and firing away from the windscreen. Your GURT thread really helped me make the decision to go this route. My aim is to minimise secondary sound sources (as per your discussion, i want the primary source to overpower the reflections) Ever thought about mouting it in the corner of the dash, against the windscreen, and facing the listener instead? That way you avoid all the possible nasties with glass reflections and such. Imagine an array of NSW2s going from dash to ceiling, how cool would that be :shock:
 

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Have you started this very interesting project already? I think it's a neat approach over all, and I'm all the more in admiration because doing it right is far beyond my technical competence right now. Would you be using commercial processors or fabbing your own using, say, DSP chips intended for multichannel receivers? Amp-wise I wouldn't think it's an issue. Apex Jr. has some surplus amps that would probably work fine, or you could DIY your own mobile gazillion-channel "Gainclone" chip amp....

I’m curious as to why you chose the Aura Whisper over the Aura Cougar for this application. The Cougar allows ~15mm closer C-t-C spacing, thereby pushing the onset of comb filtering higher up in frequency and probably extending your usable top end by a third or so. (That’s a third in the musical sense, not 33%...) Keeping CTC spacing as tight as possible is why most DIY line arrays use planars/ribbons, and commercial ones such as the Pipedreams use tiny domes. The Cougar also might be slightly less deep, allowing a smidge more flexibility in damping the backwave. (I damped mine with a layer of 2-ply cashmere from a Burberry scarf that was attacked by moths over the rear grille, and an XL cotton ball ball-sized wad of polyfill right behind that.) Then again, I’ve never played with the Cougar, and SL did pick the Whisper over the Cougar for his Pluto when either would’ve probably worked....

As for getting CLS-like sound, might it be possible to get some sort of dipole up front? (Yeah, I know, stupid question :) ) IMO, the main effect of line-source radiation in a nearfield setting is to make sonic images universally bigger. The glorious stage depth and palpability you (and I, and our Maggie-using host) find in planar speakers seems to come largely from their dipolar radiation pattern, I think. I base that thought on my own experiences auditioning three monopole line sources and two dipole/cardoid point sources, albeit in different rooms. (The monopole lines were the Linus by Jim Griffin and Rick Craig, set up by Dr. Griffin, and the commercial speaker from BG that used their 50” planar. The point sources were the Quad ESL-63US, Siegfried Linkwitz’s Audio Artistry Dvorak, and the Gradient Revolution.) The dipole/cardoid point sources had the magic, the monopole lines were both neat neat but to me ultimately more Starbucks than Julius Meinl.

PS: If you don't see a reply from me for a little while, I'm not ignoring you. I'm going to be in London for ~10 days to attend a cousin's wedding, do some shopping, and check out a few rental property prospects....[/img]
 
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Discussion Starter #8
Hey DS-21 :) Well, this particular adventure (like so many for me in our captivating hobby) is just in the "thought-experiment" stage ... at least for now. I do agree completely on the Cougar advantages though. Just maybe sometimes when you really want to crank it, to tear your skull open, ya know ... one might wish for more midrange output :wink:

It is a bit of an issue finding an existing processor with enough time delay channels to realize the full potential of the idea (assuming there's any real merit here). But a few home-based processors are linkable, so I'll keep thinking. But yeah, little power amps aren't hard to come by ... maybe even something like what SL cooked up for Pluto, for each Aura driver. It's just so tempting to think that we might be able to electronically "stand-up" the pillar (with the appropriate delay-line) to realize a vertical line array, at ear level, in the car.

Anyway, have a safe trip. We've certainly debated many things not related to car audio in the past, but please do exercise some care in London. Please keep your eyes open, I'll promise to keep my heart & mind open :D
 
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some more thoughts on the delay line ...

What's really needed is a (conceptually) simple "digital delay line". Simple digital memory (FIFO, RAM), "tapped" for each driver in the pillar. But then, of course, each driver needs a DAC & power amp. Not much power for each single driver, of course, so maybe something like the chip-amp LM3886 used by Linkwitz in Pluto. Perhaps each driver won't need it's own separate EQ ... maybe perform a combined or "group" digital EQ before the delay line.

Alternatively, maybe this is a good use for the new Alpine F#1 PXI-H990, which can somehow be linked to another one for a total of 16 channels. Not a cheap option, but certainly a more promising application than DVD-Audio ;) I gotta learn more about this new Alpine processor. Anyone know where I can find a PXI-H990 Owner's Manual online? The Alpine site doesn't seem to have it ...
 

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werewolf said:
Hey DS-21 :) Well, this particular adventure (like so many for me in our captivating hobby) is just in the "thought-experiment" stage ... at least for now.
The only things in this hobby more fun than thought experiments are listening and discovering either that you were right, or that you were wrong but now you know why.... :)

werewolf said:
I do agree completely on the Cougar advantages though. Just maybe sometimes when you really want to crank it, to tear your skull open, ya know ... one might wish for more midrange output :wink:
True, but as long as you keep your crossover reasonable I don't know how big an issue would be. However, there probably is a good reason SL went with the Whisper...

werewolf said:
But a few home-based processors are linkable, so I'll keep thinking. But yeah, little power amps aren't hard to come by ... maybe even something like what SL cooked up for Pluto, for each Aura driver. It's just so tempting to think that we might be able to electronically "stand-up" the pillar (with the appropriate delay-line) to realize a vertical line array, at ear level, in the car.
Actually, now that I've thought a little more about it, too, doing that actually shouldn't be that hard. I don't remember the model number and I've since sold the piece, but in the late 1990s Bill Burton recommended that I try rear-fill delayed using a "pro audio" processor by Roland, and dammit if that didn’t do more than anything else I’d tried to flesh out those half-left and half-right images. Surely that box (assuming the delay steps aren’t too coarse) or something similar could be easily applied to your concept. However, IIRC it was a 2-channel processor (or at least I only used two channels) and 5 or so of them would just take up a shizzle-ton of space. That’s if why if you've got the time and inclination it might be neat to use two AV receiver DSPs that combine individually settable delays for 5+ channels each and some rudimentary EQ functions with a global DAC, and fab a bespoke delay box/DAC using them. That's a level of involvement in this hobby far beyond my competence, so I don't know exactly what's involved, or if those parts are commonly available. Given my academic background and time constraints, it's also a level I'm never likely to be able to reach. I greatly admire those with the chops to do it and do it well, though.

werewolf said:
Anyway, have a safe trip. We've certainly debated many things not related to car audio in the past, but please do exercise some care in London. Please keep your eyes open, I'll promise to keep my heart & mind open :D
Honestly, I'm far more worried about the absurd Communist-style self-criticism session in place as airport so-called security by the spiritual heirs to Leonid Brezhnev currently running our government than I am of any trouble once I'm in the UK. I've got running the gauntlet down to a science by now - big orange flag on the Powerbook so the TSA jackboots don't throw 12 baskets on top of it and try to carry it away while another agent restrains my attempt to stop them (again), drawstring trousers so I don't have to wear a belt, no writing utensils on me, ceramic-case watch, driving mocs that don't have any metal in them, unlined sportcoat, and so on - but nonetheless I still arrive four hours early because I’m invariably flagged by the jackboots for the crime of having brown skin. Assuming Comrade Gonzales’s thugs don’t whisk me to a secret gulag or something for possessing a functional mind, the most ominous potential danger for me is the cuisine. When this cousin's sister married, the caterers for one of the functions gave about 300 people food poisoning; hopefully they’ll use a different one this time. More flippantly, I run the likely risk of forgetting when I see the prices at Turnbull & Asser's summer sale that the UKP is worth about twice as much as the USD until several minutes after the charge plate's been scanned. ;)
But seriously, "terrorism" is something Americans badly need to keep into perspective, despite (or perhaps BECAUSE OF) the obvious incentive of the powers that be to stoke mindless fear in our population and thus win their crusade against our civil liberties. The entire UK had considerably fewer victims of violent crimes including terrorism per 100,000 people in 2003 than we had people per 100,000 murdered or injured by non-commercial trucks and SUVs over the same time period. Despite the horrific efforts of a (thankfully incompetent) clique of four madmen that will be true in 2005 as well. So ultimately I like my odds once I'm there better than I like my odds driving to and from the airport on this end. :)
 
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Alrighty then. What we need is a plan of attack on this idea.

I think the first step is a "proof on concept". Nothing particularly fancy, pretty or (hopefully) expensive. In this experimental phase, we don't even need car-based processors or amps. What we do need, is an A-Pillar lined with good candidate drivers ... like the little Aura Cougar suggested by DS-21. We're contemplating ribbons as well .... but that seems more expensive (at least, at first glance) and time consuming. Plus, I think we'll want something closer to full-range drivers to really flush out the idea.

I've got a Honda Civic with pretty accessible A-Pillar trim. And I've got some smarts, and a bit of capital ... but precious little time :( So I'll just outline some more thoughts for now, cool?

It's quite possible, I think, to fit 16 Aura NS1's in a 24 inch A-Pillar. In a Civic, the A-Pillar trim comes off pretty easily. Some ribbing on the back side would have to be gutted, that's easy. Then, the array must get attached ... drilling & screwing. I'm not sure that it makes sense to ultimatley mount the array to the trim, rather than devise a more solid mount to the A-Pillar metal and just use the trim for cosmetic covering. But remember ... first step is proof-of-concept.

Now, how to drive the array? We'll need a good A-B comparison, of course, with & without delay. Without delay is easy : sixteen 8-ohm drivers can be wired to present a final, non-delayed load of 8 ohms. Somebody can describe this for homework :)

Delay options, for proof of concept. Yes, it's possible to do a "passive delay line", of varying degess of complexity & accuracy. In it's most simple form, the passive delay line would look like a series inductor and shunt capacitor between each driver up the pillar. If you think this would present a very low impedance to the amp at DC, you're quite correct. And hence we see the first issue with passive time delay : it's typically only approximately valid over a certain frequency range. But the Aura's will need to be high-passed at 200 Hz (at least) anyway, so I'll give this option some more thought.

Digital delay still sounds attractive to me. The ultimate form would be a custom digital delay line, probably operating at 96kHz or 192kHz (higher sampling rate through the digital delay line means better delay resolution). Of course the fundamental digital audio signal would be created by upsampling to 96kHz or 192kHz by ASRC ... another big topic, favorite of mine :) Yes, you would need a battery of DACs & amps, but each amp is pretty low power so the ultimate space & cost wouldn't be too bad. But I'm getting ahead of myself ... proof of concept needs some off-the-shelf processor with buku channels of delay. Good news is, can be a home processor ... hell we're just gonna fire this thing up in somebody's garage to prove the idea first :) Can even use some cheap, low power home amps for proof of concept.

Anyway, just a download of thoughts-to-date. Who's got some time, and some A-Pillar trim from their vehicle, to experiment? I'll supply the Aura cougars for anyone interested to experiment & report the results. I'll also look for the right processor ... home or car ... to help us through proof-of-concept. Of course, any help in finding a processor with maybe 16 delay channels, with enough delay resolution (at about 1 foot per msec, we'll need delay resolution well below 0.1msec) would be great too!
 

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maybe someone could use a couple of daisy chained behringers? How about mounting the drivers such as to incorporate a natural time delay? eg driver on top of line array is as far back as possible, and the line sort of approaches the driver as it goes down to the dash. Would take some fancy fibreglass work though. Or maybe someone could use a shorter line, say about 4-5 drivers so that the PLD when comparing the top and botton wouldnt be a big deal and we could skip the TA step altogether. As long as the line covers the listening position, and maybe a couple of inches above and below it should be no different from a longer array? I recall in jim griffins Line array white paper that you only need to make a line as long as it covers where you are listening from. or maybe i misunderstood
 

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why run it up the a-pillar? Why not skip time/A...and just run it up either the front part of a door (yes i know furter ahead of the kick drivers) or from the bottom of the apillar, in a nice stright line down to the bottom of the dash or floor, i know i could do this in my truck. I would attempt this in my car if it was a flush line, and not an pillar angle dealie-O.

oh and I have no idea how to delay such a thing, way out of my league, but I have no problem tearing up my dash more to sink the front face of the line flush with the dash.

I am scared to use a driver that small that i've never heard...anyone give me some pointers on what people normaly use these drivers for, and if they really sound good enought to hang with their big-boy friends in ones (my) ride?
 

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Hats off to DS-21

WoW a real intelectual!

aka not a sheep: nice politics, self-thought, and articulation.

Thank you.
 
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Spaceman, running up the A-Pillar places the line array at ear-height. Same reason most people lift their speakers up off the floor at home ;)

Furthermore, running the line array from dash-level down will not avoid the time delay issue. The fundamental issue is not so much the angle of the pillar, but the arrival time from each driver to your ear. Even with a purely vertical array running from dash-level down, each driver will have a different arrival time to your ear. You'll benefit from a time-delay line in this case to "steer" or "tilt" the dispersion pattern toward your ear.
 
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I just saw a thread on line arrays (in cars) over on carsound. Some interesting challenges for near-field listening, of course, especially in a small, reflective environment. An interesting reference was quoted :

http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

Still haven't read the whole paper in detail, but one intersting technique described is "power tapering" the array, as a simpler alternative to delay tapering.
 

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you taken my thunder lol

now my secert it out

are ideas are not so dissimular

i also have the array bug, very nice sounding when done right. Or as close as possible.

http://www.diymobileaudio.com/forum/showthread.php?t=17960


im starting small with this idea, but I am usen the glass to direct the planers. from the seat looking ahead at the glass you can see that the planers are at ear level.:D

I still might rework it to a MTM up there.
 

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I am really interested in doing an array also.

What kind of amp options are out there for running 6-8 pairs of cougars or whispers(which madisound is sold out of right now).

Right now I have a PPI DCX-730 for processing, which I might buy another one to add another 6 channels of delay giving me a total of 7 channels of mids per side (the farthest mid doesn't need time alignment), and if I do pairs of cougars per channel, that would give me 14 mids per side.

Geez, the amp rack on this is going to be huge.

Is there any reason why there needs to be a certain amount of speakers per side? Would 6-8 work or to do an array correctly, more drivers would be needed?

Last question, what about multiples of these amps to power the array:

http://cgi.ebay.com/150W-Motorcycle-Car-2-Channel-Amplifier-NEW-mp3-amp_W0QQitemZ200142270858QQihZ010QQcategoryZ39732QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
 
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