My understanding from all of this (and from prior experience in home and car audio) is that:
1. Avoidance of sharp edges through mounting the driver into a larger diametre sphere will assist in avoiding edge defraction. The pic below of keep_hope_alive's effort is the best execution of this principle in this whole thread - no edges because the driver is flush and the sphere gradually 'rounds away' from the driver edge.
Most people here in this thread mounting their drivers into spheres are still left with some form of small radius edge around the driver flange which, although edge defraction is minimised to a degree, it's still present as shown by the red lines in the second pic/diagram below. Regrettably, because of the size of my 3" mid, I'll be forced to end up with a similar result (I still need to be able to see out of my windscreen after all!) as I can go as big as a 5" diametre ball.
2. Mounting that driver/sphere as far away from glass, pillars, door trims, etc as realistically possible will also assist in avoiding disruptive and more immediate boundary defraction/reflections.
3. Because of physics (sphere size vs frequencies dealt with) the benefit is realised more with tweeters. Some here are mounting mids into spheres and being told that this, to a degree, will have a negligible effect, again because the spheres are too small for the lower frequencies coming from that driver.
My point and question comes about because my front stage will consist of a two way set up using wide band Audible Physics XR3M 3" cone drivers (point source ftw!) on the A-pillars and 5.25" Seas S16RNSL midbasses in the doors. I will have no tweeters as such!
The AP's will be highpassed from about 250Hz (yet to be finalised at this stage) and run all the way up to 20Khz. They'll be mounted within 15 degrees of axis to preserve their top end response. For internal volume and lower octave production they'll need to vent into the A-pillar, which in turn will vent down through the top of the dash. So far, it's looking like a 5" diametre sphere is the go for this driver.
The Seas' will be flush mounted with the door skin in the doors.
Again, it's been said that mids in spheres is a wasted effort to a degree, but what about those wide band mids that'll be producing all treble up to 20Khz?
Thanks for your help, and a massive credit to those who've contributed here in this thread.
What would be the expected result of mounting a driver in a very very shallow and barely concaved horn/waveguide that has a largish radius round off to a sphere or cone at the rear?
Would it assist by limiting and controlling the baffle defraction and stopping the sound from hitting surrounding surfaces sooner?
What would be the expected draw backs, generally speaking?
Perhaps a much larger sphere would be required for a 3" driver to allow for the guide and then the round off?
My understanding from all of this (and from prior experience in home and car audio) is that:
1. Avoidance of sharp edges through mounting the driver into a larger diametre sphere will assist in avoiding edge defraction. The pic below of keep_hope_alive's effort is the best execution of this principle in this whole thread - no edges because the driver is flush and the sphere gradually 'rounds away' from the driver edge.
Most people here in this thread mounting their drivers into spheres are still left with some form of small radius edge around the driver flange which, although edge defraction is minimised to a degree, it's still present as shown by the red lines in the second pic/diagram below. Regrettably, because of the size of my 3" mid, I'll be forced to end up with a similar result (I still need to be able to see out of my windscreen after all!) as I can go as big as a 5" diametre ball.
2. Mounting that driver/sphere as far away from glass, pillars, door trims, etc as realistically possible will also assist in avoiding disruptive and more immediate boundary defraction/reflections.
3. Because of physics (sphere size vs frequencies dealt with) the benefit is realised more with tweeters. Some here are mounting mids into spheres and being told that this, to a degree, will have a negligible effect, again because the spheres are too small for the lower frequencies coming from that driver.
My point and question comes about because my front stage will consist of a two way set up using wide band Audible Physics XR3M 3" cone drivers (point source ftw!) on the A-pillars and 5.25" Seas S16RNSL midbasses in the doors. I will have no tweeters as such!
The AP's will be highpassed from about 250Hz (yet to be finalised at this stage) and run all the way up to 20Khz. They'll be mounted within 15 degrees of axis to preserve their top end response. For internal volume and lower octave production they'll need to vent into the A-pillar, which in turn will vent down through the top of the dash. So far, it's looking like a 5" diametre sphere is the go for this driver.
The Seas' will be flush mounted with the door skin in the doors.
Again, it's been said that mids in spheres is a wasted effort to a degree, but what about those wide band mids that'll be producing all treble up to 20Khz?
Thanks for your help, and a massive credit to those who've contributed here in this thread.
Steve,
Brisbane, Australia
Running midranges in spheres is pointless simply because the wavelengths are so long. For instance, if you have a 3" midrange in a sphere and it's lowpassed at 1350hz, then the shortest wavelength that it's reproducing is 10" long. So the 3" sphere will do a little to reduce diffraction, but not a whole lot. (This ignores output above the xover point; admittedly you should factor that in.)
On the other hand, if you do it with a tweeter, the shortest wavelength reproduced is 0.675" long! So you get some serious bang for the buck with a tweeter sphere. Almost anything you do to eliminate diffraction near the tweeter will make a difference, because it doesn't take much.
Also, you mentioned that you're listening to your full ranges on-axis to maximize the top end. Keep in mind this isn't necessary if you have EQ. It's perfectly valid to cross fire them and tip-up the top end to compensate for the rolloff that occurs due to their directivity.
In fact, I'd argue that contributes to a wider soundstage.
It doesn't really impact your power handling because excursion isn't a problem at high frequency, and there isn't a ton of energy in the top two octaves unless you're in the habit of listening to dog whistles.
The graph above shows the response of a Peerless 3" on and off-axis. You'll note that it's basically flat on-axis, but output drops quickly off axis above 10khz. You can listen to these off axis, by tipping up the top octave. Only catch is that the off-axis response needs to be well-behaved, but this driver fits the bill.
Play around with it in the car, because a lot of the magic depends on the implementation.
In my 25 years of working in this industry, I've listened to thousands of cars and I can count the ones that sounded great on two hands. Most of them have serious problems and some of the worst ones are IASCA winners... 50% of these guys have plans to change all the equipment in their cars because they don't sound good. In every case so far, none of the equipment has been the cause of poor performance. In every case, it's the installation, the adjustments or the system design. AW
As I said on my post, I already understand that a 5" to 6" sphere will be of no benefit to mid frequencies.
My question was about whether a sphere of this size would benefit the higher frequencies normally the domain of dedicated tweeters, that a wide band mid is able to produce in my case.
My thinking is that it would benefit however, I'm just seeking confirmation from the experienced and knowledgable here.
As I said on my post, I already understand that a 5" to 6" sphere will be of no benefit to mid frequencies.
My question was about whether a sphere of this size would benefit the higher frequencies normally the domain of dedicated tweeters, that a wide band mid is able to produce in my case.
My thinking is that it would benefit however, I'm just seeking confirmation from the experienced and knowledgable here.
Cheers
Yes, a spherical enclosure reduces diffraction for a full range driver, as long as the driver is capable of playing to a frequency where the wavelengths are small enough.
IE, no real benefit in doing it if you have them low passed at 1350hz, but if you have them running full range, or even lowpassed at 2700 or 5400hz, you're going to hear a difference.
I guess I'd break up the candidates into three brackets:
Bracket one - great candidates for spherical enclosures are drivers with wide directivity that play to a very high frequency. Tweeters are an example of this. The smaller the better.
Bracket two - good candidates for spherical enclosures are drivers with wide directivity that play to a moderately high frequency, or drivers with narrow directivity that play to a very high frequency. Examples of this are 2" and 3" woofers.
Bracket three - poor candidates for spherical enclosures are drivers with wide directivity that play to a low frequency, or drivers with narrow directivity that play to a moderately high frequency. Examples of this are 5" and 6" woofers, or 3" and 4" woofers that are lowpassed below their upper limits. There are plenty of 3" and 4" woofers that can hit 10khz, so if you're using one without a lowpass, it's a good candidate, if you ARE using a lowpass, it's suitability for a sphere will be reduced as the crossover point gets lower and lower.
In my 25 years of working in this industry, I've listened to thousands of cars and I can count the ones that sounded great on two hands. Most of them have serious problems and some of the worst ones are IASCA winners... 50% of these guys have plans to change all the equipment in their cars because they don't sound good. In every case so far, none of the equipment has been the cause of poor performance. In every case, it's the installation, the adjustments or the system design. AW
Two things about this thread that I have concerns with:
1. Dickason has done research on diffraction and his summary of it when I spoke with him yesterday was that the impact of diffraction was nebulous. So much so, he essentially said there's no reason to worry about it because it just isn't audible.
My guess is that its due simply to the high Q of these peaks/dips. It takes fairly fine smoothing to see the differences spoken of which such disparity. Toole's research shows these are inaudible.
2. For the sphere to do any good it needs to be larger than the flange of the driver and the driver needs to be flush mounted in that sphere. Otherwise you still have diffraction off the flange itself (if after reading the testing mentioned above, you find it matters at all).
I'm not trying to bring down the mood of this thread. Just wondering how beneficial it truly is.
That said, using a sphere from hobby lobby is easier than fiberglassing a baffle to my pillars.
Two things about this thread that I have concerns with:
1. Dickason has done research on diffraction and his summary of it when I spoke with him yesterday was that the impact of diffraction was nebulous. So much so, he essentially said there's no reason to worry about it because it just isn't audible.
My guess is that its due simply to the high Q of these peaks/dips. It takes fairly fine smoothing to see the differences spoken of which such disparity. Toole's research shows these are inaudible.
2. For the sphere to do any good it needs to be larger than the flange of the driver and the driver needs to be flush mounted in that sphere. Otherwise you still have diffraction off the flange itself (if after reading the testing mentioned above, you find it matters at all).
I just pulled up Dickason's profile on LinkedIn, and a couple of things struck me. First, audio is a very VERY small world. I've obsessively studied Geddes and Danley, and if you look on LinkedIn, Geddes has about two degrees of separation from Dickason in the world of audio. On LinkedIn, here's the profiles listed on Dickason's page:
Vance Dickason (self-employed) Floyd Toole (self-employed) Sean Olive (Harman)
Wolfgang Klippel (s/e)
Ken Kantor (formerly of NHT, Tymphany)
Tom Holman (University of SoCal) Earl Geddes (s/e)
So this is a very small pool of experts, and none of them agree on diffraction, as far as I know.
So you bring up a good point, something which should have come up in the first page or two really!
Is combating diffraction a worthy goal?
I am inclined to say "yes." Twenty years ago, when I first started screwing around with audio, I had the same mindset that most beginners do. My goal was to reduce harmonic distortion by using high quality drivers, and I invested a lot of money in expensive amplifiers and crossover parts.
Twenty years later, I've practically done a 180. Everything I've learned tells me that timing problems are more important than amplitude problems.
So I would argue that the reason that guys like Linkwitz and Dickason discount the diffraction problem is that Linkwitz and Dickason are focused on amplitude problems. (IE, frequency response.)
And I would argue that the Geddes and Danley designs attack problems in the time domain, each in their own way. Geddes is a proponent of preserving the acoustic wavefront via low-diffraction cabinets and waveguides. Danley's designs are engineered so that they preserve acoustic phase across the bandwidth of the loudspeaker.
And as any good engineer knows, engineering is all about compromises. The Geddes and Danley designs do not have the best amplitude response on axis, in fact it's fairly ragged. But the key to their designs, IMHO, is that they get the time domain right. And I think that's humongously important.
Here's a real world example of what I mean. Have you ever clapped your hands in a small room? And have you noticed that there's an echo? In a small room, that echo will occur less than ONE HUNDREDTH of a second after you clap your hands. And yet the echo is very easily audible isn't it?
If you grok what I'm saying there, you'll start to understand why I think the time domain is so important. Our ears are very VERY sensitive to timing problems. You can tell when a sound is 'off' by a HUNDREDTH of a second, perhaps much less.
Conversely, it's VERY HARD to measure. Go ahead and try to figure out how to measure this stuff. It's not easy.
On the other hand, there are iPhone apps for a buck that can measure frequency response.
And THAT is why the audio world is obsessed over amplitude problems, but drops the ball when it comes to time domain problems. Problems in the time domain are devilishly difficult to analyze and quantify, while problems in the amplitude domain are trivially easy to analyze.
In my 25 years of working in this industry, I've listened to thousands of cars and I can count the ones that sounded great on two hands. Most of them have serious problems and some of the worst ones are IASCA winners... 50% of these guys have plans to change all the equipment in their cars because they don't sound good. In every case so far, none of the equipment has been the cause of poor performance. In every case, it's the installation, the adjustments or the system design. AW
Oh, in reference to my previous post, I think that ALL time domain problems are insidious. It's not just diffraction. Here's a few more examples of time domain problems:
- I think the reason that people are averse to the sound of bandpass boxes and vented boxes but like sealed boxes is because sealed boxes generally have better group delay
- I think the reason that people try horns in the car but get sick of them and go back to direct radiators is because undersized horns have terrible group delay, and that's a high price to pay for dynamics
- I think the reason that people like the sound of full range drivers, everything from $50 boom boxes to $800 Lowthers is because full range drivers are incredibly well behaved in the time domain. In fact, the only way to get better behavior in the time domain is to approximate a full range driver with an array
- I think the reason that hundreds of people on this forum have been looking for audio nirvana for decades, and yet they can't find it, is because expensive low distortion components do NOTHING to address the time domain problem, and in fact they can exacerbate it. That's why very cheap and inexpensive loudspeakers are often MORE satisfying that megabuck low-distortion speakers
- I think the reason that many people prefer vinyl over CDs is because some CD players suffer from high jitter, which is a time domain problem
- I think the reason that many people think MP3s sound weird is not because of the compression, but because the original source was poorly 'ripped', and the track has lots of jitter. I believe that compressed audio can sound indistinguishable from the original if it's very carefully ripped, and compressed at a high bitrate.
I'll probably lose all my credibility on this forum with this post
In my 25 years of working in this industry, I've listened to thousands of cars and I can count the ones that sounded great on two hands. Most of them have serious problems and some of the worst ones are IASCA winners... 50% of these guys have plans to change all the equipment in their cars because they don't sound good. In every case so far, none of the equipment has been the cause of poor performance. In every case, it's the installation, the adjustments or the system design. AW
I think they are all right, the issue I take is that of emphasis. One researcher here brings attention to one aspect of sound reproduction but in doing so they find it necessary to downplay the other aspects that are relevant. My understanding of it all is that they are all important, but in trying to see which one you should give more relative importance you face the ongoing wrath of head researchers trying to bring their idea at the forefront while downplaying the rest.
Geedes for examples uses massive pro audio drivers. No shit his design is not bound by high amplitude distortion, he effectively took care of it by using oversized drivers. If you look at Linkwitz work on decay it seems that hard cones and small cones seem to have better decay than large paper cones like the pro audio ones he uses. If he's such a big time domain buff why use a big paper cone? My guess is that he's trying to sell his beliefs about the ideal polar pattern at the expense of everything else that matters. I suppose that's just a way of getting your foot in the door with an idea. He's not the only one guilty of this but others as well, emphasis is often tied to their personal research, it is a form of bias.
At the end of the day all maters and it's up to you to go through all their work and assign weights as best as you can. They won't do it for you.
As far as diffraction goes I think it's a second order issue. Once I pick and mount all my drivers I can look and see if I can round off some edges. Without Patrick's thread I wouldn't have know about it so there is a lot of added benefit here despite it not being a primary concern.
Oh, in reference to my previous post, I think that ALL time domain problems are insidious. It's not just diffraction. Here's a few more examples of time domain problems:
- I think the reason that people are averse to the sound of bandpass boxes and vented boxes but like sealed boxes is because sealed boxes generally have better group delay
- I think the reason that people try horns in the car but get sick of them and go back to direct radiators is because undersized horns have terrible group delay, and that's a high price to pay for dynamics
- I think the reason that people like the sound of full range drivers, everything from $50 boom boxes to $800 Lowthers is because full range drivers are incredibly well behaved in the time domain. In fact, the only way to get better behavior in the time domain is to approximate a full range driver with an array
- I think the reason that hundreds of people on this forum have been looking for audio nirvana for decades, and yet they can't find it, is because expensive low distortion components do NOTHING to address the time domain problem, and in fact they can
exacerbate it. That's why very cheap and inexpensive loudspeakers are often MORE satisfying that megabuck low-distortion speakers
- I think the reason that many people prefer vinyl over CDs is because some CD players suffer from high jitter, which is a time domain problem
- I think the reason that many people think MP3s sound weird is not because of the compression, but because the original source was poorly 'ripped', and the track has lots of jitter. I believe that compressed audio can sound indistinguishable from the
original if it's very carefully ripped, and compressed at a high bitrate.
I'll probably lose all my credibility on this forum with this post
No. You don't!
Maybe I could add something
Imagine if a bass player/pianist/guitar in a group band played a delayed note than the other players. Let say 1 second late. I'm certain it will ruin the music.
So timing is important for me both in music production and music reproduction (audio system). CMIIW
As my drivers will be high passed from 250Hz, I understand that the work I will do in mounting them into spheres will be of at least some use because at least some section of the pass band (the higher end of that band) will benefit.
The fact that they're wide band drivers also helps address other the many issues I have experienced in the past with separate drivers (including the time and phase issues spoken of in this thread above).
In a car it couldn't hurt to get as many of these factors right as you can. I have a small car and before i started I had a hard time figuring out where to put my tweeters. I had read posts about avoiding as many first reflexions as possible but also read the tweeter in door could be a bad position. Yet I chose this position because there were not a whole lot of other positions to place my tweeters without running into other problems and it was the right place to avoid as much first reflections as possible. Right from the start imaging was very good. The tweeters just dissapeared. No smear in high frequencies and that's the reason I believed a round over could help even further. Now I never hear where the tweeters are mounted even when I look at them. The sound is smoother and of coarse time alignment helps to get the music sound good but the main part is the absense of difraction and very early reflection helps the speakers dissapear in my opinion.
I've noticed there are very small differences in good sound and great sound. Time alignment was the biggest key to get the right groove in the music. You know, you forget all your priorities and the music just takes over. Not that dificult to understand as that makes the difference between a good singer and a great one. Timing is everything.
So if it's possible to limit as much of these problems as you can I am sure you will be rewarded. I've noticed this in my car and came to the conclusion to build an array like Roger Russells IDS-25 for my home to get rid of the time domain difficulties between drivers.
I am certain that if you get the timing right the groove is in the music and makes you worry less about the other remaining problems. But why not try and solve as many as you are able to in your particular situation in your car/home etc?
1982 Porsche 911 SC, Pioneer P88-RSII active 2-way front + sub, Genesis Series III 4 Channel, 1&2 to Hertz ML 1600 woofers, 3&4 bridged to a JBL GTO 804 sub in the front trunk, Vifa XT25 sc-90 04 tweeters powered by a Genesis Series III Stereo 60.
I could not forget what I read about a project of a dutch guy named Tony Gee. One of the best imaging speakers he built was this one: http://www.humblehomemadehifi.com/do...ctica_copy.pdf
A low difraction speaker that seems to draw you into the music, just read his Listening impressions and measurements.
1982 Porsche 911 SC, Pioneer P88-RSII active 2-way front + sub, Genesis Series III 4 Channel, 1&2 to Hertz ML 1600 woofers, 3&4 bridged to a JBL GTO 804 sub in the front trunk, Vifa XT25 sc-90 04 tweeters powered by a Genesis Series III Stereo 60.
1982 Porsche 911 SC, Pioneer P88-RSII active 2-way front + sub, Genesis Series III 4 Channel, 1&2 to Hertz ML 1600 woofers, 3&4 bridged to a JBL GTO 804 sub in the front trunk, Vifa XT25 sc-90 04 tweeters powered by a Genesis Series III Stereo 60.
[QUOTE=Patrick Bateman;1418831]I've been working too much lately, and haven't had much time for audio projects unfortunately. I've listed some spherical speakers that I bought up a few years ago. The whole reason I bought them was to experiment with some of the ideas that I've discussed in this thread. The speakers are similar to the Aurasound Whispers that Jason is (was?) using. The nice thing about the ones that I am selling is that they don't need an enclosure - it's basically included.
Here's a pic:
Quote:
Originally Posted by Patrick Bateman
I wouldn't be surprised if you could go two octaves lower than that - all the way down to 250hz. The JBLs are really similar to the Aurasound Whispers sold by Madisound, and those drivers can go all the way down to 150 or 200hz.
The JBLs have an edge over the Auras because they're ported, which controls excursion on the low end.
Bought a case of these JBL iMac speakers off eBay to play with. I only managed to get one side in tonight but managed to get some listening impressions in before calling it a night. I had the JBL crossed at 1k, 1.2k, 1.6k, 2k, and 2.5k. Efficiency will be an issue when crossed low, and they sound a bit harsh/spitty at 1k. (Plus as Patrick said, there isn't much benefit when crossed that low anyway). Crossing at 1.5k has promise, and I'm excited to try them there.
After playing with just the one JBL installed on the passenger side, I A/Bed them against my existing DLS Nobelliums (DLS on driver side). I know this isn't the best way to compare them, but I'm limited on experience, time, and resources.
Very rough thoughts: DLS sounded smoother whereas the JBL has a colder, sterile sound. I thought there was a substantial increase in "airiness" coming from the JBL, but I'm not ready to make any sort of definitely statement yet.
It'll be very interesting to see first hand the trade offs between timing and amplitude once I get the other speaker in.
I'm not trying to bring down the mood of this thread. Just wondering how beneficial it truly is.
I certainly don't have golden ears, and I was skeptical, but I could tell a difference in before/after and A/B listening tests. Yeah, yeah, I know, psychacoustics.
Okay, I gotta admit some things in this thread are kinda confusing me. Namely, why does it make a difference how the back of the thing is shaped? Sphere vs teardrop? I see the issue with the flat surfaces, but not really the sphere vs. teardrop vs etc shape.
I just did the tweeter pods that use PVC endcaps. How exactly does this differ in a result? I smoothed the front surface so the tweeter and the PVC mate up smoothly, will changing the cylinder shape to a sphere really make a difference though? Also, would it help extra for people to wrap these spheres in foam or a similar substance to further reduce reflections?
And why exactly does the diameter of the sphere make a difference?
Okay, I gotta admit some things in this thread are kinda confusing me. Namely, why does it make a difference how the back of the thing is shaped? Sphere vs teardrop? I see the issue with the flat surfaces, but not really the sphere vs. teardrop vs etc shape.
I just did the tweeter pods that use PVC endcaps. How exactly does this differ in a result? I smoothed the front surface so the tweeter and the PVC mate up smoothly, will changing the cylinder shape to a sphere really make a difference though? Also, would it help extra for people to wrap these spheres in foam or a similar substance to further reduce reflections?
And why exactly does the diameter of the sphere make a difference?
Answer on the first page.
Kelvin
Lycan
Quote:
I'll repeat it for the miliionth time : All amps do NOT sound the same ... It's astonishing to me that nobody understands this
If you read back to post 35 there are diagrams representing the baffle step diffraction from drivers mounted into different shaped baffles-that will show you the difference between mounting options.
Post 2 details why the diameter of the sphere makes a difference
just have to say i have a kind of audio guru / mentor guy here in oz who talks abo0ut alot of the things you guys are talking about in here hs 30-40 years background is in home audio and im trying to learn from him and use it in car audio the spreical 3 quarter egg tweeter or ide i have used in my SPL car which everyone said was stupid but it ended up making the sound bareable to listen to then a few other mods for diffration and a few other bits and bbs that are very commen in home audiophiles and what the doof doof crowd call oldtimers and whalls a 150db car that will play all types of music not just bass and would play it well
now were upping the anti were making it a more tradtional SPLer by putting in 4 x 15s but stickeing to the same build principles cylindrical internals extrenls roundovers and positioning of things that will not only help the quality of the sound made but the amount of sound made it worked for a 150db car so why not more??
now were adding sound absorbtion and waveguide etc aswell as the sperical eggs and a bucnh more tricks ill staret a build log as soon as i know it all works well when i get the first listen in about a week anyway but i also wanted to say this is one of the best reads in an audio forum especially car audio
i have seen for sum time well done to you patrick great topic ohh and is that your car by the way as i have one identicle well identicle in that its a e34 5 series bmw thats it tho im still working on that car Essquees are hard to extract from a car while still making it look good to other ppl and yourself
If its not rattlling or cracking its not SPL xMplar 3:16
here is sum of the pods i have used in my SPLer car and will most likly use simalar in my essquees car the tweeter sits almost perfect so the round over is almost perfect nt quite but almost i bought these fron a matew who found a place in maylasia who mkaes them out of full on fibreglass in like a 1" 2" 3"
4" 5" 6" 7" 8" 9" 10" and so on you get the point
they are called podlets and in bigger versions call bass bombs trhere is also some other types in difernt shapes
and the have a roundin lip so you can actually screw into the lip if needed or glue to it whatever takes you fancey
Ren
xMplar
If its not rattlling or cracking its not SPL xMplar 3:16
Well I read an equation for how the diameter matters, it's the question of why the diameter matters? As opposed to small diameter with lots of open air around the thing? Having the equation in front of me and knowing why the equation works are two different things
Re: Improve Your Soundstage for $2
Vance Dickason (self-employed)
Floyd Toole (self-employed)
Sean Olive (Harman)
Earl Geddes (s/e)
Re: Improve Your Soundstage for $2
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