cuibono

circular microphone arrays?
« on: April 11, 2007, 08:26:40 PM »
I was out walking, and letting my mind wander, and I was thinking about a circular microphone array, with playback through a circular speaker array.  I was hoping to create a more 'purist' recording technique, something to emulate a true 'point source' for pickup and playback.  Someone must have tried this at sometime?

I searched around, and there is some robotics research on circular microphone arrays, which is kind of similar.  I think I might try to take six modified electret capsuls (per Linkwitz Lab), mounted around a 6" tube, and then build a speaker with 6 full range drivers mounted around the circumference, just to see what happens.  I know I've got to build amps, gainclones are easy.  I have the computer to record 6 channels...

Has anyone seen anything like this?
Yes?


Gus

circular microphone arrays?
« Reply #1 on: April 11, 2007, 09:17:57 PM »
speaker builder had a line microphone array and speaker system.  I seem to remember 64 microphones?

94
"The Linear-Array Sound System"

circular microphone arrays?
« Reply #2 on: April 12, 2007, 04:10:41 AM »
Why not a sphere instead? If you don't make it too large you can probably spread your six capsules around it evenly and find a good compromise between coverage and separation.

Then build a speaker that works the same way. I'm very interested in hearing the results.

But please don't make it egg-shaped... ;-)

Martin


JohnRoberts

circular microphone arrays?
« Reply #4 on: April 13, 2007, 10:48:08 AM »
I have long pondered this and there are dimensional limitations, trying to capture a 3 or more dimension event in less dimensions always results in errors.

One approach that I have pondered at least for popular (rock/jazz) is a several channel system where dedicated playback channels deliver bass guitar, lead guitar, drum kit, and vocals. perhaps add a channel for piano.

Dedicated speakers could be tailored for response and dispersion patterns of the typical instruments.

For symphonic playback the number of discrete sources would be prohibitive, but one of the few (IMO) credible things that Bose determined was that in a typical symphonic hall (his measurements were in Boston), something like 90% of the sound arriving at the listener is from the reverberate field. Some may discredit that as a rationalization for 901 speaker series there may be some merit for my ultimate hifi (or perhaps I'm rationalizing).

Modern digital storage mediums make synchronized multiple audio channels trivial. The good news is this could sound like a band playing in your living room, bad news is this could sound like a band playing in your living room.  :cool:

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

KarlH

circular microphone arrays?
« Reply #5 on: April 13, 2007, 11:51:40 AM »
Alembic rises from the Dead  :wink:

JohnRoberts

circular microphone arrays?
« Reply #6 on: April 13, 2007, 12:35:04 PM »
I'm sure it's an old idea, but only recently is decent  multi-channel consumer media possible. One might be able to trick a discrete surround sound system but the speaks wouldn't be optimized.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

circular microphone arrays?
« Reply #7 on: April 13, 2007, 01:48:07 PM »
Hmmm.. What about a ring of vertical line array speakers, to reproduce a sound captured by a flat ring of tiny omni directional microphones? Sounds doable, but what for? Anyway, if acoustical parameters of your living room are different it will sound very different, multi-environmental. If you damp it well, you've loose purpose of rear speakers on the ring. I believe border microphones on walls would be more useful.

Gus

circular microphone arrays?
« Reply #8 on: April 13, 2007, 02:16:53 PM »
The speaker builder article is microphones and speakers in arrays and IIRC there was a weird effect with things like wind chimes.  I will try to find my old issues of Speaker Builder however the back issues are still sold.  

I wonder how many people know of the cool tube preamp P.S. had in glass audio?   I don't have that edtion but a friend showed me the article soom time ago.

Great balls
« Reply #9 on: April 13, 2007, 02:38:13 PM »
Found out something about the spherical microphone I suggested, of course it's already been invented, it's called the Eigenmike, degned by Meyer and Agnello...

It has 24 capsules on a 73 mm sphere or so...

http://www.mhacoustics.com/page/page/2949006.htm

Martin


Eric H

circular microphone arrays?
« Reply #10 on: April 14, 2007, 09:57:03 AM »
Quote from: "JohnRoberts"
one of the few (IMO) credible things that Bose determined was that in a typical symphonic hall (his measurements were in Boston), something like 90% of the sound arriving at the listener is from the reverberate field. Some may discredit that as a rationalization for 901 speaker series there may be some merit for my ultimate hifi (or perhaps I'm rationalizing).

JR


Am I the only one that thought the 901's were brilliant when they came out?

-Eric

JohnRoberts

circular microphone arrays?
« Reply #11 on: April 14, 2007, 10:32:06 AM »
Quote from: "Eric H"


Am I the only one that thought the 901's were brilliant when they came out?

-Eric


The 901 was brilliant on several levels. Since IMO all musical playback is critically flawed by the dimensional mismatch, the 901 approach had merit as one way to attempt to recreate a symphonic sound space. Other argued that the Bozak concert grand was the only way to play believable classical music, different strokes.

The Bose was commercially clever with their active EQ box, allowing it to cover the general spectral character of other popular speaker systems for pop/rock (JBLs, etc) of the day.

They were clever from a manufacturing POV using lots of inexpensive mid range drivers wired in series parallel to realize a load impedance compatible with typical power amps. One more cynical than I could find it more than coincidental that the ratio of direct to reverberant field was 1/9th  :wink:

But you have to respect the success.

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.


 

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