Diffusors in enclosures?

Most enclosures use absorption to control reflections, has there been any success with diffusers in speaker enclosures. I believe that B&W's Matrix enclosures were an attempt at this, are they still using this technique when they're not winding up their reflections?
What other techniques have been tried? Quadratic-Residue Diffusors?

Thank you in advance for your input, as always
Regards WALKER
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Walker:

I don't know how curious you are about this, but this fellow seems to be the person to ask:
http://www.aes.org/events/111/specialevents/Heyser.cfm

His Email address is listed at the bottom of this page:
http://www.physik3.gwdg.de/~mrs/

Judging by the conversational tone of the second link, an Email might not be inappropriate. He did put his Email address on the net.

[Edited by kelticwizard on 11-28-2001 at 08:54 PM]
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Walker:

I read the review of B & W 801 Matrix in Audio magazine some years ago. To the best of my recollection, the reviewer stated that the matrix pattern inside was for strengthening the enclosure walls only. The reviewer did dwell on how well braced the enclosure was. I do not recall anything in the review about diffusing the sound in the enclosure.

Either the reviewer missed that part, or I forgot it, LOL.
 
Something might have skipped my mind over the years, but the general idea in matrix constructions is to stiffen the box, as well as dispersing and distributing the energy between the panels involved. A well calculated matrix will also break up and distribute the resonance modi of the panels.
Have I got it all wrong ??? Maybe I should not believe to much in Martin Colloms after all.....
 

AndrewJ

Member
2001-09-05 6:37 pm
The matrix enclosure was indeed designed to address the problems of enclosure wall vibrations, by strenghtening and cross coupling all the panels. It was not intended to act as a diffuser, though this might be a small by-product of the extensive bracing panels. It is in fact very difficult to provide diffusion inside the enclosure. The diffusers have to be comparable in size to the wavelengths involved, by which time they have occupied a significant portion of the internal volume, making it neccessary to increase the size of the box, which moves the standing waves down in frequency, which therefore needs bigger diffusors, which...You get the picture!
A better approach is to use multiple smaller woofers in a sub-divided enclosure. This moves the standing waves up in frequency and out of the working range of the speaker, at least for the bass section. The midrange enclosure standing waves are then best dealt with by appropriate absorbant.
 
Making The Matrix

You can find out, what B and W have to say about their matrix system, here :-
http://www.bwspeakers.com/products/...object_id=3A7556CF-4779-11D4-A67F00D0B7473B37
I spoke to friend who used to work there, and she says that it was designed with "solutions to both problems in mind".
Either they just designed it for both reseons, or just the matrix was intended to stiffen/diffuse, and the other solution was just a byproduct?