determining the "real" depth of diffusion?

dymaxian · Post by **dymaxian** » Sun Jul 18, 2004 11:37 am

Here's a deep theory question for the board gurus...

When building a QRD diffusor, or something like my idea in the other thread here

http://www.johnlsayers.com/phpBB2/viewt ... ab57baaf8e

the effective low range of diffusion is determined by the depth, right?

Now, is that the depth of the baffles, or the depth from the front edge of the diffusor to the deepest reflective surface?

For example, those baffles in my ceiling are not mounted flat to the ceiling... there's a gap of about 2" above them. Some of them will have 1" rigid fiberglass insulation panels above them (perhaps all, depending on how dead I want the room to be...)

So is the effective depth equal to the depth of the baffles, or the distance from the bottom tip to the flat ceiling above? Do diffusors like this benefit from spacing them away from the walls or ceilings the way 703 panels do?

Has anyone found out?

dymaxian · Post by **dymaxian** » Fri Aug 06, 2004 12:21 am

Is this one of those questions that needs real-world testing?

barefoot · Post by **barefoot** » Fri Aug 06, 2004 1:53 am

The depth of the deepest well governs the low frequency cutoff of a QDR. I wouldn't count on this being true for your design. My guess is this design will only be effective at fairly high frequencies (>4kHz) and low angels of incidence.

Thomas

cadesignr · Post by **cadesignr** » Sat Aug 07, 2004 5:13 am

Hello Kase. This doesn't exactly pertain to your direct question, and as a total layman, I shouldn't even post a reply to this, but I feel, especially after years of trying to understand and decipher the truth about diffusion, I came to conclusion that small room diffusion is difficult at best, is a myth when low frequency is concerned. I finally based my conclusion on my final question regarding this subject on this thread I posted at Alt. Physics.com. Draw your own conclusions, as there was NO diffinitive answer. Only opposing opinions from various professional acousticians. My original quest on this subject was prompted by pictures of various types of diffusers in Alton Everests Master handbook.
That was in the early 90's. I know this doesn't answer your question but it may help illuminate the subject. I by no means am saying that diffusers don't work in small rooms. Although, certain people with credentials have told me EXACTLY that. Yet others have told me just the opposite. I just hate seeing people waste time and money on concepts that have NO total agreement among professionals. I may be wrong, and if this ONLY serves to bring out further discussion than I have succeeded.

Although my lack of current information may ignite some flamethrowers or cause me to be run out of town on a rail.

All I know is I gave up chasing information on the subject.
http://groups.google.com/groups?q=small ... com&rnum=1
fitZ