diffusion-why wouldnt this work?

[foreverain4]

i followed a thread the other day that posted a studio with similar diffusors as below. seemed to be popular opinion that they really didnt do anything why wouldnt something like this work? seems like it would be easy (and cost effective) to build, also easy to screw to a wall...

[chris-from-ky]

I see the varying widths between slats but, I thought to be a diffusor it had to be varying depths. So, that may be the reason - wrong dimension being varied. Though it may work if you could angle the slats somehow instead of them being completely perpendicular to the wall they are fastened to.

Good question! I'm curious what Ethan, Glen, and Brian have to say.

[gummblefish]

i'll say it again. I always found a large book case to work great for absorbtion and diffusion. Different size of books, different weights and depths. Ands if you get bored you could always read one.

[foreverain4]

it would be easy to vary depths too. idealy, if these are on control room walls left and right, sound waves are not going to hit then straight on anyway, why would you have to angle them?

[foreverain4]

top view. perhaps if the spaces were smaller in between. the smaller the spaces, the higher the frequency, correct?

[RICK FITZPATRICK]

top view. perhaps if the spaces were smaller in between. the smaller the spaces, the higher the frequency, correct?

Hello foreverain. If you are going to that much trouble, why not adhere to principles that are based on known geometrys/sequences/periods, and have been tested, such as Quadradic Residue, Prime Root or even fractal types. Actually, even your design is based on Schroeder type diffusers, with wells and dividers. However, the difference is these are designed with mathimatical formuli that predict precise well depths, widths and periods etc. It would behoove you to read up on this subject, as I believe you could easily waste a lot of time and material on something that just doesn't work. , Even though common sense may tell you that sound reflects off any surface, that doesn't mean that it will result in a diffuse sound field. For instance, what very few articles mention, is you could actually make the soundfield WORSE, as these type of diffusers are 1/4 wavelength SILENCERS as well I suggest going here and read up a little. Just to illustrate the scienctific background, try reading this thread.

http://forum.studiotips.com/viewtopic.php?t=2312

I've personally asked the pros at that site MANY MANY questions regarding these type of diffusers, and there seems to be different schools of thought, disagreement, and plain old dispute sometimes. Here is a page of "diffuser"
threads. Sometimes, I think this whole subject is SUBJECTIVE
http://forum.studiotips.com/search.php?mode=results


This is why. Here is the best reply I ever heard regarding diffusion. It was by Angelo Campenella..here is what he said..

Heres a little bit of my home-spun philosphy on "diffusion":

1- Diffusion, among other things, depends on the variability if acoustic
impedace across a surface.
2- An absorber placed on a hard surface changes it to be a place where
sound is absorbed instead of reflected.
3- Ergo, places where patches of sound absoption are placed provide a
location where the sound impedance has changed and therefore can act as
a defacto diffusing element of size equal to its dimensions.
4- Therefore, one need not always build awkward objects of wood, plastic
or metal to affect some diffusion: As long as I need or can tolerate a
fair degree of absorption in the subject room, I can place absorber
patches at a variety of locations, and of variable size, and get a very
good start at diffusion.

However, you may want to read something else I have. However, its too long to post here. Let me know if you want to read it, as it is a discussion between two very well known acousticians on this very subject. Let me know and I'll email it to you. PM me if you want it.

BTW, I thought you had some very large polys in your studio? Whats the problem?
fitZ

[Ethan Winer]

Guys,

> If you are going to that much trouble, why not adhere to principles that are based on known geometrys/sequences/periods, and have been tested, such as Quadradic Residue, Prime Root or even fractal types. <

This is the best advice.

Also, the value of varying depths should not be underestimated. When you have many different surfaces all at a different distance, the negative effects of comb filtering are greatly reduced because each depth puts the peaks and deep nulls at a different series of frequencies. This is one great feature of QRD diffusors, and one big reason they're so much better sounding than "poly" curved surfaces.

--Ethan

[Keiffer]

Here's some PICs of my homemade QRDs that I have in my studio

My suggestion is for you to read about the QRD first

[RICK FITZPATRICK]

Here's some PICs of my homemade QRDs that I have in my studio

Hello Keiffer. From first impression only, I'm curious how you calculated well widths/depths and period. The reason I ask, is the depth of these look completely out of character compared to well widths, at least from your picture. Would you mind sharing your calculation method?

[Keiffer]

Hi Rick,

I don't remember all of the math behind designing a QRD. It's been several years since I last looked at this stuff..

Here's a drawing sort of outlining my design:



Also, here's a zip file with the drawing and an Excel spreadsheet that I created to aid in design.

QRD Zip file

kp-