Diffusor question

Hey guys,

I have a question for you acoustics/treatment experts. I would like to make my own 2D QRD type diffusor. I have some cheap RPG Omnifusors but instead of square wells, I would like to make mine cylindrical. I'm 99% sure this will work but I would like some input for any of you that are more familiar with the theory behind this type of diffusor. My primary reason for the different shape is to minimize parts and simplify construction. Bottom line; do QRD diffusors require square or rectangular shapes?

Thanks in advance.

Marcus

ORIGINAL: themidiroom

Hey guys,

I have a question for you acoustics/treatment experts. I would like to make my own 2D QRD type diffusor. I have some cheap RPG Omnifusors but instead of square wells, I would like to make mine cylindrical. I'm 99% sure this will work but I would like some input for any of you that are more familiar with the theory behind this type of diffusor. My primary reason for the different shape is to minimize parts and simplify construction. Bottom line; do QRD diffusors require square or rectangular shapes?

Thanks in advance.

Marcus

I think the main thing would be the predictabilty of the design. Just like the response of a rectangular room is easier to predict than an irregular shape. Part of the design is that diffusion is created several ways. From sound bouncing around after contact from the walls, back and multiple combinations of contacts in the cavities. All this bouncing around also changes the phase of the waves as they exit the diffusor and contact other waves entering the diffusor. At that point there is cancellation. Using the established designs and principles gives you a predictable spread of diffusion.

I think a tube design would eliminate some of the diffusion due to the fact that waves encountering a curved surface would be directed more toward the center of the arc. Since this is in effect channeling the wave into a specific direction, it seems to me that it would eliminate the randomization of the diffusion pattern. This would decrease the diffusion effect and possibly beam frequencies in a particular direction.

Bottom line, it would diffuse but not as good. I'm in manufacturing and if there was an easier way to build a diffuser out of tubes instead of the current design, believe me, they would be doing it and either be selling more of them for less money or putting more profit in their pocket.

well, first off,I applaud you for thinking "diffusion" before "absorption".

Too many people think that treating a room involves nothing more than throwing up 1" sonex wall to wall.

LOL..how wrong they are.

Diffussion is essential, but like any treatment, it's not the "end all-be all" answer either.

The best results I ever achieved was when I used a ratio of 50/50 in regard to diffusion/absorption.

I think diffusion is actually easier to accomplish, because besides the traps you have in mind, any object in a room - shelves, pictures, chairs, anything with an irregular surface - will act as a diffusor. To what degree and to what success, depends of course on the freq's you are trying to treat.

Bottom line is that I don't think that a diffusor needs to be any particular shape; rectangular, cylindrical, etc.

I'll tell you who is a real bad ass at this kind of stuff, and that is Nprime. Rod (NPrime) has a serious handle on acoustic principles. You may want to give him a ping.

If I can contact him, I'll send him over here to give you his input.

-D.

Here are some links. I was looking into DIY diffusers a while back, and saved these links. Some are not the type you specifically mentioned, but I posted them because you may change your mind on the type to build, or may want to build multiple types. Warning. Some of these are deep into science & math.
http://www.acoustics.salford.ac.uk/student_area/bsc3/room_acoustics/diffuser_design.pdf
http://www.acoustics.salford.ac.uk/research/arc/cox/interdisciplinary/inter_science_reviews.pdf
http://www.bbc.co.uk/rd/pubs/reports/1990-15.pdf
http://www.mhsoft.nl/DiffusorCalculator.html
http://www.pmerecords.com/Diffusor.cfm

I hope these help.
Dave