Funny you ask that today as I was looking into that just last night! I think I've decided to go with the RPG Diffractal 2'X4'EE (depending on the price) or possibly try the new Primacoustic Razorblade: http://www.cabletek.ca/Press/Razorblade_pr.htm for the rear walls. At $200 a piece, you can't go wrong!
As for the ceiling, I really don't know what to do myself. I have a hardwood floor and an 8 foot textured sheet rock ceiling. So I think I need SOMETHING for the ceiling. I want something that diffuses and doesn't really absorb as the front of my control room (the front wall, front side-walls, and front ceiling) is dead. But I also don't want it to cost much.
At one point I toyed with the idea of trying to make quadratic residue diffusers, similar to the RPG QRD models. I never got around to it, but I did get as far as chasing down the math used to calculate the well depths to use.
For someone with half decent carpentry skills it might not be to hard. Definately worth it, as covering a wall with those RPG ones could cost literally thousands.
I always meant to write a quick cgi script to do the calculation, and after seeing this thread I decided to finally knock one out. Here it is:
I figure I'll need 6-8 panels on the ceiling AND on the rear wall. Each panel is about 24" sq. and has a max. height of 6.25" They are molded plastic panels and would need to be back filled.
Thanks for the info. I like the look of the Razorblade diffusors. Although the price is higher the density and heft of design is reassuring. I may use these on the rear wall where the 8" displacement will be less a problem than overhead (7'4" ceilings!)
The RPG "Skyline" is what I had in mind originally but it is more expensive than my budget allows.
Tom, thanks for the formula page. I sure hope somebody here is better prepared than me to take advantage of your efforts. I'm not much of a wood worker (unfortunately) and am still working my way through F. Alton Everest's "Master Handbook on Acoustics"
I Have built 1 so far.As money seems to ALWAYS be an issue at this point.........I worked out the quadratic residue formula for the prime 43(like the RPG 4311 model)which is supposed to diffuse from 300 to about 6K or somewhat thereabouts.If you have a table saw with a decent guide it is pretty quick and easy to cut......everything in pairs.Glueing it all together is a little time consuming but it was worth it.I think I used 5 sheets of MDF to make it happen at $30 Canadian per sheet.I am seriously considering having a mold made so that I can whip more up as the need arises.I am DYING to get some of these in the studio room to see.......ahem....hear what happens.The only problem I can see with this would be the density thing .