high frequency diffuser/flutter control

Hi, I'm a newbee planning to build a couple of wood diffusers to compliment my Rockwool absorbers to control flutter. I have been looking at a couple commercially built diffusers and they're quite expensive. But they would be quite easy to build if I only knew the measurements. My question is really what calculator I could use to build some of these? There are quite many calculators like this: http://www.digitalaudiorock.com/cgi-bin/qrd.cgi But what should I be using for this project? Hope someone can help :-) Best regards

RPG also make something simular: http://www.rpginc.com/products/flutterfree/index.htm best regards

I understand the second picture is based on quadratic residue diffuser with prime=7 But the first picture i don't understand could it be loosely based on the same but with prime=11? The with is 20cm and the depth is 9,5cm the bandwith is supposed to be 1.000-16.000Hz any one? Best regards