jeremycox, I love your qrd. It should work ok.. be sure to place some damping material in the empty spaces.
(I have actually succeeded in making excellent qrds with foam board. :D like Formular 150. - but I used 1 1/2 inch board and made the wells 1 1/2 inches wide.)
The home-made QRD should be at least 8 inches deep.. That way you get diffusion down to 848Hz - with 1 1/2 inch wide wells.. you get excellent diffusion up to 2.26kHz. But your 4 1/2 in depth and well width of ?? 2 1/2 inches will only give good diffusion from 1.3kHz to 1.5kHz.
Yes, you will notice a nice change talking in front of it. And, yes, it will improve your room. But if you are going to put time and effort into this, why not really make it good?
Using MDF or similar you will get the best response as a strict diffusor due to the material being non-resonant and having a low absorption ratio.
You could use aluminum coil for the well dividers - found in the roofing section of stores like Home Depot and Lowes. Spray paint with a latex wall paint to finish.
I have uploaded an Excel spreadsheet so that you can calc ANY QRD you wish and look at the calculated freq. response. This spreadsheet will give you all the measurements you need to build one.
I really appreciate what you are doing. The QRD diffusor is the best thing you can do for your studio... even if it's only the ones that jeremycox has done - Great job, Buddy.
I could go on and on about the horrible dead rooms
that I have had to work in.. omg. but i wont.
Good luck everyone building these! Build a BUNCH
of em.. use them in every room.. not just the CR. You can even get away with using a small booth for recording.. and actually KEEP
the recording.. if you fill the booth with QRDs. They are a wonderful and much overlooked tool in the acoustics designer's arsenal.
Remember, commercial products are designed for (in this order).. looks, price, functionality. When you build your own.. you can put functionality on top. :D