I currently have treated my space via some purchased acoustic panels after I built my own (unattractively) with muslin etc and then handed those down to my cousin.
I would now like to add some diffusion. I will either build some 2'x4' 1-dimensional QRDs or a big polycylindrical. I am not interested in skylines due to size and ugliness.
For the QRD, I can model my work off of the common calculator online and http://www.soundcontrolroom.com/products/diffusion/qrd.htm
Question: What glue/caulking should be used to make sure all MDF components are 100% sealed? I presume any holes no matter how small will negate effectiveness ... True/false?
Additionally, is type of wood important here? MDF is used by the co above, but another offers all wood types.
On the other hand, I have considered going with polyclindrical (cheaper, but now seeming unlikely due to prospective difficulty in bending plywood and making the unit freestanding, transportable, and not just bracketed to the wall), ala this description:
If you want something easy to build and effective down pretty low, try a DIY polycylindrical. While not a 'diffusor' in the classic sense (doesn't scatter sound randomly), it can acutally have a smoother dispersion curve across a wider frequency range than a QRD.
They're really, really easy to make. Think about something that is made from a 4'x8' sheet of plywood bent and slid into 2 slats that have angled slots cut into them. Fill in behind with insulation and you're pretty well done. Bracing the edges will help but initially isn't necessary to see the benefits.
The trick with this is to make one BIG diffusor - like 6.5' wide with a large radius and maybe extending from the wall 8-10". This scatter sound evenly across the room dimension and is easily effective down into the lower vocal range (low hundreds of Hz).
How would the sound of each compare? I have never heard either before and have no way of listening.
I might go 2-3 QRDs vs. 1 polyclindrical along the longest wall. QRDs are more money and time of course but more attractive/modular and thus may be more likely ...
Any links re: 1D QRD or polycylindrical construction would be appreciated.