Originally Posted by ygayle
I'll be using room mainly for mixing, but also to record vocals and maybe some acoustic guitar. Room dimensions are 8 x 10 x 8.
Your room may be too small for diffusion. No need to worry about this (yet). You almost have a cube, not very ideal for acoustics.
The fabric prevents the escape of fibers, that could potentially end up in your lungs. Therefore if your trap/panel has an air gap, with having fibers exposed, cover it with acoustic transparent fabric. (like you would do the front)
If that fabric is not visible (like the back of a reflection panel, mounted with a gap between itself and the wall), you may use some cheaper, less "fancy" looking one like muslim, burlap, cotton, as long as it is acoustically transparent too. It can save you some money.
If there is no air gap between your trap/panel and the wall/corner, you can either use the wall as seal, or something like cardboard, paper, plastic, wood etc.
This is how I constructed my clouds and early reflection panels:
On the front I used speaker fabric at the cost of $7 per yard. The back was covered by a cheap stretch fabric at ~$2.50 per yard, that was spray-glued (mainly on sides and with very little glue) onto the back panel. The sides of the Roxul panels are covered by the outside wooden frame, no need for fabric there.
Detail view of the assembled panel (fabric in the back is black; grey on front):