My basement mixing room measures 10'6" W x 11'4" L x 7'3" H. The ceiling is suspended acoustic tiles with 8" of fiberglass batt above. The floor is concrete covered by carpeting except for a 4' x 4' patch of laminate flooring under the listening position. The front wall is sheetrock and the side walls are a mix of sheetrock and closet doors. I am installing a large amount of bass trapping per Ethan Winer's recommendations and adding first reflection absorption on each side and above the listening position.

My question regards the back wall which is sheetrock over concrete foundation wall. Should I use more absorption here or add 1D QRD diffusion?

As always, thanks for your advice.

You could use either diffusion or absorption. They both solve the problems caused by reflections at mid and high frequencies. Diffusors make the room sound a little bigger, which is a benefit. But good diffusors cost more than good absorbers, whether DIY or bought commercially. Either way, in a small room like that you should plan for bass trapping on that entire wall, wherever you don't have diffusors.

--Ethan

Thanks Ethan.

Is the diffusion more important for recording than for mixing?

Diffusion is useful for both. Basically, it makes a room sound larger than it really is.

--Ethan