Thanks Lonely, I will go check it out after I shovel the drive way...

Acoustics First Model C: 2 Dimensional / 4 Octave Diffusor is what I had in mind for my mirror sidewall reflections. It's not too deep that it will work fairly close and it has a huge bandwidth. However that was before Lonely offered his experience. I will probably end up with the units from Decware... performance / price ratio is very good compared to anything else I have looked at.

Beowulf:

1 dimensional diffusers scatter sound left/right, while 2 dimensional diffusers scatter left/right/up/down.

http://www.positive-feedback.com/Issue13/rives2.htm1D Diffusers are probably the most commonly used diffusers in studios and critical listening rooms and offer very predictable results. These diffusers scatter energy in a semi-circular pattern horizontally. Some examples of this type of diffuser are the following:

RPG Inc’s QRD Diffusor (

http://www.rpginc.com/products/qrd734/index.htm) This is the diffuser based most closely on Manfred Schroeder’s academic work on diffusers.

RealTraps Diffusor (

http://www.realtraps.com/diffusor.htm) This diffuser combines the QRD (Quadratic Residue Diffusion) math from Schroeder’s work with low frequency absorption.

Primacoustic Razorblade Quadratic Diffuser (

http://www.primacoustic.com/razorblade.htm) The diffuser uses a sequence of depths that doesn’t appear to be strictly a quadratic residue sequence, in that it is aperiodic and the width of the zero-depth reflectors isn’t consistent. The diffuser does offer a tremendous amount of phase-complexity and probably works very well indeed.

2D Diffusers are most commonly referred to as Skyline diffusers after RPG Inc’s model with that name. They scatter acoustic energy in a hemispherical pattern, both horizontally and vertically. Here are some examples of 2D diffusers:

RPG Inc’s Skyline Diffuser (

http://www.rpginc.com/products/skyline/index.htm) This diffuser is based on a primitive root number sequence instead of the more commonly used quadratic residue number sequence.

Art Diffusor Model W from Acoustics First (

http://www.acousticsfirst.com/diffuser-art-diffusor-model-w.htm) This diffuser uses both the more linear 1-D architecture with various block heights of the Skyline diffuser in a unique way.

Auralex Acoustics’ Wave Prism (

http://www.auralex.com/sustain/waveprism.asp) The Wave Prism uses a grid of dividers to separate the blocks of different heights which, according to Schroeder, offers better diffusion properties.