[Jens Eklund]

A common misconception about diffusers made of EPS is that they don’t reflect as good as wood or other dense materials. This can be true if low-density EPS is used and not painted. I did some measurements on my panels and the effect of a coat of paint is obvious:



In the low frequency region, the only thing affecting absorption is the mounting, which can actually be used to create a membrane absorber to battle modal issues. More information on the effects of mounting and the membrane effect here:
Flooring question