ASC makes a model called the Martix Panel, designed for the wall behind the listening position, if the listener's head is within two feet of that wall. It provides a mix of absorption and diffusion, so as to not make for too dead a sound. Maggie owners use tall Ficus trees behind their speakers as diffusors, and then there are LP racks which are of some benefit at scattering sound.
Diffuse Front Wall? Absorb rear wall?
I'll research existing threads, but quick basic question --- is it a basic tenet that I should use a diffusing approach for the front wall and an absorption for the rear wall behind my listening position? I bought a wall rug, put it on the front wall, and though it seemed to quiet the room down in some good ways, it seems to have sucked some of the energy and sparkle from the soundstage. thanks.