Diffuse Front Wall? Absorb rear wall?

May I ask what fq. range diffuser do you use behind speakers? Currently I have 1 mounted behind each 34 1/2" tall speaker. Diffuser panels are 2x4’ raised 1’ above floor. This design is tested effective in the neighborhood of 3100 hz on up. Does this sound ok (no pun intended)? I'm a little limited with placement being that theres a wall mounted LCD 3' above floor level. 

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.

Basic answer-yes. Maximum diffusion (phase+time) behind the speakers will allow you to best hear what your speakers produce. I like a combination of diffusion and absorption on the rear wall.

After speaking with one of the well known manufacturers of acoustical products, based on their recommendation, for my new room I will be treating the front corners and first and second side reflections with absorption/traps; and the back wall with a few of their absorption/diffusion combo products. I will then evaluate further to decide if i need anything else. 

@meerzistar. I ordered mine from ATS on Amazon. Each diffuser is about 8" deep and scatters from 325 Hz up to 3000. In the past few days, I've added more ASC tube traps and they really clean up the strident sounds. What really helped was a pair of 16" diameter traps 4' tall, one in each front corner (w/smaller diameter traps perched on top so the whole column goes up to the ceiling. Then, more tube traps on the first order reflection points against the side walls. So, now I have the best of both worlds, ambiance and timbre. Here's were you can find more info about the diffusers. http://www.atsacoustics.com/acoustic-diffusers.html