difussor's

I built five 2 x 4 foot quadratic diffusors for my front wall. I bought the plan from Acoustic Fields. Check out their website they offer a lot of good information. They really added depth, width and clarity to the soundstage. It was a lot of work but well worth it.

Diffusors (at least 1D diffusors) will not deaden the sound in the room, but can clear up and stabilize imaging while leaving liveliness in. If you have dipoles, then diffusors behind the speakers is probably a good idea. Otherwise, they usually work best behind or to the sides (but should be at least 4 or 5 feet away from your listening seat).

If you don’t mind a little (actually very little) work, and are in the USA near some lumber or big box hardware stores, you might want to try my DIY 2D diffusor design (actually designed via computer simulations rather than math formula or cut’n’try). See: http://www.diyaudio.com/forums/everything-else/269366-making-easy-diy-depot-sound-diffuser-panels-st...

If you are in a metric country (and don’t mind a little more woodwork), take a look at Tim Perry’s "Lean Fusers" at: http://arqen.com/sound-diffusers/

While checking back here, I noticed an error in my post above -- my DIY diffusor is a 1D diffusor,  Which is probably the kind you want, 2D diffusors tend to diffuse too much energy toward to floor and ceiling, so that much of it dissipates before it reflects around off multiple surfaces to reach your ears; not a lot different effect than just using an absorber, IMO.

I'm curious as to why one would wish to place diffusors on the front wall with forward firing speakers?  The rear wall and or ceiling would be the correct location.  I would tend to think live end front wall and dead end back wall would be the place to start.