GuitarHacker gives good info.
To expand on this though .. I have found that putting sound treatments on the wall behind me (where the speakers are pointed at) DID make a noticeable difference.
Less 'room' and less standing bass. Cleaner.
YMMV
You need to experiment in your own unique room.

That said, when I mounted my speakers on the wall I did include pads between the speaker and the mount. Couldn't hurt.


Make your sound your own!
.. I do not work here, but the benefits are still awesome