In addition to the above suggestions... If you want to reproduce the lowest bass octaves, stiffen your floor from below. If you have heavy speakers, seperating them from the overall cross bracing and bracing them to the sub floor in the basement or crawl space also helps. Treating first reflections with something like ASC tube traps gives a significant improvement in the mid bass to midrange.
Listening Room Upgrade
I am having the carpeting replaced in my listening room and am looking for any ideas on how to improve the acoustic properties of the room while I am at it. The only ideas I have come up with are to put down 1/4" plywood flooring to stiffen the floor and to use non-synthetic carpet. Any help with material choices and installation methods is greatly appreciated. My current floor consists of modern floor trusses(18" O.C.) with 3/4" tongue and groove flooring. I do not think I can use a material greater than 1/4" for the sub-floor because of matching considerations with an adjoining room. God bless.