Room acoustics

How about a thread on room acoustics and ways to improve the in-room performance of your system and its speakers? Subjects covered could be the physics of room response, measurement of response in your own room, and how to deal with imperfections, above and below the Schroeder frequency, like damping, bass traps, speaker positioning, (multiple) subwoofers, and dsp equalization. Other subjects could be how to create a room with lower background noise for greater dynamic range, building construction, or what to do in small rooms.
I am a bit busy just now, but as soon as I have time I will try to kick off with some posts and links.
Great thread so far with a lot of information. When taking FR measurements, what kind of smoothing needs to be applied? IOW, what is the minimum Q of a mode that should or needs to be dealt with?
geoffkait, Yes you might be right because the guy was telling me that since he got his room done professionally his systems didn't sound as good. He has had hundreds of speakers and components and even 100,000 system. It definitely helped sales. I probably wouldn't of bought them. You have to watch out when buying equipment. But back to room acoustics I have read many articles on room acoustics and to get it done right you need somebody to come in and measure all the room nodes and so forth. You can probably buy a few acoustic panels and reflective panels. It probably would help to a certain degree. But as I pointed out before get somebody that knows what their doing if that is important to whoever really wants to put that kind of money into a room. Audiophiles can be obsessive to a large degree. I just want to be happy and listen to the music on a nice system. Yes that guys  100,00 system sounded phenomenal especially in that room. But like I said he wasn't happy until he got that done. That just goes to tell people how important Room Acoustics really are. Laterr  
@robd2 (why don't these @things work?)

I'll generate that graph when I'm back from the dentist.
@toddverrone much better, now you can see more of what's going on. Here are a few targets for you to hit with your tuning from the excellent Acoustic Frounteers guide.

Resonances from 35Hz­300Hz should not extend beyond 350ms before decaying into the noise floor or reaching a level of ­40dB.

Below 35Hz this standard is relaxed to 450ms.