Originally Posted by sheltonct
My guess is any typically constructed room can use a degree of acoustic treatment.
Yes. All rooms need bass trapping and first reflection treatment.
However, if your ears don't know any better
The first time you hear a properly treated room it will be very obvious, no matter what your level of audio expertise.
(in fact, if they keep getting happier with just better gear over time)
At some point folks are just fooling themselves thinking the sound is better. This is why so many people wrongly believe that a good room is needed to hear the improvement from high-end gear and cables, etc. In fact, a good (treated) room is needed no matter what level of gear you have. Once you get to a certain level of quality, which is not expensive with electronic gear, paying more gets you nothing. It's not the gear! It's the source material, the loudspeakers, and the room, in approximately that order.
how do you begin to judge to what degree and which treatments you need?
You already got good advice about the Room EQ wizard software. But if you don't have a computer connected to your system you can just play a few low frequency sine waves and walk around the room while each plays. The peaks and nulls and bass variation will be very obvious. There are several such test signals on my company's site including a test tone "CD" you can make. Look here:http://www.realtraps.com/info.htm
Also, I have to disagree with the usefulness of the Acoustic Treatment "master thread" here at AVS. It outgrew its value years ago, and now is too long, contains too many conflicting and outright wrong opinions, and will likely confuse more than help. See my Acoustics FAQ
. It's a fair amount to read, but is infinitely shorter than the sticky thread, and all the advice is to the point and accurate.