How do I dampen my listening environment?

I said "It should be the same size as you wall. Otherwise how would you know what is missing?"

If the first reflection point is the only point of reflections you are worried about then sure one small mirror will do. But the first reflection is only a small fraction of the reflections we hear. Dont forget to put mirrors on the front wall, rear wall, ceiling and floor! They may be 2nd, 3rd 4th... reflection points but add up much more than one single reflection point.

Bob

Octave Doctor PHP

Acoustat

I may have this wrong, but from what I have read there are only four reflection points on the side walls that matter in a two speaker setup. The reason is that each speaker has only one reflection point on each side wall that directs sound to the listening position. All the other reflections off the side walls pass either in front of or behind the listening position. The mirror technique for locating these reflection points works because a mirror on the side wall will reflect light coming from the speaker position to the listening position only when placed at the reflection point.

When I used a mirror to locate the side wall reflection points in my listening room, I used a mirror about 1 foot x 1 foot and the trial and error method. It was a PITA because I didn’t have any readily available furniture on which I could place the mirror at eye level when sitting in the listening position, and I had to improvise by stacking things. So, yes, a larger mirror would have made the whole process easier for me, but a larger mirror wasn’t necessary to determine 3rd, 4th and other reflection points. The easiest way to use the mirror to locate the reflection points is to have another person hold the mirror and move it around until the person sitting in the listening position can see the light from the speaker reflected.

Other reflections in the room can cause excessive reverberation or ringing, but this is different in nature from the problem caused by 1st and 2nd reflection points. Excessive reverberation causes smearing and overhang and muddies the sound. First and second reflection points create a time difference in a specific sound reaching the listener and makes it hard to determine the location of the sound within the soundstage. In other words, imaging of specific sound sources is impaired. The solution to both problems is absorption of the unwanted reflections. However, ringing (detected by clapping hands) is solved by distributing sufficient sound absorbing materials around the listening room. First and second reflection points are solved by having sound absorbing material at those specific points.

Dougmc said, "but this is different in nature from the problem caused by 1st and 2nd reflection points. Excessive reverberation causes smearing and overhang and muddies the sound. First and second reflection points create a time difference in a specific sound reaching the listener and makes it hard to determine the location of the sound within the soundstage. In other words, imaging of specific sound sources is impaired. The solution to both problems is absorption of the unwanted reflections. However, ringing (detected by clapping hands) is solved by distributing sufficient sound absorbing materials around the listening room. First and second reflection points are solved by having sound absorbing material at those specific points."

I agree 100%. What I was getting at is that 1st and 2nd reflection point are just the tip of the iceberg.
The initial post question was "How do I dampen a room?". The answer to that is you need more than the 1st and 2nd reflection points covered. Which is why you need a full room mirror including the ceiling and floor!

Bob
If the first one hundred db suck, why continue?

I think it was me that mentioned the mirror thing. I did a lot of research on the subject, forgot most of it. It's not seeing the light reflected, it's being able to see the tweeter's reflection in the mirror. You have someone move the mirror across the wall at the heighth of the tweeter. Once you can see the tweeters reflection in the mirror, that's where the panel goes. This works for the second reflection point as well. You can treat you ceiling with panels but it's going to have to be the ceiling or the floor. No way getting around it.The idea of heavy curtains, book shelves loaded with books, bass traps in the corners can all make a huge difference and become very expensive as well. You really need to throw an area rug and nice pad down though. I can't imagine you're ever going to be completely happy without it.

The mirror idea is a proven method but hardly necessary. Ever go for a bank shot when shooting pool? Simple geometric principle, like a bank shot on a pool table. I think I'll bring a mirror along to my next match.