Foam bass traps and diffusor panels

I like Auralex (look at Auralex.com) better than tube traps. Tube traps are like a turntable, you never know when you have the things exactly right in the room or what position and degree of rotation. I have had great results with Room Lens also. Auralex makes some excellent diffusor systems also.
See my pictures on my system.
Sgr

Correction: my room dimensions are 21'5'' x 16'8'' x 8'. I have my speakers positioned according to formula-
Room width x 0.447= distance from the back wall;(7'5'')
Room width x 0.276= distance from the side wall (4'7'')
According to Rives these distances should be 5'9'' and 4'4'' respectively.
My sitting position is in the apex of the triangle with all sides of equal length. Initially it used to be closer to speakers, with the same bass response pattern. Moving it farther away didn't change the sound much, with the exeption of the subjective impression of sitting in the middle of the concert hall instead of the front raw.
Actually the ideal width of my room with the same lenght should be 13'3'' vs. my 16'8''.

Now I understand more of your problem. You have undoubtedly dimensional induced bass standing waves. Have you done a check with a sound level meter (Radio Shack) with a test disc (Rives is adjusted to the RS meter) to find out where your bass rises and suckouts are? And, more importantly how broad or narrow they are? When you measure at the listening position remove the chair and walk back and forward a bit and see what happens (ditto for the speakers) - this will help you ID which frequency is, or might be, problematic because of seat/speaker positioning, and which frequency is a room node problem (as that won't change much with speaker/seat changes. Its the pits - I've got a 9db rise at 32 hz that I just can't get rid of so I feel for you.

Thank you, Newbee! I do have an SPL meter, but haven't gotten around to the test disc yet. That's definetely a next step. I'm also waiting to complete some reconstruction project- building a new wall, the left side of my basement is open to the adjacent part. So I don't want to make any changes now until I've completed the wall, which definetely should change the whole picture.
Wanted to hear your comments, though, on the speakers placement measurements- should I go with the Rives or with the above formula? Regards.

Well, FWIW, Rives places my speakers within a few inches of where I had already located them by ear/meter/disc - I didn't move them. His program had the seat a foot more forward than I set it, coming much closer to an equalateral triangle. I have found with most speakers I prefer something closer to a 11 to 10 ratio with the speaker being further from the speakers than the speakers from each other. For me the process was (1) finding good basic imaging, (2) realigning seat and speakers to get the bass as flat as possible, then (3) fine tuning the imaging over a period of many months - no more than an inch at a time, with a considerable intrim period between movement. Slow gets it done right - at least thats what the turtle thinks. Let us know how it works out.