I have the CS6's as well but have found that the bass in my setup rolls off more or less nicely into the mid-20hz range. I am driving them with a Krell FPB-300. I have found that using different amps can cause changes in the frequency response especially in the deep bass. My speakers are also a little over 4 feet from the rear wall. I found that I got the smoothest overall response where they are now, not closer or further out from the rear wall. It sounds to me that you are getting a room interaction problem to get the spike in the 20hz region after they start rolling off in the 32-50hz region. How close are they to the rear wall?
Room Acoustics Problem?
By Audiogon standards, I have a mid-level system with Brystons (BP-25, 7B-STs), Thiel CS6's and the Perpetual Technology DACs (posted not too long ago on Virtual Systems). I'm annoyed by a saturated sounding mid-range and was exploring some options with the help of fellow Agoners on other posts. Then, I ran into Sean's March 3 post on how to run a more accurate frequency distribution reading with the Radio Shack SPL meter and the Stereophile CD. Here goes: At an 80db base, 20-25 Hz is OK, 32-50 drops off to -6db, 3db spike at 63, 80-315 OK, 3db drop at 400, 500-4000 OK, 4-6 db spike at 5000 & 6300, 10000 OK, 12500 and over drops off like crazy (3 moving to 10 db). OK is defined as plus or minus 2db. Does this sound like a room acoustics problem? Big room, lots of cushy furniture, hard wood floor. Is there something else I should be looking at? Help! Thanks in advance.