ATC C6 Sub- How Good is it??

After reading a review fromm 2000 on the concept7 system it seems that the c6 sub had a big drop off around 40HZ-Is that normal for such a expensive sub- if i understand that it means that the sub loses punch under 40HZ- am i missing something or for such an expensive sub should it not be flat to at least 25HZ- bill- again you do not hear much about this sub-

I don't think you need to spend $9000 grand on a sub to have excellent bass response. Check out subs by James, the EMB1500, Manley Labs tower of power, that is supposed to be the baddest sub on the planet. You might want to check out avsforum.com that has a forum devoted to subwoofers.

A good sub is not just about frequency response - harmonic distortion and power output are also important. The THD is quoted less than 1 % for this sub, which is low for this frequency range and driver size. It is driven by 1000 watts. It is rare that your room will be linear in low frequency response so adjustments are often necessary (placement, notch filters)...but distortion, once you have it, cannot be eliminated and can effect clarity in lower mid range.

I think this explains the high cost, but as Shiva points out, depending on your requirements, there are plenty of good subs out there and a great many significantly less than $9000.