Why, one front/one back sub, a double distance?

No double distance. If you sit equidistant from the two (one sub in front and one behind) then you should enter that distance (from you to one of the subs) in your pre/pro. Also make sure the subs are in phase. This will ensure that sound from your sub arrives in phase with that from your main speakers (assuming you put the correct distance into your mains on the pre/pro)

Finally without performing actual measurements with a microphone and a sweep I don't think you can even begin to know what the actual sound is like at the listening position. If it sounds better by putting in the wrong distance then you have room modal issues or placement issues of a sub is wired out of phase.

Typically, Audyssey will measure the "distance" of the subwoofer(s) as significantly longer than the physical distance because the delay, not the distance, is the critical measure. In the real world, that delay is sum of the physical distance and the time-delay introduced in the processing circuitry of the sub channel.

Kal

Hi Pmcneil, you said "a response flat below 10 htz:;and there is no other way to get this at any price)."

That is a great lowwww bass response, how did you measure this? And I would love to see a graph of it. My sub is flat to 12hz, I use the free program from the Home Theater Shack "REW" with a calibrated mic. What program do you use?

Bob

Have you tried running the rear sub "anti-phase"?