Move your sub

Best bass sound is when you sit on the subwoofer in your listening position. You really "feel " the bass...

contuzzi, erj1953,

I am using (2) JL Audio F-113 subs slightly behind and the side of  the main speakers. 
First I set them with there own JL calibration mic. 
Then, I own a DEQX Premate along with its many features it has an electronic crossover. With its calibration process you can set levels including delay. All of this frees the sub for placement most anywhere in the room.
I also have ASC Bass Traps in the corners of the room. 

ozzy

@avanti1960  +1! about always connecting subs from the main speaker amplifier.  As you said, it integrates so much better with the main speakers.  I cannot tell where the mains leave off and the subs pick up with the bass!

I've had just the opposite experience connecting my JL subs to the speaker connection (high level inputs).  It changed the tonality of my system and seemed to soften dynamics. 

Using the outs from my pre-amp has been better.  I'm now going to try actually crossing over to my mains to check that out.

 

I tried one subwoofer, but I always had the impression, real or not, that I wasn't getting true stereo.  So I added another.  Both were positioned below or next to the main speakers because I wanted the wave front to be as coherent as possible - which doesn't happen when the mains and the subs aren't in the same areas.  Anyway, I continued to use the subs when I got my Martin Logan ESLs until one day when I disconnected them and found the sound much improved.  The subs (actually sub, since on was blown by a recent power outage) are now working with a pair of Celestion SL6si's.