In my upgrade trek, my SV sub is next. Right now i've got an SV 20-39PC w/original driver. If i was to go with duel subs, like let's say, duel 20-39PC+'s, how would i go about calibrating them ? With my current sub i just go to the test tone for my sub on my Ref50. Do i only turn one of them on and do one at a time ? Or, do you turn the amp and phase to identical positions on the back of the powered woofs ? Assuming these two subs would be right next to each other.. (left & right of each other or, front & back to each other ? ) Thanks gang..