Hi There.I have the "Acoustimass® 10 speaker system" and a "Harman Kardon AVR7550HD 7.2 Channel Audio/Video Receiver" , how can i utilize all 7 channels and 2 sub woofers , where i can plug in 2 more speakers and one sub-woofer, please advise.
Looking at the manual for your receiver on line you have two banks of speaker binding posts, front and rear L&R on the left bank and center and back rear L&R on the right bank, you have two sub line outs to feed to powered subs with single RCA type cords, sub 1 is on the far lower left in the pre out section and sub 2 is above and to the right of it in the analog audio section. Hope this is of some help, you'll want to review the manual to properly configure everything.
For 7.1 you would have a pair of surrounds to the left and right of your seating position. And an additional set of rear surrounds are placed behind your head. A second subwoofer is ideally placed opposite of your primary subwoofer and away from corners.
Depending on the Acoustimass Series you own, it may or may not be possible to upgrade to 7 channels. But a second sub an option.
The subwoofer will plug in to the PURPLE RCA line level labeled "SUBWOOFER 2"