Can I Bi-amp my center channel?
TXRZ50 receiver and below does not have the ability of Bi-amping the center but only the front speaker. Connect the low-frequency to the Front Speaker terminals, and the high-frequency to the Surround Back Speaker Terminals. The only model in the Onkyo line that does have the ability of both fronts and center Bi-Amping is TXRZ70.
TX-RZ70 Front/Center Bi-Amping