It just happens that my sub sits in the left corner of the room. From my sitting position, the popping sure sounded like it was coming from the QS-8. I was actually able to stop the popping by changing the Onkyo setup from -10db to -15db out to the sub.

David M60's, VP150, QS8's, Onkyo TX-SR805 HSU VTF3-MK3 Samsung HL-T6187S Oppo DV-981HD