I tried to use my old speakers. a set of Klipsch RF-62 II.The problem is the AVR850 doesn't has enough power to drive the B&W 804D2 !!!
when those are connected instead of the B&W 804D2 to the receiver, there are no errors of disconnections. could be there is some wrong with the speakers? how can I verify it?!!!
https://geoffthegreygeek.com/understanding-speaker-sensitivity/