The 3808 is one of the more powerful receivers. Tested into 2ch at 187 wpc at 8 ohm (.1%thd), into 5ch at 119 wpc at 8 ohm (.1%), into 7ch at 113 wpc at 8 ohm (.1%)....\n\n\nI had a hard time finding any reliable specs. Denon have minimal on their site.\nEppie has given the correct advice to sort this out. I think this is one of the strangest faults we have ever had reported. The only connection I can think of between the cone moving and speakers, is if some circuit is getting woken up by the back EMF created by moving the cones. It could feed back to the PA input first stage via negative feedback. The specs you quote show enough power to blow the speakers. Since he uses 5 channel stereo it is highly plausible to blow up all the speakers.\n\nI know one thing, unless the speaker wiring is a mess, he has either dud speakers or a dud receiver.