I have the same type of sound coming from Klipsch RF-7's, also bi-amped, if you mean mid/highs get one channel of the amp(755) and the two tens get thier own channel of the amp(755). Two tower speakers are getting four channels of the 755 Amp. This has been going on for a year and I have just assumed it was the caps dischaging once the amp was going into standby mode. I don't think it is hurting the speakers.