I replaced my rear Bose speakers and just could not shake this buzzing when the bass hit. I discovered it was comming from the rear grills, and not the speakers themselves. I discected them and removed the felt from around the 6x9 oval section and reinstalled them. The buzzing is now gone! Im not sure if it is a coincidence, or not. But I have been trying to tackle the buzzing for 6 months and now it is gone. If it comes back I will update.

Jay