Rick,

You may want to pull the QS8 down and make sure all the allen screws holding the drivers are all good and tight. Then before you re-assemble it to the bracket, you might want to get some Quake Hold or Quake Secure (Google it ) and put some between the bracket and the speaker and the bracket and the wall, then tighten it all back down...You might also want to check to make sure you don't have a broken grill connector as at the right frequency, it may buzz...

Suggestions of my .02...

WhatFurrer

"Meddle not in the affairs of Dragons, for you are crunchy and good with ketchup..."