hi,
I don't have a sub in my car, but I found since having really stiffened up my car's suspension - my rear view mirror used to vibrate while driving. I went to Clarke Rubber and got a piece of 1mm thick/5cm wide/1 foot length of rubber. All I did was cut a couple of pieces of this rubber and slipped it behind the mirror mount itself where it would 'slip' in - doesn't vibrate as much any more....if that makes sense.
