Take a look at this link
http://www.audioholics.com/tweaks/do...ter-seat-riser
I build mine with 2 x 6 and stacked them together to get a 12" riser ... I didn't stuffed with fiberglass or anything to absorve the sound, but it doesn't vibrate. I used marine carpet (you can find it at Lowes, Home Depot, etc.); I like it because is thin.
If youre planing on using buttkickers, is better if you use isolator to detach the riser from the floor ... it will give you a better experience, or you can use the isolator for every seat.
