For your consideration Neoprene rolls comes in various thicknesses and widths,W/Without adhesive. I purchased a 54" roll 1' wide and 1/4" thick with adhesive. This turned to be enough cover 4 speaker stand top plates completely with some left over.
I think these pads work great. Keeps my speakers secure, and absorbs quite a bit of vibration.

http://www.amazon.com/Cleverbrand-Ne...5213785&sr=8-3