A lot of our production and broadcast friends have these JBLs 4408a monitors and a Hafler P3000 in the rack. Well the foam surrounds wear out over time on these suckers but it's an easy fix. Simply Speakers has foam surround kits they sell for about $25.  It's very easy to do and they've created one of the best instructional videos that make it easy to tackle if it's your first time repairing a speaker surround. We highly recommend these kits.  This is the kit we tested.