Polyfill acts to increase apparent volume of a sealed enclosure. Every pound of polyfill increases apparent volume of an enclosure by 0.1 cubic feet for a maximum increase of approximately 10% of total volume. The material should be loosely packed for such applications. I have never actually used the material so I cannot comment on it damaging drivers.Paperwork with my speaker (10" CSS) mentions placing 1lb of polyfill in the sealed enclosure. But do they mean loose polyfill or the stuff on a roll? I'm worried this loose stuff can get into the voicecoil etc?