[Bi-amped powered Advents]

Are you working with the Powered Advent speakers referred to as Powered Advent Loudspeakers (PALS)?

[Powered Advent Speakers]

I have two pair of PAL's.  When I refurbished them I needed to remove the black foam bricks but they just turned to dust as I tried to remove them.  I replaced with batting material from a fabric store.  The material can be purchased in various thickness and I used the 4 inch thick material.  It looks similar to fiberglass but is a synthetic material that is white.  It worked very well for me and it is not "prickley" like fiberglass.  The store was a fabric/sewing retailer call JoAnns.  It is located in the quilting/batting area.