I have a Radio Shack (RCA derived) center channel speaker that has the woofer surrounds destroyed. I put too much power to this RCA Pro C555 (Radio Shack Cat# 40-5011 and they started to distort. After removing the grille, it was immediately apparent that the foam surrounds had rotted and begun to disintegrate. I took them apart and the only thing I can see wrong is that they need re-coning. These speakers feature a Linaeum tweeter. Have not tested the tweeter. I found a surround repair kit at Amazon that is supposed to be correct for them.
Center Channel Speaker info - Catalog Info
Surround Kit - Repair Kit
I have no desire to try my somewhat shaky hands at re-coning these woofers. This speaker had very good sound for a long time but not worth my time to repair it. If you were looking for a box to build a decent looking center channel of your own design, these would provide a very well made box for you to start out with. If anyone out there is interested, contact me and it's yours.