Best products for baffle material s ?

I have a pair of concept 90 CM1/CM2. The cabinet for the CM1 is a phenolic material and is completely braced in a matrix (the original matrix speaker). The speaker cabinet sounds inert with the unscientific knuckle rap test. I don't recall what the original baffle material is. Is it phenolic, and how thick is it? I know the cabinet must be completely air tight as any air leak causes the woofers to bottom out. I can't see how you could gain much by changing the baffle material.
Granite rings and really is not a sensible choice in my estimation.

Rh I had no idea the CM1 woofer could bottom out. I have always maintained screw torque but never driven the speakers very hard. But even so the cabinets are nowhere near inert. (However I drive them with a 200 watt Spectral amp with ample current; lots of clean power available for dynamics-but even so these little B&W's don't have good dynamics.) Making the baffle inert will improve dynamics considerably.

"09-10-14: Ptss
How about 3/4 or 1&1/2 inch black granite countertop green glued onto 3 inches thickness of MDF? Very non-resonant?"

Corian would probably still be the better choice. It has the consistency of mdf but is solid like granite. You wouldn't have to mix materials to get the best results.

Rh, would you like to sell your CM2's? I don't see them in your
system.

Ptss, I sent you a private message via A-Gon. I would consider selling the CM2 bass modules.