http://melhuish.org/audio/diy35.htm

Scroll about halfway down for some good piezo modifications. Damar varnish is available at craft stores in the art section, and rope caulk can be found in hardware stores. I think modeling clay could be just as effective as rope caulk and would be easier to find. It also would not hurt to put rope caulk on the basket of the woofer also.

David