First met Mr. Foley at NOMAD, held annually in Danbury Ct. (thanks to the Patons...as usual). He's a nice guy and told me (humourously I think) that the only material suitable for the diaphragm was the wrapper from the New York Times!
Moon, if you wanna REALLY have fun, get a couple of big funnels from an auto supply place and stick 'em in each side. You now will have the LOUDEST STEREO KAZOO in the universe! I use it in kids' shows. Have fun.