I've got a Sena SMH10 and use it on my Schubeerth C3, Arai Vector-II, etc., and the sound quality is fine for me, however, that might be due to partial hearing loss from riding years ago for long periods at high speeds w/o any hearing protection.

It is my understanding that the new Sena 10S and 20S have noticeably improved speakers over the SMH10 and that they are plug-n-play to retro-fit to the SMH10 it that helps anyone.