I picked up a pair of thin, 1.5" (2"?) speakers at the local electronics store and installed them in my Shoei by pulling out the liner and the styrofoam around the ears, and melting holes with a soldering iron. A little wiring and a surplus coiled mic cable from the surplus shop gave me a fairly clean, fairly audible installation. I ride with earplugs and the audio (radio) turned all the way up. It sounds awful from the outside, lots of distortion, etc, but with earplugs, it's not bad. (Earbuds never worked for me, but I know many people swear by Koss "The Plug" earphones.)