I have worn traditional headphones for years.  I find them more comfortable than most ear buds.  The seal the ear piece gives aids in better audio experience and especially with comfort.  Here's my suggestion:   Add a foam donut that would serve as a soft comfortable ear cup to aid in both speaker placement, adhesion and speaker performance.  The foam ear cup would conform to both the rider's ear and the helmet ear socket.  The inner edge of the foam cup would match with the outer edge of the speaker and help center the speaker to the ear canal.  I would assume that wind noise, etc. would be diminished by the concentration of sound to the ear and allow the rider to run the speakers at a lower volume which (guessing here) would aid battery life. 

I ride with the Fly Trekker helmet and the SyMax II flip helmet.  Looking at the helmets in my garage it appears that nearly all of them have remarkably similar ear cups despite a wide range of manufacturers.  I would be more than happy to assist in testing this idea.  I think it would be an exciting improvement to an already great product!

Greg