The helmet speakers are great for commutation at lower speeds .... Behind the great big windshield of the Harley. In the wide open expanses at higher speeds ear buds are the way to go.
If you want to take it to the next level, get "EarFit" ear buds... Not cheap, but it's like sitting in a sound studio at all speeds... I found with over the counter ear buds, the sound level on my iPod would have to be set at 60 to 70%, with speakers at a 100% and with EarFits the volume never has to go above 30%.
There are apparently really quite helmets out there bring down the noise level substantially, but well over $600, so that's an area I would not be able to comment on.
2011 BMW R1200GS Triple Black, 2010 HD Heritage Softail, 1983 Yamaha RZ350, 1978 Yamaha XS650 SE,1967 Honda CD125, 2007 Kawasaki Super Sherpa, 2004 Yamaha BWS, 2007 Yamaha BWS, 1973 Honda CT 90 Trail, 1980 Honda C70 Cub.