Rumble Road amplified speakers....best I have ever heard. I've had the RR's on my last 3 bikes (covering 8 years). Currently have my R3 setup with satellite radio and the RR's and can hear them perfectly at any speed. Many of the other handlebar systems you will hear sound "tinny"...not these. Very well made product, easy to install and look nice on the bike.
The speakers have a self-contained amplifier built into the speaker housing that provides plenty of power. Here's the link:
MH Instruments: Motorcycle Speakers and Accessories
Best of luck and hope this info helps.