The Logitech mm50 Portable Speakers for iPod uses 3 pressure drivers to maximize bass and minimize distortion. The rechargeable Li-ion batteries last up to 10 hours and you can charge both the speaker system and iPod battery simultaneously. Using 3-D sound processing that widens the stereo effect this system's sound seems to come from an area about two feet wider than the speaker itself. And with a custom travel case you can take the big sound from this small package anywhere.