.... The USB connection makes it possible to control the speakers with a very cool software package on the computer.
The subwoofer has two stero minijack inputs and a USB input. The subwoofer then outputs to the satellite speakers. If you try to connect just the USB, you get NO sound. Maybe there is some way to direct the sound in your computer through the USB port, but I don't see how. Whether or not you control the speakers with the software or with the physical controls on the speakers, you still have to plug the sound card into the speakers.
I don't think this is a negative and the sound is still great. But don't buy these speakers if you think you will connect them only through USB or if you do not have a sound card.