"The Ultras have a more modern day look when compared to the ProMedia GMX D-5.1 they reviewed last month. They also have a certain "Are you ready to rock!?" aura about them. With a subwoofer enclosure that is 20 percent larger, the ProMedia Ultra 5.1 subwoofer incorporates a series of refinements designed to increase efficiency for more total output, lower distortion and deepen bass extension. These improvements include a lower tuning frequency, a voice coil that is 60 percent longer and a larger, slotted port. The subwoofer is a bass-reflex type with dual 8-inch side-firing woofers and convex driver dust caps for unsurpassed high output linear bass response."