M&K Sound X10 THX Ultra2 Certified Dual 10" Active Subwoofer (Black) You will receive:1 X10-BLK Subwoofer Having invented the subwoofer four decades ago, M&K Sound is uniquely qualified to present a new generation of superb bottom-end reproduction systems, capable of astounding, detailed low-end impact and authority. The X Series subwoofers build on the proven M&K Sound concept of dual drivers operating in push-pull configuration in a sealed enclosure for in-room response flat to well below 20 Hz with transient speed, precision and weight that other subwoofers simply cannot match. The X Series subwoofers follow the World Known THX program and each individual model deliver performance well within the very strict THX requirements.