Sony SA-WM500 150 Watt Active Subwoofer (Discontinued by Manufacturer) Built-In Amplifier with 150W into 6 ohms from 20 Hz-200 Hz at 0.7% THD Bass Reflex Design with 12" Driver Frequency Response 24-170Hz Line Output for Additional Subwoofer Advanced SAW (Super Acoustically Loaded) Bass Reflex Design