Yamaha YST-SW215 8" Powered Subwoofer (Discontinued by Manufacturer) 8-inch cone driver and built-in 120-watt amplifier Down firing driver radiates sound in all directions YST Active Servo Technology for expanded base response 30 to 200 Hz response, plus line level and speaker level inputs Measures 11-7/16 by 14-3/16 by 12-7/16 inches (width by height by depth)