Yamaha YST-SW325 8-Inch Advanced YST II and QD-Bass Subwoofer, Black (Discontinued by Manufacturer) 150-watt active subwoofer with high-efficiency PWM amplifier and luxurious wood finish cabinet 8-inch multi-range cone woofer with magnetic shielding; 25 Hz to 180 Hz frequency response Advanced YST II system produces stable, energetic low-range tones; 50 to 150 Hz high-cut filter QD-Bass system radiates sound in 4 horizontal directions; Bass Action Selector System (BASS) Auto standby mode; measures 12.38 x 14.94 x 14.75 inches (W x H x D); 2-year warranty