MartinLogan Depth i High-Performance Triple 8-Inch Servo-Control Subwoofer (Single, Dark Cherry) BalancedForce triple woofer alignment for near-total cancellation of cabinet vibrations that muddy the bass Three high-resolution 8-inch aluminum cone woofers with triple servo control for ultimate precision bass 25Hz Level Control (+/- 10dB) to compensate for acoustically destructive room interaction in the low-frequencies Frequency response: 20120 Hz 3dB; Anechoic through LFE effects input 350 watt (900 watt peak) high-resolution amplifier