Yamaha's Advanced Active Servo Technology employed in this subwoofer is a complementary amplifier/speaker system utilizing negative impedance feedback in the amp and a Helmholtz resonator in the speaker to provide strong and accurate bass from small speakers. The subwoofer is magnetically shielded so it can be placed near a TV monitor or receiver without fear that it will degrade the picture. The user adjustable continuously variable high-cut filter sets the highest frequency the subwoofer will deliver. It can be set anywhere from 50 to 150 Hz. For instance, if the filter is set at 75 Hz, only frequencies 75 Hz or below will be delivered by the subwoofer. This allows the sub's output to be matched to the other speakers in the system and the room's acoustics for a seamless presentation. The volume control permits the perfect matching of the sub's output to the overall volume of the system. For convenience, the YST-SW45 has a signal sensing circuit. When the subwoofer detects an audio signal, it turns its po... Minimize