Yamaha YST-SW20 Subwoofer Speaker

Exclusive Yamaha system allows the amp and the speakers to work together to boost the power of a stereo speaker's output. Instead of an ordinary woofer unit, the YST-SW20 has a Helmholtz Resonator that intensifies the sound waves inside until they are output as much stronger sounds. Total impedance (resistance to current flow) has to be zero, so the amp's circuitry produces negative impedance, canceling out the speaker impedance. The result is bass sound that is very powerful. The speaker can be located near a TV or video monitor without distorting the picture. The subwoofer will turn itself on automatically when it senses a music signal. It will also turn itself off automatically shortly after the music signal stops. The built-in power amplifier allows a wide application from audio to lower-powered HiFi A/V and multi-media systems.