Impressively deep bass output from a powerful subwoofer with a beautiful exterior. Yamaha's Advanced YST II (Yamaha Active Servo Technology II) combines negative-impedance and constant-current principles to drive the speaker cone with extremely tighter control. Using Advanced Negative Impedance Converter (ANIC) circuits, this system dynamically optimizes effective speaker impedance to maintain excellent linearity. This means more stable and accurate low range response, not to mention higher sound pressure levels. This means more stable and accurate low range response, higher sound pressure levels, and the ability to reproduce clear bass without muddiness.