Yamahas Advanced Active Servo Technology 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. High amplifier power assures enough power to deliver shattering movie theater-like bass effects, and the down firing 10-inch long stroke cone driver translates the power into clear bass sound. The PWM digital drive amplifier is extremely efficient and stable. The YST-SW315 has a frequency range of 20 to 160 Hz.