New shape subwoofers with Yamahas latest technologies, including Advanced YST II, Linear Port and down-firing design plus best matching for front surround systems and micro component systems.Advanced Yamaha Active Servo Technology (Advanced YST) is a unique system in which the speaker and amplifier work together to cancel out impedance so the speaker unit has a perfectly linear motion. Advanced YST helps to ensure the highest levels of sound pressure and overall performance.