Yamaha's YST-SW315 offers 250 high-efficiency watts--enough power to deliver shattering, movie-theater-like bass effects. Full enjoyment of Dolby Digital and DTS surround sources requires deep, clear bass. This is especially true with 5.1- and 6.1-channel sound, because the ".1" channel is dedicated to the bass frequencies. That means you not only need a subwoofer, but a high-power subwoofer capable of handling extremely low frequencies. The YST-SW315's down-firing 10-inch driver translates power into clean bass sound, and the YST-SW315 boasts a frequency response of 20 to 160 Hz (-10 dB at the extremes of the range). The YST-SW315 delivers high power at deep bass frequencies, with excellent stability and low power consumption. This is made possible by the sub's highly efficient PWM (pulse-wave modulation) digital-drive power amplifier. The amplifier achieves superior conversion efficiency by minimizing power loss from the power transistors. It delivers stable audio power while minimizing AC power consumption and heat production. As it requires no output filter coil, it's extremely quiet with low distortion.
Yamaha's patented Advanced Active Servo Technology (Advanced YST) generates incredible bass from small speaker enclosures. This system uses negative-impedance feedback in the amp and a Helmholtz resonator in the speaker to provide strong and accurate bass.
QD-Bass (Quatre Dispersion Bass) technology uses a down-firing driver with square, pyramid-shaped reflective plates to radiate sound efficiently in four horizontal directions. The reflective plates (not used in other brands' down-firing subwoofers) negate any effects caused by the floor surface and reduce resonance between sound waves reflected from the floor and the unit. Most other systems use circular cones, but the YST-SW315 avoids firing sound into the legs of the cabinet by radiating in four directions. Changing the height of the pyramid varies the acoustic load, permitting relatively simple hig
