Powerful Subwoofer with Advanced Technology for Top-Class Sound Quality. Ideal Match for 225 Series Speakers. QD-Bass (Quatre Dispersion Bass) Technology Advanced YST II (Yamaha Active Servo Technology II) PWM Digital Drive High Efficiency Amplifier Linear Port for Minimizing Extraneous Noise 150 W Dynamic Power BASS (Bass Action Selector System) 20cm (8) Multi-Range Driver with Magnetic Shielding 28200Hz Low Frequency Reproduction Auto Standby with Sensitivity Selector (HIGH LOW and OFF) Low (0.5W) Standby Power Consumption Powerful Smart Bass High amplifier power assures enough power to deliver shattering movie theater-like bass effects and the down-firing 8-inch cone driver translates the power into clear bass sound. The YSTSW225 has a frequency range of 28 to 200 Hz. Yamaha s BASS (Bass Action Selector Switch) tailors the sub s output for video or music at the touch of a switch. The subwoofer is magnetically shielded so it can be placed near a TV monitor or receiver without degrading the picture. For convenience the YSTSW225 has a signal sensing circuit. When the subwoofer detects an audio signal it turns its power on. When it senses no signal for several minutes it shuts itself off. Advanced YST Yamaha s patented Advanced Active Servo Technology (Advanced YST II) generates incredible bass from small speaker enclosures. Advanced YST II is the ideal method of combining amplifiers and speakers for maximum performance. This system s advanced negative impedance converters intelligently adjust the negative impedance generation as the speaker moves creating a hard rigid cone that prevents deep resonant waves from leaking out of the speaker cone. This means the full power of the waves is forced out through the air port resulting in clear powerful bass. QD-Bass Technology QD-Bass Technology uses down-firing drivers with square pyramid-shaped reflective plates to radiate the sound efficiently in four horizontal directions. The reflective plates negate any effects caused by the floor surface and reduce resonance between sound waves reflected from the floor and the unit. Also most other systems use circular cones but by radiating in four directions to avoid the legs of the cabinet QD-Bass reduces turbulence caused by reflection from the legs. Changing the height of the square pyramid varies the acuostic load permitting relatively simple high-cut adjustment and improved bandpass properties. The QD-Bass system provides extraordinary power and smooth frequency response from an extremely compact unit. It also allows greater freedom of placement since the sound radiates with equal effectiveness in all directions. High-Cut Filter The user-adjustable continuously variable high-cut filter sets the highest frequency the subwoofer will deliver. It can be set anywhere from 50 to 150 Hz. For instance if the filter is set at 75 Hz only frequencies 75 Hz or below will be delivered by the subwoofer. This allows the sub s output to be matched to the other speakers in the system and the room s acoustics for a seamless presentation. Other Features Other features that make the YSTSW225 a pleasure to own and operate include dual inputs that allow the sub to accept either line level or speaker level input signals. You also get a volume control which permits the perfect matching of the sub s output to the overall volume of the system. Three-way speaker terminals accept banana plug and a variety of other connectors as well as speaker wire. The YSTSW225 s cabinet is constructed of thick MDF to increase rigidity and reduce vibration and resonance and the handsome black ash finish blends in with room decor and complements many furniture styles.