YST-SW005

The effectiveness of Advanced Yamaha Active Servo Technology (Advanced YST) is based upon two principles: the Helmholtz Resonator and negative-impedance drive. Active Servo Processing speakers reproduce the bass frequencies through an "air woofer," which is a port or opening in the speaker cabinet. This port is used instead of, and performs the functions of, a conventional woofer. Low amplitude signals inside the cabinet can, due to the Helmholtz Resonance principle, be output from this port as high amplitude waves if the design is such that the size of the port and the volume of the cabinet are in a certain proportion. In addition, the wave amplitudes inside the cabinet must be precise and of sufficient power, in order to overcome the "load" presented by the air within the cabinet. This is accomplished by employing an amplifier that is capable of supplying special signals. If the electrical resistance of the voice coil could be reduced to zero, the movement of the speaker unit would become linear with respect to signal voltage. To achieve this, a special negative-impedance output drive amplifier is used, so the impedances cancel out and become zero. By employing negative-impedance drive circuits, the amplifier is able to generate precise, low-amplitude low frequency waves with superior damping characteristics. These waves are then radiated from the cabinet opening as high amplitude signals. This amplifier/speaker combination is capable of reproducing an extremely wide range of frequencies with excellent sound quality and low distortion. Advanced Yamaha Active Servo Technology improved upon this basic concept by adopting Advanced Negative Impedance Converter (ANIC) circuits. These circuits allow the converter to dynamically vary in order to select the optimum values for speaker impedance variation. With these new circuits, Advanced YST provides even more stable performance and higher sound pressure levels, resulting in more natural and energetic bass reproduction.