Yamaha NS-P300 Owner's Manual - Page 14

ACTIVE SERVO TECHNOLOGY (for SW-P30) The theory of Active Servo Technology is based upon two Thus it is this problem that is resolved through the major factors, the Helmholtz resonator and negative- employment of a design in which the amplifier functions to impedance drive. Active Servo Processing speakers supply special signals. If the electrical resistance of the voice reproduce the bass frequencies through an "air woofer", coil could be reduced to zero, the movement of the speaker which is a port or opening in the speaker's cabinet. This unit would become linear with respect to signal voltage, and, opening is used instead of, and performs the functions of, to accomplish this, a special negative-impedance output-drive a woofer in a conventionally designed speaker system. amplifier for subtracting output impedance of the amplifier is Thus, signals of low amplitude within the cabinet can, used. according to the Helmholtz resonance theory, be output By employing negative-impedance drive circuits, the amplifier from this opening as waves of great amplitude if the is able to generate precise, low-amplitude low-frequency design is such that the size of the opening and the volume waves with superior damping characteristics, and these of the cabinet are in the correct proportion to satisfy a waves are then radiated from the cabinet opening as high- certain ratio. amplitude signals. The system can, therefore, by employing In order to accomplish this, moreover, the amplitudes the negative-impedance output drive amplifier and a speaker within the cabinet must be both precise and of sufficient cabinet with the Helmholtz resonator, reproduce an extremely power because these amplitudes must overcome the wide range of frequencies with amazing sound quality and "load" presented by the air that exists within the cabinet. less distortion. The features described above, then, are combined to be the fundamental structure of the Active Servo Technology. Highamplitude bass sound Cabinet Port Negative-impedance output drive Air woofer (Helmholtz resonator) Active Servo Processing Amplifier Signals Signals of low amplitude 14