Yamaha YST-SW011 owner manual Advanced Yamaha Active Servo Technology

Advanced Yamaha Active Servo Technology

The theory behind Yamaha Active Servo Technol- ogy is based on two factors: the Helmholtz resona- tor and negative-impedance drive. Active Servo Processing speakers reproduce the bass frequen- cies through an “air woofer,” which is a port or opening in the speaker’s cabinet.

This opening is used instead of, and performs the functions of, a woofer in a conventionally designed speaker system.

Thus, signals of low amplitude within the cabinet can, according to Helmholtz resonance theory, be output from this opening as waves of great ampli- tude if the size of the opening and the volume of the cabinet are in proportion to satisfy a certain ratio. In order to accomplish this, moreover, the amplitudes within the cabinet must be both precise and of sufficient power because these amplitudes must overcome the “load” presented by the air in the cabinet.

This problem is resolved by a design in which the amplifier supplies 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 accomplish this, the system utilizes a special nega- tive-impedance output-drive amplifier that sub- tracts the output impedance of the amplifier.

By employing negative-impedance drive circuits, the amplifier is able to generate precise, low-ampli- tude, low frequency waves with superior damping characteristics.

These waves are then radiated from the cabinet opening as high-amplitude signals. The system can, therefore, by employing the negative-imped- ance output drive amplifier and a speaker cabinet featuring a Helmholtz resonator, reproduce an extremely wide range of frequencies with out- standing sound quality and low distortion.

The features described above combine to create the fundamental structure of conventional Yamaha Active Servo Technology.

Our new Active Servo Technology — Advanced Yamaha Active Servo Technology — adopts Advanced Negative Impedance Converter (ANIC) circuits, which allow the conventional negative impedance converter to dynamically vary to select an optimum value for speaker impedance variation. With these new ANIC circuits, Advanced Yamaha Active Servo Technology provides a more stable performance and improved sound pressure com- pared to conventional Yamaha Active Servo Tech- nology, resulting in more natural and dynamic bass reproduction.

High-amplitude bass sound

Cabinet	Air woofer
	(Helmholtz resonator)
Port
Advanced Negative
impedance Converter
	Active Servo	Signals
	Processing
	Amplifier

Signals of low amplitude

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