Advanced Yamaha Active Servo Technology

The theory behind Yamaha Active Servo Technology is based on two factors: 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’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 amplitude 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 negative -impedance output-drive amplifier that subtracts 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-impedance output drive amplifier and a speaker cabinet featuring a Helmholtz resonator, reproduce an extremely wide range of frequencies with outstanding 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 compared to conventional Yamaha Active Servo Tech- nology, resulting in more natural and dynamic bass reproduction.

 

 

 

Cabinet

Air woofer

 

 

 

(Helmholtz resonator)

High-amplitude

 

 

 

 

 

 

Port

 

 

 

 

 

 

bass sound

 

 

 

 

 

 

Advanced Negative

 

 

 

 

 

 

 

 

impedance Converter

Active Servo

 

Signals

Processing

 

 

 

 

 

Amplifier

 

 

 

 

 

Signals of low amplitude

5