Yamaha NS-P300 Owner's Manual download pdf (Page 14)

The theory of Active Servo Technology is based upon two

major 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 the Helmholtz resonance theory, be output

from this opening as waves of great amplitude if the

design is such that the size of the opening and the volume

of the cabinet are in the correct 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 that exists within the cabinet.

Thus it is this problem that is resolved through the

employment of a design in which the amplifier functions to

supply 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, and,

to accomplish this, a special negative-impedance output-drive

amplifier for subtracting output impedance of the amplifier is

used.

By employing negative-impedance drive circuits, the amplifier

is able to generate precise, low-amplitude low-frequency

waves with superior damping characteristics, and 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 with the Helmholtz resonator, reproduce an extremely

wide range of frequencies with amazing sound quality and

less distortion.

The features described above, then, are combined to be the

fundamental structure of the Active Servo Technology.

Signals of low amplitude

Air woofer

(Helmholtz resonator)

Negative-impedance

output drive

High-

amplitude

bass

sound

Signals

Active

Servo

Processing

Amplifier

Cabinet

Port

ACTIVE SERVO TECHNOLOGY (for SW-P30)

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Yamaha NS-P300 Owner's Manual Page 14

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