9
Advanced YAMAHA Active Servo Technology (on the SW-P270)
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-
amplitude, 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 Technology, resulting in more natural
and dynamic bass reproduction.
High-amplitude
bass sound
Cabinet
Port
Air woofer
(Helmholtz resonator)
Advanced Negative
impedance Converter
Active Servo
Processing
Amplifier
Signals of low amplitude
Signals
00_NS-P270/276_UB.book Page 9 Friday, December 2, 2005 4:36 PM
