Yamaha HTR-5940 AV - Manual (Page 140)

11
In 1988, Yamaha brought to the marketplace speaker
systems utilizing YST (Yamaha Active Servo Technology)
to give powerful, high quality bass reproduction. This
technique uses a direct connection between the amplifier
and speaker, allowing accurate signal transmission and
precise speaker control.
As this technology uses speaker units controlled by the
negative impedance drive of the amplifier and resonance
generated between the speaker cabinet volume and port, it
creates more resonant energy (the “air woofer” concept)
than the standard bass reflex method. This allows for bass
reproduction from much smaller cabinets than was
previously possible.
Yamaha’s newly developed Advanced YST II adds many
refinements to Yamaha Active Servo Technology,
allowing better control of the forces driving the amplifier
and speaker. From the amplifier’s point of view, the
speaker impedance changes depending on the sound
frequency. Yamaha developed a new circuit design
combining negative-impedance and constant-current
drives, which provides a more stable performance and
clear bass reproduction without any murkiness.
ADVANCED YAMAHA ACTIVE SERVO TECHNOLOGY II
High-amplitude
bass sound
Port
Cabinet
Advanced impedance
Converter
Active Servo
Processing
Amplifier
Signals of low amplitude
Air woofer
(Helmholtz resonator)
Signals