Yamaha YST-SW012 - Manual (Page 9)

5
Advanced Yamaha Active Servo Technology II
In 1998, 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 ampli-
fier’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.
High-amplitude
bass sound
Cabinet
Port
Air woofer
(Helmholtz resonator)
Advanced impedance
Converter
Active Servo
Processing
Amplifier
Signals of low amplitude
Signals