Owner's Manual

8 En
English
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.
Today’s bass reflex speakers use a Helmholtz resonator to improve
their bass reproduction.
However when reproducing bass that is in the frequency region of this
Helmholtz resonator, air moves violently in and out through the port
between the interior and exterior of the speaker, sometimes producing
noise due to the turbulent air flow at the end of the port.
The port and the cabinet resonate at a frequency that is determined by
their dimensions and shape. On the other hand, turbulence in the air
flow at the end of the port contains a broad range of frequency
components that are not present in the input signal. This noise occurs
because the broad range of frequency components includes
components that match the resonant frequencies of the port and
cabinet, causing strong resonance.
The Twisted Flare Port developed by Yamaha changes
the way in which the port widens toward its end, and
also adds a “twist” to suppress airflow turbulence at
each end of the port and thus prevent noise from
occurring.
This substantially reduces the “muddy sound” and
“wind noise” that until now have been characteristic of
bass reflex speakers, allowing bass to be reproduced
clearly.
ADVANCED YAMAHA ACTIVE SERVO TECHNOLOGY II
TWISTED FLARE PORT
High-amplitude
heavy bass sound
Port
Cabinet
Advanced impedance
Converter
Active Servo
Processing
Amplifier
(Inaudible) signals of ultra-low amplitude
Air woofer
(Helmholtz resonator)
Signals
Bass sound
(audible sound
pressure radiated
from diaphragm)
Conventional Port
Air turbulence on both ends of the port creates noise
Air turbulence is
produced.
Turbulence is
diffused, air flow
becomes smooth.
Twisted Flare Port