Advanced Yamaha Active Servo Technology Ii; Twisted Flare Port - Yamaha NS-SW300 Benutzerhandbuch

ADVANCED YAMAHA ACTIVE SERVO TECHNOLOGY II

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.
Cabinet
Port
High-amplitude
heavy bass sound
Bass sound
(audible sound
pressure radiated
from diaphragm)
(Inaudible) signals of ultra-low amplitude
1 En
Air woofer
(Helmholtz resonator)
Advanced impedance
Converter
Active Servo
Signals
Processing
Amplifier

TWISTED FLARE PORT

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.
Air turbulence is
produced.
Conventional Port
Air turbulence on both ends of the port creates noise
Turbulence is
diffused, air flow
becomes smooth.
Twisted Flare Port