Yamaha NS-SW200 Owner's Manual

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1 EnIn 1988, Yamaha brought to the marketplace speaker systems utilizing YST (YamahaActive Servo Technology) to give powerful, high quality bass reproduction. This techniqueuses a direct connection between the amplifier and speaker, allowing accurate signaltransmission and precise speaker control.As this technology uses speaker units controlled by the negative impedance drive of theamplifier and resonance generated between the speaker cabinet volume and port, it createsmore resonant energy (the “air woofer” concept) than the standard bass reflex method. Thisallows for bass reproduction from much smaller cabinets than was previously possible.Yamaha’s newly developed Advanced YST II adds many refinements to Yamaha ActiveServo 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 soundfrequency. Yamaha developed a new circuit design combining negative-impedance andconstant-current drives, which provides a more stable performance and clear bassreproduction, without any murkiness.Today’s bass reflex speakers use a Helmholtzresonator to improve their bass reproduction.However when reproducing bass that is in thefrequency region of this Helmholtzresonator, air moves violently in and outthrough the port between the interior andexterior of the speaker, sometimes producingnoise due to the turbulent air flow at the endof the port.The port and the cabinet resonate at afrequency that is determined by theirdimensions and shape. On the other hand,turbulence in the air flow at the end of the port contains a broad range of frequencycomponents that are not present in the input signal. This noise occurs because the broadrange of frequency components includes components that match the resonant frequenciesof the port and cabinet, causing strong resonance.The Twisted Flare Port developed by Yamaha changes the way in which the port widenstoward its end, and also adds a “twist” to suppress airflow turbulence at each end of the portand thus prevent noise from occurring.This substantially reduces the “muddy sound” and “wind noise” that until now have beencharacteristic of bass reflex speakers, allowing bass to be reproduced clearly.ADVANCED YAMAHA ACTIVE SERVO TECHNOLOGY IIHigh-amplitudeheavy bass soundPortCabinetAdvanced impedanceConverterActive ServoProcessingAmplifierAir woofer(Helmholtz resonator)Signals(Inaudible) signals of ultra-low amplitudeBass sound(audible soundpressure radiatedfrom diaphragm)TWISTED FLARE PORTConventional PortAir turbulence on both ends of the port creates noiseAir turbulence isproduced.Turbulence isdiffused, air flowbecomes smooth.Twisted Flare Port