Yamaha NS-PA41 Owner's Manual

Also see for NS-B40: Owner's manual Owner's manual Owner's manual Owner's manual Owner's manual

8 EnEnglishIn 1988, Yamaha brought to the marketplace speaker systems utilizing YST (Yamaha Active Servo Technology) togive powerful, high quality bass reproduction. This technique uses a direct connection between the amplifier andspeaker, allowing accurate signal transmission and precise speaker control.As this technology uses speaker units controlledby the negative impedance drive of the amplifierand resonance generated between the speakercabinet volume and port, it creates moreresonant energy (the “air woofer” concept) thanthe standard bass reflex method. This allows forbass reproduction from much smaller cabinetsthan was previously possible.Yamaha’s newly developed Advanced YST IIadds many refinements to Yamaha Active ServoTechnology, allowing better control of the forcesdriving the amplifier and speaker. From theamplifier’s point of view, the speaker impedancechanges depending on the sound frequency.Yamaha developed a new circuit designcombining negative-impedance and constant-current drives, which provides a more stableperformance and clear bass reproduction,without any murkiness.Today’s bass reflex speakers use a Helmholtz resonator to improvetheir bass reproduction.However when reproducing bass that is in the frequency region of thisHelmholtz resonator, air moves violently in and out through the portbetween the interior and exterior of the speaker, sometimes producingnoise due to the turbulent air flow at the end of the port.The port and the cabinet resonate at a frequency that is determined bytheir dimensions and shape. On the other hand, turbulence in the airflow at the end of the port contains a broad range of frequencycomponents that are not present in the input signal. This noise occursbecause the broad range of frequency components includescomponents that match the resonant frequencies of the port andcabinet, causing strong resonance.The Twisted Flare Port developed by Yamaha changesthe way in which the port widens toward its end, andalso adds a “twist” to suppress airflow turbulence ateach end of the port and thus prevent noise fromoccurring.This substantially reduces the “muddy sound” and“wind noise” that until now have been characteristic ofbass reflex speakers, allowing bass to be reproducedclearly.ADVANCED YAMAHA ACTIVE SERVO TECHNOLOGY IITWISTED FLARE PORTHigh-amplitudeheavy bass soundPortCabinetAdvanced impedanceConverterActive ServoProcessingAmplifier(Inaudible) signals of ultra-low amplitudeAir woofer(Helmholtz resonator)SignalsBass sound(audible soundpressure radiatedfrom diaphragm)Conventional PortAir turbulence on both ends of the port creates noiseAir turbulence isproduced.Turbulence isdiffused, air flowbecomes smooth.Twisted Flare Port