Yamaha NS-SW050 Owners Manual - Page 8

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 negativeimpedance 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 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 eliminates 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 Turbulence is diffused, air flow becomes smooth. Twisted Flare Port Air turbulence on both ends of the port creates noise 5 En