Motional feedback
Motional Feedback (MFB) is a feedback control (or an acceleration negative feedback principle) of a Hi-Fi - the speaker , inter alia, in the early 1970s -Jahren from Philips has been further developed. Who originally invented MFB can no longer be traced today. The first patent for it applied for on January 1, 1933, a person named Smythe.
An accelerometer, for example in woofers , enables the actual membrane movement to be adapted to the desired audio signal . This allows very low frequencies to be generated by relatively small sound transducers . Any distortion caused by the housing or the woofer itself is intercepted and compensated for.
Since these loudspeakers were made by hand (mostly in the Netherlands ) and the production costs were quite high, they could not establish themselves on the market when cheaper home electronics became more popular in the 1980s . In German-speaking countries, similar systems with accelerometers are used in the fully regulated speakers from Backes & Müller , Silbersand and Schanks Audio .
Velodyne, Linn and meroVinger Audio are now also building a “servo system” for actively operated bass chassis: The chassis have an accelerometer that measures the membrane movements, which are compared with the input signal, which leads to better controlled chassis movements through correction circuits. According to the Linn company, a practically linear frequency response from 19 Hz can be achieved.
literature
- Gustav Büscher, A. Wiegemann: Little ABC of electroacoustics. 6th edition, Franzis Verlag, Munich, 1972, ISBN 3-7723-0296-3
- Helmut Röder, Heinz Ruckriegel, Heinz Häberle: Electronics 3rd part, communications electronics. 5th edition, Verlag Europa-Lehrmittel, Wuppertal, 1980, ISBN 3-8085-3225-4