Motional Feedback (MFB) is an active high fidelity

loudspeaker A loudspeaker (commonly referred to as a speaker or speaker driver) is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A ''speaker system'', also often simply referred to as a "speaker" or " ...

system which was developed by the Dutch

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...

brand in the early 1970s. The loudspeakers have built-in

amplifiers An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It may increase the power significantly, or its main effect may be to boost the v ...

and feature a

feedback Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled ...

sensor on the

woofer A woofer or bass speaker is a technical term for a loudspeaker driver designed to produce low frequency sounds, typically from 50 Hz up to 1000 Hz. The name is from the onomatopoeic English word for a dog's bark, " woof" (in contrast to th ...

. The sensor measures the output

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

of the woofer and compares it to the amplifier input signal. This results in a very low

distortion In signal processing, distortion is the alteration of the original shape (or other characteristic) of a signal. In communications and electronics it means the alteration of the waveform of an information-bearing signal, such as an audio signal ...

and furthermore a more extended low frequency response in a relatively small enclosure. Any distortion induced by the enclosure or the woofer itself is immediately corrected by the feedback loop. To a degree, the sensor-feedback system also compensates for non-optimal room acoustics. Although the Motional Feedback

technology Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, science, ...

had been experimented with for several years, Philips was the first

company A company, abbreviated as co., is a Legal personality, legal entity representing an association of people, whether Natural person, natural, Legal person, legal or a mixture of both, with a specific objective. Company members share a common p ...

to successfully create a working

prototype A prototype is an early sample, model, or release of a product built to test a concept or process. It is a term used in a variety of contexts, including semantics, design, electronics, and Software prototyping, software programming. A prototyp ...

and create a

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

product line of loudspeakers and

equipment Equipment most commonly refers to a set of tools or other objects commonly used to achieve a particular objective. Different job Work or labor (or labour in British English) is intentional activity people perform to support the needs and ...

. The product manager of the Philips High Fidelity group, Piet Gouw, was responsible for the launch of most of the Motional Feedback loudspeakers and other high fidelity equipment. Today, at the age of 86, Gouw is an active member of MFBfreaks.com, the home of Motional Feedback

collectors Collector(s) may refer to: Arts and entertainment * Collector (character), a fictional character in the Marvel Comics universe * ''Collector'' (2011 film), a 2011 Indian Malayalam film * ''Collector'' (2016 film), a 2016 Russian film * ''Collec ...

. He shares historical stories and answers questions on the MFBfreaks.com

forum Forum or The Forum (plural forums or fora) may refer to: Common uses * Forum (legal), designated space for public expression in the United States *Forum (Roman), open public space within a Roman city **Roman Forum, most famous example *Internet ...

. Today, Motional Feedback is used by high-end audio

designers A designer is a person who plans the form or structure of something before it is made, by preparing drawings or plans. In practice, anyone who creates tangible or intangible objects, products, processes, laws, games, graphics, services, or exp ...

. Grimm Audio / Tentlabs have developed the Pro-ls1s-dmf, a digital motional feedback subwoofer which, according to the company, lowers low frequency distortion by 30dB. https://www.grimmaudio.com/pro-products/pro-loudspeakers/pro-ls1s-dmf/ A commercia
product
aimed at the end-consumer market is developed and build by Dutch Archidio, and uses the same technology as the original Philips implementation.

References

External links

MFBfreaks.com - Official Philips Motional Feedback (MFB) collectors' website with Piet Gouw stories

Another Philips MFB website

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Panasonic MF-800 Motional Feedback power amplifier and speakers from the 1960s using Luxman technologyPanasonic Motional Feedback Article from the Miami News, October 19, 1964.
Loudspeakers