page_title: Loudspeaker
section_title: Magnetostatic loudspeakers
hierarchical_section_title: Loudspeaker / Other speaker designs / With a diaphragm / Magnetostatic loudspeakers
caption_attribution_description: A pair of late 1970's Magnepan MG-1 speakers. The speaker on the right has had its cover removed, revealing the planar drivers. This is a sheet of Mylar with a larger region of heavier gauge wire glued on to form the bass/midrange area and a smaller area of finer wire producing the treble. The Mylar sheet is tensioned a few millimeters above matching rows of permanent magnets so that the whole sheet vibrates like a drum skin when current from an amplifier is passed. The large surface area means the sheet is well damped by the air it moves. Being very light the sheet can stop and start noticeably quickly. This characteristic combined with the lack of chesty colouration caused by a speaker box is what makes the addictively realistic Magnepan sound. Later and more expensive models also use a true ribbon tweeter to extend the treble range. These units are renowned for their speed, accuracy and complete lack of "spit and sizzle". There are a couple of minor drawbacks: They are large; approximately the size and shape of a smallish interior door and to produce enough bass room placement is very important due to the motion of the mylar sheet suffering cancellation by reflected sound waves. People who love these speakers but are forced to adopt disadvantageous room positioning may resort to using a high quality sub-woofer. Magnepan remain popular today and provide a true high end sound at a reasonable price. Current models are listed at Magnepan's site: Magnepan
context_page_description: A loudspeaker is an electroacoustic transducer; a device which converts an electrical audio signal into a corresponding sound. The most widely used type of speaker is the dynamic speaker. The sound source must be amplified or strengthened with an audio power amplifier before the signal is sent to the speaker.
  The dynamic speaker was invented in 1924 by Edward W. Kellogg and Chester W. Rice. The dynamic speaker operates on the same basic principle as a dynamic microphone, but in reverse, to produce sound from an electrical signal. When an alternating current electrical audio signal is applied to its voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction, which causes a diaphragm attached to the coil to move back and forth, pushing on the air to create sound waves. Besides this most common method, there are several alternative technologies that can be used to convert an electrical signal into sound.
context_section_description: Instead of a voice coil driving a speaker cone, a magnetostatic speaker uses an array of metal strips bonded to a large film membrane. The magnetic field produced by signal current flowing through the strips interacts with the field of permanent bar magnets mounted behind them. The force produced moves the membrane and so the air in front of it.  Typically, these designs are less efficient than conventional moving-coil speakers.
caption: Magnetostatic loudspeaker
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