Ribbon microphone
Aribbon microphone,also known as aribbon velocity microphone,is a type ofmicrophonethat uses a thinaluminum,duraluminumor nanofilm of electrically conductive ribbon placed between the poles of a magnet to produce a voltage byelectromagnetic induction.Ribbon microphones are typically bidirectional, meaning that they pick up sounds equally well from either side of the microphone.
Principle of operation
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In amoving-coil microphone,thediaphragmis attached to a light movable coil that generates a voltage as it moves back and forth between the poles of apermanent magnet.In ribbon microphones, a very thin light metal ribbon (usually corrugated) is suspended between the poles of a magnet. As the ribbon vibrates, a voltage is induced at right angles to both the ribbon velocity andmagnetic fielddirection and is picked off by contacts at the ends of the ribbon. Ribbon microphones are also called "velocity microphones" because the induced voltage is proportional to the velocity of the ribbon and thus of the air particles in the sound wave, unlike in some other microphones where the voltage is proportional to the displacement of the diaphragm and the air.
One important advantage that the ribbon microphone had when it was introduced is that its very lightweight ribbon, which is under very little tension, has a resonant frequency lower than 20 Hz;[1]in contrast to the typical resonant frequency of the diaphragms in contemporary high quality microphones which used other technology. The typical resonant frequency of those microphones is within the range of human hearing. So even the very early commercially available ribbon microphones had excellent frequency response throughout the nominal range of human hearing (20 Hz to 20 kHz for a young adult).
The voltage output of older ribbon microphones is typically quite low compared to a dynamic moving coil microphone, and a step-uptransformeris used to increase the voltage output and increase theoutput impedance.Modern ribbon microphones do not suffer from this problem due to improved magnets and more efficient transformers and have output levels that can exceed typical stage dynamic microphones.[2]
Ribbon microphones were once delicate and expensive, but modern materials make certain present-day ribbon microphones very durable, and so they may be used for loud popular music and stage work. They are prized for their ability to capture high-frequency detail, comparing very favorably withcondenser microphones,which can often sound subjectively "aggressive" or "brittle" in the high end of the frequency spectrum. Due to their bidirectional pick-up pattern, ribbon microphones may be used in pairs to produce theBlumlein Pairrecording array. In addition to the standard bidirectional pick-up pattern,[3]ribbon microphones can also be configured to havecardioid,[4][5]hypercardioid,[6]and variablepattern.[7][8][9]
As many mixers are equipped withphantom powerin order to enable the use of condenser microphones, care should be taken when using condenser and ribbon microphones at the same time. If the ribbon microphone is improperly wired, which is not unheard of with older microphones, this capability can damage some ribbon elements;[9]however, improvements in designs and materials have made those concerns largely inconsequential in modern ribbon microphones.[10]
History
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In the early 1920s, Drs.Walter H. SchottkyandErwin Gerlachco-invented the first ribbon microphone.[11]By turning the ribbon circuit in the opposite direction, they also invented the firstribbon loudspeaker.A few years later, Dr.Harry F. OlsonofRCAstarted developing ribbon microphones using field coils and permanent magnets. The RCA Photophone Type PB-31 was commercially manufactured in 1931, greatly impacting theaudio recordingandbroadcastingindustries.Condenser microphonesat the time could not compare to itsfrequency response.Radio City Music Hallemployed PB-31s in 1932.[12]The following year, RCA introduced theType 44A Velocity Microphone.Its tone and pattern control helped reduce reverberation. Many RCA ribbon models are still in use and valued by audio engineers.[13]
TheBBC-Marconi Type Awas an iconic ribbon microphone produced by theBBCandMarconibetween 1934 and 1959.[14]Also of note is the ST&CColes 4038(or PGS – pressure gradient single), designed by the BBC in 1954 and still used for some applications to this day. Its historical uses varied from talks to symphony concerts, and it is regarded as a delicate, fine traditional microphone.[15]The GermanBeyerdynamic M 160was introduced in 1957, fitted with a smaller microphone element with two 15 mm ribbons combined to create a highly directional pickup pattern. The microphone proved to be popular in recording studios.[16]
Around 2002, relatively inexpensive ($80 – $200) ribbon microphones manufactured in China and inspired by the RCA-44 and older Soviet Oktava ribbon microphones became available.[17]UK based Stewart Taverner and his company XAudia developed "The Beeb", modifying vintageResloribbon microphones for better tone, performance and increased output.
In 2007, microphones employing ribbon elements made of strongnanomaterialsbecame available, offering orders of magnitude improvement in signal purity and output level.[18]
The ribbon microphone is an electrically simple design with no active circuitry; it is possible to build one from a kit, or with basic tools and materials.[19]The acoustic complexity of ribbon microphones is comparable to other types of air coupled transducers.
See also
[edit]References
[edit]- ^US 1885001,Olson, Harry & RCA, "Apparatus For Converting Sound Vibrations Into Electrical Variations", issued 25-Oct-1932.
- ^James B. Calvert (2003-08-31)."Microphones".Retrieved2011-01-22.
- ^RCA Engineering Products Department."Instructions for Velocity Microphone Type 44"(PDF).Radio Corporation of America.Retrieved10 October2019.
- ^RCA Engineering Products Department."Type KU-3A Unidirectional Microphone"(PDF).Radio Corporation of America.Retrieved10 October2019.
- ^RCA Industrial Electronic Products."Type BK-5A Uniaxial Microphone"(PDF).Radio Corporation of America.Retrieved10 October2019.
- ^Beyerdynamic."M160 product webpage".Beyerdynamic.Retrieved12 February2021.
- ^RCA Engineering Products Division."Type 77-DX Polydirectional Microphone"(PDF).Radio Corporation of America.Retrieved10 October2019.
- ^"Broadcast Audio Equipment for AM FM Television (Third Edition)"(PDF).Radio Corporation of America. 1957.Retrieved10 October2019.
- ^abKen Lanyon (2001-03-15)."Recording Engineer's Quarterly, March 2001".Recordingeq.com.Retrieved2011-01-22.
- ^Tomi Engdahl (1997–2000)."Powering microphones".Retrieved2011-01-22.
- ^"Walter Schottky".2003-06-03. Archived fromthe originalon 2009-10-19.Retrieved2011-01-22.
- ^Jim Webb."Twelve Microphones That Made History".Retrieved2011-11-19.
- ^1931 Harry F. Olson and Les Anderson, RCA Model 44 Ribbon Microphone,Mix Magazine, 2006-09-01, archived fromthe originalon 2008-03-24,retrieved2011-01-22
- ^S. O. Coutant (1951-09-21)."The British Broadcasting Corporation Type AX Marconi Ribbon Microphone".Coutant.org.Retrieved2011-01-22.
- ^Stephen Murphy (2004-01-01)."Coles Electroacoustics 4040 Studio Ribbon Microphone".Pro Audio Review.Retrieved2011-01-22.
- ^"Beyerdynamic M 160".TEC Awards.RetrievedJuly 25,2021.
- ^Lynn Fuston,The Chinese Connection,EQ Magazine,retrieved2011-01-22
- ^Efrain Viscarolasaga (2008-02-11),Local firms strum the chords of real music innovation,Mass High Tech: The Journal of New England Technology,retrieved2015-04-17
- ^Matthew Shechmeister (Jan 2011),Ribbon Microphones: Audio Icon You Can Build in Your Garage,Wired.com,retrieved2011-01-22