ResonantLive Sound Archive

Equipment file · Moving-coil microphone

618A dynamic microphone

Western Electric · 1931

Evidence status · documented

Identity and core specifications are documented; some historical fields remain unavailable.

The Western Electric 618A, developed by Bell Labs engineers E. C. Wente and A. L. Thuras, was among the first commercially produced dynamic microphones. A duralumin diaphragm drove an aluminium-ribbon coil in a cobalt-steel magnet field, giving a quoted range of 35 to 9,500 cycles per second with no polarising voltage.

Introduced
1931
Category
Moving-coil microphone
Intended use
Broadcasting, recording and public address
Production
Western Electric

Equipment photographs · 1

US patent 1,869,178 (1932): moving-coil sound translating device of the 618A era

1 / 1 · US patent 1,869,178 (1932): moving-coil sound translating device of the 618A era

US patent 1,869,178 (1932): moving-coil sound translating device of the 618A era·Albert L. Thuras (Bell Telephone Laboratories)·Public domain (US patent)

Why it mattered

  1. 01

    Low impedance, no polarising supply and ruggedness suited remote and PA use better than carbon or condenser designs.

  2. 02

    It set the template for the moving-coil microphones that became standard in live sound.

Engineering record

Transducer
Duralumin diaphragm with aluminium-ribbon coil in a cobalt-steel magnet field; no polarising voltage[1]
Frequency range
Substantially uniform from about 35 to 9,500 cycles per second[1]

Original pricing

No reliable period price located

2026 equivalent

Not calculated without a reliable original price.

Public price evidence was not sufficient to publish a defensible original figure.

Use in the field

Used for Franklin D. Roosevelt's Fireside Chat broadcasts[2]

Manuals & original documents

Sources

  1. 1No. 618A Moving Coil Type Microphone, Instructions for UseWestern Electric · manual
  2. 2Western Electric 618A Dynamic MicrophoneMix · reference · 2008-08-28

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