ResonantLive Sound Archive

Equipment file · Bidirectional ribbon microphone

44-BX ribbon microphone

RCA · 1931 (44-A); 1940 (44-BX)

Evidence status · documented

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

Harry F. Olson's ribbon research at RCA led to the Type 44-A velocity microphone in 1931. In 1940 RCA updated it with improved magnet material as the 44-B and 44-BX, and marketed it as the standard microphone of broadcasting; the 44 and related 77 series stayed in production until 1957.

Introduced
1931 (44-A); 1940 (44-BX)
Category
Bidirectional ribbon microphone
Intended use
Broadcast studios, remotes and sound reinforcement
Production
RCA, Camden, New Jersey, until 1957

Equipment photographs · 1

Restored RCA 44-BX ribbon microphone

1 / 1 · Restored RCA 44-BX ribbon microphone

Restored RCA 44-BX ribbon microphone·Roadside Guitars·CC BY-SA 2.0

Why it mattered

  1. 01

    Its smooth figure-eight response gave engineers strong pattern control and good gain before feedback.

  2. 02

    It was one of the most widely used studio and scoring microphones of the 1930s–50s.

Engineering record

Transducer
A corrugated aluminium ribbon about 2.5 microns thick in a permanent-magnet field; figure-eight pattern[1]
Magnet material
The 44-B/44-BX of 1940 used improved magnet material over the 44-A[2]

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 on CBS network radio, including by Frank Sinatra in the 1940s[1]

Manuals & original documents

No authoritative manual or original document has been located for this profile.

Sources

  1. 1RCA 44-BXMuseum of Microphones · archive
  2. 21931 Harry F. Olson and Les Anderson, RCA Model 44 Ribbon MicrophoneMix · reference · 2006-09-01

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