WNYC Altec (Western Electric) 639A "Bird Cage" Microphone
Designed by the Bell Telephone Laboratories and originally manufactured by the Western Electric Company beginning in 1938 the Altec 639A and 639B multi-pattern microphones have, for years, enjoyed an unprecedented acceptance by all phases of the audio industry. In 1941 Altec began putting their name on the microphone.
The 639A could be set to various directional patterns while maintaining high quality performance. Using a velocity ribbon microphone in combination with a dynamic pressure microphone, the 639A offered three patterns. “R” provided a “figure eight” pattern by utilizing just the velocity microphone. “D” selected just the pressure microphone for a non-directional pattern. “C” provided a cardioid pattern by combining the two microphones in series. Frequency response in any setting was 40 Hz to 10 KHz. Western Electric also built a “B” version with six selectable pattern settings. For an excellent history of this microphone go to: MIC HISTORY.