The polydirectional microphone was introduced in the 1940's with the ability to switch directionality from a narrow cardioid pattern to a wide omnidirectional pattern. "During the 1950's Neumann microphones also were sold through Telefunken, and carried the Telefunken logo. Thus the U47 was also known as the 'Telly'. It was reported about 'The Voice', Frank Sinatra, that he wouldn't sing without his 'Telly', the Neumann U47." (from Neumann History)
"The M49 was introduced to the German Radio Broadcasters in 1952. Because of its unprecedented versatility it conquered the international recording studios rather quickly. Due to the innovative feature "remote pattern control" it found widespread application as the important main microphone above large orchestras. Other applications were as a spot microphone for wind and string instruments, for piano and as the favorite announcer's microphone." (from Neumann History)
In the 1950s, the axial microphone became popular with a ribbon transducer located in the end of a slender cylinder, ideal for portablility. KM54 - "After the introduction of the KM54 in 1954, it very quickly acquired an excellent reputation as a voice microphone for radio and television. It was used in many chambers of parliament and served at the lectern of the United Nations General Assembly in New York. It was equally successful as a supporting microphone for musical recordings. The KM 54 was produced from 1954 to 1969. Thousands of highly revered 54s are still in service today." The Gotham Audio Corp. ran an ad in 1961 featuring JFK speaking at UN into pair of Neumann mics - "President John F. Kennedy Addressing the UN on the Berlin Problem - Sept. 25, 1961" - "Neumann is honored to serve United Nations communication through the accurate and reliable performance of their world famous microphones."
electret omnidirectional mic diagram from Olson 1977
electret omnidirectional mic diagram from Olson 1977
The electret electrostatic microphone ca. 1970 has a permanently-charged plastic film diaphragm plated on one side. The addition of a field effect transistor allows high impedance input and a uniform frequency response of 30-15,000 Hz.