First Dynamic Microphones

Our previous sessions have dealt with ribbon microphones by RCA, one of the two prime makers of broadcast and sound equipment in the mid 20th century. This time we’ll turn to the other of these major makers,  Western Electric Company. RCA and Western Electric were fierce competitors in this era. I think I am safe in saying that the majority of radio stations from the 1920s through around 1950 used either RCA or Western Electric equipment, or a combination of both. Western Electric was the manufacturing arm of Bell Telephone but also made broadcast equipment designed by Bell Telephone Labs.

In 1949 Federal anti-trust laws forced Western Electric to divest of their broadcasting equipment manufacturing. Both these companies made just about everything needed to equip a station from microphones and audio control to transmitters and antennas.

About the time RCA came out with the revolutionary ribbon microphone Western Electric developed the first high-quality dynamic microphone. The dynamic uses the same basic principle as the ribbon; a moving conductor in a magnetic field to generate the audio signal from sound waves. Instead of a moving foil ribbon the dynamic uses a round-shaped diaphragm that has a coil of wire attached that moves in the magnetic field; it’s a small electric generator.

Another way of explaining a dynamic microphone is to think of it as a loudspeaker in reverse! A loudspeaker takes a signal from a radio receiver or amplifier and turns that electric signal into sound we can hear. A microphone, as we explained before, takes that sound we hear and translates it into an electrical signal so it can be amplified and sent to a loudspeaker, as in a PA system, or for broadcasting or recording.

Western Electrics’ new dynamic microphone was dubbed the model 618 and came out about 1931. The model 618 was an omnidirectional or non-directional mic that was relatively small in size and very rugged making it excellent for studio as  well as remote broadcasting, especially in the outdoors.

This mic was not sensitive to wind and breath noises like the ribbon mic and it was relatively insensitive to handling noises making it excellent as a hand mic for interviews. The model 618 was a great improvement over the earlier noisy carbon and bulky condenser mics of that era. The 618 was a big hit with the radio industry and these mics were used clear into the ’50s.

RCA, of course, would not be left behind by Western Electric so they shortly came out with a very similar looking mic they called the model 50A. Internally the RCA model 50a used a slightly different way of embedding the wire into the diaphragm so as not to infringe on Western Electrics’ patents but externally they looked very similar.

You’ll see both of these mics in news photos and newsreels of the day; they were used for President FDR’s “Fireside Chat” broadcasts. If you look closely at these photos you’ll see that CBS and Mutual Broadcasting System (MBS) used the Western Electric and NBC and the Blue networks used the RCA because NBC was owned by RCA.

A few smaller manufacturers also made mics that looked very much like the Western Electric and RCA units but these smaller outfits could not compete with the two giants in the broadcast industry and their mics were used mainly in PA systems and some smaller radio stations.

The dynamic type microphone is one of the most used units up to this very day and Western Electric was the start of it all. These pioneering mics were all omnidirectional picking up sounds from all around; later a small company, at the time, named Shure Brothers designed the first unidirectional dynamic mic called the “Unidyne”.

Most dynamic mics today are unidirectional, picking up sound from the front side of the microphone and rejecting sounds from the rear, thus preventing sound system feedback (howling) and eliminating background noises, and all based on Shure’s groundbreaking development of the late 1930s.

We’ll save that story for another session.