Dynamic Mics

History

Dynamic microphones were first patented as early as 1874. But it was E. C. Wente and Albert L Thuras, at Western Electric, who developed the first practical dynamic mic in 1931 (they also invented the first practical loudspeaker in 1926). The mic was the Western Electric 618A, which was an instant success due to its low noise and frequency response up to 10kHz.

The Shure SM57, the most famous dynamic mic, can trace its origins back to 1937 when the cardioid Unidyne mic was developed by Benjamin Bauer, an engineer at Shure.

Then, in 1959, another Shure engineer, Ernie Seeler, created the sugnificantly improved Unidyne III. During development, the Unidyne III was exposed to much abuse, and this resulted in the design for the SM57 (SM stands for Studio Microphone). The SM57's ruggedness and sound qualities resulted in it being one of the most widely used microphones to this day.

Technology

Dynamic microphones, also known as moving-coil microphones, work in a similar fashion to a loud speaker. The dynamic mic has a coil of fine wire attached to a diaphragm. The coil moves inside a strong magnet. The movement generates an electrical current that corresponds to the audio. This is a simple and robust arrangement. Generally speaking, dynamic mics are able to withstand more abuse than other types, which is why they are often used in live performances where they may be subject to being bumped, dropped, etc. It also helps them withstand the high sound pressures in front of guitar cabinets, a typical use in recording studios.

Examples:

Starting with perhaps the most ubiquitous of all, the Shure SM57. This mic is used for everything from vocals, to guitar cabinets, to horns, for both live performance and recording. There are probably SM57 mics in every recording studio in the world!

Next is the SM58, which is the same mic as the SM57, but with the addition of the ball-head wind screen and pop filter, making this mic excellent as a hand-held vocal mic. It will look very familiar, because, for several decades, most live performances you have seen, probably involved the SM58 as the vocal mic of choice for both main and backgorund vocals.

The Shure SM7b is the effective top-of-the-line dynamic mic used for vocals and very popular in radio, podcast, and vlogging roles, which applies also to the ElectroVoice RE20. The RE20 is also a workhorse in radio, podcast, and vlogging scenarios. Additionally, the SM7B is refined enough to be used for vocals in recording studios