Rugged mic using a coil and magnet — less sensitive than condensers, ideal for loud on-set environments.
Technical Details
Dynamic microphones operate with a 0.02-0.05 mm thin Mylar diaphragm to which a copper wire coil with 50-100 turns is attached. The permanent magnet generates a magnetic field of 0.1-0.3 Tesla, producing voltages of 1-10 mV with diaphragm movements. The impedance is between 150-600 Ohms, and the maximum sound pressure level reaches 130-140 dB SPL. Designs vary between large-diaphragm microphones (Ø 25-34 mm) for studio applications and small-diaphragm variants (Ø 12-20 mm) for mobile use. Polar patterns range from omnidirectional to cardioid and hypercardioid.
History & Development
Ernst Siemens developed the first dynamic microphone in 1877 as an advancement of his electromagnetic telephone. RCA launched the first professional ribbon microphone, the 44A, in 1931, while Electro-Voice introduced the RE20 as the first modern dynamic microphone for broadcasting in 1938. Shure revolutionized live sound in 1966 with the SM58, offering extreme robustness and feedback resistance. Since the 1980s, Neodymium magnets have enabled more compact designs with higher output voltage.
Practical Use in Film
On "Mad Max: Fury Road" (2015), sound mixer Ben Osmo used Shure SM57 microphones mounted directly on vehicles to record engine noise without windscreens – only dynamic microphones can withstand such mechanical stress. For dialogue recording in noisy environments, as in "Dunkirk" (2017), hypercardioid dynamic microphones are used because they attenuate background noise by up to 20 dB. In action scenes with explosions or gunshots, they offer the advantage of operating without batteries and handling sound pressure levels up to 140 dB, while condenser microphones already distort at 120 dB.
Comparison & Alternatives
Compared to condenser microphones, dynamic microphones exhibit lower sensitivity (-55 vs. -37 dBV/Pa) but higher mechanical stability and do not require phantom power. Ribbon microphones, as a special form of dynamic transducers, offer a more natural sound but are more fragile and expensive. For outdoor recording, dynamic microphones are increasingly replacing condenser microphones, as modern preamps can compensate for the lower output voltage. In controlled studio environments, condenser microphones remain the standard due to their higher resolution and extended frequency response up to 20 kHz.