Dynamic Microphone

In a dynamic microphone, sound waves cause a movable wire or coil to vibrate in a magnetic field and thus induce a current, to then be converted back to sound.

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Fig 1 - Shure SM57 Microphone

In a dynamic microphone, sound waves hit a thin metallic diaphragm that is attached to a coil of wire. The diaphragm vibrates the coil in response to the sound wave. A magnet that is positioned inside the coil produces a magnetic field. It is the motion of the coil in the magnetic field which generates the electrical signal. The principles are the same as those used to generate electricity; electromagnetic induction.

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Fig 2 - Inner workings of the dynamic microphone

The motion of the diaphragm produces current, and that the amount of current is determined by the speed of that motion. For this reason, dynamic microphones are known as being velocity sensitive.

The most common type of microphone is the dynamic due to it being an all-round solution for many recording situations.

The sound produced from a dynamic microphone can be described as being mellow and well rounded.

Virtually all dynamic microphones have a cardioid polar response pattern. With a cardioid pattern, the microphone filters out noise from its rear, helping to isolate the sound source for the recording.

Advantages

Key advantages to a dynamic microphone:

  • Rugged and able to handle high sound pressure levels, like those delivered by a kick drum
  • Provide good sound quality in all areas of microphone performance
  • They do not require a power source to run
  • They are relatively cheap

Disadvantages

Key disadvantages to a dynamic microphone:

  • Heavy microphone diaphragm and wire coil limits the movement of the assembly, which in turn restricts the frequency and transient response of the microphone¬†
  • Generally not as suitable as condenser microphones for recording instruments with higher frequencies and harmonics, such as a violin

Summary

Dynamic microphones can be used for many applications, produce an excellent sound and are suitably rugged - great for travelling on the road. They are best avoided when recording high frequency content on an important recording.

For reliable, every day tasks you will not find a more multifaceted, trustworthy device than a good quality dynamic microphone