Similar to science classes in school, when a magnet is placed close to a coil of wire, it induces an electric current. Dynamic microphones utilize this electromagnetic principle by using coils of wire and magnets to produce electrical energy, which can then be transformed into audio signals.
Certainly, you still recall the law of conservation of energy, which states that energy cannot be created or destroyed, only transformed from one form to another. Thus, the energy from the sound waves produced by our voices or musical instruments is not lost; instead, it is transferred to the membrane or diaphragm within the microphone capsule.
When the diaphragm vibrates in response to incoming sound waves, the coils attached to it rapidly move towards and away from the magnet, essentially vibrating. This movement mirrors the sound waves it receives. As a result, an electric current is generated in the coil, which is then transmitted through the microphone cable.
Typically, the setup matches the image shown below:
Certainly, the electricity produced by dynamic microphones is minimal, measuring just a few millivolts, which is referred to as the mic level signal. This signal must be amplified to achieve a line level signal (0.5 – 2 volts), typically present in pre-amp mixers, audio interfaces, DVD players (if equipped with a mic input), and similar devices.
Once the audio signal has gone through the pre-amplification process and reached line-level, it is then boosted by a power amplifier to drive loudspeakers (such as PA speakers or home speakers).
As previously stated, loudspeakers perform the reverse role of microphones by transforming electrical energy into sound waves.
The loudspeaker's performance is essentially the inverse of a dynamic microphone. Observing the speaker's cross-sectional image reveals a similarity to the image above.
FUN FACTS:
A speaker can function as a microphone, and a microphone can serve as a speaker. However, the sound quality will be poor because they are not designed for these purposes.
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