The term "dynamic" has many meanings, especially in terms of sound and music. However, in this case, it has little to do with "dynamic range" or "dynamic performance". In this case, it refers to the electromagnetic phenomenon: when a conductor moves in a magnetic field, an electric current is generated.
Therefore, a dynamic microphone is a microphone that converts sound into electrical signals through electromagnetic effects. They are divided into two categories: dynamic and ribbon microphones.
On the back of the transparent film, you can see the coils surrounded by permanent magnets.
Mobile coil microphone (also known as "dynamic microphone")
Dynamic microphones are probably the easiest to understand because they are basically constructed like a speaker: the coil is glued to the back of the membrane, and there are strong magnets around the coil. When a sound wave hits the microphone, the membrane will move to the rhythm of the sound wave, and the coil on its back will also move with it. The relative movement of the coil in its (fixed) magnetic gap induces a small signal voltage in the coil. There is a microphone, a device that can convert sound into electrical signals.
Dynamic microphones are generally suitable for use on stage because they are very sturdy and do not require an external power source. In recording studios, engineers usually prefer condenser microphones, or in some cases ribbon microphones, which, although not so sturdy, provide excellent sound reproduction.
The dynamic microphone is currently the most common dynamic microphone. Since "moving coil microphones" are a long concept, most sound engineers prefer to call them "dynamic microphones" or "moving coil microphones", thus treating ribbon microphones as a different category. Technically incorrect.
Aluminum ribbon sensor: Two permanent magnets in a metal frame form a magnetic gap, in which a thin aluminum ribbon can move with sound waves.
The working principle of the ribbon microphone is the same as that of electromagnetic induction. However, ribbon microphones do not have membranes and coils, but instead use a very thin narrow strip of aluminum foil. In other words, the diaphragm itself is an electrical conductor that moves inside the magnetic gap. Such a thin aluminum tape is much lighter than a film connected to a coil of copper wire. Therefore, the ribbon microphone can track the movement of sound waves more accurately than a moving coil box.
However, there is only one conductor inside the magnetic gap instead of the entire coil, and it also produces a much lower output. Therefore, ribbon microphones contain a step-up transformer that multiplies the output voltage of the transducer by approximately 30 times. Even so, ribbon microphones generally have lower sensitivity (ie, the output level at a given sound pressure level) than dynamic microphones. Therefore, ribbon microphones require very low noise preamplifiers and have large gains.
Essentially, ribbon microphones are bidirectional, meaning that they are as sensitive to sounds from the front as those from the back. But the sound waves emitted from the side will not move the ribbon.
Ribbon microphones are very fragile and must be handled very carefully. Another disadvantage is that the treble response of most ribbon microphones is very limited.
A relatively new development is the so-called active ribbon microphone, which contains an amplifier circuit for higher output. Active condenser microphones require phantom power, just like condenser microphones.
Hardcore popular science articles may be rather dry and difficult to understand, so let's write them to audio workers in need.