Differences between a condenser and dynamic microphone

The only use of a microphone is to capture sound, but there are on the market many kinds of microphones that operate on different principles. The condenser and dynamic microphones are two most common forms of professional microphones. The terms condenser and dynamic refer to the method in which the microphone generates an electrical signal.

The dynamic (moving-coil) microphone operates by electromagnetic induction to generate an output signal voltage: the diaphragm is attached to a coil of fine wire, the coil is mounted in the air gap of the magnet such that it is free to move back and forth within the gap when the sound wave strikes the diaphragm and it vibrates in response. The coil attached to the diaphragm moves back and forth in the field of the magnet inducing a small electrical current in the wire. The magnitude and direction of that current is directly related to the motion of the coil, it is an electrical representation of the sound wave.

The diaphragm of a condenser microphone is a very thin plastic film, coated on one side with gold or nickel, and mounted very close to a conductive stationary back plate. A polarizing voltage is applied to the diaphragm by an external power supply or by the charge on an electret material in the diaphragm or on the backplate charging it with a fixed static voltage. The diaphragm and back plate are separated by a small volume of air and they form an electrical component called a capacitor (condenser). The value of capacitance varies depending by the way the diaphragm vibrates in response to a sound, as it moves closer to and farther away from the back plate. The movement induces an electrical charge in the back plate, an electrical representation of the diaphragm motion.

Dynamic microphones are passive devices since they do not require any power to operate. Condenser microphones are active because they require an external power source in order to maintain its charge.

One major drawbacks of the dynamic microphone relates to the mass of its moving coil. Due to this mass the dynamic mic has a relatively poor transient response, a small output signal, less sensitive on the average than the condenser mic, which typically requires a lot of amplification. Using a dynamic microphone may be challenging when trying to pick up soft or distant sounds. These sounds generally require a lot of amplification that can create noise in the sound signal.

Because the diaphragm of the condenser microphone is not loaded down with the mass of a coil, it can respond very quickly to transients. Also, the condenser capsule can be made very small.

A condenser microphone is usually more fragile and expensive than a dynamic microphone. As a result the condenser mics are used most often in a controlled studio environment. Dynamic microphones are well-suited for both studio and live performance use. A condenser microphone will be more successful in picking up these ambient sounds without adding extra noise.

Both dynamic and condenser microphones can pick up different frequencies and have various directional responses. Using mics that pick up varied frequencies can help separate recorded sounds, such as those from voices speaking in traffic, different instruments in the room or on a stage. The directional response, or the angle from which the microphone will pick up signals, can also help isolate sounds.