Microphone Capsule Technology

Microphones used in video production are characterized primarily by their form factor, capsule technology, and pick-up pattern.

A microphone may employ one of several technologies for translating vibrating air particles into electrical energy that in turn is fed to your camcorder or sound recorder through the microphone cable. The two most widely used microphone capsule technologies in video production are dynamic capsules and condenser capsules.

Dynamic microphones

With a dynamic microphone, sound waves move a thin diaphragm connected to a moving coil. The movement of the coil within a magnetic field translates the sound energy into an alternating current that can be sent directly down a microphone cable, no additional circuitry is requires (the basic physics behind this is that the movement of a coil within a magnetic field creates an electrical current). A dynamic microphone is essentially the inverse of a conventional speaker. A speaker has a moving coil and magnet connected to a cone. The speaker translates the electrical signal applied to it into the physical movement of the cone, creating sound waves that correspond to the signal applied.

The advantages of dynamic microphones include:

• Less expensive than condenser microphones, and
• More rugged than condenser microphones, and
• Don’t require an external power source.

The disadvantages of dynamic microphones include:

• Not as accurate as condenser microphones,
• Much less sensitive than condenser microphones,
• Due to their lower sensitivity, they are limited to close-proximity recording applications.

Due to their specific characteristics, the dynamic microphones used most often in video production are hand-held “reporter” microphones. These work well for vox pop and on-camera reporter segments because they can be held in close proximity to the sound source and due to their low sensitivity don’t pick up a lot of ambient sound. Dynamic microphones are also widely used as vocalist and public address microphones as well as for recording high sound pressure level sound effects which will oversaturate more sensitive condenser microphones.

Condenser microphones

With a condenser microphone, sound waves move a thin diaphragm placed between charged metallic plates. The movement of the diaphragm between the plates creates a change in capacitance. Electronic circuitry and a power supply are required in order to translate the changes in capacitance into alternating current that can be sent along a microphone cable. Condenser microphones are  powered by either phantom power or a small battery (many professional microphones only work with phantom power only, some models give you a choice of phantom power or battery for power). Plug-in power is the consumer equivalent of phantom power.

The advantages of condenser microphones include:

• More sensitive than dynamic microphones,
• More accurate sound reproduction than dynamic microphones, and
• The increased sensitivity allows for greater source to microphone distances.

The disadvantages of condenser microphones include:

• More expensive than dynamic microphones,
• More sensitive to extreme environmental conditions,
• Requires a power source, and
• More prone to handling noise due to their increased sensitivity (requires the use of a good shock mount).

Due to their specific characteristics, condenser microphones are more widely used in video production than dynamic microphones. Common applications include lavaliere microphones worn on subjects, camera-mounted microphones, and boom-mounted microphones. Their high sensitivity makes them effective for recording sounds when there is a large source to microphone distance, for example booming subjects overheard or recording sound effects at a distance.

See also:

• Microphone Form Factors,
• Microphone Pick-up Patterns,
• Microphone Frequency Response,
• Microphone Placement,
• Sound Fundamentals.