Microphones 101 A: Types of microphones

Dynamic Microphones
There are two basic types of dynamic microphones. These are moving-coil dynamic microphones and moving-ribbon dynamic microphones.

Moving-coil Dynamic Microphones

Moving-coil dynamic microphones are versatile and ideal for general-purpose use. They use a simple design with few moving parts. They are relatively sturdy and resilient to rough handling.

They are robust, relatively inexpensive and resistant to moisture, and for these reasons they are widely used on-stage. They are usually better suited to handling high sound pressure, such as from close-up vocals, certain musical instruments, and amplifiers. They generally have no internal amplifier and do not require batteries or external power.

How Moving-coil Dynamic Microphones Work

When wire is moved within a magnetic field a current is generated in the wire. Using this induction principle, the dynamic microphone uses a wire coil, magnet, and a thin diaphragm to capture the audio signal.

The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates an electrical current in the coil, which is channeled from the microphone along wires.

Moving-ribbon Dynamic Microphones
CAD Mics: Trion 7000

Moving ribbon dynamic microphones are generally more fragile than their moving-coil cousins and usually spend more time in the studio than on stage. (However, many Trion 7000s have been seen on several high-profile tours.) Ribbon microphones have a mellow sound of their own and work well on brass instruments, guitar cabinets, and other aggressive sources.

How Moving-ribbon Dynamic Microphones Work
Like the moving-coil dynamic microphone, the moving-ribbon dynamic microphone utilizes induction. However, instead of a coil of wire, a thin corrugated aluminum ribbon is suspended in the magnetic field. As this ribbon vibrates sympathetically to impinging sound an electrical current is generated in the ribbon.

Condenser Microphones

CAD Mics:Trion 6000, Trion 8000, C195, GXL2200, GXL1200, GXL2400, M179, M177, M9, e60, e70, e100-2, e300-2, ICM417, CM100, ST100, MG115, MG120

Condenser is a legacy term meaning capacitor, a device that stores energy in the form of an electrostatic field. Although the term is obsolete in engineering it is still used to describe microphones that use a capacitor to sense acoustical energy.

Condenser microphones tend to be more sensitive and responsive than dynamic microphones, making them useful for capturing subtle nuances and intricate detail. They are not always ideal for high sound pressure work as their high sensitivity can cause overload distortion in some mixers and preamps.

How Condenser Microphones Work

A capacitor consists of two conductive plates near each other. In the condenser mic, one of these plates is made of a very thin, light, flexible material and acts as the diaphragm. The diaphragm vibrates in the presence of sound waves, varying the distance between the plates, which varies the capacitance.

A bias voltage is required across the capacitor to sense this change in capacitance. This voltage can be supplied internally by a fixed electrostatic charge or externally.

As the capacitance changes so does the voltage across the capacitor. This voltage can be sensed by a vacuum tube or a field-effect transistor. In either case, power is needed to run the circuit. This power can be provided by internal batteries, an external power supply, or in the case of some CAD equitek microphones, both.

Phantom Power

Phantom power (labeled as +48 V or P48 on some audio equipment) is a method that sends DC power through microphone cables. It is called "phantom" powering because the supply voltage is effectively invisible to balanced microphones which do not require it, e.g. most dynamic microphones.

It is best known as a common power source for condenser microphones, though many active DI boxes also use it. Stand-alone phantom power supplies are available, but usually they are conveniently integrated into mixers, microphone preamplifiers and similar equipment.


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