MicrophoneC apter 1Design

While all microphones are designed for the common purpose of converting variations in sound pressure to electronic signals, different technologies have their benefits depending upon the application.This chapter examines the merits of different design types, capsule sizes, polar patterns, electronics and more.

Microphone Types

The three main types of microphones in common use today are dynamic, ribbon and condenser. Each has unique attributes appropriate for different applications.

Dynamic microphones

The dynamic or moving-coilmicrophone is the easiest to understand. It is the classic technology taught in grade school as the inverse of the common speaker. A plastic or metal diaphragm is attached to a copper coil that is, in turn, suspended in a magnetic field. Sound pressure waves hitting the diaphragm cause it to move, and with it, the coil within the magnetic field. The resulting magnetic fluctuations translate to electrical fluctuations

generally corresponding to the physical fluctuations of the

original sound wave.

 

 

output signal

-

voltage

+

 

 

Due to the requirement of attaching the coil directly to the

 

 

 

 

 

diaphragm, dynamic diaphragms are thicker and, therefore, less

 

 

 

 

 

sensitive than the ribbon and condenser microphones

 

 

 

 

 

discussed shortly. These same design considerations also give

diaphragm

fixed magnet

 

 

 

the ability to take the greatest amount of sound pressure

 

 

 

 

 

before distorting, as well as the greatest amount of physical

 

 

coil

 

 

In dynamic mics, sound pressure moving the

abuse. Dynamics are also the easiest and least expensive to

make. Dynamics also to tend to color the sound in the range of

diaphragm causes the attached voice coil to interact

with a magnetic field to produce an electric signal

about 5k to 10k, and start to sound thinner when more than about a foot away from the source.

metal ribbon diaphragm

For these reasons, dynamic mics are most often found in the average stage situation. After all, live performance environments are much more likely to subject mics to torture such as high volume, sweat, the elements, shock and being dropped. In the studio, dynamic mics are most often used to close-mic drums due to the possibility of wayward drum sticks. Large-diaphragm dynamics are often used on kick drums due to high sound pressure levels and low-frequency content.

+

- output signal voltage

fixed magnet

In ribbon mics, sound waves cause a thin metal ribbon to move within a magnetic field to produce a current

Ribbon microphones

Ribbon mics are another form of dynamic microphone distinct from the moving-coil variety. A very thin metal ribbon suspended between the poles of a powerful magnet moves in response to sound waves, thus cutting through the magnetic field and inducing a flow of electrons. The resulting low-voltage output is typically fed to a step-up transformer and sent down the mic cable. The extreme thinness of the ribbon makes this type of mic the most sensitive, especially at very low sound levels. They are most often used in close-miking situations and, because they are also the most fragile and costly mic design, ribbons are typically reserved for very controlled conditions.

Like moving-coil dynamics, ribbon mics color the sound in a way that is often employed to warm up brassy sounds. (Ribbons are a great choice for recording sax, for example.) They also tend to

Choosing & Using Microphones

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M-Audio manual MicrophoneC apter 1Design, Microphone Types, Dynamic microphones, Ribbon microphones