Microphone Review

• the “heart” of the microphone

• It vibrates to corresponding changes in air pressure

determined by the strength of the magnet and the 

amount of movement by the conductor

Moving Coil

Ribbon

 transducers which changes 

acoustical energy into electrical 

impulses

 produced by moving a conductor within a 

magnetic field

The diaphragm is usually made of mylar

Thickness is approximately 0.35 mils

Attached to the diaphragm is the voice coil which is suspended to a high flux magnetic field

used to achieve a flat frequency response

The diaphragm has a resonance 

in the middle frequencies

ribbon uses the electromagnetic 

theory of induction

? A thin corrugated sheet of 

metal, usually aluminum, 

suspended in a magnetic field

works on an electrostatic principle

capacitor is capable of storing a charge

determined by:

 The composition and surface areas of the plates

The dielectric or substance between the plates, air

The distance between the plates 

Depends on variations in internal 

capacitance

Tube type condensers require a special cable between the mic and power supply

The cable contains extra conductors which carry the voltage separate from the audio

The audio and DC supply voltage travel 

in the same conductors (48 Vdc)

Usually available on the console

The mic will draw the required power while 

dynamic mics will ignore the power

A transformer at the console input will not pass DC voltage therefore the only path to travel is to the microphone

 Another transformer at the microphone routes the voltage in the appropriate direction

 The return of the DC voltage is down the shield to the negative side of the supply

The polarizing charge is stored permanently within the diaphragm or back plate

No form of powering is required to charge the diaphragm

 The pre-amp will still require power

A well designed capsule will retain its charge for at least 10 years

It is predicted it would take 30 to 100 years for the capsule sensitivity to drop 3 dB