(1) Capacitor Microphone Characteristics. The capacitor microphone operates on the storage
of an electrical charge. The head of the microphone contains two plates. One is a stretched diaphragm,
the other is heavy backplate. The backplate is insulated from the diaphragm and spaced parallel to the
rear surface of the diaphragm.
(2) As sound waves enter the microphone, the pressure causes a change in the spacing of two
plates thereby varying the internal capacitance. This produces a signal voltage proportional to the
pressure component of the wave. It then gets amplified and passed through the output transformer so
conversion from high impedance to low impedance may occur.
(a) Frequency Response: Widest of all microphones; nearly covers the complete audio
spectrum
(b) Directivity: Earlier models all omnidirectional, may now be obtained with omni-, bi-,
and unidirectional characteristics
(c) Sensitivity: Exceptional
(d) Impedance: High impedance. The output transformer converts the high impedance of
the microphone capacitor head to a low impedance
(e) Other Characteristics: Has very faithful signal reproduction. The disadvantages of
this microphone are its fragility, and cost. Its extreme sensitivity may prove a disadvantage, depending
upon the recording requirements.
h. Special Purpose Microphones.
(1) Wireless or FM Microphones. All wireless microphones work according to a basic FM
transmission principle. The performer wears or holds a medium sized microphone which is connected to
a small pocket transmitter. The sending antenna of this transmitter is either worn around the waist or
pinned along the trousers or skirt of the performer. The most flexible wireless microphones are entirely
self-contained. For example, the "Vega Microphone" has its transmitter built into the microphone itself.
The sending antenna either sticks out of the microphone or serves as the neck cord by which the
microphone is worn. A special receiving station, with one or several antennas, can be located as far as
1,000 feet from the microphone. This receiving station amplifies the signal and sends it to the master
audio mixer.
(2) Despite the obvious advantages of wireless microphones, their operation has been
restricted to specific production tasks. Most often wireless microphones are used in restricted remote
locations. Less frequently they are used in studio productions because the audio quality transmitted by
the wireless system is somewhat below that of the regular cable method.
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