(3) Principles of operation. A metallic ribbon is suspended between the poles of a permanent
magnet which vibrates freely in a magnetic field. This ribbon, constructed of a thin aluminum strip,
serves as the diaphragm. Movement of this ribbon by a sound wave causes the magnetic lines of force
to be cut crosswise, creating a corresponding voltage between the two ends of the ribbon.
(a) Frequency Response: 20 - 15,000 Hz
(b) Directivity: Basically bidirectional
(c) Sensitivity: Excellent
(d) Impedance: Low
(e) Other Characteristics: Since the ribbon is easily damaged, never use it outdoors
g. Capacitor (Condensor) Microphone. These microphones get extensive use in recording
studios because of the broad frequency range, low distortion, little internal noise, and excellent
sensitivity (fig 2-29). But, due to their principle of operation, they require a preamplifier as an integral
part of the housing, plus a power supply for the preamplifier. They also require an output transformer
that converts the extremely high impedance of the microphone capacitor head to a low impedance for
unlimited cable length. Their quality and principle of operation combine to make them the most
expensive professional microphones.
Figure 2-29. Capacitor (condensor) microphone
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