Specifications

which is why this part of the spectrum is called
a “noise skirt”.
Phantom Power
to IEC 2681 5/DIN 45596
Condenser microphones require an operating
voltage. It can be fed to the microphone either
by a-b powering or phantom powering. In a-b
powering, the operating voltage is fed to the
balanced audio wires without using the shield.
a-b powering is incompatible with dynamic
microphones since the operating voltage would
flow through the moving coil and destroy it.
In phantom powering, the negative terminal is
connected to the cable shield and the positive
terminal is split via decoupling resistors to the
balanced audio wires. Since both audio wires
carry the same potential, no current will flow
through the coil of a dynamic microphone so
there is no risk of destroying it even if the phan-
tom power is accidentally left on.
When adding phantom power to a single ended
(grounded) input or an input with no front-end
transformer, either capacitors or an optional
transformer need to be wired into the audio
lines as shown below, to prevent leakage cur-
rents from entering the input stage.
Polarity
If you use more than one microphone for a
recording, they should be of the same polarity.
This means that if the diaphragms move in the
same direction, the output voltages of all
microphones should have the same polarity. If
they don't there will be signal cancellation
effects causing sound coloration – particularly
in the bass range – as soon as you mix the
microphone output signals together.
Polar Pattern
The “polar pattern” of a microphone indicates
its sensitivity to sounds arriving from different
directions. Omnidirectional microphones
“hear” equally well in all directions while all
others prefer sound from one (unidirectional) or
two (bidirectional) directions. The polar dia-
gram shows the three-dimensional “hearing
performance” of a microphone as a single
curve (see fig. 5). It is sufficient to plot only one
half of the curve (0° through 180°) since the
other half (180° through 360°) is symmetrical.
In this way, the directivity can be shown (see
218
GLOSSARY
Hypercardioid
Ultra-directional
Omni-
directional
Cardioid
Figure-of-eight
Fig. 5
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