Description
The AT933PM/C is a wide-range miniature
condenser microphone with a cardioid polar
pattern. It is designed for quality sound reinforce-
ment and other demanding sound pickup appli-
cations. The AT933PM/C is furnished with a vinyl-
coated steel hanger that allows it to be positioned
inconspicuously over a choir, orchestra, stage,
etc., for very low-profile situations.
The microphone features a 50' (15.2 m)
permanently-attached miniature cable. The cable
may be cut to any length and connected to screw
terminals on the AT8534(A) wall/ceiling plate
power module provided. The AT8534(A) power
module features a white-finished standard
electrical cover plate for easy, secure installation.
It can be powered from any external 9V to 52V DC
phantom power supply. Output is low impedance
balanced.
Four additional interchangeable elements
are available to permit selection of angle of
acceptance from 90
°
to 360
°
.
Audio-Technica design engineers have
utilized the newest low-mass diaphragm technology
in the quest for superior performance. The
permanent charge is now on the fixed back plate,
rather than the moving element. With A-T fixed-
charge “back plate” construction, a gold-vaporized
diaphragm just 2 microns thick (about .000079")
can be used. This considerably reduces moving
mass, thus improving frequency response and
transient response while reducing distortion.
The microphone is enclosed in a rugged
housing with a low-reflectance black finish. It is
also available in white as the AT933PMW/C, with
a white-finished microphone housing, cable and
steel hanger, for applications where the micro-
phone must be hung against a light background.
Installation and Operation
The combination of small size and excellent
response makes the AT933PM/C ideal for
suspension over choirs, instrumental groups or
theater stages. A uniform 120
°
angle of accep-
tance provides well-balanced audio pickup. The
microphone should be located forward of the
front-most source, above the rear-most source,
and “aimed” between them (Fig. 1). Increasing the
height of the mic above the sources will tend to
equalize sound levels between them, but may
also increase background/reverberant sound
pickup. Whenever possible, the distance from the
mic to the rear-most pickup should be no more
than twice the distance to the front source, to
maintain front-to-rear balance (Fig. 1).
AT933PM/C
Cardioid
Miniature
Condenser
Hanging
Microphone
with
Wall/Ceiling Plate
Power Module
Width of pickup is approximately three times
the distance to the closest performer. If additional
mics are needed for wide sources, they should
not be closer together laterally than three times
the distance to the front source, to avoid phase
cancellation (Fig. 2).
To orient the microphone in the proper
direction, twist the housing slightly in its wire
holder (clockwise rotation moves the microphone
to the right; counterclockwise rotation moves
it to the left).
The provided foam windscreen simply slips
over the head of the microphone, effectively
reducing noise from wind or ventilation air currents.
The AT933PM/C offers a low-roll-off filter.
As supplied, the AT8534(A) power module is
wired for flat response. To enable the low-roll-off
filter, clip the jumper wire “JW” on the AT8534(A)
circuit board. Low roll-off is useful in reducing
room rumble, low-frequency air movement
noise, and low-frequency vibration.
The AT8534(A) wall/ceiling plate
power module is designed to be
mounted in a standard single-gang
electrical box. For safety and best performance,
use the electrical box
only for the AT8534(A); do
not include any AC power conductors. (Also route
the mic cable as far away from AC power cables
as possible.)
Feed the small cable from the mic through
the strain relief on the power module plate. Tie a
loose knot in the cable at the desired length and
push it down gently into the recess in the back of
the strain relief to secure the microphone. Cut
excess cable, strip the mic cable wires and attach
them to their respective input terminals. Screw-
terminal output connections of the AT8534(A) are
the same as those of an XLR-type plug: shield to
Terminal 1, balanced signal and phantom power
to Terminals 2 and 3. Output is phased so that
positive acoustic pressure produces positive
voltage at Terminal 2, in accordance with industry
convention.
Do not connect the output cable
shield to the box. Double-check to make certain
that all input and output leads have no bare wires
or loose strands that could touch each other, the
circuit board or the electrical box. Then attach the
power module plate to the electrical box.
While a modern condenser microphone is
not unduly sensitive to the environment, tempera-
ture extremes can be harmful. Avoid leaving the
microphone in the open sun or in areas where
temperatures exceed 110
°
F (43
°
C) for long
periods of time. Extremely high humidity should
also be avoided.
Figure 1
Figure 2
MIC A
MIC B
3 TIMES
DISTANCE “X”
120
°
120
°
LESS THAN
2 TIMES “X”
DIST
ANCE “X”
120
°
ANGLE OF
ACCEPTANCE
Frequency Response
(Typical)
LEGEND
Roll-off
12" or more on axis (flat)
Frequency in Hertz
Response in dB
10 dB
20k
10k
5k
2k
1k
500
200
100
50
