AT933Rx /C
Cardioid
Miniature
Condenser
Hanging
Microphone
Description
The AT933Rx/C is a wide-range miniature
condenser microphone with a cardioid polar
pattern. It is designed for quality sound reinforce-
ment, professional recording, television, and
other demanding sound pickup applications. The
AT933Rx /C is furnished with a vinyl-coated steel
hanger adapter that allows it to be adjusted for
correct positioning.
The microphone features a 50' (15.2 m)
permanently-attached miniature cable. Its free
end connects to the provided AT8533x power
module via internal solderless screw terminals for
simple cable-length adjustment in the field. It can
be powered from any external 9V to 52V DC
phantom power supply. A recessed switch in the
power module permits choice of flat response or
low-frequency roll-off to help control undesired
ambient noise.
Four additional interchangeable elements
are available to permit selection of angle of
acceptance from 90
°
to 360
°
.
The microphone is enclosed in a rugged
housing with a low-reflectance black finish. It is
also available in white as the AT933RWx/C.
Installation and Operation
The combination of small size and excellent
response makes the AT933Rx/C ideal for suspension
over choirs, instrumental groups or theater stages.
A uniform 120
°
angle of acceptance 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).
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 cancel-
lation (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.
Figure 3
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
Figure 4
Shield strands,
fully twisted
Yellow-Yellow
Red-Red
1
/
8
" strip reds
and yellows
1
/
2
"
1"
Terminal
screws
Case
grounding
contact
Yellow-Yellow
Red-Red
Shield
PC board
switch side
S
Y
R
Output is low impedance balanced. The
output connector of the power module mates with
XLRF-type cable connectors. The balanced signal
appears across Pins 2 and 3, while the ground
(shield) connection is Pin 1. Output is phased so
that positive acoustic pressure produces positive
voltage at Pin 2, in accordance with industry
convention.
To shorten the cable, remove the three
screws from the base of the power module and
slide the outer case up the cable to reveal the cir-
cuit board and screw terminals. Loosen the three
terminal screws and remove the cable from the
module. Next, slide the case off the cable, cut the
cable to the desired length (allowing a few extra
inches) and slide the case back onto the cable.
Tie a single knot in the cable about two inches
from the cut end. Following Figure 3, cut the
cable off 1" down from the top of the knot and
carefully remove
1
/
2
" of the outer jacket.
Strip the mic cable wires and attach them
to their respective terminals (Fig. 4).
Make certain that the terminals are
clamped on the conductors, not on the
insulation, and that there are no loose
strands of wire which might touch other
terminals. Replace the case, being certain that it
goes
over the case grounding contact and that
the roll-off switch is accessible. Finish by replac-
ing the three base screws and testing for proper
operation.
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.
