Audio Technica OmniPlate AT841a Product Information

Description
The AT841a is a wide range condenser
microphone with an omnidirectional (half
space) polar pattern. It is useful in surface-
mounted applications such as high-quality
sound reinforcement, professional recording
and conferencing, television, and other
demanding sound pickup situations. Its small
size makes the AT841a ideal for use
in applications where minimum visibility
is required.
Positioning a properly designed miniature
microphone centrally on a large, flat,
unobstructed surface yields distinct
advantages. Sensitivity is increased for
improved signal-to-noise ratio. Phase
distortion due to reflected sound energy from
the boundary itself is eliminated.
The microphone features a 25' (7.6 m) cable
with TA3F-type connectors for use between
the microphone and the AT8531 power
module provided. It can be powered from an
external 9V to 52V DC phantom power
supply or from a 1.5V AA battery. Current
demands are so low that a premium battery
will provide about 1200 hours of continuous
use. A built-in 3-position switch on the power
module allows selection of off, on/flat
response or on/low-roll-off.
The microphone is enclosed in a rugged
die-cast case and protected by two layers
of perforated steel. The combination of heavy
die-cast case and rubber non-slip bottom pad
minimizes mechanical coupling of surface
vibrations to the microphone. The low-profile
housing has a low-reflectance black finish.
The microphone is also available in white as
the AT841Wa, with a white-finished
microphone housing and cable.
Installation and Operation
To install the battery, remove the cap from
the top of the power module. Insert the
battery, being certain to observe battery
polarity as marked (+ end toward the cap
release button). For longest battery life, the
switch should remain off except when the
microphone is in use. While standard
carbon-zinc AA batteries will operate the
microphone satisfactorily, alkaline or mercury
cells are preferred for longer service life.
Only "leakproof" batteries should be used.
The battery does not have to be in place to
use in phantom power mode. Phantom
power requires 9V to 52V DC.
The symmetry and area of the mounting
surface directly affect the sensitivity of the
boundary microphone at low frequencies.
Ideally, the mounting surface should be
circular; however, square or rectangular
surfaces are most often used. If the
mounting surface is rectangular, the smaller
dimension tends to determine low-frequency
cutoff. The microphone should be centered
on the surface and positioned with the front
of the microphone facing the sound source
along the longer dimension of the mounting
surface. The sound source should not be
below the plane of the mounting surface.
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.
While a modern condenser microphone is
not unduly sensitive to the environment,
temperature extremes can be harmful.
Exposure to high temperature can result in
gradual and permanent reduction of the
output level. 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.
Architects and Engineers Specifications
The microphone shall be a fixed-charge
condenser with an omnidirectional polar
pattern designed for use in surface-mount
boundary applications. The frequency
response shall be 30 Hz to 20,000 Hz. The
microphone shall operate from an external 9V
to 52V DC phantom power source, or
alternatively, from a 1.5V AA/UM3 battery.
Nominal open-circuit output voltage shall be
7.9 mV (phantom) or 6.3 mV (battery) at 1
kHz, 1 Pascal. Output shall be low
impedance balanced (200 ohms-phantom,
270 ohms-battery).
A 25' (7.6 m) cable with TA3F connectors
shall be supplied for connection between the
microphone and the power module. The
included power module shall house the
battery and contain an off/on/low-roll-off
switch. The power module shall terminate in
a 3-pin XLRM-type connector.
The microphone shall be 2.56" (65.0 mm)
in diameter and height shall be 0.59"
(15.0 mm). Weight shall be 2.8 oz (80 grams).
The microphone shall be housed in a die-cast
case with a two-layer perforated steel grille.
Finish shall be low-reflectance black [white].
The Audio -Technica AT841a [AT841Wa]
is specified.
AT841a
AT841Wa
MICRO
OMNIDIRECTIONAL
CONDENSER
BOUNDARY
MICROPHONES
Frequency Response
50 100 200 500 1k 2k
Frequency in Hertz
12" or more on axis (flat)
LEGEND
Roll-off
10 dB
5k 10k 20k