Audio Technica OmniPlate AT841a, OmniPlate AT841Wa Product Information

Description

The AT841a is a wide range condenser
microphone with an omnidirectional (half
space) polar pattern. It is useful in surface­mounted 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

LEGEND

Roll-off

12" or more on axis (flat)

Frequency in Hertz

Response in dB

10 dB

20k

10k

5k

2k

1k

500

200100

50

AT841a
AT841Wa

Polar Pattern

Dimensions

Audio-Technica U.S., Inc., 1221 Commerce Drive, Stow, Ohio 44224
Audio-Technica Limited, Old Lane, Leeds LS11 8AG England

Form No. 0310-0859-01-B/W P50870-01 © 1998 Audio-Technica U.S., Inc. Printed in U.S.A.

2.56"

65.0 mm

65.0 mm

2.56"

0.59"

15.0 mm

AT841a/AT841Wa SPECIFICATIONS

†

ELEMENT Fixed-charge back plate

permanently polarized condenser

POLAR PATTERN Omnidirectional in hemisphere above

mounting surface

FREQUENCY RESPONSE 30-20,000 Hz
LOW-FREQUENCY ROLL-OFF 80 Hz, 18 dB/octave
OPEN CIRCUIT SENSITIVITY PHANTOM –42 dB (7.9 mV) re 1V at 1 Pa*

BATTERY –44 dB (6.3 mV) re 1V at 1 Pa*

IMPEDANCE PHANTOM 200 ohms

BATTERY 270 ohms

MAXIMUM INPUT SOUND LEVEL PHANTOM 133 dB SPL, 1 kHz at 1% T.H.D.

BATTERY 119 dB SPL, 1 kHz at 1% T.H.D.

DYNAMIC RANGE (TYPICAL) PHANTOM 104 dB, 1 kHz at Max SPL

BATTERY 90 dB, 1 kHz at Max SPL

SIGNAL-TO-NOISE RATIO

1

65 dB, 1 kHz at 1 Pa*

SWITCH Off, on-flat, on-roll-off
BATTERY TYPE Use only “leakproof” AA/UM3 1.5V battery
BATTERY CURRENT 0.4 mA typical
BATTERY LIFE 1200 hours (alkaline battery)
PHANTOM POWER REQUIREMENTS 9-52V DC, 2 mA typical
WEIGHT

MICROPHONE 2.8 oz (80 grams)
POWER MODULE 5.2 oz (147 grams)

DIMENSIONS

MICROPHONE 2.56" (65.0 mm) diameter,

0.59" (15.0 mm) height

POWER MODULE 3.27" (83.0 mm) H x 2.48" (63.0 mm) W x

0.87" (22.0 mm) D

OUTPUT CONNECTOR (POWER MODULE) Integral 3-pin XLRM-type
CABLE 25' (7.6 m) long, 0.13" (3.2 mm) diameter,

2-conductor, shielded cable with TA3F
connectors

ACCESSORIES FURNISHED AT8531 power module; battery;

soft protective pouch

†

In the interest of standards development, A.T.U.S. offers
full details on its test methods to other industry
professionals on request.

* 1 Pascal = 10 dynes/cm

2

= 10 microbars = 94 dB SPL

1

Typical, A-weighted, using Audio Precision System One.

Optional Accessories:

• CP8201 line matching transformer
(Lo-Z to 50,000 ohms).

• AT8202 adjustable in-line attenuator for
use with balanced Lo-Z microphones.

• AT8314 2-conductor, shielded, vinyl-jacketed,
broadcast-type cable with XLRF-type
connector at microphone end, XLRM-type
connector at equipment end. Available in
10', 20', 25', 30', 50' & 100' lengths.

• CP8506 four-channel 48V phantom power
supply (AC powered).

• AT8801 single-channel 48V phantom power
supply (AC powered).

POWER MODULE

AT8531

audio-technica

MADE IN JAPAN

OFF

PUSH

3.27"

83.0 mm

2.48"

63.0 mm

22.0 mm

0.87"

SWITCH

Roll-off

Flat

Off

Push Button

To Release Cap

AT8531 Power Module

One-Year Limited Warranty

Audio-Technica microphones and accessories purchased in the U.S.A. are warranted for one year from date of purchase by
Audio-Technica U.S., Inc. (A.T.U.S.) to be free of defects in materials and workmanship. In event of such defect, product will
be repaired promptly without charge or, at our option, replaced with a new product of equal or superior value if delivered to
A.T.U.S. or an Authorized Service Center, prepaid, together with the sales slip or other proof of purchase date.

Prior approval from A.T.U.S. is required for return.

This warranty excludes defects due to normal wear, abuse, shipping
damage, or failure to use product in accordance with instructions. This warranty is void in the event of unauthorized repair
or modification.

For return approval and shipping information, contact the Service Department, Audio-Technica U.S., Inc.,
1221 Commerce Drive, Stow, Ohio 44224.

Except to the extent precluded by applicable state law,

A.T.U.S. will have no liability for any consequential, incidental,
or special damages; any warranty of merchantability or fitness for particular purpose expires when
this warranty expires.

This warranty gives you specific legal rights, and you may have other rights which vary from state to state.

Outside the U.S.A., please contact your local dealer for warranty details.

200 Hz

1 kHz
4 kHz
8 kHz

LEGEND

SCALE IS 5 DECIBELS PER DIVISION

90

60

120

30

150

210

240

270

300

330

180

0