SPECIAL PURPOSE MICROPHONES
Description
The AT854R is a multi-channel boundary
microphone with four cardioid condenser
elements mounted in a single housing. It is
ideal for high-quality sound reinforcement and
a variety of video and audio conferencing
applications, especially when used with an
Audio-Technica automatic SmartMixer®. Its
low-profile design makes the AT854R suitable
for use in applications where minimum visibil-
ity is required.
The four channels of the AT854R, mounted in
quadrants, are separate and independent.
They can be powered and used individually or
in any combination. This permits system
integrators to use their own proprietary DSP
algorithms for microphone control when
incorporating the AT854R into an existing sys-
tem.
Positioning a properly designed boundary
microphone centrally on a large, flat, unob-
structed surface yields several distinct advan-
tages. Directionality of the individual
elements is increased by 3 dB, promoting
enhanced gain before feedback and further
suppression of ambient noise. Sensitivity is
increased for improved signal-to-noise ratio.
Phase distortion due to reflected sound energy
from the boundary itself is eliminated.
The AT854R requires 9-52V DC phantom
power for each operating channel. A 30'
(9.1 m) cable with a miniature multi-contact
metal-body plug for connecting to the micro-
phone is included. The cable is custom-
manufactured with four separate shielded and
jacketed pairs inside a rugged overall jacket.
Its output end has four XLRM-type connec-
tors for plugging into a mixer, allowing individ-
ual control of each channel.
The microphone is enclosed in a rugged case
and protected by two layers of perforated
steel. The combination of heavy case and rub-
ber non-slip bottom pad minimizes mechani-
cal coupling of surface vibrations to the
microphone. The low-profile housing has a
low-reflectance black finish.
Installation and Operation
The symmetry and area of the mounting sur-
face 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 micro-
phone should be centered on the surface and
positioned with the microphone elements fac-
ing the sound sources. The sound sources
should not be below, or higher than 60˚ above,
the plane of the mounting surface.
Channel numbers are as shown on the top of
the mic housing. Outputs are low impedance
balanced. The balanced signal appears across
the MiniCon connector’s Pins 2 and 3 for Mic
1, Pins 4 and 5 for Mic 2, Pins 6 and 7 for Mic
3 and Pins 8 and 9 for Mic 4. The ground
(shield) connection for all microphones is
Pin 1. Output is phased so that positive
acoustic pressure produces positive voltage
at the even-numbered pins, which correspond
to Pin 2 of each XLR connector of the supplied
cable. A table on the back of this sheet sum-
marizes cable connections.
While a modern condenser microphone is not
unduly sensitive to the environment, temper-
ature extremes can be harmful. Exposure to
high temperatures 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 four-channel fixed-
charge condenser with cardioid polar patterns
designed for use in surface-mount boundary
and conferencing applications. The frequency
response shall be 70 Hz to 16,000 Hz. The
microphone shall operate from an external 9V
to 52V DC phantom power source. Nominal
open-circuit output voltage shall be 14.1 mV at
1 kHz, 1 Pascal. Output shall be low imped-
ance balanced (100 ohms).
A 30' (9.1 m) cable with a miniature multi-con-
tact plug at one end and four XLRM-type con-
nectors at the other shall be supplied for con-
nection between the microphone and elec-
tronics inputs. The microphone shall have a
maximum width of 5.91" (150.0 mm), and a
height of 1.09" (27.6 mm). Weight shall be
16.4 oz (465 grams). The microphone shall be
housed in a die-cast case with a two-layer per-
forated steel grille. Finish shall be low-
reflectance black.
The Audio-Technica AT854R is specified.
Frequency Response - Each Channel
