Architects and Engineers Specifications
The microphone shall be a fixed-charge
condenser with a unidirectional polar pattern
designed for use in surface-mount boundary
applications. The frequency response shall be
30 Hz to 15,000 Hz. The microphone shall
operate from an external 11V to 52V phantom
power source. Nominal open-circuit output
voltage shall be 17.7 mV at 1 kHz, 1 Pascal.
Output shall be low impedance balanced
(200 ohms).
The microphone shall have a touch-sensitive
switch that may be set to one of three operating
modes: touch-on/touch-off, momentary on, or
momentary off. An integral LED indicator and
contact closure shall follow the touch switch
operation. For applications requiring the
microphone to operate independently of the
touch switch, a “Local/Remote” mode shall be
provided. When the “Remote” mode is select-
ed, the microphone audio output shall always
remain “on” regardless of the status of the
contact closure and LED. The microphone shall
include a switch to select low-frequency roll-off.
A 20' (6.1 m) unterminated cable shall be
supplied for connection between the
microphone and electronics input. The cable
shall be attached to the microphone via internal
screw terminals and shall have an unterminated
5-conductor output for connection to a variety of
electronics. The cable shall be configurable for
back- or bottom-of-mic exit. The microphone
shall have a maximum width of 2.87" (73.0 mm)
and a maximum length of 4.33" (110.0 m).
Weight shall be 5.8 oz (165 g). The
microphone shall be housed in a rugged case
with a two-layer perforated steel grille. Finish
shall be low-reflectance black.
The Audio-Technica AT891R/C is specified.
Description
The AT891R/C is a condenser boundary
microphone with a hemi-cardioid (half-space
cardioid) polar pattern. It features a touch-
sensitive on/off switch, indicator LED and
external contact closure ability for controlling
remote devices such as tally lights, camera
calls, speaker zones and other equipment. The
touch switch can be configured for touch-
on/touch-off, momentary on (“press to talk”), or
momentary off (“press to mute”). The indicator
LED and external contact closure follow the
operation of the touch switch.
A “Remote” mode enables the AT891R/C
microphone element to operate independently
of the touch switch, LED and contact closure.
This mode is ideal for applications such as
teleconferencing and video conferencing that
use echo cancellers and other processing
equipment, which often require continuous
audio from the microphone. The touch switch
and contact closure are used to mute the audio
within the external processing equipment,
rather than at the microphone itself.
The AT891R/C can be powered from any
external 11V to 52V DC phantom power supply.
A switch on the bottom of the unit permits
choice of flat response or low-frequency roll-off
to help control undesired ambient noise. A 20'
(6.1 m) unterminated cable is attached to the
microphone via internal screw terminals and can
be routed from either the back or the bottom of
the housing for maximum positioning flexibility.
The microphone is enclosed in a rugged case
and protected by two layers of perforated steel.
The rubber non-slip bottom pad minimizes
mechanical coupling of surface vibrations to the
microphone. The low-profile housing has a low-
reflectance black finish.
Installation and Operation
The AT891R/C requires 11–52V phantom power,
which operates the microphone and switch
circuitry. The electronics in the microphone take
up to 30 seconds to stabilize after power is
applied; during this start-up period, some
thumps or other sonic disturbances may be
heard upon switching if the system is “live.”
The AT891R/C has a touch-sensitive switch
that can be configured to operate in three
modes: touch-on/touch-off (TOUCH ON/OFF),
momentary on (MOM. ON), or momentary off
(MOM. OFF). Slide the switch marked “SW.
FUNCTION” (located on the bottom of the
microphone) to the appropriate mode. Note that
only one mode can be active at a time.
For applications that require the microphone
to remain active regardless of the touch
switch function setting, a “Local/Remote”
control function is provided. When the switch
marked “CONTROL” (located on the bottom
of the microphone) is in the “Local” position,
the audio output is controlled internally by the
touch switch. When the “CONTROL” switch
is in the “Remote” position, the microphone
audio output will remain active or “on”
all the time. Refer to the table below for
switch/LED/closure states.
The microphone’s 20' (6.1 m) cable may be
attached to exit the microphone from either the
back or the bottom. (If you need to extend the
cable length, be certain to use the exact same
type of cable used on the microphone: the audio
signal should use two-conductor shielded cable,
and the three control wires should not be under
the audio shield.) The microphone comes with
the cable exiting at the back. To route the cable
from the bottom of the microphone, you will
need a very small (No. 0) Phillips screwdriver.
1. Partially loosen the screw in the center of
the microphone base; press up on the screw
head to loosen the grille assembly. Then
remove the screw.
2. If necessary, carefully push out the
perforated steel grille by gently pushing the
screwdriver through the two mounting holes
on the bottom. The grille and foam
windscreen should pop off easily.
3. To remove the wires from the screw
terminals, loosen the screws, and then
gently pull the wires out.
4. Untie the knot in the cable and pull it out
through the strain relief.
5. Remove the rubber strain relief from the
rear opening of the microphone.
6. Feed the cable through the hole in the
bottom of the microphone.
7. Leaving a little slack for connecting the
wires to the screw terminals, knot the cable
inside the microphone to prevent strain on
the connections. (Once the microphone has
been installed, secure the cable below the
mounting surface.)
8. Reconnect the wires to the screw terminals
using the labels as a guide [see Figure A].
9. Tighten the screws to secure the wires. Do
not use the rubber strain relief with the
bottom-exit configuration.
10.Replace the perforated steel grille (with
foam windscreen) and secure with screw.
11.Cover the rear hole with the provided plug.
Output is low impedance balanced. The
balanced signal appears across the red and
yellow wires, while audio ground is the shield
connection. Output is phased so that positive
acoustic pressure produces positive voltage on
the yellow wire.
The blue and white wires are the contact
closure. A black “ground” wire is provided to
maintain ground integrity when the contact
closure is connected to an external device.
When connecting the contact closure output to
other equipment, be careful not to exceed the
switch current and voltage ratings outlined in
the specifications.
While a modern condenser microphone is
not unduly sensitive to the environment,
temperature extremes can be harmful. Avoid
leaving the microphone in the open sun
or in areas where temperatures exceed
110 degrees F (43 degrees C) for long periods
of time. Extremely high humidity should also be
avoided.
AT891R/C
UNIDIRECTIONAL
CONDENSER
BOUNDARY
MICROPHONE
WITH LOCAL OR
REMOTE SWITCHING
UniPlate
CONTROL Switch in “Local” Position
SW Function
Microphone Audio
LED
External Contact Closure
TOUCH ON/OFF
Follows switch function
Follows switch function
Follows switch function
MOM. ON
“On” when switch is pressed
“On” when switch is pressed
Closed when switch is pressed
MOM. OFF
“Off” when switch is pressed
“Off” when switch is pressed
Open when switch is pressed
CONTROL Switch in “Remote” Position
SW Function
Microphone Audio
LED
External Contact Closure
TOUCH ON/OFF
Always “On”
Follows switch function
Follows switch function
MOM. ON
Always “On”
“On” when switch is pressed
Closed when switch is pressed
MOM. OFF
Always “On”
“Off” when switch is pressed
Open when switch is pressed
