Crown Audio Mini-Boundary MB-3 - Manual

POLAR
PATTERN
MINI-BOUNDARY™
MICROPHONE
MB-3
Horizontal-Plane Polar Response
Fig. 2
Fig. 1
Frequency Response
Frequency in Hz
T he Crown ® MB-3 is a miniature boundary
microphone for multi-miking applications
such as teleconferencing, distance learn-
ing, boardrooms, courtrooms, and security
applications. This low-profi le, circular mic per-
manently installs into a hole drilled in a table,
lectern, or ceiling.
Thanks to its supercardioid pickup pattern, the
MB-3 greatly reduces ambient noise and pickup
of room reverberation. The result is a clearer,
more intelligible sound.
On the bottom of the mic is a tubular power
module with a 3-pin XLR-type output connector.
It is powered by 12-48V phantom power, and
has a low-impedance balanced mic-level output.
How to Paint the Microphone
1. See Fig. 5. Using a small screwdriver, pry
open the FRONT side of the mic cover (grille
assembly).
2. Remove the foam liner.
3. Wearing a dust mask, spray-paint the grille
assembly. Be sure grille holes are not clogged.
4. Allow to completely dry.
5. Make sure the LED is properly aligned.
6. Carefully place the grille assembly over the
base, and snap in place.
Installation
Tables: In a table, typical placement for each
mic is an arm’s length from the user. Install one
microphone in front of each person, or one be-
tween every two people.
Lecterns: If the microphone will be used on
a lectern, install it on an open surface. Do
not install in a cavity or recessed area as the
frequency response and polar pattern will be
degraded.
Ceilings: When mounting mics in the ceiling,
use as few mics as possible, and put them
in front of the people speaking—not directly
overhead.
Note: The system gain-before-feedback may
not be adequate in ceiling mount applications
because the mic is far from its user.
1. Drill a 1.125-in. (2.858-cm) diameter hole for
each mic.
2. Insert the mic tube through the hole. Orient
the mic so the word “Crown” is readable by the
user.
3. Compression of the gasket under the mic is
essential to prevent rotation of the mic. Under
the table, or behind the ceiling or wall panel,
slide the ring over the tube and tighten the set
screw.
Fig. 3
Vertical-Plane Polar Response
FRONT REAR
– 20 –15 –10 –5 –0
60˚ 90˚ 120˚
150˚
180˚ 0˚
30˚
+ 5
1 kHz
5 kHz
200 Hz
FRONT
REAR
0˚ 30˚
60˚
90˚
120˚
150˚ 180˚ 210˚
240˚
270˚
300˚
330˚
–20
–15
–10
–5
–0
1 kHz
5 kHz
200 Hz
+15
+10
+5
dB 0
–5
–10
–15
–20
–25
–30
–35
20 100 1K 10K
130˚
0˚
Ideal for teleconferencing, distance learning,
boardrooms, courtrooms and security
Small and inconspicuous
Installs permanently in a table top, wall or
ceiling
Half-supercardioid polar pattern reduces
pickup of background noise, room acoustics
and feedback
On-surface mounting eliminates phase
interference from table sound refl ections,
giving a natural sound
Features
Specifi cations
Type: Phase Coherent Cardioid.
Element: Electret condenser.
Frequency response (typical): 50 Hz to 15,000 Hz at
30 degrees incidence to surface (see Fig. 1).
Polar pattern: Half-supercardioid (supercardioid in
the hemisphere above the primary boundary). See
Figs. 2 and 3.
Impedance: 150 ohms, balanced (recommended load
impedance 1000 ohms or greater).
Open-circuit sensitivity (typical): 22 mV/Pa* (–33
dB re 1 volt/Pa).
Power sensitivity: –30.5 dB re 1 mW/Pa*. EIA rating
–125 dBm.
Equivalent noise level (self-noise): 22 dB SPL typi-
cal (0 dB=0.0002 dyne/cm 2 ), A-weighted.
S/N ratio: 72 dB at 94 dB SPL.
Maximum SPL: 120 dB SPL at 3% THD.
Polarity: Positive (inward) pressure on the diaphragm
produces positive voltage on pin 2 with respect
to pin 3.
Operating voltage: Phantom power, 12-48 volts DC
on pins 2 and 3 with respect to pin 1 of output
connector.
Current drain: 4 mA nominal.
Connector: 3-pin pro audio, XLR-M type.
Cable: None supplied. Use two-conductor shielded
mic cable.
Materials: High-impact molded plastic and steel mesh
mic grille, steel chassis.
Finish: Satin black.
Net weight: 2.7 ounces (78 grams).
Dimensions: See Fig. 4.
Optional accessories: PH-1A phantom power supply
(1 channel, battery or DC-adapter powered).
Operating temperature range: –10° to 50° C, or 14°
to 122° F.
*1 pascal = 10 dynes/cm 2 = 10 microbars = 94 dB SPL.