Crown MINI-BOUNDARY MB-3 User manual

MB-3
MINI-BOUNDARY
MICROPHONE
Horizontal-Plane Polar Response
Fig. 2
Fig. 1
Frequency Response
Frequency in Hz
The 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-profile, circular mic
permanently 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 connec-
tor. It is powered by 12-48V phantom power,
and has a low-impedance balanced mic-level
output.
Features
•Small, inconspicuous.
•Installs permanently in table top, wall or
ceiling.
•Clean, clear, natural sound.
•Low-Z balanced mic-level output prevents
hum and high-frequency loss.
•Removable grille assembly can be painted.
How to Paint the Microphone
1. Using a small screwdriver, pry open one side
of the base, then the other side (Fig. 5).
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
between 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 fre-
quency 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.
Specifications
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
typical (0 dB=0.0002 dyne/cm2), 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). PH-4A phantom power supply (4
channels, AC powered).
*1 pascal = 10 dynes/cm2= 10 microbars = 94 dB SPL.
™
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˚
www.audiovias.com

Crown International, Inc.
P. O. Box 1000
Elkhart, IN 46515-1000
TEL: [phone]
FAX: [phone]FAX
MB-3
©2000 Crown International, Inc.
Specifications subject to change without prior notice.
Mini-Boundary™ is a trademark and Crown®is a
registered trademark of Crown International, Inc.
02/00 103277-3
Fig.5
MB-3 Schematic
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. Under the table, or behind the ceiling or wall
panel, slide the ring over the tube and tighten
the set screw.
4. Plug a mic cable with a female 3-pin XLR-
type connector into the mic. Connect the other
end of the cable to a phantom power supply. Or,
if your mixer has phantom power, connect the
mic cable directly to a mic input and turn on
phantom power.
Architects’ and Engineers’ Specifications
The microphone shall be the Crown model MB-
3 or equivalent. The microphone shall be a
half-supercardioid electret condenser type. The
microphone shall use the principle of phase
coherency achieved by mounting a small-
diameter element very near a boundary. This
eliminates comb filtering in the audible spec-
trum.
The microphone will exhibit excellent off-axis
response and gain-before-feedback. The mic
shall have a bottom-mounted 3-pin pro audio
XLR-type male connector. Powering shall be by
12-48V phantom power.
Fig. 4
Nominal sensitivity shall be 22 mV/Pa. Maxi-
mum SPL shall be 120 dB SPL for 3% THD.
Equivalent noise shall be 22 dBA nominal.
Frequency response shall be 50 Hz to 15 kHz
with a uniform off-axis response, about 20 dB
down at the rear nulls.
The Crown model MB-3 is specified.
Warranty
Crown professional microphone products are
guaranteed unconditionally against malfunction
from any cause for a period of three years from
date of original purchase. See enclosed war-
ranty sheet for additional information.
Service
If the microphone does not function properly,
check that it is aimed correctly and is con-
nected as described in this data sheet. If there
is hum or no signal, first repair or replace the
cable.
If you determine that the microphone
product(s) is defective, return the complete
product in its orignal packaging to: Crown
Service Department, Plant 2 SW, 1718 West
Mishawaka Road, Elkhart, IN 46517. For
further assistance or technical support call
800-342-6939.
VCC
VCC
R2
R1
W1
W3
W2
C1
R8
R6
R5
3
2 1
8
4
U1A
C2
C4
C12
C5 R11
R12
R15
2
1
7
6
5
3
4
U2
VCC
C7 A3M
12
3
P1
C9
C10
C11
R17
CONNECTOR
INSERT
PINS
Q1
R13
C8
R14
R16
C6
R3
R4
R9
R10
6
5 7
U1B
VCC
C3
R7
+
–
+
–
+
+
+
+
+
MICROPHONE CAPSULE
MICROPHONE ELECTRONICS
BOTTOM VIEW
PHONE PLUG
FRONT
SCREWDRIVER
AFTER REASSEMBLY
RESEAT WASHER
LIFT WASHER AND
PRY OPEN HERE AND
ON OPPOSITE SIDE
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