Crown MINI-BOUNDARY MB-2 User manual

POLAR
PATTERN
Use twisted-pair cable between each user switch
and interface.
Safe operating temperature range: –10° to +50° C,
or +14° to +122° F.
Materials: High-impact molded plastic and steel
mesh mic grille, steel chassis.
Finish: Satin black.
Net weight: 0.7 ounce (20.1 grams).
Dimensions: See Fig. 4.
Required accessory: MB-100 interface.
*1 pascal = 10 dynes/cm2= 10 microbars = 94 dB SPL.
MB-2
MINI-BOUNDARY
MICROPHONE
Horizontal-Plane Polar Response
Fig. 2
Fig. 1
Frequency Response
Frequency in Hz
The Crown®MB-2 is a miniature boundary
microphone for multi-miking applications
such as teleconferencing, distance learning,
boardrooms, and courtrooms. This tiny mic plugs
into a table-mounted jack.
A low-profile rectangular microphone, the MB-2
has a bottom-mounted phone plug. It plugs into a
stereo phone jack previously installed in the table.
The contractor supplies the phone jack, which is
a Switchcraft 152B Thick Panel Phone Jack or
equivalent. A locating pin (removable) prevents the
microphone from being rotated.
Thanks to its supercardioid pickup pattern, the
MB-2 greatly reduces ambient noise and pickup of
room reverberation. The result is a clearer sound.
The MB-2 must be used with an MB-100 interface
(not included). The interface performs these
functions:
• Powers and equalizes up to four mics.
• Provides programmable switching to turn
the mic on or off if desired (switches not
provided).
• Plug-in microphone inputs.
• Provides balanced outputs from the interface.
MB-2 Advanced Features
• Paintable removable grille assembly.
• A common interface for up to four mics re-
duces the size and cost of the system.
• Low-Z balanced output prevents hum and
high-frequency loss.
• On/off switches can be added.
• Switches can be internally programmed for
touch-on/touch off, momentary on, or mo-
mentary off.
• Defeatable LED.
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 foam liner.
3. Wearing a dust mask, spray-paint the grille as-
sembly. Be sure grille holes are not clogged.
4. Allow paint to completely dry.
5. Make sure the LED is properly aligned.
6. Carefully place the grille assembly over the LED
and snap in place.
Specifications
All specs apply to each output of the interface with a
mic connected.
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/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 interface output ter-
minal 1 with respect to terminal 3, and on terminal
4 with respect to terminal 6.
Operating voltage: Interface requires 18-48V phan-
tom power.
Current drain: 5 mA nominal with LED on, 4 mA
nominal with LED off.
Mic connector: Stereo phone plug. Mates with
Switchcraft 152B Thick Panel Phone Jack or
equivalent (not supplied). Order from Crown as an
MB-JK.
Cable connectors (supplied with MB-100 interface):
• Two pluggable terminal blocks (PTBs) in line with
the microphones. Each input connector handles
up to two mics.
• Two PTBs for output connectors to your mixer.
Each output connector feeds two mixer mic
inputs.
• Two PTBs for remote switch sensing. Each PTB
connects to two remote switch sensors.
Cable: None supplied. Use two-conductor shielded
mic cable between phone jack and pluggable
terminal block. Use two-conductor shielded mic
cable between interface output and mixer input.
™
• Ideal for teleconferencing, distance
learning, boardrooms and courtrooms
• Plugs into a table-mounted jack
• Half-supercardioid polar pattern reduces
feedback, room acoustics and background
noise
• Clear, natural sound
• Small and inconspicuous
Features

Crown International, Inc.
1718 W. Mishawaka Rd.
Elkhart, IN 46517-9439
TEL: [phone]
FAX: [phone]FAX
www.crownaudio.com
MB-2
4/08 103276-6A
Fig. 3
Fig.5
Vertical-Plane Polar Response
Installation
1. Typical placement for each mic is at arm’s length
from the user. Install one microphone in front of
each person, or one between every two people.
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.
2. If you want to flush-mount the jack, counter-
bore a hole 0.625-in. (1.59-cm) diameter, 0.10-in.
(0.254-cm) deep. In the center of the counterbore,
drill a hole 0.5-in. (1.27-cm) diameter for each
mic’s cylindrical phone jack. Insert the jack in the
hole and thread on the nut.
If you do not want to flush-mount the jack, drill a
hole 0.5-in (1.27-cm) diameter for each mic’s cy-
lindrical phone jack. Insert the jack in the hole and
thread on the nut.
On the bottom of the MB-2 is a removable 0.0625-
in. (0.159-cm) diameter pin to secure the mic in
position. Drill a hole for this pin 0.801 in. (2.0345
cm) from the center of the phone-jack hole, in the
desired direction.
3. Wire the mic to the MB-100 interface as de-
scribed in the interface data sheet.
4. Plug each mic into its jack. Orient the mic so
the word “Crown” is readable by the user (right-
side-up).
Architects’ and Engineers’ Specifications
The microphone shall be the Crown model MB-2 or
equivalent. The microphone shall be a half-super-
cardioid 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 spectrum.
The microphone shall exhibit excellent off-axis
response and gain-before-feedback. Each mic shall
have a bottom-mounted stereo phone plug.
The user shall supply a cylindrical phone jack.
The mic shall be used with a pluggable terminal
block and an MB-100 interface (not included). The
interface shall provide operating voltage to each
microphone, and convert its output signal to low-
impedance balanced.
Nominal sensitivity shall be 22 mV/Pa. Maximum
SPL shall be 120 dB SPL for 3% THD. Equivalent
noise shall be 22 dBA nominal. Frequency re-
sponse 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-2 is specified.
Warranty
Crown professional microphones are guaranteed
against malfunction 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 configured
and connected as described in the MB-100 in-
terface data sheet. Check the slide-switch setting
in the interface. If there is hum or no signal, first
repair or replace the cable.
If you determine the microphone product(s)
is defective, return the complete product in its
original packaging to: Crown Factory Service,
1718 West Mishawaka Road, Elkhart, IN 46517-
9439. A Service Return Authorization (SRA) is
required for product being sent to the factory for
service. An SRA can be completed on line at
www.crownaudio.com/support/factserv.htm.
For further assistance or technical support call
800-342-6939.
Dimensions
Fig.4
©2008 Crown Audio®, Inc. Specifications subject
to change without prior notice. Latest information
available at www.crownaudio.com. Mini-boundary is a
trademark, and Crown and Crown Audio are registered
trademarks of Crown International.