Crown Mini-Boundary MB-3 Datasheet

POLAR

˚

˚

˚

PATTERN

MB-3

he Crown® MB-3 is a miniature boundary
microphone for multi-miking applications

T

such as teleconferencing, distance learn­ing, boardrooms, courtrooms, and security
applications. This low-profi le, 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 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 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
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.

MINI-BOUNDARY™
MICROPHONE

Features

Ideal for teleconferencing, distance learning,
boardrooms, courtrooms and security

Small and inconspicuous

Installs permanently in a table top, wall or
ceiling

Specifi cations

Typ e: 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 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/cm2 = 10 microbars = 94 dB SPL.

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

Fig. 1

Frequency Response

+15
+10

+5

dB 0

–5

–10

–15

–20
–25

–30

–35

20 100 1K

Frequency in Hz

0˚

130˚

Fig. 2

Horizontal-Plane Polar Response

330˚

300˚

270˚

240˚

210˚

FRONT

REAR

180˚

0˚

–0

–5

–10

–15

–20

30˚

150˚

Fig. 3

Vertical-Plane Polar Response

60˚ 90˚ 120˚

1 kHz
200 Hz

30˚

FRONT

0˚

–10

–0

+

5

–20–15

–5

5 kHz

1 kHz
200 Hz
5 kHz

REAR

10K

60˚

90˚

120

150

180

Fig. 4

Fig.5

4. Plug a mic cable with a female 3-pin XLR­type 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.

Application

To obtain the clearest sound, connect each MB­3 to an automatic (gated) microphone mixer.
Adjust the automatic mixer so that it turns off
all mics except for the one in use. One mic by
itself sounds much clearer (less reverberant)
than several mics on at once.

For more application help, see the Crown Micro­phone Application Guide for Teleconferencing
and Distance Learning, available online at www.
crownaudio.com > Applications > Applications
Guides.

Architects’ and Engineers’ Specifi cations

The microphone shall be the Crown model
MB-3 or equivalent. The microphone shall be a

BOTTOM VIEW

Screwdriver

FRONT

Lift washer and pry open

Reseat washer
after reassembly.

the grille assembly here.
Pull grille assembly up
and over the opposite side.

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 fi ltering in the audible spectrum.

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.

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 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 specifi ed.

Warranty

Crown professional microphone products are
guaranteed against malfunction for a period of
three years from date of original purchase. See
enclosed warranty sheet for additional informa­tion.

MB-3

Service

If the microphone does not function properly,
check that it is aimed correctly and is con­nected as described in this data sheet. If there
is hum or no signal, fi rst repair or replace the
cable. A Service Return Authorization (SRA) is
required for product being sent to the factory
for service. A SRA can be completed on line at
www.crownaudio.com/support/factserv.htm. If
service is required, return the microphone in its
original packaging to: Crown Factory Service,

1718 West Mishawaka Road, Elkhart, Indiana
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.

Crown International
1718 W. Mishawaka Rd.
Elkhart, IN 46517-9439
TEL: [phone]
FAX: [phone]FAX
www.crownaudio.com

©

2007 Crown Audio® Inc. Specifi cations 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. Printed in U.S.A.

10/07 103277-11