AKG MB3 User Manual

T

MINI-BOUNDARY
MICROPHONE

™

MB3

he AKG/Crown® MB3 is a miniature
boundary microphone for multi-miking
applications such as teleconferencing,

distance learning, 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 connec­tor. It is powered by 12-48V phantom power,
and has a low-impedance balanced mic-level
output.

Features

•

•

ceiling.

•

•

Small, inconspicuous.
Installs permanently in table top, wall or

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 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.

Specifications

Type:

Phase Coherent Cardioid.

Element:
Frequency response (typical):

30 degrees incidence to surface (see Fig. 1).

Polar pattern:

the hemisphere above the primary boundary).
See Figs. 2 and 3.

Impedance:

load impedance 1000 ohms or greater).

Open-circuit sensitivity (typical):

22 mV/Pa* (–33 dB re 1 volt/Pa).

Power sensitivity:

EIA rating:

Equivalent noise level (self-noise):

typical (0 dB=0.0002 dyne/cm2), A-weighted.

S/N ratio:
Maximum SPL:
Polarity:

diaphragm produces positive voltage on pin 2
with respect to pin 3.

Operating voltage:

on pins 2 and 3 with respect to pin 1 of output
connector.

Current drain:
Connector:
Cable:

mic cable.

Materials:

mesh mic grille, steel chassis.

Finish:
Net weight:
Dimensions:

Optional accessories:

supply (1 channel, battery or DC-adapter
powered). PH4A phantom power supply (4
channels, AC powered).

Electret condenser.

Half-supercardioid (supercardioid in

150 ohms, balanced (recommended

–125 dBm.

72 dB at 94 dB SPL.

120 dB SPL at 3% THD.

Positive (inward) pressure on the

4 mA nominal.

3-pin pro audio, XLR-M type.

None supplied. Use two-conductor shielded

High-impact molded plastic and steel

Satin black.

2.7 ounces (78 grams).
See Fig. 4.

50 Hz to 15,000 Hz at

–30.5 dB re 1 mW/Pa*.

22 dB SPL

Phantom power, 12-48 volts DC

PH1A phantom power

*1 pascal = 10 dynes/cm2 = 10 microbars = 94 dB SPL.

Fig. 1

+15
+10

dB 0

+5

–5

–10
–15
–20
–25
–30

–35

Fig. 2

300˚

270˚

240˚

20 100 1K

Frequency Response

Frequency in Hz

Horizontal-Plane Polar Response

0˚

FRONT

–0
–5
–10
–15

–20

330˚

210˚

REAR

180˚ 150˚

130˚

0˚

10K

30˚

60˚

90˚

120˚

1 kHz
200 Hz
5 kHz

Fig. 3

Vertical-Plane Polar Response

60˚ 90˚ 120˚

30˚

FRONT REAR

0˚

+5 –0 –5 –10 –15 –20

1 kHz
200 Hz
5 kHz

150˚

180˚

Fig. 4

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 readable label faces 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 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

VCC

R1 R2

W1
W2
W3

C1

MICROPHONE CAPSULE

© 2015 HARMAN International Industries, Incorporated. All rights reserved. AKG is a trademark of AKG Acoustics GmbH, registered in the
United States and/or other countries.
Features, specifications and appearance are subject to change without notice.

www.akg.com

AKG ACOUSTICS GMBH LAXENBURGER STRASSE 254, 1230 VIENNA/AUSTRIA
AKG ACOUSTICS, U.S. SERVICE 24950 GROVE VIEW ROAD, MORENO VALLEY, CA 92551, U.S.A

C2

VCC

+

C3

R3

R4

MB3 Schematic

Fig.5

BOTTOM VIEW

PHONE PLUG

FRONT

AFTER REASSEMBLY

RESEAT WASHER

SCREWDRIVER

LIFT WASHER AND

PRY OPEN HERE AND

ON OPPOSITE SIDE

mic cable directly to a mic input and turn on
phantom power.

Architects’ and Engineers’ Specifications

The microphone shall be the AKG/Crown model
MB3 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 small­diameter element very near a boundary. This
eliminates comb filtering 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.

VCC

3 +
2 –

4

R5

R6

R7

6
5 +

8

R8

–

U1A

C4

U1B

C5

1

+

C12

R9

R10

7

R11

VCC

U2

C7 +

R12

+

C6

MICROPHONE ELECTRONICS

3 2

4

5 6

R13

R14

1
7

C8

+

MB3

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 AKG/Crown model MB3 is specified.

Warranty

AKG/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 warranty sheet for additional
information.

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, first repair or replace the
cable.

If you determine that the microphone product
is defective, return the complete product in its
original packaging to one of the addresses
below. For further assistance or technical
support call the international helpdesk at

[phone].
.

R15

R16

Q1

C9

R17

C10

C11

1 2

P1

A3M

3

CONNECTOR
INSERT
PINS