AKG MB3 User manual

T
MB3
MINI-BOUNDARY
™
MICROPHONE
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 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.
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).
Fig. 1
+15
+10
+5
dB 0
–5
–10
–15
–20
–25
–30
Frequency Response
0˚
130˚
• 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).
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
–35
20 100 1K 10K
Frequency in Hz
Fig. 2
Horizontal-Plane Polar Response
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,andsnapin 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
betweeneverytwopeople.
Lecterns: If the microphone will be used on a
typical (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.
Currentdrain: 4mAnominal.
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.
300˚
270˚
240˚
330˚ 0˚ 30˚
FRONT
–0
–5
–10
–15
–20
REAR
1 kHz
200 Hz
5 kHz
60˚
90˚
120˚
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.
Finish: Satin black.
Net weight: 2.7 ounces (78 grams).
Dimensions: See Fig. 4.
Fig. 3
210˚ 180˚ 150˚
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.
Optional accessories: PH1A phantom power
supply (1 channel, battery or DC-adapter
powered). PH4A phantom power supply (4
channels,ACpowered).
*1 pascal = 10 dynes/cm
2
= 10 microbars = 94 dB SPL.
30˚
0˚
Vertical-Plane Polar Response
60˚ 90˚ 120˚
1 kHz
200 Hz
5 kHz
FRONT REAR
[phone]
150˚
180˚

Fig. 4
Fig.5
FRONT
BOTTOMVIEW
PHONE PLUG
SCREWDRIVER
LIFT WASHER AND
PRY OPEN HERE AND
ON OPPOSITE SIDE
MB3
Nominal sensitivity shall be 22 mV/Pa. Maxi-
mum SPL shall be 120 dB SPL for 3% THD.
Equivalent noise shallbe 22 dBA nominal.
Frequency response shall be 50 Hz to15 kHz
with a uniform off-axis response, about 20 dB
down at the rear nulls.
The AKG/Crown model MB3 is specified.
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 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
AFTER REASSEMBLY
RESEAT WASHER
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-supercardioidelectretcondensertype. 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
responseandgain-before-feedback.Themic
shall have a bottom-mounted 3-pin pro audio
XLR-type male connector. Powering shall be by
12-48V phantom power.
Warranty
AKG/Crown professional microphone products
are guaranteedunconditionallyagainst
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 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
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].
.
VCC
R1 R2
W1
C2
VCC
8
3 +
U1A
1
C5 R11
MICROPHONE CAPSULE
W2
C1
W3
2 –
R5 4
R8
C4
C12
+
VCC
3 2
U2
1
4
7
5
6
R15
C9
C10
12
VCC
+
C3 R3
R4
R6
R7
U1B
6 –7
5 +
R9
R10
C7 +
+
C6
R12
C8
+
R13
R14
R16
Q1
R17
C11
P1
3 A3M
CONNECTOR
INSERT
PINS
MB3Schematic
MICROPHONE ELECTRONICS
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
© 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