T
MB4
MINI-BOUNDARY
™
MICROPHONE
he AKG/Crown
®
MB4 is a miniature
boundary microphone for multi-miking
applications such as teleconferencing,
distance learning, boardrooms,
courtrooms, and security applications.
Double-sided sticky tape is provided for
attaching the unit under shelves, on walls,
etc.
Thanks to its supercardioid pickup pattern,
the MB4 greatly reduces ambient noise
and pickup of room reverberation. The
result is a clearer sound.
The MB4 has a 15-foot attached cable
leading to an XLR-type output connector
with built-in mic electronics. It is powered
by 12-48V phantom power, and is low-
impedance balanced.
Features
• Tiny, inconspicuous.
• Can be used without putting holes in
the table.
• 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).
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
• 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
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
1.
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.
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.
Orient the mic so the readable lable faces
the user (right-side-up).
3.
Plug a mic cable with a female XLR-type
connector into the power module. 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.
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.
Current drain:
4 mA nominal.
Connector:
3-pin pro audio, XLR-M type.
Cable:
Permanently attached, black, 15-foot
(4.572 m), 2-conductor shielded cable from mic
to power module or interface. No other cable
supplied. Use two-conductor shielded mic cable
from power module to mixer.
Materials:
High-impact molded plastic and steel
mesh mic grille, steel power module.
Finish:
Satin black.
Net weight:
2.7 ounces (78 grams).
Operating temperature range:
-10° to +50°C, or +14°
to +122°F.
Net weight:
Microphone: 0.7 ounces (19.8 grams)
Power module: 2.8 ounces (78.6 grams)
Dimensions:
See Fig. 4.
Included accessories
: Double-sided tape for
fastening under shelves, etc., for theatrical
applications.
Optional accessories:
PH1A phantom power
supply (1 channel, battery or DC-adapter
powered). PH4A phantom power supply (4
channels, AC powered).
*1 pascal = 10 dynes/cm
2
= 10 microbars = 94 dB SPL.
Fig. 1
. Frequency Response
Fig. 2
. Horizontal-Plane Polar Response
Fig. 3
. Vertical-Plane Polar Response
