Crown Audio MB-3 specifications Features, How to Paint the Microphone, Specifications

POLAR

PATTERN

MB-3

he Crown® MB-3 is a miniature boundary Tmicrophone for multi-miking applications such as teleconferencing, distance learn-

ing, boardrooms, courtrooms, and security applications. This low-profile, circular mic per- manently 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.

MINI-BOUNDARY™

MICROPHONE

Features
Ideal for teleconferencing, distance learning,	Half-supercardioid polar pattern reduces
boardrooms, courtrooms and security	pickup of background noise, room acoustics
Small and inconspicuous	and feedback
	On-surface mounting eliminates phase
Installs permanently in a table top, wall or	interference from table sound reflections,
ceiling	giving a natural sound

How to Paint the Microphone

1. See Fig. 5. Using a small screwdriver, pry

Specifications

Type: Phase Coherent Cardioid.

Fig. 1

Frequency Response

open the FRONT side of the mic cover (grille

assembly).

2. Remove the foam liner.

Element: Electret condenser.

Frequency response (typical): 50 Hz to 15,000 Hz at 30 degrees incidence to surface (see Fig. 1).

+15

+10

+5

dB 0

0˚

Polar pattern: Half-supercardioid (supercardioid in

–5

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

Impedance: 150 ohms, balanced (recommended load impedance 1000 ohms or greater).

–10

–15

–20

–25

–30

–35

130˚

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 be- tween 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.

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.

20 100 1K 10K

Frequency in Hz

Fig. 2

Horizontal-Plane Polar Response

330˚	0˚	30˚
	FRONT
	–0
300˚	–5	60˚
	–10
	–15
	–20
270˚		90˚
240˚		120˚
		1 kHz
		200 Hz
	REAR	5 kHz
210˚	180˚	150˚

Fig. 3

Vertical-Plane Polar Response

60˚		90˚	120˚
			1 kHz
			200 Hz
			5 kHz
30˚			150˚
FRONT			REAR
0˚	–5	–10 –15 –20	180˚
+5 –0