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E2002, Shure Incorporated
MODEL MX391 SERIES MICROPHONES
OVERVIEW
Shure Microflex
MX391 Series microphones are small, surface-
mounted electret condenser microphones designed for mounting on
conference tables, stage floors, and lecterns. Their high sensitivity
and wide frequency range make them especially suitable for picking
up speech and vocals in sound reinforcement and recording applica-
tions.
FEATURES
S Flat frequency response across the vocal range for uncolored
sound
S Interchangeable cardioid, supercardioid, and omnidirectional
cartridges that provide optimal choice for each application
S Sleek, low-profile design for unobtrusive appearance
S Balanced, transformerless output for increased immunity to noise
over long cable runs
MODEL VARIATIONS
MX391 and MX391W (white) models have an attached 4 meter (12
ft) cable terminated with a 4-pin mini connector and a separate pream-
plifier. A rubber strain relief is provided for applications where you
want to remove the 4–pin mini connector and connect the micro-
phone cable directly to screw terminals in the preamplifier.
MX391LP and MX391WLP (white) models have an attached 4
meter (12 ft) cable terminated with a 4–pin mini connector, but do not
include a preamplifier. Instead, the microphone can be connected di-
rectly to a Shure wireless body-pack transmitter.
Microflex
boundary microphones come with one of three inter-
changeable cartridges, as indicated by the model number (found on the
bottom of the microphone base).
MX391/C series. Cardioid pickup pattern for general sound rein-
forcement applications. Pickup angle (–3 dB) = 130°.
MX391/S series. Supercardioid pickup pattern for sound rein-
forcement applications requiring narrow or more distant cover-
age. Pickup angle (–3 dB) = 115°.
MX391/O series. Omnidirectional pickup pattern for recording or
remote monitoring applications. Pickup angle = 360°.
SPECIFICATIONS
Polar Pattern (Figure 4)
Cardioid (MX391/C, MX391W/C, MX391LP/C, MX391WLP/C)
Supercardioid (MX391/S, MX391W/S, MX391LP/S, MX391WLP/S)
Omnidirectional (MX391/O, MX391W/O, MX391LP/O,
MX391WLP/O)
Environmental Requirements
Operating Temperature Range: –18° C to 57° C (0° F to 135° F)
Relative Humidity: 0 to 95%
Dimensions
See Figure 2
Wiring Diagram (Figure 1)
PIN 2 = RED LEAD
PIN 1 = SHIELD (use only HALF of
the shield, the other half solder to
cable clamp)
PINS 3 and 4 = BLACK LEAD
(jumped)
4
3
1
2
WIRING DIAGRAM
Figure 1
PREAMPLIFIER SPECIFICATIONS
These specifications apply only to the MX391/MX391W micro-
phones when used with the supplied preamplifier. All measurements
taken with the microphone mounted on a wooden surface 76.2 cm
x 76.2 cm (30 in. x 30 in.) and with the sound source incident at 30°
with respect to the surface plane.
Frequency Response (Figure 3)
50 to 17,000 Hz
Output Impedance (at 1000 Hz)
Rated at 150Ω (180Ω actual)
Open Circuit Sensitivity
Cartridge Type
1 kHz ref. 1 V per
Pascal *
Cardioid –29.6 dB (33.5 mV)
Supercardioid –28.3 dB (38.5 mV)
Omnidirectional –21.5 dB (81.4 mV)
*1 Pascal = 94 dB SPL
Maximum Sound Pressure Level
(1 kHz at 1% Total Harmonic Distortion, 1 kΩ load)
Cardioid: 118.8 dB
Supercardioid: 117.5 dB
Omnidirectional: 110.7 dB
Signal to Noise Ratio (referenced at 94 dB SPL)
Cardioid: 71.4 dB
Supercardioid: 72.7 dB
Omnidirectional: 79.5 dB
Model MX391 Series Microphones
Specification Sheet