Shure Microflex MX391 Series User Manual

MICROFLEX MX391 SERIES
BOUNDARY MICROPHONES
GENERAL

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 applications.
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 pre-
amplifier. 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°.
2002, Shure Incorporated
27C3027 (BE)
Microflex
Boundary Microphones User Guide
PERMANENT INSTALLATION
Screw holes in the microphone base and a bottom exit hole for the
microphone cable are provided for permanent installation of the
boundary microphone. To re-route the microphone cable through
the bottom exit hole, use the following steps (Figure 1):
1. Remove the grille from the microphone base by loosening the
single screw on top of the grille.
2. Remove the 4–pin mini connector from the end of the cable by
cutting the cable just below the connector.
WARNING: Do not attempt to detach the cable from the micro-
phone interface.
3. Secure the cable with your thumb or finger so that it does not
come loose from the strain-relief posts as you thread the cable
out from the rear exit hole.
4. Re-route the cable through the bottom exit hole and pull snug.
IMPORTANT: Be sure the cable is pressed firmly down be-
tween the strain relief posts before replacing the grill.
5. Set the grille back into place and thread the screw through the
perforated metal grille and into the microphone interface and
tighten.
6. Use the supplied template (Figure 3) to drill screw holes and a
bottom exit hole in the mounting surface.
7. After threading the cable through the bottom exit hole in the
mounting surface, either re-attach the 4–pin mini connector
(Figure 2) or wire the cable to the screw terminals in the pream-
plifier (use the supplied rubber strain relief to secure the con-
nection).
NOTE: For detailed instructions on re-attaching the 4–pin mini
connector, contact the Shure Applications Group.
REPAINTING THE MX391 SERIES
Before applying paint to the MX391 series, remove the grille from
the base, remove the foam from the inside of the grill, and mask the
microphone cartridge and interface. Also mask the cable where
necessary.
Microphone Interface
Service Loop
Screw Hole
RE-ROUTING THE CABLE
ADJUSTING PREAMP GAIN (Figure 4)
This MX microphone includes an adjustable gain preamplifier, allow-
ing the user to specify a 12 dB or 0 dB gain setting. The preamp ships
at the 12dB setting. Gain may be decreased by 12dB by moving the
preamp jumpers to the 0dB setting.

MX391 Series
Screw Hole
Strain Relief Post
FIGURE 1
Printed in U.S.A.