Crown GLM-100, PZM-10, MB-3, PZM-11, PZM-11LL Application Manual

CROWN MICROPHONE APPLICATION GUIDE:

SECURITY AND SURVEILLANCE

© 2001 Crown Audio, Inc. All rights reserved PZM®
is a registered trademark of Crown International.
Also exported as Amcron®

102100-2
11-01

Crown International
P.O. Box 1000,
Elkhart, Indiana 46515-1000
[phone] Fax [phone]

CROWN MICROPHONE

APPLICATION GUIDE

SECURITY AND SURVEILLANCE

This guide offers tips on using Crown microphones
to safeguard areas such as warehouses, offices, park­ing garages, and building entries. Using these micro­phones, a security officer can detect break-ins or
other undesirable activities. We’ll also describe how
to pick up police i nterviews and ps ychiatric sessions.

First let’s look at Crown’s line of mics for security
applications. All the mics are very small, and are
designed NOT to look like microphones, so they are
nearly invisible. They provide clear pickup of
speech.

In all these microphones, th e low frequencies below
the voice r ange a re f iltered ou t to r educe rumble f rom
trucks, machinery and air conditioning. At high fre­quencies, the response is boosted to help articulation.
Because of their tailo red re spo ns e, the Crow n secu ­rity mics pick up conversations or other de sired
sounds with extra clarity.

Some of the model s are Pressure Zone Microphones
(PZMs) . The y use a min ia tu re m ic cap su le m o unte d
very near a sound-reflecting plate or boundary, in the
Pressure Zone . In this zone, di rect sound from the
sound source combines in phase at all frequ encies
with reflected sound off the boundary. The benefits
are many :

• 6 dB more sensitivity

• 6 dB les s no i s e

• a wide smooth frequency response free of phase
interference

• excellent clarity and “reach”

• hemispherical (half-omni) pickup pattern

• consistent pickup anywhere around the micro­phone.

Other models are Mini Boundary (MB) mics. They
use a miniature, unidirectional mic capsule mounted
very near a boundary. Because they are directional,
MB mics can pick up less room reverb than PZMs
do. The result is an even clearer sound.

Below are notes on each Crown microphone model:

PZM-10

This is a miniature PZM that looks like a light
switch. The m ic ha s built-in elec tronics, which are in
an attached tu be. The tube mou nts in a ceiling, panel,
wall or table. It comes with an XLR-type connector
and requires 12-48V phantom power.

PZM-11

Like the PZM-10, the PZM-11 resembles a light
switch. It mounts in a standard electrical outlet box.
The mic comes with a screw-terminal connector and
requires 12-48V phantom power.

The

PZM-11LL

is the same as the PZM-11, but has a
line-level output. This lets you record directly into a
VCR with ou t a mi c pream p . The PZM - 11LL can be
powered in two ways: 24V AC or 12-24V DC. In
video security systems, 24V AC is usually availa ble,
and this can be used to power the mic. The output
connector is screw terminals.

The

PZM-11LL WR

is the same as the PZM-11LL,

but is weathe r resistant.

MB-3

This is a miniature supercardioid mic with attached
electroni cs that mounts i n a ce iling panel, wa ll or
table. The mi c comes with an XLR-type connector
and requires 12-48V phantom power.

GLM-100

This mini omnidirectional mic is easy to install tem­porarily. Just tape it to any convenient surface. The
mic has an XLR-type output and runs off phant om
power.

The

GLM-100/E

is the same, but can be connected
directly to a wirele ss tran sm itte r. At the end of the
mic cable, you solde r on a co nne ctor th at mates with
your transmitter.

APPLICA TIONS

Large rooms (warehouses, parking
garages, offices, etc.)

One way to cover a large room is with PZMs on the
ceiling (Fig. 1).

Figure 1

How fa r apart should the mics be to get unif orm co v­erage? Use the 2-to-1 rule. The spacing between
mics should be two times the distance from mouth to
ceiling. Fo r exam ple , if the ceiling is 5 f eet above the
talkers’ mouths, the mics should be 10 feet apart.
Then the mics will pick up eve ryone about equally.
In general, use as few mics as possible that will do
the job.

If several mics are on at the same time, the recorded
sound might be reverberant or muddy. It helps to run
all the mics into a gated mix e r (autom at ic mix e r),
which turns on only one mic at a time – the one near­est the pers on speaking. This kee p s the sound clear.

If the ceiling is very hig h , mount the PZM-11 or
PZM-11LL on support posts and/or walls, about 10
feet off the floor (out of reach).

Medium size room (small office,
group therapy room, home, etc.)

Here you have a choice of PZM mics or the MB-3
mic. The PZMs are omnidirectional; the MB-3 is
unidirectional.

If the mic must b e mounte d in the ceiling near a wall,
and most talkers are in the mid dle of the room, the
MB-3 is a better choice (Fig. 2). It will pick up less
room reverbe rat ion th an the PZM wo uld in the same
location.

Figure 2

If the mic can be mounted in the ceiling near the mid­dle of the room, and most talkers are in the middle of
the room, the PZM is the better choice (Fig. 3). It
will pick up less roo m rev erb than the M B-3 would in
the same location.

Figure 3

Since the MB-3 is unidirectional, why doesn’t it pick
up less reverb than the omnidirectional PZM? If the
MB-3 is overhead of the talkers, it picks them up
approximately 90 degrees off axis, where its output is
reduced by 9 dB. So it picks up talkers rather
weakly, but picks up reverb strongly on-axis.

The MB-3 works best when talkers are in front of the
mic and within its 60-degree pickup angle. For
example, when the mic is near a wall and the talkers
are in the middle of the room (Fig. 2).

Police interview room or psychia-
trist office

Mount a PZM-10, PZM-11, or PZM-11LL in the
ceiling direct ly ove r the inte rvie w tab le (Fi g. 4).
Another placement is in a wall close to the table at
mouth height. Since the mic rese mbles a light
switch, it does not intim id ate the inter viewe e.
.

Figure 4

If possible, deaden the room acoustics by adding cur­tains, carp et, or acoustic-tile ceiling. This reduces
room reverb and provides a clearer sound.

Subway station

Mount PZMs of your choice in posts, in the ceiling,
or in wa lls.
Mount the mics 10 feet above the floor, out of reach
(Fig. 5).

Figure 5

If the mics will be 10 feet fro m p eop le on the aver­age, mount the mics 20 feet apart to pick up everyone
about equally. That is, the mics should be no more
than twice as far apa rt as the y are fro m the peo ple.

Entry

Mount a PZM in an overhang, or mount an MB-3
aiming dow n over the entry (Fig. 6). It is best not to
expose the mi crophone to rai nfall.

Figure 6

GLM-100 techniques

The GLM-100 miniature mic is easy to in stall and is
for temporary use. Simp ly tape it to a wall, ceiling,
or upper corner of a room.

If possible , pla ce the G L M so it has a line of sigh t to
the person speaking. A mic behind a barrier or fabric
tends to sound muffled.

By following the suggestions in this guide, you
should be able to discreetly pick up speech and other
sounds with clarity .