1280 Chapter 34
Special-purpose DSP processors included with some
packaged loudspeaker systems often include sophisti-
cated loudspeaker protection including limiters and
even sliding high and low-pass filters.
34.3.5.3.5 Protecting against Weather, Physical Damage
and Pests
Physical damage may be caused by overexcited fans at a
sporting event or by vandalism. When possible, locate
the loudspeakers out of the reach of potential vandals.
In some facilities, it may be necessary to build protec-
tive cages to prevent damage or theft. Some manufac-
turers offer vandal-resistant loudspeakers for use in
correctional facilities and schools.
Weather and pest damage can best be avoided by
choosing loudspeakers designed to resist these prob-
lems. When possible, locate loudspeakers in protected
areas such as under a balcony or awning. Loudspeakers
in outdoor summer amplitheaters may be removed and
stored for the winter season or covered for protection
from winter damage.
34.3.5.3.6 Age-Related Loudspeaker Damage
The foam surrounds on some cone-type loudspeakers
will deteriorate and fail after 10–15 years of use. It’s
best to choose loudspeakers with long-lasting surround
materials, such as impregnated cloth, to avoid this prob-
lem. It’s also possible for cones to age and sag after
many years, causing the voice coil to rub against the
pole piece. When this happens, recone or replace the
loudspeaker.
34.4 Electronic Components for Sound Rein-
forcement
34.4.1 General Specifications fozr Sound
Reinforcement
Electronic devices for professional and commercial
sound reinforcement systems should have balanced
inputs and outputs. Line level outputs should be +4 dBu
nominal with 20 dB head room for a +24 dBu peak out-
put level. Many digital audio devices have a maximum
output of +18 dBu, which is acceptable if the system is
designed for this maximum level. The devices should be
rack mountable except for those intended to mount on
desklike mixing consoles. They should utilize
high-quality electronics with low levels of hum and
noise; wide smooth frequency response; and low distor-
tion. For most applications, the devices should conform
to a recognized safety listing such as UL (Under-
writer’s Laboratories).34.4.2 Mixers and Mixing ConsolesSee Chapter 25 for a thorough discussion of all kinds of
mixing consoles. There are several types of mixers and
mixing consoles commonly used in sound reinforce-
ment systems. Simple rack mixers, like the one shown
in Fig. 34-36, may be all that’s needed for a college lec-
ture hall or for a religious facility with a spoken worship
style. Automatic mixers, as discussed in Section 34.4.3,
can reduce the need for an operator in these simple
systems.
Choose a desk-type mixing console, like the one in
Fig. 34-37, for live theater or for any facility that hosts
live entertainment events. Modern religious facilities
often include dramatic and musical performances as part
of their worship services. These facilities need a
desk-type mixing console. The versatility of a desk-type
mixing console means the operators must be well trained
in the artistic and technical aspects of its operation.
Tour sound systems use desk-type mixing consoles.
Larger tour sound systems may also use a
special-purpose type of mixing console known as a
monitor mixer. A monitor mixer is specifically designed
to mix the monitor loudspeakers on a performance
stage. For this reason, the stage monitor mixer is
normally located at stage left or stage right where the
operator can see and hear the monitor loudspeakers.
Digital mixing consoles, like the one shown in Fig.
34-38, perform the same functions as their analog
cousins but they have additional features, such as
memory scenes and multifunction outputs, that cannot
be implemented on analog consoles. A memory scene
stores most or all settings on the console in a digital
memory location for recall at the touch of a button. AFigure 34-35. A versatile high-quality compressor/limiter. Courtesy dbx Professional.