Sound System Design 132734.6.3.9 Dealing with Weather-Caused Deterioration
The outdoor environment is considerably more hazard-
ous to the life span of a sound system than an artificially
lighted, temperature-, and humidity-controlled indoor
environment. Wind, rain, snow, ice, lightning, direct
sun, widely varying temperature, salt air near the ocean,
birds, squirrels, vandals, and pollution are just a few of
the hazards faced by an outdoor sound system. Most of
these hazards, of course, are felt by the loudspeaker sys-
tem since the remainder of the sound system will usu-
ally be installed in a relatively safe indoor environment.
However, avoid placing system electronics in a small
room (equipment shack) that is exposed to direct sun
and/or has poor ventilation. Also, protect or remove
microphones, mixers, and so on that may be used in an
exposed announcer’s booth.
Use an effective lightning arrester above any system
that might be exposed to lightning. Earth ground any
metal gridwork and the metal chassis of loudspeakers to
prevent static charge buildup, which can ultimately lead
to arcing from the loudspeaker frame to the voice coil.
Provide some type of static charge bleed to ground on
any balanced, transformer-coupled loudspeaker line for
the same reason. A pair of 1 M: resistors, one from
each side of the line to ground, works well.
Choose a loudspeaker system intended for outdoor
use. Outdoor loudspeaker enclosures and component
horns should be coated with some type of weather-resis-
tant finish such as epoxy paint, fiberglass, or the new
specialty polyurethane coating now used by several
loudspeaker manufacturers. Although a black or gray
color is traditional, a white or other reflective color will
help prevent heat buildup in hot sunlight. Fiberglass
horns and enclosures should be painted white since the
fiberglass resin will eventually evaporate in hot, direct
sunlight if allowed to absorb heat.
Paper cone loudspeakers should be treated to resist
damage from high humidity (this is a good idea in
humid indoor environments, such as swimming pools,
too). Simply spraying the cone with a waterproofing
such as Scotchguard™ will help considerably and does
not affect the performance significantly. The
diaphragms of high-frequency drivers should either be
made of a phenolic-type material or should be treated
by the manufacturer to resist damage from humidity
(most are). These treatments will also help prevent
damage from pollution.
To protect against actual rain, install loudspeakers
and horns pointing slightly downward if at all possible.
If a horn must be pointed upward, use a curved adapter
throat (available from the manufacturer) to point the
driver downward. The adapter throat should have a
weep hole in the bottom of the curve to allow water to
drain out.
For additional protection against driving rain, some
manufacturers use a layer of weather-resistant reticu-
lated foam between two layers of grille cloth. Using a
horn-loaded enclosure helps by recessing the loud-
speaker cone. A layer of hardware cloth, or perforated
aluminum, in addition to the grille cloth, can help
prevent birds and squirrels from nesting in the enclo-
sures and can help prevent damage from vandals
throwing rocks, bottles, and so on. The hardware cloth
can often be placed over the mouth of a horn, too.
Salt air can be extremely corrosive to metallic
portions of loudspeakers, including metallic
high-frequency driver diaphragms and metal horns. Use
fiberglass or weather-resistant plastic horns, and coat
low-frequency enclosures with epoxy paint or fiber-
glass. Consult with the manufacturer to choose
low-frequency loudspeakers and high-frequency drivers
that will resist damage from the salt air.
Especially when using a packaged loudspeaker
system outdoors, consider the durability of the connec-
tors. Conventional ¼ inch phone plugs, XLRs, or other
indoor-type loudspeaker connectors will deteriorate
outdoors from exposure to moisture and dust. Neutrik
Speakon connectors are better but are not suitable for
long-term outdoor exposure. The best solution is to
eliminate the connector altogether and provide a direct
cable connection into the loudspeaker system.
No matter how much care is taken in protecting
outdoor loudspeaker systems, they will deteriorate faster
than similar indoor systems. Thus, the system design
should provide for easy access and repair, Fig. 34-87.34.6.3.10 Simulating the Indoor Environment OutdoorsMany orchestras perform a yearly series of summer
concerts in an outdoor amphitheater. Patrons enjoy pic-
nics and music in an informal atmosphere. They may,
however, notice that the orchestra’s sound is not quite as
rich or full as it would be during an indoor concert. The
problem, of course, has nothing to do with the musi-
cians and everything to do with the lack of beneficial
reflections in the outdoor environment.
While the outdoor environment can probably never
be as good for orchestral music as a great concert hall,
steps can be taken to improve the richness of the sound.
Perhaps the most common approach is to reinforce
the orchestra through a stage/shell-area loudspeaker
system in conjunction with a series of remote loud-
speakers (or small clusters) positioned to provide simu-