Handbook for Sound Engineers

Sound System Design 1323

speakers just to overcome the loss caused by friction in
the air.

In many speech-only systems, the loss is simply toler-
ated. Intelligible, if somewhat telephone-quality speech,
does not require frequencies much above about 3 kHz.
Except in extreme situations, adding a few extra
high-frequency horns and performing some additional
equalization will result in an acceptable system. Obvi-
ously, the additional equalization should be performed on
the long-throw loudspeakers only since the distance from
the short-throw loudspeakers to their listeners will be
considerably less than for the long-throw loudspeakers.

34.6.3.2 Using Distributed Systems Outdoors

There are several reasons to consider a distributed sys-
tem for an outdoor facility. Overcoming excess attenua-
tion of high frequencies is one reason. Avoiding the
effects of wind and temperature layers is another reason.
Distributed systems may reduce annoying neighborhood
leakage.
In some stadiums, there is no desirable location for a
central cluster. A round or oval stadium with full round
seating is one example. The usual scoreboard location
will often be awkward for coverage of nearby seating.

Sometimes existing lighting blocks the only workable

cluster location. In these or other similar situations, a

distributed cluster type of system may be the solution.

The clusters can be placed under balconies (under one

seating section to cover the one below) or on lighting

poles. It is acceptable to place loudspeakers behind the

heads of the spectators if this location does not cause

artificial echoes or other problems.

The distributed approach may also work well in

small outdoor systems such as a high-school football

field system. When the audience sits in one or two rela-

tively small sets of bleachers on either side of the field,

it is often easier to place horns on existing lighting poles

near the bleachers than to build a large central cluster at

one end of the field, Fig.34-82.

In any distributed system, consider sight lines and

watch out for potential artificial echoes.

34.6.3.3 Echoes Outdoors, Artificial and Otherwise

Normally, echoes are created by sound from a source,

such as a loudspeaker cluster, reflecting off a hard sur-

face and reaching a listener at a time that is delayed

enough to be perceived as an echo. About the only way

to deal with these echoes, outside of treating (or remov-

Figure 34-82. Distributed clusters in a stadium. Courtesy Seatle Mariners.