Appendix B - System Design Guide; Selecting And Positioning Ceiling Loudspeakers; Ceiling Systems: Size Vs. Coverage - Electro-Voice EVID Installation And Operation Manual

Selecting and Positioning
Ceiling Loudspeakers
Several key criteria determine the type and
quantity of ceiling speakers to employ in a job.
Specific EVID™ Ceiling Series models accom-
modate each job, depending on how these cri-
teria are specified.
• Room size
• Coverage density desired
• Coverage angle specification of the speaker
• Ceiling height
• Audio program material being played
The information below, and the free design
program downloadable from
www.electrovoice.com (under downloads/speak-
ers), will help you optimize your EVID design.
In the traditional approach to overhead-
distributed systems, loudspeakers are placed in a
grid whose dimensions are dictated by the room
height and the directivity of the speaker ele-
ments.Two basic placement patterns prevail:
square spacing and hexagonal (or crisscross)
spacing. See Figure 22.
Grid Edge-to-edge Minimum
Figure 22: Coverage patterns
In addition to the spacing pattern, the
designer must choose between three coverage
density types, designated respectively as edge-
to-edge, minimum overlap and center-to-center.
The greater the overlap, the more uniform the
coverage.The illustration below shows these
various layout patterns.
Ceiling Systems: Size vs.
Coverage
In the past, system designers usually specified 8-
inch cone loudspeakers for distributed overhead
10
Appendix B — System Design Guide
Center-to-
overlap center
EVID™ Ceiling Series Installation and Operation Manual
systems, at least in part because they represented
the traditional choice. EVID systems, however,
allow for far more flexible options.
In many cases, you can achieve excellent
results — at a significant savings — by using 4-
inch transducers.This is especially true in jobs
that do not require extended low-end response or
high SPL levels. 4-inch transducers, such as those
used in the C4.2, offer wider dispersion to allow
for fewer speakers to be employed in the job. For
example, due to its smaller cone diameter, the
C4.2 exhibits significantly wider dispersion (130
degrees) than the C8.2 (110 degrees) at the -6 dB
points.
The effect of this characteristic on an overhead
system is indicated in Figure 23. In replacement
applications where existing speaker positions are
used, the C4.2 (shown in angle A) offers greater
overlap and, thus, more uniform coverage than an
older conventional 8-inch unit (shown in angle
B).When specifying a new system, you can take
advantage of the C4.2's wider dispersion to
decrease the number of speakers required to
Ceiling
A
B
Figure 23: Size vs. coverage
cover a given area.This will result in even greater
savings.
Of course, the C4.2 is somewhat less sensitive
than the 8-inch C8.2.The difference is
–5 dB.The C4.2 will also have slightly reduced
low-frequency capabilities below 65 Hz.
However, neither of these factors is a significant
problem in many distributed systems.The C4.2 is
conservatively rated to handle 80 watts of con-
tinuous power equal to or greater than most
other brands of 8-inch units, so its continuous
SPL output will be more than adequate.
Moreover, its low-frequency output can easily be
augmented with the addition of the C10.1 sub-
woofer. For these reasons, the C4.2 represents a
great way for you to provide good audio cover-
A
B