Telex EVID Ceiling Speaker Systems - Manual (Page 12)

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
accommodate each job, depending on how
these criteria 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.electro-
voice.com (under downloads/speakers), 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 elements. Two basic placement pat-
terns prevail: square spacing and hexagonal
(or crisscross) spacing. See Figure 22.
In addition to the spacing pattern, the
designer must choose between three cover-
age density types, designated respectively
as edge-to-edge, minimum overlap and cen-
ter-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 over-
head systems, at least in part because they rep-
resented 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 transduc-
ers, 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 signif-
icantly wider dispersion (130 degrees) than
the C8.2 (110 degrees) at the -6 dB points.
The effect of this characteristic on an over-
head 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 specify-
ing a new system, you can take advantage of
the C4.2’s wider dispersion to decrease the
number of speakers required to cover a given
area. This will result in even greater savings.
Of course, the C4.2 is somewhat less sensi-
tive 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 sig-
nificant problem in many distributed systems.
The C4.2 is conservatively rated to handle 80
watts of continuous power equal to or greater
than most other brands of 8-inch units, so its
continuous SPL output will be more than ade-
quate. Moreover, its low-frequency output
can easily be augmented with the addition of
the C10.1 subwoofer. For these reasons, the
C4.2 represents a great way for you to pro-
vide good audio coverage while maintaining
a competitive edge in price quotes in installa-
10 EVID™ Ceiling Series Installation and Operation Manual
Appendix B — System Design Guide
Grid Edge-to-edge Minimum
overlap
Center-to-
center
He
xagonal
Square
Figure 22: Coverage patterns
Ceiling
A
B
A
B
Figure 23: Size vs. coverage