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3.0 Designing an EVA Array (cont')
3.4 Other Design Examples
3.41 Dealing with the relatively High Low-frequency Variation of Short Arrays
The example of Figure 4 is a three-module array addressing a flat floor from a trim height of 23 feet, with
the first row 10 feet away and the last row 80 ft away. The array has been aimed 10° down in accordance
with the accepted practice of aiming single loudspeakers or vertical clusters of conventional loudspeak-
ers. High frequency coverage (important for vocal intelligibility) is a fairly uniform ±3 dB from front to back
throughout the venue. At 500 Hz, however, the coverage is distinctly biased, rising from -2 dB in front
to a high of +7 dB about 25% of the way back, then falling gradually back to -3 dB at the rear. This is
a function of the relatively short (4.7 ft) three module array. The variation at 100 Hz (not shown) is even
greater, falling from +9 dB at the front to -2 dB at the rear. This means that if the sound is well balanced
at point "B" (a likely FOH location), it will be "tubby" or "boxy" up front and intelligibility may suffer.
Figure 8 shows the same venue and modules with an array design that provides more uniform "track-
ing" of the three frequencies. Attenuation has been applied to both the upper and lower modules and
the tilt angle has been raised from -10° to -1°. At first glance, this would appear to be wasting energy on
the back wall, but polars show the all-important main lobe to be aimed at the last row of seats instead.
Spectral balance of the three frequencies is now smooth and uniform throughout most of the venue and
level variance is a very acceptable +4 dB to -3 dB as dictated by the 500 Hz response of the 4.7 ft array
length.
Figure 8:
A three-module EVA example of Figure 4, modified to improve the
front-to-back "tracking" of all three predicted frequencies
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Electro-Voice EVA Series User Manual
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