Community ENTASYS Application Manual page 19

GENERAL INFO ON LINE ARRAYS
The directivity control of a line array is generally only within the plane of the line. That is, if the drivers in a line array are
arranged vertically (which is most often the case), the directivity control will be in the vertical plane. In the horizontal plane,
directivity will be fairly broad. For this reason, line arrays cannot be rotated on their side and still maintain high vertical
directivity.
P E R F O R M A N C E C O M PA R I S O N O F A L I N E A R R AY
A N D
P O I N T S O U R C E SYS T E M I N T H E SA M E R O O M
Perhaps one of the best ways to understand the differences between a line array and a point source system is to design a
system for the same room using each type of system and compare them. It would be prohibitively costly to actually execute,
install, and evaluate each system in this manner, however this comparison can be carried out virtually using acoustical
computer modeling. Two designs were prepared and modeled in the same room using EASE 4.2. The example used was a
small house of worship with a 2.0 - 2.5 second reverb time.
The ENTASYS line array system is shown in Figure 13. This system uses columns of two stacked ENTASYS Full-Range
loudspeakers on each side at the front of the main seating area. One additional ENTASYS Full-Range loudspeaker is flown to
provide coverage to the balcony area.
By comparison, Figure 14 shows a point source system in the same space. This system uses a main cluster of two Community
SLS960 and two SLS915 loudspeakers covering the floor area. Three SLS915 loudspeakers are used on a delay to provide
coverage to the balcony area.
Note that on the SLS center cluster design, a high mounting position was necessary to preserve sightlines for the religious
symbols. If those sightlines were not a consideration, the array could be lower and the intelligibility would be higher for the
front of the audience especially. Sightlines of this nature are a common important consideration to the loudspeaker design.
The sightline issue is completely avoided by using the ENTASYS system design.
The direct SPL on the room surfaces is shown in Figures 15 - 22. The odd number figures reflect the ENTASYS system,
while the even numbers illustrate the point source system.
The SPL maps confirm that both systems provide good coverage to the audience areas, averaging approximately 95 dB SPL for
the direct field. However, the point source system maintains this SPL slightly better from the front to the back of the room
due to its high elevation.
The potential intelligibility of each system is compared in the graph shown in Figure 23. This shows C50 for each system in
this room. C50 is a measure of the clarity and correlates well with intelligibility. (Higher values indicate greater clarity and
potential intelligibility.) The ENTASYS system offers, on average, about 2 - 3 dB greater clarity below 5 kHz than the point
source system, indicating greater potential intelligibility. This is further confirmed by the predicted %Alcons (percentage
articulation loss of consonants) of 13.3% for the point source system and 10.6% for the ENTASYS system.
It should also be noted that the point source system design delivers considerably higher SPL to the altar area (Figure 16 &
Figure 18) than the ENTASYS system design (Figure 15 & Figure 17). This would confirm the ENTASYS system's potential
for considerably higher gain before feedback – another distinct advantage.
From a cost perspective, the point source system utilizes seven loudspeakers (all requiring rigging to be flown), four channels
of amplification, and a signal delay unit. The ENTASYS system employs just five loudspeakers (only one requiring rigging), three
channels of amplification, and a signal delay unit. While the loudspeakers used in the point source system are physically larger
and capable of reproducing some lower frequencies that the ENTASYS systems will not, adding a VLF208 dual 8-inch
subwoofer below each ENTASYS on the front wall would deliver comparable low frequency output, while still coming in at or
below the cost of the point source system.
Community ENTASYS Application Guide - Page 19