Community ENTASYS Application Manual page 51

DESIGN APPLICATION EXAMPLES
Overhead Distributed Design Approach
For the overhead design, Community iBOX i2W8T loudspeakers are mounted along the roof joists and aimed down at the
audience area. The optional autoformer (ENT-750T) will be employed to maintain a high line voltage and low current (similar
to the amplification scheme discussed on Page 48); thereby, allowing each row of loudspeakers to be driven by one channel of
an amplifier (specifying an amp with sufficient voltage output to drive the 70.7V/100V line).
Results
Here again, the audience areas in Figure 47 display fairly uniform coverage of approximately 100 dB (+/- 1.5 dB), except for a
small area half-way back where the SPL reaches 103 dB. The potential intelligibility of this system is also good, with a C50
averaging -1.5 dB (+/-1.0 dB). The STI is approximately 0.56 with the %Alcons being about 8.2%. Since the sound sonics are
above the audience, the design may have to be improved to discretely power and signal delay the loudspeakers to synchronize
with presentations and natural sound from the presenter at the front of the room.
Loudspeakers and Power Amplifiers Used in This Design
•
(8) Community iBOX i2W8 Loudspeakers with Autoformer (i2W8T)
•
(1) Two channel amplifier rated at 1,250 W per channel into 4 ohms (70.7V /100V)
•
(1) High pass filter or DSP unit
Comparison of the Different Design Approaches
The two design approaches should yield similar intelligibility in this space. The ENTASYS system offers a slight advantage in
minimizing reflected energy off the ceiling area, while the rear radiation from the loudspeakers in the distributed system
generates considerably more energy in the range below 800 - 1,000 Hz.
The distributed system generates approximately 3 dB more, and covers a lower frequency range, though this low frequency
issue is easily remedied by adding a subwoofer, such as the VLF208.
While both systems provide adequate coverage, the major component cost of the ENTASYS system is 35% less than the i2W8
overhead distributed system, including the subwoofer and additional amplifier. When the increased labor costs for the
distributed system's multiple loudspeaker locations is factored into the equation, it becomes clear that ENTASYS offers a real
advantage.
Figure 45: SPL Map of Audience Area in a Multi-Purpose Room
Community ENTASYS Application Guide - Page 51