Multi-Purpose Room (Cafeteria/Gym/Auditorium) - Community ENTASYS Application Manual

Multi‐Purpose Room (Cafeteria/Gym/Auditorium)
Design Approach
This example shows a multi-purpose room which functions as a cafeteria, gymnasium, and auditorium (typically found in many
elementary and middle schools). The room has no acoustical treatment, resulting in a mid-band RT of around 2 seconds. The
sound system will be tasked with reproducing both music and speech. As a school project, budget is a consideration, thus a
minimum number of loudspeakers will be employed. Intelligibility is a key requirement, as is music playback, therefore low
frequency extension loudspeakers will be placed directly below the arrays to provide reproduction at frequencies
below 200 Hz.
The audience area, comprising a flat floor/court area with fold-away bleachers at the rear of the room, is drawn in EASE Focus
as shown in Figure 42. The loudspeaker array is located on the front wall, resulting in an audience area spanning
approximately 5 - 62 ft (1.5 - 18.9 m) away from the speakers. The very front of the audience area is potentially a bit too close,
but the flexibility of this room's usage patterns can hopefully avoid locating seats this close under most circumstances. Using an
array comprising three ENTASYS Full-Range modules, mounted at a height of 15.3 ft (4.7 m) with a downward angle of
2 degrees, achieves relatively consistent SPL across the audience area.
The configuration and position of the array are transferred from EASE Focus to the EASE model. Since EASE Focus only
models in two dimensions, the azimuth (horizontal aiming angle) of the arrays must be adjusted in the EASE 3D model to
achieve optimal coverage. The arrays are aimed inwards at 23 degrees.
Despite the ultra-wide azimuth of the ENTASYS column line-arrays, the center of front seating will require a supplemental
"front fill" loudspeaker. In this case, the i2W8 was chosen. The ENTASYs units must be signal-delayed to synchronize with
the enter front-fill loudspeaker.
Since ball sports can damage an ENTASYS loudspeaker, it is recommended that the installation contractor provide a robust
dent-resistant heavy gauge steel grille or cage fabricated and fastened to the wall or other sturdy mounting points in such a
way so as to protect the entire loudspeaker. Make sure that any perforated grille has an open area of at least 75% to allow
reasonable sound passage. The grille and mounting should be stiff to withstand high velocity strikes from basketballs, hardballs,
hockey pucks, or whatever the various sports may launch at the loudspeaker.
Results
Tall full-range arrays accommodate sitting and standing audiences along the flat floor and sloped rear seats. The audience area
shown in Figure 43 indicates relatively uniform direct SPL of 102 dB (+/-2 dB) on the floor, and 101 dB (+/-2 dB) in the
bleachers. In the few side seats near the array the SPL is slightly louder at about 105 dB. The system exhibits good potential
intelligibility with an overall C50 of -0.5 dB (+/-2 dB). The STI is approximately 0.53 with the %Alcons being about 9.5%.
What To Look Out For
Rooms of this type with no acoustical treatment can be problematic. The ENTASYS design detailed above achieves consistent
coverage and good intelligibility without exciting the reverberant field excessively. If desired, placing absorptive materials on
the wall and/or hanging absorptive banners/baffles from the ceiling can decrease the room's reverberant and increase
intelligibility. Note that the top full-range module can be configured straight or "tip curved" to provide very good HF
propagation to the rear audience area. In this case, the straight configuration offers the advantage of not projecting a strong
HF beam on the highly reflective ceiling which would have otherwise created an undesirable and obvious specular HF echo.
Loudspeakers, Brackets, and Power Amplifiers Used in This Design
Two arrays, each configured (top-to-bottom) as a Full-Range module (curved top), Full-Range module (straight), and Full-Range
module (curved bottom).
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(6) ENTASYS Full-Range Modules (ENT-FR)
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(4) ENTASYS Coupler Brackets (ENT-CB)
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(2) ENTASYS Pan-Tilt Brackets (ENT-PB)
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(2) VLF212 Subwoofers
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(1) Two channel amplifier rated at 3,600 W per channel into 4 ohms
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(1) Crossover with a high pass filter or DSP unit with output delays
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(1) i2W8 and appropriate amplifier and DSP channel.
DESIGN APPLICATION EXAMPLES
Community ENTASYS Application Guide - Page 46