Large Public Space - Community ENTASYS Application Manual

Design Approach
The example shown in Figure 44 illustrates a less conventional application – an announcement system installed in a large
public space with an estimated mid-band RT of approximately 2 seconds. This structure's relatively high 15 ft (4.6 m) ceilings
would make the cost of installing multiple ceiling speakers prohibitive.
Due to the multiple loudspeaker locations, an equivalent EASE Focus model isn't really feasible. However, as has been
previously shown in this application guide, EASE Focus can be employed to get a general sense of the coverage pattern of the
planned array configuration.
The potential listening area covers the entire public space at an average standing ear height. Multiple loudspeaker locations are
employed, as shown in the figure, each comprising two Full-Range modules at a height of 11.9 ft (3.6 m), angled downward 2
degrees. The azimuth (horizontal aiming angle) of each array varies according to its mounting location and the required
coverage area. Each of the 35 array locations are shown in the figure, along with the signal delay time for that array.
Since the potential maximum SPL will certainly exceed that required for announcements, the optional ENTASYS autoformer
will be used. This will allow the input signal to be decreased using lower power taps on the autoformer, as well as allowing for
the use of smaller amplifiers. Selecting the input to the autoformers at the 63 W tap for 2 columns (modules) will reduce the
maximum output level by approximately 10 dB. The optional ENT-750T autoformer accessory for the ENT-FR allows higher
voltage, lower current (and power) on long distance transmission cables to overcome cable losses. Higher voltage on the
amplifier to autoformer cable is then stepped down to appropriate levels at each loudspeaker via selectable taps. This also
allows reduced wire gauge cable which results in greater installation labor and cable cost savings. Sonically, the low-insertion
loss ENT-750T autoformer diminishes overall output by 1dB with nominal impact to frequency response. (Contact the
Community Technical Applications Group (TAG Team) for more detailed information.)
While this example utilizes a parking garage, the implementation of ENTASYS in a similar manner to many large public spaces
such as shopping malls, food courts, airport or train terminals, etc. can be equally advantageous.
Results
The system exhibits good uniform coverage, with maximum values ranging from 103 - 107 dB. Our autoformer tap selection
should reduce this to 93 - 97 dB, still possibly a bit louder than will be required. While there are variations in the public space,
the overall potential intelligibility is good. The values for C50 range from -10 dB to +5 dB. The STI averages about 0.48 while
the %Alcons is approximately 12.8%.
What To Look Out For
In this environment, there will be little opportunity to improve intelligibility by adding acoustical treatment. System
performance will be maximized by careful aiming of the arrays and setting of the delay times to minimize multiple arrival times
from different arrays.
Independent level adjustment of the arrays in the different delay zones may also help to optimize the overall perceived sound
quality. This is easily accomplished by adjusting the input sensitivity of each amplifier channel or the DSP output feeding a
particular zone.
With so many loudspeaker locations, one might be concerned about multiple sound arrivals presenting confusing artificaial
echoes for the listener. A simple auralization study in EASE demonstrated that the multiple arrivals actual integrate well
supportive as reflections in this particular model. Reference Pages 54-55, regarding early reflections and their effect on the
quality of sound.
Loudspeakers, Brackets, and Power Amplifiers Used in This Design
Thirty-five arrays, each configured as two Full-Range modules (straight):
•
(70) ENTASYS Full-Range Modules (ENT-FR)
•
(35) Coupler Brackets (ENT-CB)
•
(35) Pan-Tilt Brackets (ENT-PT)
•
(35) ENTASYS Autoformers (ENT-750T)
•
(5) Two channel amplifiers rated at 600 W per channel into 8 ohms (to drive 70.7V/100V distribution lines)
•
(1) DSP unit with a high pass filter and eight output channels of signal delay
DESIGN APPLICATION EXAMPLES
LARGE PUBLIC SPACE
Community ENTASYS Application Guide - Page 48