Community ENTASYS Application Manual page 30

SYSTEM DESIGN GUIDELINES
High Ceiling, Shallow Room - Long RT
Sometimes rooms are encountered that are very wide in relation to their depth. These shallow rooms can present a challenge
in adequately covering the audience area without employing numerous loudspeakers. The room shown in Figure 28 is typical
of a multipurpose room found in schools, houses of worship, or municipal meeting rooms. It is 50L x 80W x 20H ft (15.2 x
24.4 x 6.1 m) with an elevated stage area 4 ft (1.2 m) high that measures 18W x 40W x 16H ft (5.5 x 12.2 x 4.9 m).
Here we have employed two arrays, each comprising two Full-Range ENTASYS systems. They are located 11 ft (3.4 m) above
the floor, angled downward 4 degrees and aimed inward 5 degrees. Again, this positioning can be accomplished even with a
greatly reduced ceiling height, should conditions dictate. A room such as this could have a reverberation time in the 2.5 - 3.0
second region. If additional low frequency directivity control is needed, a Low Frequency module may be added to the arrays
shown here.
The uniformity of SPL in the audience area is very good, ranging from about 108 dB in the very front near the loudspeakers to
around 102 dB at the back. The average SPL over most of the audience area is approximately 104 dB. It is only significantly
louder in the front area right next to the loudspeakers.
The wide horizontal radiation does a very good job of providing coverage to the entire audience area. Here again we see some
energy reflecting off the side walls. The loudspeakers are far enough away to not require acoustical treatment, though any
coloration caused by those reflections can be reduced by placing some diffusive material or some midrange and high frequency
absorption behind and to the sides of the loudspeakers. (Again, the later arriving lateral reflections from the side walls may be
beneficial in increasing intelligibility.) Reference Page 54, regarding early reflections and their effect on the quality of sound.
The sound directed toward the stage area is significantly less than that being radiated forward, and should result in good gain
before feedback. Overhead microphones suspended above the performers, which often do not work well, may perform
adequately in this situation. The main lobe of energy radiated from the rear of the arrays is just below where these
microphones would be positioned, making them likely to deliver acceptable gain before feedback.
Figure 28: SPL Map of Shallow Room with High Ceiling
Community ENTASYS Application Guide - Page 30