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3.0 Designing an EVF/EVH Cluster (cont’)
3.3More on Coverage Patterns, Multiple Coverage Patterns, the Need for Clusters of Loud- speakers and How Far a Single Cluster Can “Reach” into a Venue
The coverage patterns or angles mentioned previously are defined where loudspeaker output is 6 dB down from maximum, usually
3.31 Basic Clustering Guidelines
The aiming angles of systems in a cluster are related not only to room geometry but also to the particular coverage patterns selected. A rough design can be based on the plan and elevation views of a room, rep- resenting the loudspeakers by the angles of their horizontal and vertical coverage patterns, e.g., 60° x 40°. A wide or “short throw” coverage pattern, such as 120° x 60°, is good for aiming down into the front rows of a rectangular venue to reach all of the seats left to right. Narrower patterns, such as 60° x 40° and 40° x 30°, are appropriate as “long throw” devices that send sound to the rear of the audience without also “blasting out” the front rows.
Sophisticated software is also available, which allows the designer to build a room model and place and aim loudspeakers within it, assessing the uniformity of coverage. An example is EASE 4.2 (Enhanced Acoustic Simulator for Engineers), developed by Acoustic Design Ahnert
A common practice is to widen the horizontal coverage of a single loudspeaker by placing two systems side by side and aiming them in such a way that their horizontal patterns do not overlap. Individually, each system will be 6 dB down at the overlap point. Together at the overlap point, they will sum coherently to the
If these two systems are “underlapped,” with, say, their axes 75° apart, the overall coverage angle will be wider but the level near the array axis will drop. If the two systems are overlapped to any great degree, e.g., their axes only 45° apart, the overall coverage angle will be reduced and the interference discussed in section 3.5
The degree to which
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