Martin Audio WLXGS User Manual page 17

Coverage angle for tightly packed flat fronted arrays
-6dB Coverage
Here is a simplified formula for calculating the main coverage angle of a tightly packed flat fronted array.
* = approximate speed of sound in m/s. Varies with temperature (see Section 2a).
Arcsin means "the angle whose sin is ..."
Flat fronted cluster coverage patterns will be confined to one main lobe whose mid-bass crossover directivity
is proportional to the size of the cluster.
All material © 2007. Martin Audio Ltd. Subject to change without notice.