The is not a user guide for a specific speaker; it is a treatise on acoustic physics applied through the lens of one of the world’s greatest loudspeaker manufacturers.
JBL has historically been a leader in horn design and pattern control. The manual dedicates significant space to the concept of Directivity Index (DI) and the $Q$ of a loudspeaker. jbl sound system design reference manual
You might ask: With software like JBL’s own Venue Synthesis (V5) or L-Acoustics Soundvision, is a 1980s manual still relevant? The is not a user guide for a
Choosing between traditional clusters for high-impact localized sound or line arrays for consistent SPL over long distances. jbl sound system design reference manual
The mechanics of high-frequency reproduction and the importance of phase plugs.