KF900 Series And PPST:
The requirements of large scale sound reinforcement present the sound system designer with a conundrum of the first order. On one hand, covering the entire audience area with the necessary sound pressure levels (SPL’s) requires many drivers and/or multiway loudspeaker systems. On the other hand, creating a coherent wavefront providing intelligibility and musicality dictates that the number of transducers be kept as low as possible.
Experiments in the 1970’s, such as the Grateful Dead’s “Wall of Sound,” yielded poor results but pointed the way toward the array-optimized loudspeakers that held sway from the 1980’s to the present. Yet even the best integrated arrays project only a few hundred feet and are plagued by high frequency attenuation and dubious intelligibility.
Link for PDF: PPST PHASED POINT SOURCE TECHNOLOGY