Obviously, the technique described above does not apply to L&R line-arrays that provide a wide coverage pattern, because there’s no way to isolate one part of the horizontal coverage from another. While I have nothing against line arrays, perhaps it’s time to look again at the highly successful horizontal arrayable loudspeakers that were pioneered in the 80’s by companies such as Apogee, Meyer and quite a few others. Line arrays do a great job when long projection distances are needed, such as in a deeper-than-wide room configuration, but they are not intrinsically the right choice for every application. Like a good mechanic who has tools that serve many needs, a good sound system designer will have multiple approaches to system configurations that best serve the desired end results.
The short answer is most of the time. Whenever the room geometry is approximately square, then it’s a fifty-fifty toss-up. But keep in mind that the side walls must not be overly reflective acoustically. Some houses of worship have huge floor-to-ceiling stained glass on their walls’ sides. Others, especially older cathedrals, are built of highly reflective masonry. Even hotel ballroom air-walls tend to be very reflective, unless covered with draping.
When the room geometry is wider than it is deep, especially very wide like a fan-shaped performing arts center or a worship facility, that’s when mono is an absolute must. In such case, the addition of a central loudspeaker cluster can do wonders to even out the sound throughout the room. Even more so, it is often possible to cover the entire room from just a very wide central loudspeaker cluster, which has the great benefit of eliminating time smear among left, center, and right loudspeaker arrays. I designed many successful sound systems that were based on the “single-source” principal; i.e., all primary sonic energy emanates from a single central cluster. Small, ancillary delayed loudspeakers might also be used to augment the primary speaker system for coverage in the side balconies or rear balconies, but the majority of the sonic energy will come from the main central loudspeaker cluster. In highly reverberant environments, such a