Are there places in your facility that don't sound as good or clear as others? Sometimes adding another loudspeaker may be the answer......sometimes. Unfortunately, in many cases this will make the problem worse. This can at times be hard to unravel if it has already happened. Because a decision has been made and money spent, there will be an incentive to justify things and maybe add some more loudspeakers to fix new spots that now sound muddy because of the additional uncorrelated energy in the room.
"What?", you say. Well, even if the new loudspeaker is timed and level matched with the rest of the system, more energy was added to the space by this addition. This energy will find its way to areas outside the intended target. This creates a sound field which is smeared in time. The net effect of which is lack of intelligibility for speech, and lack of impact for music, which is often what we were trying to correct in the first place. Sometimes, adding a high pass filter to the additional loudspeaker is all that is needed. Sometimes not.
In the end it is best to design a room that can be covered with the least amount of loudspeakers. Most often, however, we must work with the rooms we are given. Ideally the space should be optimized before sound system changes are made. This avoids duplicated effort when it is later decided to get to the root of the problem, which is always the room. All the dsp and steerable arrays in the world can't fix poor acoustics. Sometimes they are the only answer when other constraints cannot be mitigated, but they should never be the first choice.