These include:
—Loudspeaker type
—Loudspeaker placement
—The number of loudspeakers
Designers do their best work when they’re given control all three. If the client or architect fixes one or more of these variables, then the system designer has less to work with and sound reproduction will suffer.
Loudspeaker Location
The ideal place for a loudspeaker isn’t available. It’s the location where the sound source being reinforced is positioned.
Imagine a small theatrical group or classical music ensemble performing in a small space. No sound reinforcement is required, and the sound from each source is heard in the proper spatial relationship to the other sources.
As the room size is increased, the instruments may require amplification. Musical ensembles have used localized amplification for many years, and “personal” sound systems are still marketed for small venues today – the current incarnation of the “Wall of Sound” used by the Grateful Dead several decades ago.
The location of the acoustical source is the natural place for the sound to come from. This approach can be impractical for many applications, and it is not very versatile, so a compromise is called for. The first choice is to place the loudspeaker directly above the source being reinforced, taking advantage of the human listeners poor ability to localize sound in the vertical plane.
If a loudspeaker is placed to the left or right of a talker, it will be obvious to the observer that the sound is not coming from the talker. If it is placed above the talker, the human hearing system is deceived into thinking that it is coming from the talker. The eyes effectively pull the sonic image down to correlate with the vision. Overhead placement also allows sound to be projected to the back of the room without overpowering the front rows of the audience.
With these considerations, it makes perfect sense to place loudspeakers directly above the stage.
Size vs Efficiency
Loudspeakers must be large to have control over where the sound goes—period. A tiny loudspeaker radiates sound in all directions.