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QUICK GUIDECommission an Installed Sound Environment
Appendix B
THE PROBLEM
If you can not cover the whole audience area with one speaker system, you can setup additional
speakers further into the hall to cover the audience areas that are set away from the stage.
However, the audience sitting close to these additional speakers will SEE the performance in front
of them but HEAR the performance coming from the direction of the additional speaker nearest to
them.
The result is that the sound experience for these people is not ideal – it is much more desirable to
perceive the sound coming from the direction of the band.
THE SOLUTION
We can bring the perceived direction of sound back to the front PA while still maintaining enough
level to cover the areas that are set away from the stage.
The trick is to add a delay to the additional speakers (thus called “delay speakers”) so that the sound
from the front PA arrives at the audience closest to a delay speaker about 15 ms BEFORE the sound
from the delay speaker arrives.
As the first sound arriving is then from the front PA, the perceived direction of the main sound is
therefore also from the front PA, while the sound from the delay speaker is perceived as a single
reflection of the sound from the front PA, and is not perceived as a secondary auditory event. Thus
the sound from the delay speaker has no effect on the perceived direction of the sound, resulting in
a rich sound experience.
Further, it is now possible to increase the sound pressure of the delay speaker up to 10 dB higher
than the front PA without affecting the perception of sound direction.
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