Crossovers

Crossovers separate frequencies and sends their signals to the proper speakers. In other words, bass frequencies are sent to the subwoofers, midrange and high frequencies to the other speakers, etc. Full range speakers produce all frequencies and don’t need crossovers. Few people need subwoofers, delays or crossovers in small buildings and small PA Systems.

Delays

Delays are not the same as delay pedals for guitars. This delay, is a rack-mounted unit that performs a basic control function for speakers. It allows a secondary set of speakers, (or more) to be physically separated from the primaries by a good distance, and to speak at a set number of milliseconds later, than the primaries.

To Illustrate:
At the NTCC National Campground Tabernacle in Missouri, we have such a setup. You will see a pair of speakers hanging over the pulpit facing the congregation, and another pair of speakers half-way to the back, facing the same direction. If the speakers “spoke” at the same time, a person sitting in the back would perceive the sound coming from above his head.  By slightly delaying the speaking of the second speakers, the people perceive the sound to be coming from the platform, instead of from directly over their heads. The delay unit is the reason for this. With outdoor PA Systems, you hear an echo effect, and you can understand the sound, because the delay unit causes all the speakers to speak at different times. Ever heard someone far away hammering, but their hammer movement wasn’t synchronized with the sound of the hammer? Sound waves are physical things moving through the air, and it takes time for them to travel at, well, the ‘speed of sound’. Without a delay unit in a large auditorium sound system, that’s what your audience would experience; unsynchronized sound.

by Mike Kekel