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Is Speaker Placement Important?

Blake Engel, All Church Sound

Yes! Speaker placement is very important.

First, let's look at natural sounds we hear each day. Say you're taking a walk in the morning and are about to cross an intersection when you hear a loud noise. You look to your left and see a car coming--apparently it doesn't have a muffler. The car stops, and then proceedes to cross the intersection. As it passes in front of you, the noise is right in front of you for an instant, and then it's off to your right.

Now, why did you look to the left when you heard the noise? Well, it's because the sound got to your left ear a little sooner than it got to your right ear--your brain processed this information, and told your head to turn to the left. When the car was in front of you the noise got to both ears at the same time, and so you looked straight forward. As the car passed and went off to your right, the sound reached your right ear first which told your brain that the car was on your right.

OK, yeah, you could have just LOOKED to your left and seen the car--and followed it with your eyes as it passed. But your eyes and ears work together. Your ears tell you there is sound, and you'r eyes help you identify what's making the sound.


Is this important to our understanding of speaker placement? It sure is! Look at figure 1. It shows a typical speaker setup where there are two speakers--one on each side of the room (shown as black squares). We call this a "Left-Right" speaker system.

A listener at point "A" will be looking to the right at the person speaking (the oval on the platform), and yet the sound will be coming from directly in front of them or even a little off to their left. This causes the brain to work overtime trying to match up the two events--the ears say the source of the sound is a little off to the left, while the eyes say the source is to the right. This is one cause of listeners fatigue which results in a short attention span.

The listener at point "B" is looking just just about straight ahead, and is hearing sound from both speakers. The sound waves of the two speakers interact with eachother and they will either add up to twice the sound level, or they'll cancel each other out! This doesn't happen at all frequencies (pitches) of sound, but at specific ones based on the distances of the listener to the speakers and their position relative to the two. If the person moves just a few inches to the right or left, the sound will change.

The other choice is to use a point-source speaker system. This can be in the form of a single speaker, a single speaker with fill speakers for the front sides, or a large array of speakers to cover a very large or wide room. The main difference between a Left-Right system and a point-source system is that in a point-source system the sound comes from only one location, not two like the left-right system.

Take a look at figure 2. As you can see, the sound waves come only from one place, so there's no sound wave interaction of the direct sound. (Now, there will always be some sound wave interaction between the direct sound and the reflected sound waves--this can't be totally eliminated. Besides, the goal is to cover the congregation with DIRECT sound--not reflected sound.)

What about the height of the speaker? Does that matter too? Glad you asked! Figure 3 shows the situation when a speaker is mounted low to the ground. The first few rows get a blast of volume, absorb a lot of the sound, and leave very little for those in back. Another volume problem deals with the inverse-square law. This law states that if you double the distance from a sound source, the volume will be half. Thus, if the front row of people in figure three are 10 feet from the speaker, the people at the back (who are 40 feet away) hear one-fourth the volume. (half the volume at 20 feet, double the distance again to 40 feet, and it's half the volume again.) (Keep in mind this doesn't take into account the reflections heard in the room--there are times when the reflected sound can be louder than the direct sound).
Figure 4 shows the solution--mounted high, the front row is now 20 feet from the speaker, and the back row is about 45 feet away. There's only half the volume at the rear--this is acceptable. Speaker placement is VERY important--we've only talked about the very basics. We havn't even touched on speaker angles or placement in the sweetspot. Call us for more information!