Internet Sound Institute - Sound Systems: Multipurpose Room

Sound Systems: Multipurpose Room

Many schools have multipurpose spaces which must serve many different school departments. The athletic department needs the space for volleyball, basketball or wrestling. The music department uses the room for choir or band concerts. The drama department performs dramas and musicals in the same area. Spring graduation ceremonies cap off the school year. All these events demand extremely different sound requirements. Engineered sound systems for these multiple-use rooms are usually described as either a distributed or a central cluster system.

Distributed System

In a distributed system, the loudspeakers are usually mounted in the ceiling in a pattern with enough density to provide coverage to all listeners (as in Figure 1).

Figure 1
Example of loudspeaker placement for a distributed system.

Pro's: If designed correctly, this type of system can provide good coverage with good sound. Sports announcing works well with this type of system.

Con's: The distributed system does not easily provide good localization. That is, it's very difficult to localize where the talker or singer is without seeing them. For example, localization is very important for a music production or drama. It isn't very natural to see a drama in front of you and perhaps hear the sound from above or behind you. Also, a distributed system can be quite expensive if high quality components are used.

Central Cluster System

The other main type of sound system is the central cluster. Here, a combination of loudspeaker components are placed together in an array which provides sound to all the areas needing coverage. The cluster is usually placed overhead near the ceiling.

Pro's: This type of system can provide very high quality sound with good localization. It can also be cost-effective compared to a distributed system.

Con's: Due to the nature of localization, a decision must be made as to where the "front" will be located. This is especially important to consider if the space is a gymnasium with no permanent stage. Once the loudspeakers are installed, the stage cannot be moved to the other side of the gym!

Proper Design

Let's explore other important aspects of the central cluster loudspeaker system.

Localization: Localization means the amplified sound will appear to come from the talker. It is generally accepted that our ears/brains can locate position side to side better than vertically. Therefore, when the amplified sound comes from overhead and in front, we can more easily accept that the sound is coming from the talker. This provides a more natural listening

environment.

Good Coverage: A properly designed system can provide a room with very even coverage. This means the sound level (volume) will be very even from the first row to the back row and from side to side. In other words, no dead spots! Because the loudspeaker(s) is mounted high overhead, the difference in distance the sound travels to get to the back row and the front row is diminished (see Figures 2a and 2b).

Figure 2a

Figure 2b
The volume change from the front to the back row is much less in "b" than in "a."

With proper loudspeaker selection and positioning, it is possible to compensate for the differences in distance. The key to success is proper design.

Low Interference: The other major benefit of a well-designed central cluster is its ability to provide sound with the least amount of interference. What this means is that a listener in the audience should only hear sound from one loudspeaker. If sound is heard from two loudspeakers and the loudspeakers are at different distances from the listener, the combined sound may be difficult to understand (as shown in Figures 3a and 3b). In fact, if the two loudspeakers are far enough apart, the listener may even hear two distinct sounds.

Figure 3a
Each listener hears sound from one source.

Figure 3b
The listeners in the middle hear sound from both sides of the room.
The sound may be difficult to understand.

We Can Help

A properly designed central cluster can provide a great sound system. However, notice our emphasis on a properly designed system. That's the most crucial point. A sound system must be designed for every different room. What works for your school may not at all meet the needs of the next school. Even a central cluster may or may not meet the needs of your school.

Don't forget that room acoustics play an important role in how well the sound system works. The acoustics must be taken into account in the sound design.

If you are unsatisfied with your present system or it's not meeting your needs, please give us a call. We have the experience, understanding and technology to provide you with a sound system that will meet your school's needs with clear, natural sound.

by Ron Huisinga © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

< Back