Loudspeakers: Coverage Pattern

Every loudspeaker system has a directional pattern. That pattern is often different at various frequencies or tones. Generally, the better loudspeaker systems will produce more consistent patterns at the different frequencies. Understanding and knowing the directional patterns of your loudspeaker system is very important. It will give you the knowledge to position the loudspeaker system for the most optimum sound to your listeners.

The specification sheet will provide details on the coverage patterns for your loudspeaker system. Don't throw those away! Typical loudspeakers may have 90° by 40° or 60° by 40° coverage. For example, a loudspeaker with a 90° by 40° pattern would produce the most volume in a horizontal pattern that would be 45° on each side of the on-axis line of the loudspeaker. The vertical pattern would be 40° or plus and minus 20° above and below the on-axis line (see Figure 1).

Figure 1

Fortunately, in real life, you don't need to have a sextant or angle meter to accurately set the position of the loudspeaker system. Your ears are a very good test instrument. With a little training, they will tell you where to aim the loudspeakers to achieve the best coverage from your loudspeaker system.

After the loudspeaker systems are set-up, feed a noise source to the loudspeakers. This could be pink noise from a test generator or test CD. You could also use the noise from a FM radio that is tuned between stations. Listen to one loudspeaker system at a time. Cup your ears toward the loudspeaker system and listen for just the high frequencies. Now walk around the room while facing the loudspeaker system. You should be able to clearly hear the areas the loudspeaker system is covering with high frequencies. The high frequencies are the most important frequencies for clarity and intelligibility. If the listener does not hear the high frequencies, they will not understand the words. Position the loudspeaker system for even coverage of the seating area and try to minimize the sound hitting the side walls. Also minimize the overlapping areas between loudspeaker systems. The best intelligibility will occur when the listener hears the high frequencies from only one loudspeaker system.

Poor placement will have the audience complaining about the poor sound quality of your system. However, careful and knowledgeable placement of your loudspeaker systems will produce a very appreciative audience.

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

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