Church acoustics matter. Nothing can improve the quality of your church sound system as much as determining the proper church speaker placement for your system.
Upgrading your speakers can make changes in the range of 1 to 5 decibels. But simply changing your speaker position can make differences in excess of 15dB in response! Who would buy a loudspeaker product with a +/-15dB swing in response? Regardless of what speaker system you currently use, a basic understanding of the room & loudspeaker interaction and the applied fundamentals can help you make a substantial improvement in your systems performance.
Church Speaker Placement
There are no magic formulas for ensuring great sound in every room. We can however, identify and gain an understanding of basic acoustical principles for church speaker placement. Some basic equipment, including a 20′ measuring tape, a test CD with a variety of test tones, an inexpensive analog sound pressure level meter and a calculator can reveal more information than you may want to know.
Like a speaker, every room has its own frequency response. To make things more complex about church speaker placement, the response varies with the listener’s location and the room’s dimensions, construction and furnishings. Room dimensions determine standing wave frequencies. In general, rooms with dimensions that are divisible by a common factor, like 10′ x 20′ x 30′, tend to compound standing waves at one frequency.
Room dimensions with non-equal or divisible dimensions are best. Vaulted ceilings, non-parallel walls and irregular surfaces help reduce slap echoes, but have little effect on low frequency standing waves. Room construction affects bass reinforcement, the noise floor and adjacent room noise. The average drywall wall resonates around 70Hz. Doors rattle, windows sing, air vents whoosh. Just grab your test CD or tone generator, play a sweep tone and listen. The difference in sound you will hear during the sweep is almost entirely due to room coloration.
Let’s begin by discussing how the length of a wave relates to its frequency. This understanding will allow you to take a methodical approach to understanding room response problems. Sound nominally travels at about 1130′ per second. The human ear can typically detect frequencies from 20 vibrations per second (Hertz)to roughly 20,000 vibrations per second. We can calculate the wavelength (“l”) of any frequency by simply dividing 1130 (“v” or velocity) by the frequency (“f”), using the formula l = v/f. For example, that trying to dampen a 100Hz bass wave that is 11’3″ long with a pillow 12″ x 12″ x 1.5″ stuck into a corner is futile.
We can also use the formula to determine the fundamental standing wave frequency for a given room dimension by dividing the round trip of that dimension by 1130 (v). That is, if our room is 20′ long, the round trip distance is 40′. Divide 1130 (v) by 40′(f) for a fundamental standing frequency of 28.3Hz (l). Let’s go one step further with our formula and newfound wavelength knowledge and see how we can apply it to understanding the problems of room acoustics.
Early reflections are signals that have bounced off the walls, ceiling and floors and arrive at our listening position later in time, mixing with the direct signal. They are called early or “first” reflections because listening tests have shown that when multiple reflections are received within 20 milliseconds of the direct sound, they are perceived as part of the original. This alters the tonal balance and confuses vocals and dialog.
