This simple question cannot be answered quite so simply. In order to better understand why loudspeakers sound different, we need a bit more information. There are different parts to the puzzle.

Different Listening Environments

If you have ever traveled with a music ministry team, you know that your sound system will sound different in almost every auditorium, sanctuary, fellowship hall and gymnasium that you encounter. Put the same sound system outdoors and a completely different sound occurs. What usually has the most impact on sound character is the acoustical nature of the room.

Let's suppose I am a member of my church's sound committee and we are searching for an updated sound system. During the investigative process, I attend a performance at the local high school auditorium and am impressed by the fact that one single loudspeaker can seemingly fill the room with natural sound at a good listening level. I then report at the next committee meeting that I have discovered the loudspeaker that will work "wonders" in our sanctuary. You know the rest-we buy the same loudspeaker and install it in our sanctuary only to find that we cannot understand a single word that is spoken.

What went wrong?

We did not take into account how that particular loudspeaker interacts with our particular room. That one loudspeaker may have "filled" the room because it spreads out sound energy to a very large area. This would be acceptable if the room acoustics tend to be very dry, meaning low reverberation. However, putting that same loudspeaker in our worship space, which has a very large room volume, hard reflective walls, floor and ceiling, resulted in disaster. For our worship space, a loudspeaker that is more directional (controlling more of the sound energy to one defined area) would be required to keep sound from reflecting off the hard surfaces of the room. We need to keep more of the sound energy directed at the listening audience rather than at the ceiling.

Same Loudspeaker in Different Locations in the Same Room

You may have experienced this at home after moving your stereo system loudspeakers to different locations in the same room. Perhaps you noticed a change in the low-frequency or bass response. To get the same tonal balance, you had to adjust the bass tone control up or down. This is due to an acoustical principle where room boundaries are involved. For example, when a loudspeaker is hung in mid-air, away from the ceiling, floor, and walls, it will have the least amount of bass response. This location is called free-space loading of the loudspeaker. Now move that same loudspeaker to the floor (one room boundary) and you will notice a 3 dB increase in bass response, which is a noticeable increase. This is called half-space loading. Now move that same loudspeaker to the middle of one wall and keep it on the floor. The loudspeaker is now at a point where two room boundaries meet (the wall and floor). You will hear another 3 dB in bass response, or 6 dB more bass response than the free-space location. This is due to the quarter-space loading. You can probably guess what happens when you move the loudspeaker to the corner where three room boundaries meet (floor and two walls OR ceiling and two walls). You will experience another 3 dB increase in bass response due to the eighth-space loading of the loudspeaker. The bass response at this location is now 9 dB louder than when the loudspeaker was hanging in free air.

One other factor that will influence different sound quality is the sound system operator. For instance, if you have the same person mix and adjust the sound system for every event in your facility, chances are you will have very consistent sound from week to week and service to service. Having the same sound system operator, however, is very impractical for many churches. If you have more than one sound system operator, the sound system may sound different each time you have a service or event. Making certain that all of your operators are equally trained is one way to avoid this. An additional approach would be to assign one individual as a "producer" to provide constructive direction to the sound crew. This particular person does not have to be technically oriented. However, one needs to have good hearing and have a humble, servant-minded interest in how things sound.

The Big Picture

Keep in mind that there is more to selecting a loudspeaker than reading a brochure, listening to loudspeakers at a retail store, or choosing a product on price alone. Loudspeakers sound different for a variety of reasons. Make certain you find a contractor who knows all the pieces to the puzzle so you get the whole picture and nothing but the picture.

Roger Fortner