July 2009 Ask the Pro:Speakers
Two of the most commonly asked questions by churches regarding sanctuary speakers are regarding placement of the speakers and selection considerations.
Should we have a center-mounted speaker cluster for our room or a side-mounted speaker system?
In a very large church with a very high ceiling, there are two advantages to a ceiling-mounted speaker system. A properly designed system will give a more even sound distribution throughout the room, and the ratio of distance from the front seats and back seats to the speakers is fairly small. This means that the volume is quite constant throughout the room. In a church with a ceiling height over 30 feet and a seating capacity over 800, this should be considered. In a smaller church, however, these advantages are lost.
As far as disadvantages go, the ceiling-mounted speakers reduce your gain before feedback by about 3db, which means that you can get twice the volume from side-mounted speakers before feedback. With the pulpit located under the ceiling speakers, the feedback can be even worse. Furthermore, no matter where you sit in the room, you will always hear the sound from way above your head with a ceiling mount, but the people speaking and singing are directly in front of you, which can be distracting. With side-mounted speakers (about 8 feet above the floor) in most of the room, the apparent sound is directly in front of you at the proper height.
You can have a stereo sound system with side-mounted speakers. This is an advantage if you sing with soundtracks. You can't have stereo sound with ceiling-mounted speakers. Also, installation and future service costs are reduced with side-mounted speakers because no special lifts are required to mount them.
This is not to say that a central cluster is always a bad idea, but it is an old idea that is giving way to the side mount. Most modern theaters have side-mounted speakers now instead of central clusters.
What do I need to know about selecting main speakers?
There are two different categories of speakers: home stereo and live sound reinforcement. The speakers you find in stereo and electronics shops are for home stereo use only. They are "Near Field" speakers for use in a small room and are designed for the dynamics of recorded music. These speakers are not capable of projecting the sound effectively and evenly in a church. They are made for small living rooms. They are also not capable of handling the dynamic range of live sound. They will distort or burn out under live sound conditions. It makes no difference how much you pay for these speakers. A $2,000 set of stereo speakers will sound great in your home with recorded music, but they just don't do the job in live sound.
Live sound reinforcement speakers, on the other hand, are designed for just that. They are a poor choice for home use, but a good one will work well in church applications. There are still several factors to be considered, however.
As with microphones, some manufacturers make some great speakers, while others don't. Most music stores cater to low-budget musicians who are more interested in a loud speaker at a low cost, than an accurate speaker at a reasonable cost. These are usually the "road" speakers in black boxes with handles. Of course, there are some good sounding "road" speakers, but you need to be very careful what you select to make sure they reproduce sound accurately or project it evenly throughout your room.
When making a speaker selection, consider the program material (what it is going to reproduce). Will it be used just for speech, string and wind instruments, recorded music and vocals? Will it need to reproduce organ foot pedals or bass guitar? Selection is also based on your room size, shape, and acoustical characteristics. The speakers need to reproduce the program material accurately and distribute it evenly throughout the room.
A complete set of specifications on a speaker can tell a lot, especially if you understand the electronics and physics involved. Frequency response is a useful specification, as long as it is accompanied with the roll-off points in terms of +/- decibels. You also need polar patterns to relate the frequency response to dispersion angles. Power handling is meaningless without knowing the efficiency of a speaker. A 100-watt speaker can be louder than another operating at 500 watts depending on its efficiency. Although this is all very useful information, there can be a lot more learned by a careful spectrum analysis and A-B listening comparison.
Although these are probably the most important factors, there are few speaker system manufacturers who effectively address accurate frequency response with constant directivity. Because many speakers are made for "road" use where low cost, loudness, and lots of bass seem to be the selling features, these concepts are secondary.
When comparing speaker systems, you will find that although many sound good at first, when compared with an accurate speaker, they are, in fact, missing certain frequency bands. In most cases, a poor speaker will give you lots of bass, and possibly highs, but they are missing the mid frequencies. You will actually hear instruments on a good speaker, which you won't on a poor one.
Once you have accurate frequency response, however, you also need to maintain it throughout the coverage angles required (constant directivity). This really separates the truly professional speakers from the others. Many speakers that sound accurate when you sit directly in front of them lose their high frequency response as you move off axis. This means that only a very small portion of the congregation receives good sound.
This article is courtesy of Alectro Systems, www.alectrosystems.com.