A lot of people are unhappy with the PA speakers in our sanctuary (myself included) here at the Lanham IDD7. A few people have suggested putting speakers in the back of the sanctuary pointed forward, or around the edges. The idea is to re-create the “surround sound” effect in home-theater systems and cars. Of course we recognize that stereo sounds better than mono in our headphones, car stereos, and home theaters. So why doesn’t it work for covering a large seating area?
The answer is simple. “Stereo” is used in sound reproduction to re-create the natural acoustic effects and artifacts that you would experience in the ambiance of a live production. For example, you might have speakers on all four walls in your living room to recreate the ambiance of a large concert hall or theater. The rear speakers might have some delays and reverb effects to create a feeling of spaciousness. But when you install speakers to cover the large seating area of a sanctuary or concert venue, there are some other factors to consider:
1. Double-coverage. – If multiple speakers cover the same seating area, there will be distortion due to phase cancellation, since the sound arrives at slightly different times.
2. Apparent sound source. – You should hear a sound coming from where your eyes see the source.
3. Uneven coverage. – The sound source should evenly cover the seating area with good clarity.
4. Echo/Delay. – The listener hears a delay between the original source, PA speakers, wall reflections, etc. All of these aberrations may reduce intelligibility and will definitely contribute to listener fatigue.
5. Poor Low-Frequency Characteristics. – Low frequencies are often overlooked, but are an important consideration in contemporary music, and a lot depends on the acoustics of the room. In small rooms, resonant modes will create problems. If a drum set is used in a reverberant room, there might be a buildup of low frequencies. At my home church, music often gets overwhelmed by the voices, and the cymbals are much louder than the kick drum.
So how do we improve the acoustics? In my case, we want better coverage, a feeling of “presence” to experience the music. But, we have only two 12 inch JBL speaker boxes with a VERY narrow coverage pattern in a 60 foot wide, 250 seat room. This doesn’t work; there’s just not enough coverage. And with the narrow ceiling and carpeted floor, we have a real lack of sound reinforcement. Spillover from the stage monitors makes for too much mid-frequency muck. Our low reverb time is desirable for contemporary music and speech intelligibility, but requires better sound reinforcement than what we have.