The following tests will help you understand the performance of the sound system and the interaction relative to the acoustics of your church or hall. These tests are only meant to show potential weakness which should be followed up with a detailed test to find solutions. At the end of this article, each test is explained. (You may want to print these files direct to your printer. It's about 5 pages long.)
Name of Church ____________________________Age of Existing sound System ______ yrs.
Age of the Existing Church ________yrs.* These tests should be done with a computer
* Computer Systems accepted are TEF - MLSSA - Bruel & Kajr - ArielEach test is a window into the world of church sound. To the non church community, the acceptance of poor sound is common. For the church community, poor sound week after week is insulting, degrading and costly. Today, there are many churches that have better sound than any local establishment within a 20 mile radius. These are not expensive systems, just well designed systems. Each test will let you know the strengths and weakness of a church sound system and its acoustics.
Articulation score of Sound SystemThe sound system or Sound Reinforcement System" is just that. It is a transparent mechanical device to boost the volume of the presenter. If the room already has a good score, the sound system can add a percentage or two in the first 8 rows(or first 1/3rd of the seating area) and give the same score to 95% of the rest of the seating area. The last 5% will have scores within 2 or 3 percent. These areas usually seats that have nearby walls that have reflective surfaces that cause a natural amount of interference. If in these areas the level dopes further, either a satellite speaker or wall changes are needed. Generally, treating the wall costs less.
If the score in the first 8 rows are lower with the sound system on, then you have the wrong sound system design for your church. For testing purposes, the person speaking should be able to be 14" from a microphone for the test. If the person must be closer, then you have either the wrong system design or there is an acoustical problem like a RT60 over 2.5 seconds, standing waves or your speaker system is using an omni directional speaker.Dead spots of 8dB or moreIt is rare for a church sanctuary to have a dead spot(1). Almost all dead spots are created by a sound system. Dead spots come in two types, poor coverage or phase drop outs. Both of these problems go together. A properly designed system avoids these problems. If a proper system is in place and there are problems, then the system is just amplify the physical problems the room has. Sound systems can not and never will be able to mask acoustical problems.
At this point you can either fix the room and get on with better sound or do as many have done. They will degrade the sound system with a series of compromises that starts the endless cycle of seeking the elusive Phoenix. - A new bird that rises out of the ashes of it's parents fiery death. It is a bird that does not, did not, nor can exist with the current laws of physic. It was a creature that was created in someone's imagination for inspiration, not compromise. These are the sound system that have desperation soldered on every connector, wire and speaker bracket. FIX THE ROOM!!!
All multiple source speaker systems(2) create dead spots caused by phase. It is due to overlapping coverage of the speakers. When two speakers, spread further than 20 feet and have a mono(3) sound source, the overlapping sounds will be louder is some places because the sounds are summed together when in phase. This boost can be up to 6dB. When the two sounds are out of phase, the sound drops up to 6dB. When wall reflections are included in the picture, it is common to take an SPL(4) meter and find many hot and dead spots in a single row of seating. This can be seen best with "Pink Noise" being played through the system at speech levels. If the church passes all of the acoustical tests and you have seen in a row of seating the sound level change more than 6dB, then the sound system design needs to be changes.Phase cancellation with a test tone
If your church has a good point source type system and there is more that one speaker in the source point, then speaker alignment, timing and volume levels can adjusted to minimize audible phase problems. If you have a multiple source speaker system, then the phase problem has already shown it alarms. This test is really meant for fine tuning. Even a poorly set up point source system, phase is a matter of adjustment, not open heart surgery.SPL(Sound Pressure Level) from front to back Use SPL MeterThere is a formula for sanctuary design that works like this. H=1 x W=2 x L=3. This is not an absolute, but churches with these proportions have better sounding houses of worship, regardless of worship type. In a room with these proportion, they can count on a proper system to given them the desired goal of +/- 3dB coverage. If the room klength is less than 3 times the height, the coverage will be better. If the room is longer, satellite speakers on a delay will solve any problems.
When the physical shape of the church is disproportional, then coverage can be anything. However, when a multi-source system is used, coverage is already a problem. As many churches have, they install speakers on either side of the platform, about 10 to 12 feet high. That is about the reach of a 6 ft. step ladder. According to the Laws of Physics, sound pressure drops 6dB every time you double the distance. Typically, the measured distance to the first row of seating and the speaker will be "x". Usually the distance to the back row of seating will be "x" time 3.
In an example, let us use a church that is 20 feet high, 40 feet wide and 60 feet long. The speakers are mount 12 feet off the floor and 25 feet apart. The distance to the first row is 9 feet. The distance to the back row is 45 feet from the front of the speaker. Therefore, the distance doubles at 18 feet and again at 38 feet. If the sound level is 60dB at the front row, it will be down more that 12dB at the back. What will the sound man do? Turn up the sound for the back. People in the front get blasted, people in the back can't hear. Sound familiar?Realism (Close eyes, point to sound)
The ideal listening situation is to have the source and amplified sounds coming from the same place. Any other situation is a compromise. Remember, our ear are on the side of our heads. This automatically forces your to look at what you hear. It is also the most relaxed form of listening. If human were designed with ears at the top of our heads, then speakers placed where ever it was convenient would work quite well.Listening Fatigue factor (Subjective value)
Listeners Fatigue is an unwritten scale of how much extra work the brain does in matching the sound to the source. In a left/Right speaker system or a system with rows of speakers around you, the sound you hear will come from many places. In this seat the sound is to the left. In that seat the sound is behind you. The further the sound is from it's source, the harder the brain works in matching the two event. The harder the brain works, the shorter the attention span and the more likely a tired person will nap or relax their eyes into a pre sleeping position.
Listeners fatigue is almost impossible to measure because if a sound system has a high score, it will automatically have all of the previous problems mentioned earlier. Think about it. A person spends a lot of the time filling in the blank because of poor intelligibility, straining to hear because the sound is either too loud or not loud enough. Then you disassociate the sound from the person speaking. What part of "sleeping in the pews" don't you understand? Sound systems that are poorly designed will have a problem with listeners fatigue. This is not an option. It is the results. If your noticing people falling asleep every week at church and the acoustic are good but the sound system has you pointing to the speakers on the right or left side of the church, then you know it not the message. It the messenger! Fix the sound system!Intelligibility rating (Subjective value by church members)
This is for those who don't have a computer or don't have the cooperation of the church people to do a proper speech test. Just listen and be honest with yourself. Do you understand everything being heard and is it loud enough. If you have been reading the previous explanations, you will know what to look for.Maximum working distance before feedback
This is the distance in which a person can speak from a microphone and amplify their voice to the whole room. The test is simple. Have a mic set up at the pulpit. Bring the system up to the verge of ringing. When the ringing starts, turn the level back until the sound system seems stable. Count or say something into the mic to confirm that the system will not go into feedback or "oscillation". Next, turn the sound system off and go to the pulpit. (having other people helping would be better.) Now, practice speaking at a level that you know is loud enough for people in the front 2 rows to hear well without the sound system on. If you have an SPL meter, the level is about 65 to 70dB at 3 feet or 60dB at 12 feet, which is the typical distance to the first row of seats from most pulpits.
Now is when the test begins. With a couple of friends in the pews, turn the sound system on. Speak towards the mic at the same level as you practiced. Start at about 6 inches from the mic and start reading something you are not familiar with from the bible. Perhaps the Genealogies from Genesis. As you are speaking, start moving back from the mic every 10 to 15 words. As you voice disappears from the sound system have each person raise their hands when they can no longer hear you. Please notice that this includes hearing you even though they don't hearing an amplified sound. If your sound system is set up right, there is a level of amplification that is so transparent, that you will not hear an amplified type of sound. The only way to tell is to turn the system off. When all of the people can hear you, measure the distance between you and the mic. Now, take a step back. Do the same test in reverse. Start speaking, Move to the mic. As each person hears you, have they lower their hands. When everyone can hear you, mark the spot and measure the distance.
The two distances will be different. The difference can be 2 to 6 inches. Split the difference and that gives you your maximum working distance. To keep everything in perspective during the test, turn on any ceiling fans, lights and heating/cooling system to create the typical worship service conditions. It is not unusual for a church with good acoustics, an NC below 35 and a properly matched sound system to have a working distance between 16 to 36 inches. This means that the minister to take a step back or to either side of there speaking position without the sound level dropping so much that people can't hear. It also means that for those few time the minister forgets to keep the mic between him and the people, his voice won't totally disappear.
From the experience file, there have been a few churches in which high quality, good sound levels were achieved up to 64" away. This is possible but not common. It is common for 48 inches of working distance with reasonable conditions. When a church is full of people, this level will drop depending on what part of the service your targeting for. For these purposes, the target is for sermon preaching which is the most common request.System design life
If you have been scoring between 8 to 10 on all of the previous questions, isn't the answer obvious?
It never cease to amaze me how often churches replace their sound systems. The average is 3 or 4 times before they acquire something that is their final system. Typically, churches make no investment in sound during construction. As a result, the first sound system is a temporary system. The second system is from a member of the church who uses whatever experience they acquired from local experts. The third system is often from a music store or a contractor who designs systems for all kinds of venues and church sound is hit and miss. The forth and hopefully the last sound system design change comes from a person who is an expert in church sound and compromise is not in the vocabulary.
The timing for all of this can vary from 6 month to 30 years. In one church, I installed their final system design 3 months after the church first opened. It was their 4th system. The first 3 system combined cost more the system they settled on. There is only one other event that can short circuit a good church sound system.
All too often, a new church member who has broadcast or live music experience in the audio field will come along and claim that the already perfect sound system is flawed. As a real trouper, they pull every string they can to replace the system. The result is always a failure unless all that they are doing is upgrading the equipment while keeping to the original design and speaker locations. What most people don't understand is that church sound is a very unique discipline. It is a specialized as most doctors are. A person can be a Dentist, an Optometrist, a Surgeon or a GP. Each of these people carry the tittle "Dr.", but, would you go to an Optometrist for hip replacement surgery?
Yet, every day, people with good intentions try to help churches without first hand knowledge of what they are doing. The results are costing the church community over a billion dollars a year in North America. Church sound really does not cost much, but if it is done cheaply, the cost is much more than people realize. This also is true for churches that meet in converted warehouses, factories or commercial places.Music qualityA subjective quality? Not really. The goal of a good sound system it to be transparent. Regardless of the denomination of a church, there is only one honest test that I trust. When the sound system is set up, have a person play a guitar and violin. Record their playing as you would reinforce they sound during a service or performance event. Have the person play a passage that they can repeat over and over again. Make several recordings if needed. Now, play back the recording while the person is playing the harmony part of what they played earlier. With a good system, the playback and the live sound should sound so close that a person walking in would ask the question, "where's the other people in the band?" This is when the sound system moves from being just a "PA" system to being an instrument that can join with the musician as an extension of themselves. Likewise, it is also the same when applied to the minister. A sound system that is this good, gives the minister a choice to use the sound system as a tool rather than a toy.
Most church sound systems that meet the standards outlined here are superior to the sound systems in most theaters and live show bands. Don't be fooled by high priced computerized mixers, processed speakers and state of the art wireless systems. If a speaker system is in the wrong location for the room, do you think that high priced sound equipment is able to push the laws of physics aside and work like magic?
I find it very interesting that people who own a system as described here, and go to see shows like Phantom of the Opera in New York, Toronto or London, come back a report a sense of disappointment. The notice that the sound system in their church is clearer and just as music. They are disappointed because they had read in the Newspapers that the sound at this show was the best ever on Broadway. People from some of the churches I have worked on went to see shows in Branson or Vegas and returned to confirm that their humble little church can do everything the secular community boast about and do it all better and more.
To have a sound system that sounds like broadcast FM radio or "studio sound" will never happen in a church. But the quality of the system should be no less than the best any acoustical instrument can do without amplification. When this is achieved, the sound system becomes an instrument. The soundman becomes part of the musical team. A person with talent a need a place for it to grow, a church sound system of this quality can make a big difference. A master violinist can make any instrument sound good. A budding student of the violin can excel with a "Masters instrument."System headroom
There are several ways to describe system headroom. For church sound systems headroom means how much amplification is there from the time you begin to hear a person speaking from 12 inch from mic at 60dB until the system goes into feedback. Others describe headroom as to how loud a system can be before distortion. As a playback system, if a church system is designed right, there will be plenty of headroom for any music you through at it.Echoes or added reverberation created by sound system ( May require Computer*)
When a sound system is design right, this should not be a problem if the church passes the NC and RT60 tests. However, many times when a church has a multi source sound system, the system often adds to the reverb time in the sanctuary. This is mostly noticed for churches that have great choir and organ rehearsals but Sunday things fall apart. If the sound system is on when the pulpit mic or other mics used to amplify the choir, the overall reverb time will increase. This longer time will through off the choir. If your in doubt, turn off every mic during choral or organ music presentation during Sunday services. Most people will notice a difference. In some churches that I have worked on, the congregation noticed a big improvement in the quality choir's singing, but still complained about the low level of the choir. Again, system design has a major impact on music as well as speech.
Copyright (c) 1996 JdB Sound, Acoustic Lab.
Last updated, January 29, 1996