A Review of Acoustics and Audio System of a Church

Central Baptist Church in Brantford Ontario

Originally printed in Professional Sound Magazine, September 1992 - - (this is a long document)

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The Beginning

The selected Church for this first review will be of a sound system and acoustical treatment installed several years ago. It is at Central Baptist Church in Brantford, Ontario, Canada. The church was built in 1972. It seats about 700 People.

The room dimensions are 88 feet long, 79 feet wide and 18 feet high. The floor slops down from the seating area to the pulpit area about 12 inches. Mr. Dave Yake of Yake Enterprises and JdB Sound Acoustics were the contractors for the whole project.

Central Baptist Church is a Fellowship Baptist Church. That generally means that the sanctuary should have an average to short reverberation time that support pre-recorded music as well as strong congregational singing. As much as there is a heavy emphasis for strong preaching, it sometimes comes at the expense of having a room that could be more musical. In larger rooms you can easily strike this balance but in church buildings with low ceilings, this can be best achieved with an electronic reverberation system. What is also interesting is that the "Fellowship Baptist" as a denomination has been unable to define in writing what is suitable sanctuary acoustics for a Fellowship Baptist style of worship.

The unique story in this church was the acoustical nightmare and the sever limitations it had put on a sound system that should have worked reasonably well to meet the churches needs. The original sound system design was a good first start.

At the time of building the church, the architect had promised good acoustics. Here is a classic case where the Architect took a poor room shape(a square shell) and removed any possibility of making the church usable without open heart surgery. If you could see a top view, just by looking at the it, one can easily see where the problem spots would be. All the problems were predictable, even in 1972.

The two major problems were was that the church was a square shell and the Architect tried to fix it with it con-cave surfaces made of drywall. There are a total of 8 con-cave sections. This has proven to be the worst possible way to finish a room.

Shortly after the church first opened, someone did some acoustical treatment. According to the product literature the church only needed about 120 Geocoustic II tiles from Pittsburgh Corning Corporation. The church installed over 400 hundred tiles and this was not enough. Nor was there enough low frequency absorption. However, from 1972 until 1989 the church put up with the problem.

The first Visit and Proposal

In 1985, JdB Sound Acoustics and Yake Enterprises was called to recommend the church a new sound system. Upon arrival, they asked if the sound system would make the choir and piano sound better. To test their request the piano was played without the sound system on. The piano sounded poor. With the sound system on, it sounded worse. If the source is poor, how can you make it better? We knew enough not to be trapped into providing a sound system to a client that no matter what the budget or equipment you used, the results would be poor.

At this point we declined to do any work without an acoustical assessment. We were positive that if the church just simply replaced the sound system, the problems would still continue. To our surprise, the church board elected to not start the project until they could raise more funds. At the time we were the highest bidder by 50%. I was later told that we would have had the contract, but because we withdrew our quote and the opportunity to make a profit, it caused the church board to reconsider our warning.

The Second Visit and a Contract

Shortly afterwards there were changes in church personnel and nothing was done until 1989 although the church had been talking to other sound companies and acoustical experts in that 4 year period. In 1989, we were finally asked to do an acoustical and sound system report. In the report it stated the if the existing acoustics were changed or improved upon, the current sound system would work much better. The only reason to change the sound system was to fill in the holes and bring the sound system up to 1989 technology. With this perspective, the church went ahead with all the recommendations in the report.

The History of the Acoustics and Audio

We had on file details of the preliminary work and measurements to give us some idea of the problems. In drawing 1, (These drawings will be in the Book, Why Are Church Sound Systems and Acoustics So Confusing? Third Edition for 1998?) it shows the top view(floor plan) of the church. The ceiling is flat and the floor has a slight slop. From the top view there are 6 large curved walls. Each curve is from floor to ceiling. The pulpit area is tear drop shape. (Although this looks nice for an executive office building atrium it does make the setting up for choir events very awkward.)

Drawing 2 shows the areas in which the sound levels would change radically before our acoustical treatment was done. These level changes were from 4 to 10 decibels (dB), i.e., Dead spots. Around the area of the piano the problem was different. It was a consistent reduction of 7dB in the whole area. Also, the sound of the piano seemed trapped in the area. (These before measurement were done with an SPL meter and a MLSSA measurement system.) These measurements were without the existing sound system turned on. However, when the sound system was engaged, the dead spot areas increased. At first, we tried to design a sound system solution without the need for acoustical treatment. From all the calculations and known laws of audio physics, there was no doubt in our mind of what had to be done.

By using part 1 of the evaluation guide from the book, you can get a picture of what type of room the church had in the chart below.

To be fair, the old sound system was not scored because of the condition the acoustics of the church were in. However, what should be said is this. The church did have a cluster type system in the bulk head. The speakers were Altec 311 horns with driver and bass cabinets. The electronics were vintage 1960's. When the new acoustical treatment was applied before the sound system was changed, the congregation thought that the new sound system was already installed. The new sound system was installed 2 weeks later. During that time the congregation was able to get the full benefit of the old sound systems performance but, they also were able to see and hear the limitations the sound system had on music and flexibility.

Visiting the Church 3 years later on May 21/1992

Upon my arrival to the church, the first thing I notice is how the room seemed well balanced. There were the 400 plus Geocoustic II tiles from Pittsburgh Corning Corporation in a "Patch Layout". Below them were 70 units of 5 foot 11" half round Tube Traps (from Acoustic Sciences Corporation) on all the walls in a perimeter. The only evidence that there is a sound system is the mixer desk at the back of the one set of pews. The desk is raise slightly and moveable. There is no sign of a speaker system but there is a bulkhead over the pulpit area in the shape of a tear drop. Although the room is balanced, the RT60 did seem short and the numbers show that.

The Visual Inspection of the sound system

The first thing done was a visual inspection that started with the pulpit and platform area. The 16 mic inputs on the platform were well laid out and with large numbers. The were three monitors outputs as well.

Next was the inspection of the speaker system. In consisted of 3 Tannoy P100 Dual Concentric speaker. They were mounted in the bulk head over the pulpit. The speakers are not visible except for where you see grill cloth. From the grill cloth openings, it appears that one speaker is out of place. Apparently, there are plans in the works to rebuild the platform and remove the bulkhead. The current speaker setup is temporary. (This was a recommendation made earlier.) Tannoy, for many years was the only company that made 15" Dual Concentric speakers. Today, other companies make similar point source speakers.

Moving to the next part of the audio chain, I checked out the equipment rack. The rack is in what used to be the old sound booth. Before the upgraded sound system, it was impossible to mix or adjust the right levels for the seating area from the booth. Therefore the mixer was move out into the seating area.

At the bottom of the rack are two amplifiers. An SCS 2450 and an Ashley Fet 1500 Each amplifier has a total output in bridge mode of 800 watts or more but the amps are used in 2 channel mode. Total power available 1600 watts. Total power being used 900 watts. Other comparable amplifiers would be Hafler, Soundcraftsman, Crest, the New Bryston 4B and other high performing products.

Above the amps in the rack were three equalizers. Two of the eq's are Rane ME30's for floor monitors. The third Equalizer is an Ashley GQ30 for the main speaker system. Other good performing equalizers are from EV, Altec, Klark Teknik and Micro Audio.

To see the mixer I had to go into the sanctuary. The mixer is enclosed in a wooden desk. The desk is divided into four parts. Sound, recording, storage and lighting. The mixer is an Allen and Heath 16 channel SR Plus board. According to the Spec. sheet the mixer is supposed to have a gain of 98 dB. However the mixer is set up so that it is only using 92dB of gain. The mixer is well laid out and it was easy to follow the signal flow and to find all the different function. As much as I like Allen and Heath, the mixer could use a few extra features such as PFL on aux. A & B and the low mid eq set at 400 rather than 250 hertz. Other comparable mixers are the Soundcraft 200 Series, Soundcraft Delta boards, Studiomaster Stagemix Series and some of the newer Ramsa stage mixers. Every wire was marked and well labels and everything was easy to find throughout the system.

On the other end of the mic cables are a variety of microphones. For test purposes, I use a Shure SM58. It is a standard and a reliable microphone. Since most people are familiar with it, it gives us all a common reference from which to judge the live test. On the pulpit is a Shure SM85. In 1996, a Countryman Mic has been added to the pulpit.

The Evaluation Test

The evaluation test was done with a MLSSA System (Maximum Length sequence acoustical system analyzer), a set of ears and a tape measure. All the tests were done with the room empty.

Part 1 reflects the condition the sanctuary is currently in. Considering the earlier room score 45%, the acoustical treatment did an excellent job in bring a bad situation to a very suitable condition, and be within what the Fellowship Baptist Church denomination would like. With all the curved walls, the sound was erratic throughout. When the first graph of the before measurements were done, we realized that there was no way to make the room brighter, nor could a flat panel be used without creating more problem. There were two key elements needed. Absorption in low frequency and diffusion in high frequency. The only product we new of at the time was Tube Traps from ASC who now have a web site. The people at ASC helped in designing the system.

When I measured the room, the results were quite impressive. As best as I could, I took measurements where the mics were positioned in the first set of measurement. Both graphs show the RT60 in 1/3rd octave increments in two positions. (This is an automatic function with MLSSA using the Schroeder Plot -.1 to -25dB setting.) Also added to the graph is a line that suggests what an average church should look like on paper.

The after graph shows a room with a below average RT60 but it is a consistent RT60 throughout. The deviation is less than a quarter second from 250 hertz to 20,000 hertz. Whereas before, the deviation was 1 second at 500 hertz and a half second at 1250 and 2500 hertz.

Then of course there is the other possible way to liven up the room. Why not remove the carpet? In this case it would not be a good idea. With a low ceiling it may put enough energy back into the room to emphasis the walls again and then you would need more Tube Traps. If the roof were another 10 feet higher, the room would have given us something to work with.

The final test and the people

One of the first people I meet at the church was Ed Supplee, the music director. He has been at the church for only 8 months. He had previously worked with a sound system in a Texas bible college where they had a 2000 seat auditorium. Ed was very pleased with that system. His comment was that the system in Texas was more high tech but in performance, there was no difference. Coming to Central was neither a step down nor up. Just a good solid performing system. As for preaching, he felt very comfortable with the system. Ed thought it was above average from his experience.

The other person interviewed is the sound man at the church. Peter has been enjoying the system since it was first fired up in 1989. He said the church had been doing Gospel and Music presentations that they would have not been able to do with the old sound system. (The only complaints come from people saying that the system is too loud. Those were also the days when Peter is not there.) Also, the quality of those singing of both members and visitors has gone up dramatically too. Moving the sound operators' position from the booth up stairs down to the main floor was a real help. He said "The only time I need a headset is for monitoring the tape recorder or for queuing up a tape for a special singer." Peter also felt that the power in the system gave real control.

On the down side, Peter wished for a better mic capsule on the wireless. The other item was acoustics treatment. Peter would have liked more Tube Traps around the choir loft area, but this and a few other concerns mainly had to do with the compromises made and the future proposed changes to the platform area. The speakers were installed so that they can be easily moved when the bulk head is removed and the platform is rebuilt. Until then, what can you do!

In summary I have to give the acoustic solution a 9 the sound system solution a 9 and the system setup a 10. As a person sitting in the audience you will most likely not notice the sound system and enjoy the good services they have at Central Baptist Church.

Foot note. Even though I was doing an evaluation on my own system, we could not find anyone who would do any evaluation who had as much church experience as we had. Even when I was will to pay for a report. It is hard to be fair and in this day of age, it is harder yet to be honest and not over opinionated. If you have a church you want reviewed in this manner, please call.

Below is a sample of doing the evaluation test as described in the book and on the web site.

Part 1

Average reverb time - 1 second.                                 Score 7 

Reverb time at 200 hertz  -  1.25 seconds.                      Score 5 

Reverb time at 3000 hertz  - 1.09 seconds                       Score 10 

Echo test 1 - no                                                Score 10 

Echo test 2 - no                                                Score 10 

Articulation test  - 6% loss or 94%                             Score 10 

_______________________________________________________________________

Total Score out of 60                                   Score 52 or 86 %

Part 2

Dead spots of -8dB  - 2                                         Score 10 

Phase cancellation = Audible near front                         Score 1 

SPL from front to back -  3dB                                   Score 9 

Realism - Pulpit                                                Score 10 

Listening Fatigue factor - Low                                  Score 10 

Articulation score of sound system - 94%                        Score 10 

Maximum working distance before feedback - 32"                  Score 10 

System design life - permanent                                  Score 10 

Music quality  - HI IF quality                                  Score 10 

System headroom - 12dB                                          Score 7 

Echo's - No echo's                                              Score 10 

_______________________________________________________________

Total Score out of 110                                  Score 97 or 88 %

Part 3. Hardware

Amplification - 500 watts on cluster/ 700 people                Score 9 

Equalization (EQ) - 1/3rd octave                                Score 9 

Flexibility  (Number of output mixes) - 10                      Score 10 

Separate and Adjustable recording output - yes                  Score 10 

Separate hearing impaired output - yes                          Score 10

______________________________________________________________

Total Score out of 50                                   Score 48 or 96 % 



Total Score of Church and sound system                  Score 197 or 98.5%



Some statements and Specs have been blanked out under the understanding that it is part of the "intellectual Knowledge" guidelines and were not part of the original article. Such knowledge has value and can be purchased through investing in the book ""Why Are Church Sound Systems and Church Acoustics So Confusing?"Info on a book on Church Sound System & Church Acoustics

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Copyright (c) 1996 JdB Sound, Acoustic Lab.

Copyright © Oct. 1996
by JdB Sound, Acoustic Lab.