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Posts Tagged ‘Church Sound Systems’

Dead Spots – Sound System or Acoustics?

Posted by jdbsound on April 9, 2018


An unwelcomed guest in any church is Mr. Deadspots. Unfortunately, deadspots in churches are more common than you think. There are two main types of deadspots. Some are frequency related/comb filtering interference and others are dips in sound levels greater that 6dB created by the room.

It is common to see frequency related deadspots in Left/Right sound system regardless if they are Line Arrays or point and shoot speakers. These deadspots are created by interference patterns in a mono speech system as a persons voice is always mono.  These deadspots are where you shift from one foot to another and notice a sound change. In these cases it becomes a problem when on one foot you hear the highs but not the lows. When you shift your position onto the other foot, you hear the lows and the highs disappear. People with hearing aids or early stages of hearing lose notice this the most. People with good hearing notice the change too but learn quickly to put up with it. Some young people think of it as a passive noise filter. If the music is too bright, stand to one side of your seating position. If the music is too boomy, shift to the other side of your seating position. Really! Isn’t that like buying a headset and controlling the sound changes with what angle you tilt your head. It might sound like a great idea until you find yourself with a lot of neck pain. No thank you.

Sound level dips are usually acoustically related. These are created with standing waves, bass building up, hollow walls, room corners, and parallel surfaces that include walls, ceilings and floors and concaved surfaces. In all of these cases, often mid and bass energy build up and the highs are absorbed with carpets, padded pews and people. By the nature of churches and how they are used, carpeted floors and padded seating often represents how the church sounds when it is 50% full. That means that if your attendance is often over 50%, the effects of padded seating and carpeted floors has little to no impact. If church attendance is often over 70% a carpeted floor makes the room more intimate during times of prayer and solemn reverence. In the end, carpets and padded seating is a good thing.

However, because of people in the room, once that room attendance is above 50% the people absorb enough highs that extra mids and bass energy is left behind as is being amplified between parallel surfaces. This excess energy automatically masks the highs. When the highs are masked, speech and music intelligibility drops. The kicker is, if you go around the room with a sound level meter, often the sound levels don’t drop much, even when you stand in a spot where the highs (when you measure just the highs) drop off over 6dB. That is because the excess bass energy is so strong that it fools the sound meter as the meter is reading an average sound level. When you take sound level readings by frequency, then you notice the high number of deadspots in the room. Get a tone generator in a cell phone or computer app and play a constant tone at 55dB at 500 Hertz, 1000 Hertz and 3000 Hertz and then start walking around. At 500 Hertz you shouldn’t notice much of change until you get close to walls. At 1000 Hertz you will notice more changes. At 3000 Hertz, if you are hearing a lot of changes, imagine what 25% of your church audience is experiencing.

Here is a church that had both acoustical and sound system created deadspots, with a central cluster. By nature of a central cluster, in a good room, it gives the best coverage and performance for speech. There is no better way to design a church sound system unless your ceiling is less than 14 ft. high. Choice of speakers, coverage patterns and speaker placement impacts sound too but these are mainly tone qualities and gain before feedback related. It may have up to a 2 or 3% impact on overall intelligibility as well.

corner view pano Ebeneezer Church_s

In this church example, it already has a fairly good quality speaker system in the ideal location for the room. It is designed as a central cluster and by nature, in this setup, it should perform well. However, it didn’t matter if you used the main speaker system or used portable speakers on stands, with any sound amplified you could find deadspots all over the room. On top of that, if you raised your voice in the room, once you were more than 18 feet from someone, understand what was being said was difficult to impossible depending on dictions of the person talking and how good is one’s hearing. When the proper acoustical fix was applied, all of those problems went away and the church didn’t need to upgrade the speaker system.

The church decided to leave the sound system alone as the gain before feedback improved and all of the deadspots disappeared. Since this is a traditional church that has no intentions to do anything contemporary, the acoustical fix was designed to not change the overall reverb time. Before and after reverb time remained about the same. 1.7 seconds.  It was the frequency response of the room that saw a major change. As the graphs shows below, where the mixer for the worship space was located, it was also one of many spots where weird measurements were recorded before. We found dozens of spots where the room measurements went squirrely. This is typical of the results of measuring a Left/Right speaker system, not a cluster system. These weird results were a result of room acoustics and not the sound system.  We used our own test speaker for all room testing.

Sound Booth Before and After

After checking our test equipment for errors, it was then realized that by just moving the mic over a few inches, you would get a very different result. In some places, the sound was perfectly fine but move over a few inches and it was not. Our ears are about 8 inches apart. In one row of seating, the largest distance we could move the test mic between a good spot and bad spot was 14 inches. Pew seating is 18 inches.  Every seating position had both good and bad sound. What we were measuring was sound masking in the mids and lows.  The energy was so strong that it masked the highs.  Not only that but the highs were most likely also being canceled from nearby wall reflection between 1800 to 5000 Hertz.  It gave the impression that there was something wrong with the sound system.

In this church, people marked their seating positions by placing personal pillows in spots where the sound was better. Sure enough, testing these spots showed better sound before the acoustical treatment was applied. After the acoustical system was installed, the sound was the same no matter where you sat including the sound booth.

Deadspots in churches are more often a result of worship space design and not a result of sound system design (unless you have the wrong speaker system design for your room). When a church replaces a well-designed sound within 10 years, and have little to no overall improvement after an upgrade, that should be a BIG RED FLAG that you most likely have a serious acoustical problem and no amount of money spent on the sound system can make those problems go away. Besides, these days, acoustical fixes cost less than sound system fixes. As a caveat, our experience has been this. Churches that have fixed their acoustics and then wanted on to expand their music programs, they were able to upscale their sound system with a much higher budget as they upgraded, it actually lead to better performance rather than an exchange of one set of problems for another.

Bottom line is, get your church properly tested. Have someone who knows how to properly diagnose the data, and then design your church a proper acoustical management system. Install the acoustical system and watch the congregation respond and grow. Don’t be surprised if other churches want to use your church for musical and recording events. Your property value may go up too.

Note – The acoustical system is made up of 8 and 12 inch half round plaster covered foam diffusers on 3 walls.  The side walls use a gradient pattern to maximize room performance. On the back wall there are 24 units of 7 ft. x 2 ft. x 18 inch plaster covered foam diffusers that are hollow which allows for additional passive room equalizing in the near future. Project completed by church members.

By Joseph De Buglio
JdB Sound Acoustics

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Can Acoustical Spreadsheets Save Your Church Acoustics?

Posted by jdbsound on June 20, 2016


There are dozens of acoustical spreadsheets that come with the promise of a viable acoustical fix.  Some sheets are for studios and some are for home theatres.  There are also other spreadsheets for larger rooms.  As rooms get larger, (as in Christian Churches and worship centers) those spreadsheets become less accurate.  Sure, the better spreadsheets adds more variable to compensate for the limitations, but the limitations are still there. Furthermore, with all of the spreadsheets, you have to add an additional line to include a fudge factor.  In some spreadsheets you need to add multiple fudge factor lines.

When a person tries to use an acoustical spreadsheet, they are only looking at one parameter of the rooms acoustics.  You are only looking at “time.”  The problem is, for churches, and I MEAN ALL ROOMS WHERE MORE THAN 150 PEOPLE GATHER TO WORSHIP – there are other parameters that are equally or more important than “time.” Acoustical problems always come in layers.  The minimum number of layers of acoustical sound management in a worship space is 4 layers.  As a worship space becomes larger, the more layers you have to attend to.  “Time” becomes only a fraction of the real acoustical problems you are faced with.  Obviously you can’t see them but you can measure them if you are trained to recognize when you hear them.

Romanian Church Kitchener Ontario Pano 1.jpgThe problem with spreadsheets is that they are not looking issues such as standing waves – and every church – regardless of shape has standing waves (unless the space is acoustically managed in the first place which also means this article is not for you.)  Spreadsheets are not looking at excessive noise from early and late reflections.  They are not looking at bass buildup often found in the corners of a room.  They are not looking at flutter echoes and full syllable echoes.  These are all sound effects than can’t be dialed out with equalizers, delays, algorithms and the next miracle digital gadget or software. (Yet that is how most sound system designers try to deal with room acoustics.)

Regardless of a persons acoustical training, knowledge or experience,  a spreadsheet cannot tell you when standing waves are masking flutter echoes.  A spreadsheet cannot tell you when bass build up is masking a standing wave issue.  A spreadsheet can’t tell you how much the early and later reflections are reducing music and speech intelligibility. 

All that a spreadsheet can tell you is how much “time” it takes for a sound to decay in a room either as an average number.  Some spreadsheets are much more detailed and they have been written as an attempt to calculate a room in octaves or by 1/3rd octaves.  If it was only that easy.  Measuring and calculating time is just a sliver of the acoustical signature of a space people worship in. 

church of our lady small.jpg

It takes a lot of training to learn Church acoustics.  The same applies to Studio Acoustics, Recital Halls, Concert halls and lecture halls.  All of these rooms have specific acoustical needs and they all require a unique set of skills to properly fix them.   

What makes a church so complicated is in how a church is used.  When a church is designed as a “church,” it becomes the most multipurpose space there is because of all the ways a worship space is used.  When you say you want the worship space to be more “Multi-Purpose” or more flexible in it use, you are actually limiting what a basic worship space is supposed to be able to do. 

At the end of the day, an acoustical spreadsheet is only a small snapshot into church acoustics.  It can’t help with congregational singing, it can’t help with a noisy stage for a praise and worship team or choir and it can’t help with drum issues or speech intelligibility. 

What often happens is with the spreadsheet, it will guide you to a solution that is based on absorption.  When an acoustical fix is based around absorption, you wind up “killing” the room for all music – especially contemporary music and congregational singing – and the masking effects of the other acoustical issues get worse.  Sure, the room sounds more tame than it was before, but the ability to understand speech is either no better than before or it has gotten worse.  Before you know it, everyone gets in ear monitors and all of the members of the worship team have to sign an insurance liability waver stating that they will not sue the church for any future health problems with hearing loss.  Seriously, is that the kind of acoustical fix you want? 

Front view of creekside church_edited-1.jpgThat is what you get when you turn to an acoustical solution based only on spreadsheet calculations.  To top it all off, the results are not much better when using computer simulation software programs.  Simulation programs only show you the results at one frequency at a time.  The computer generated image may be 3D but the patterns they show are only one frequency at a time – even when it is averaged out.  To see large room acoustics in a simulation, you need to be able to see the results in 4D.  Hologram can’t show you 4D images.  That ability hasn’t been invented yet.  You need to be able to see sound in 4 dimensions because all sounds are complex.  Every sound made on earth is a combination of wave lengths that are generated at the same time. Some parts of a sound are measured in feet and some in inches.  There is no way to visually see 100 Hertz, which is 11 ft long, and 4000 Hertz which is 3.5 inches long, at the same time in the same place yet in real life, that is what is happening with sound.  We all take sound for granted but the complexity of sound is extensive.

But doesn’t sound follow the rules of fluid dynamic and other laws of physics?  Of course it does, but only when you examine one frequency at a time and that frequency is never a pure tone.  It is always complex.  The only place you can measure and see a pure tone is in a machine like an oscilloscope and the moment you launch that sound into the air, it becomes complex.  Just as sound is complex, so are the acoustical fixes for churches. 

jdbsound test room.jpg

This is one way to test an acoustical solution before you recommend it to a church.  Have your own testing facility.  Whatever research is done in this room, it mathematical translates perfectly when it is scaled up into a larger space.

As a mantra, remember this:  for all Christian churches, acoustical problems come in layers and whatever fix you choose, it has to address all of the layers in one step – which is possible if you want an affordable fix.  There are many tools in the Acousticians Tool Box to fix a worship space. There are diffusers, resonators, traps and other devices that can address the needs of a church’s acoustics. There are also stand-alone electronic solutions that work in certain worship spaces. You need a lot of training to know which ones you need, what combinations you need and how to use them, and the last place you want to do your training and experimenting is on your customers. 

If you are doing Church Acoustics or trying to fix your own church, don’t do it as an experiment and you know it will be an experiment the moment someone in your committee say something like, “lets try this as see what happens.”  With those words, the acoustical solution is already doomed.  Experts like myself can tell you the results the second you decide to try something and long before you apply the materials. 

History shows that after a church spends it’s money on a thing such as acoustics, it will not be able to afford to fix any mistakes for decades.  If the results makes the room worse or no better than before, then you are subjecting the church members to more sound abuse for years to come and we don’t want that.  Spreadsheets don’t fix churches, good training and expert help does. (It’s also cheaper in the end to get expert help.)

Finally,  consider this.  The internet has become a treasure trove of knowledge.  That knowledge is often presented as expert information offering sure fire solutions.  I scan the internet often to see what is out there.  There is a lot of great information and there are a lot of myths.  When you collect all of that info, it only holds a fraction of the total knowledge about church acoustics.  If we were to put a percentage on it, the internet holds about 2% of the total knowledge there is for church acoustics.  The books hold another 8% of what there is to know about church acoustics.  Church acoustics is so complicated that often, a seasoned acoustical expert like myself will have to fix one of a kind acoustical fixes often.  Those unique fixes are often not shared because others may think that the one of a kind fix would be needed in every other church that has the same problem.  You can have 10 churches with the same acoustical problem but in every one the fix has to be modified because of the other variables that have to be included.  The rest of the knowledge about church acoustics is held by experts because the church community hasn’t taken ownership of that knowledge yet and there is no system in place for churches to share their experiences in order to avoid mistakes in the future.  What is missing is the wisdom in knowing what acoustical fixes will enhance worship verse what acoustical fixes exchanges one set of problems for another set of problems. Problems which holds back and undermines the real worship experience the church leaders want you to participate in. 

All church can have great acoustics and sound.  If each church denomination or independent church were to set-up their own “Church Sound Standards” for the performance of their sound systems and worships space acoustics, churches will become the kind of places where people want to go.  Once a standard is set, every church will have a Worship everyone can enjoy and appreciate. 

Joseph De Buglio

Acoustician and Expert in Church Acoustics.

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New Church Sound System Equalization Schedule

Posted by jdbsound on February 17, 2016


Notice to all Clients of JdB Sound Acoustics.

If you are in a new church building or you have done major renovations in your church, you will have to re-equalize the sound system many times in the first few years.  Here is the schedule you should follow.

  1. First-year – After the 1st month, 3rd month, 6th month, 9th month and 12th month
  2. The second-year – After the 4th month, 8th month and 12th month.
  3. Third-year – same as year 2
  4. The fourth-year – after the 6th and 12 months.
  5. Fifth-year – same as year 4
  6. Sixth to the seventh year, every 1 each.
  7. After that, do touchup to do loudspeaker decay drifts. (as speakers get older, the surrounds and cone can become stiffer and less compliant and that changes the frequency response of the speaker.  Equalization often compensates for mechanical aging.)

It takes up to ten years for most buildings to fully cure or longer depending on how much concrete and wood is used in the walls and floors.  For that reason, the humidity of the church becomes lower and lower as the church ages which also changes the sound of the worship space.

Also, depending on the climate area you are in, you should be re-equalizing your church sound system for each season.  more so the further you are from the equator.  If you have a digital processor or mixer, you can have presets for the room changes.

If your church is somewhat airtight and the HVAC system is properly designed to maintain temperature, even during worship services, the tuning cycle after 6 years can be relaxed for Displacement HVAC systems.

Joseph De Buglio

 

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I Hate Mute Switches!

Posted by jdbsound on April 19, 2015


At my church, we still have an analog Mixer.  It has 24 channels, 4 sub groups, Left/Right and Mono out.   We use the sub groups.  Vocal, Drums, Instruments and Leadership mics.  The mixer has mutes on every channel, on each of the mute groups and on the 3 master outputs.  Fortunately, we have a church were the acoustics are stable.  We can run all of the mics open without feedback for normal worship levels. Monitors are stable and so on.  It is also a good sound rig.  When I run the mixer, I turn every channel on and shut off any mute switches.  I control all of the levels with the sub groups.  I don’t want any surprises.

This Sunday it was my turn to run the mixer as we are on a weekly rotation.  Thursday night was rehearsals.  Missed the rehearsal.  Friday night the Youth used the sanctuary and someone used the mixer.  Things were changed but it only took about a minute to set everything back.

As usually, you arrive at the church early for a pre service warmup. Dialed up a great monitor mix.  Everything seem right and as typical, we rehearse and warm up with the FOH speakers off.  When the worship team stopped it was time to turn on some background music.  Turned on the CD player, saw activity on the channel, raiser the fader for the channel and the channel was assigned to the Mono Main Out.  Raise the mono out and nothing happened.  What!!!

Checked the power switch to the powered speakers.  Check to make sure the processor was on and passing a signal.  Nothing.  Called the head tech for the church, he checked everything out. He checked the mixer and he agreed with me and thought that the power switch was faulty.  He removed the power switch and bypassed it.  Still no sound!  Double checked and found that the power lights on the back of the powered speakers were indeed on.  The head tech and I stared at each other confused wondering why there was still no sound.  Then he looked at the mixer again and this time noticed that the Mute switch on the Master Mono Main out was engaged.  He hit the mute switch and the rest of the sound system came to life.

In the year of mixing at the church, the Main Left/Right and Mono outs have never been muted.  The mixer is a spilt mixer where 16 channel are on one side of the mixer, 8 channel on the other side of the mixer and the Groups and master outs are near the middle of the mixer.  For some reason we were blinded in not seeing the red mute lights in that area of the mixer as there are other red lights in the area for other things.

Later I learned that a recently hired youth leader came from a church were the sound system was so unstable that you had to mute everything all the time.  They muted anything that wasn’t needed and because they left the mixer on 24/7, they had the habit of muting the master outputs as well.  The head sound tech and I had a good laugh at the whole experience.  For me, I should have known better as this is about the 3rd time something like this has happened.  This is the first time with powered speakers, but before I had people thinking there was something wrong with the mixer.  So please, unless you have a wonky unstable system, please don’t use the master mute switches.  They are great for a studio but not for live sound.

Joseph De Buglio

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Singing at 105dBa!

Posted by jdbsound on April 10, 2015


Congregations can sing at 105dBa.  At least that is what they do in churches that I have fixed and that does happen in other churches too, that perform well.  When they do sing that loud, what do you do?  Or, what do you do when the congregation is starting to drown out the sound system?

  1. Keep pushing the sound system to keep up with them.
  2. Keep the sound system at 90dB and let the congregations voices dominate.
  3. Lower the sound system FOH levels so that the congregation can enjoy what they are doing.
  4. Push the sound system to drown out the congregation as always regardless if the sound system is distorting or not.

Please tell us what you do when mixing.

Joseph De Buglio

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Question! What would you do to fix the Acoustics of this Church?

Posted by jdbsound on April 1, 2015


You have a church that seats 750 people.  It is a simple rectangle room with 30 ft walls, 40 ft to the peak, 80 ft wide and 140 ft long.  The reverb is 2.2 seconds at 300 hertz and 1.3 seconds at 2000 hertz.  An Energy Time Curve test show reflections over 30dB at one second on the ETC in the 300 hertz range.  The floors are carpeted and the pews are padded seats and backs.  All of the walls and ceiling are insulated drywall on 12 inch centers.  Basically there is about 30dB of excess energy at 300 hertz.  300 Hertz has a wave length of 3.75 ft. The church has already tried 4 different sound systems over 10 years and all of them were designed and installed by companies that are supposed to be the best in the business and they all started off saying that the room needs to be fixed – but church board members vetoed anything that would change the aesthetics of the room – but it was OK to hang 2 ugly line arrays which lasted only 6 months.

The church is now asking for another sound system but this time all of the professional audio companies turned down the project and said to the church don’t call us back until you fix the room.  Now the church board has relented and they are allowing acoustical panels to be mounted on the walls. What acoustical method or system would you use to fix the problem?  What will reduce energy 30dB in this space?

For all the walls in the church, between windows, doors and bulkheads, there is only 35% of the total wall space available to mount acoustical panels on. Major issues are – Stage noise, floor monitors as loud as main speaker system in the first 10 rows.  Only 20% of the congregation is ever singing. Speech intelligibility is below 85% in full range – if you roll off the sound system at 200 hertz speech intelligibility improves to 88%.  Gain before feedback is very poor after 3 or more microphones are turned on at the same time. Subs never really sound right.  Pastor hears echoes all the time off the side walls when preaching. Drummer can never hear himself or the other worship team members – even with the headset monitors. The are currently using electronic drums but they have tried drum shields and booths without much satisfaction.

The church used to have a 40 voice choir but they never sounded very good and now with over $150,000 invested in a praise and worship team with all the latest state of the art technology and higher trained sound engineers, they sound no better than what the choir did years ago – but they are better at entertaining people!

(note: this is a fictional church but this is based on actual events that have happened recently in three southern Ontario Churches.)

Joseph De Buglio

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Church Aesthetics

Posted by jdbsound on March 19, 2015


Acoustics decides the Aesthetics of a church. If the acoustics are bad, the aesthetics looks one way. When the acoustics are good, the aesthetics looks another way. Did you know that the average person without training can virtually tell what the aesthetics looks like in a church by how it sounds? Did you also know that churches with good acoustics when first built often have better aesthetics that lasts the lifetime of the worship space?

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The Testing Room Part 1

Posted by jdbsound on July 13, 2014


test room 002

The test room is well underway in becoming reality. Here is a photo of the crew transforming one of the rooms in my new home into a test lab.

test room 001

This room will allow us to measure and test an unlimited number of configurations of equalizing and matching the acoustical fixed for churches.  Since computer simulations don’t work with this technique of acoustical sound management for churches this is the next best thing.  In earlier testing in other room years ago, the tests done translated very will into larger spaces.  In the past, this testing was only to find the most common acoustical problems churches have.  Since then, churches have been demanding even better room control and this test room will allow us to customize the acoustics of any worship space.

It is our hope that the ability for room testing will be ready in the next two weeks.

Blessings

Joseph De Buglio

 

 

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Windermere United Church, Toronto, Ontario, Canada

Posted by jdbsound on March 18, 2013


windermere 3_edited-1

Completed their Sound System and Acoustical upgrade in Summer of 2012.

In the last year, all of the complaint about sound have been exchange for a growing church.

Click on the photo to see the full size image.
To see other images of this church please use this link – http://www.flickr.com/photos/jdbsound/sets/72157632984258138/

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Pastor Guide To Acoustics

Posted by jdbsound on December 20, 2012


Here is an article I recommend reading.  It sings the same story share at this website.  Don’t know about the results but if it is similar, it would be amazing.

Pastor’s Guide to Acoustics
link: http://www.worshipfacilities.com/go.php/editorial/19635

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All Sound Systems are like magnifying glasses of the room acoustics

Posted by jdbsound on December 10, 2012


Is your sound system making the right impression?  Are the acoustics of your church allowing your sound system to make that great first, second and third impression at your church?

Once again the subject of getting more performance out of the next sound system upgrade keeps coming up. When a church is constantly seeking to get more performance out of a sound system at every upgrade and not be  enjoying the best sound possible then it’s time to fix the room instead of putting it off and investing into more equipment. This is the message your sound system is broadcasting.  Are you listening or are you waiting for the next technology breakthrough for that sliver of improvement?

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Calvary Worship Centre, Surrey, BC. Canada

Posted by jdbsound on November 9, 2012


Image

The acoustical system at Calvary Worship Centre is now about 95% complete.  The church hired me back to confirm the acoustical results and to finalize the sound system setup.  The Midas Pro2c Mixer and Danley Speaker system are a great match.

This is not the largest church to use this acoustical and sound system combination, but it is the largest church to change their acoustics in less than 30 days.  The fastest church repair was done in 7 days in Brentwood, England.  The largest Church I have worked on was 6500 seating.

A member of Living Hope Church in Surrey BC where they have been using the same acoustical system for over a year commented with saying Calvary has the same balance of sound as does Living Hope which is a modest 270 seat church.  Calvary Worship Centre can seat up to 2000.  That is remarkable considering that one place is built as a “proper” church and the other is a converted warehouse and both spaces perform the same.  (I was reminded that Living Hope Church thought they already had good acoustics but tried the Solomon system as a short term experiment.  The experiment turned it a permanent installation and the congregational singing and worship has never been more exciting.)

A Member of Calvary Worship Centre said, “The sound is far better than I dared hope for this 20,000 sq ft space given my previous church experience in a very similar venue.  Also, the total price was less than I expected it might be including your fees and the acoustic treatment.”

As one person mentioned at another church fixed with half round diffusers in Little Rock, Arkansas USA, he said, “you can tell if you have a good room by the number of people singing.  Before only about 20% of the audience was singing most of the time and for familiar hymns about 25% were singing.  Now it’s about 85% of the audience is singing all the time and you can hear the excitement and power of all those voices ring out.”  Imagine that – worship and excitement in the same sentence.

Click on the Photo to see the full size version.

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Direct Boxes…..

Posted by jdbsound on May 26, 2012


Direct Boxes

Original Article Copyright (c) 1988 Joseph De Buglio, JdB Sound, Acoustics
Updated 1997, 2012

From JdB Church Sound & Acoustics

This information has be written for the layman and should not be used as technical information. Many terms and descriptions are simplified for educational reading.

Thank you.

What are they and why do we need them?

It’s 10:00am Sunday morning. The invited Gospel group just showed up an hour late. You have 45 minutes to set up, do a sound check and rehearse the group long enough to know what kind of sound they are best known for.

One by one the performers enter with their instruments. This group is planning to use the church sound system. Rumor told them that this church had a very good system. You see one electronic organ, two electronic keyboards, one string bass with a pickup and one electric guitar with an amplifier head. Finally, you see an electronic drum kit.

At the front of the church you have 16 mic inputs. You need 5 vocal mics and 9 inputs for the instruments. That leaves you with a pulpit mic and a tape player input.

Fortunately, you were prepared. Earlier in the week you rented 1 speaker director, 5 passive direct boxes and 2 active direct boxes. The church already owned 2 passive direct boxes.

By 10:30, the sound check was finished with the soundman sitting at his mixer in the pew and 10 minutes later the group finished their rehearsal and floor monitor check. At 11:00am, service started and the group performed very well. Most people were not aware that the group set up in only 45 minutes. Is this really possible? Ever since the 16mm film projector was used in the church and connected to the sound system, churches have needed a direct box (or DI box). DI boxes are used to change the output signal from one source and change the level and impedance to match a microphone level signal input into a mixer. The most common application of a direct box is when connecting an electronic keyboard or similar electronics to a sound system. The DI box allows you to connect into a snake or existing mic lines and send the signal up to 700 or 800 feet away. By converting line level signal to a balanced signal mic level, you also avoid RF problems and crosstalk in the mic cables back to the mixer.

There are 5 quick and convenient type of boxes

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Passive Direct Box

The most common DI box is the Passive Direct Box. This unit is often used to connect Guitars, Keyboards and other electronics that have a line level out from the instrument. Often the line level voltage is between .5 volts to 3 volts (Some DI’s units can handle an input signal of +8dB (or 10 volts)). As a passive unit, the signal is as good as the transformer that is built within it. An important feature of many good quality DI boxes is ground lifting. Since there is no universal standard for audio equipment and instruments, grounding problems often occur (Perhaps the new ISO9000 standard may help…. but let’s see what happens in the next few years.) Many DI boxes are able to isolate grounding problems between various items of equipment. Generally, by going through a DI, you loss from 3 to 6dB of signal.

** Note: Not all DI boxes sound the same. As the signal levels get higher, the DI box may add some distortion. On an electric Guitar it may be a good thing. On a Keyboard it can sound awful. Before you blame the soundman for that poor keyboard or instrument mix in the monitors, try a different DI box or even an Active box.

Active Direct Box

The second most common DI box is the Active Direct Box. These units either work from a battery or phantom power from a mixer. An active DI box can handle higher signal levels and put out a higher signal level. Furthermore, the frequency response is often better too. When you are performing in a room that has low reverberation and good performance qualities, it is better to use the active DI box. Also if you plan to use a digital signal in reinforcement or recording, use the active DI box. Generally, a DI has 0dB signal loss.

Active Direct Box with Preamp.

A new type of Direct Box may have a built in preamp that works off the Phantom power of a mixer or it might have batteries or it might have an AC/DC adapter. I haven’t had a chance to test one, but the are supposed to boost a signal level up to 10dB. Some of these units can also work as a mic preamp as well but that is only when your mixer dies and you need 1 mic to get through the show. But that would only work if you have a box that is self powered or with an AC adapter.

Speaker Director Box

The less common DI box is called the Speaker Director Box. A speaker director is used when the only signal output available is from an amplifier. Many older 16mm film projectors use a 10 watt tube amplifier for driving a 10 watt speaker. A tube amplifier should always have a nominal load of 4 ohms or higher on the output or the amplifier will burn itself out. A good speaker director will present to the amplifier a proper load and convert the signal to mic levels to either a 150 or 600 ohms. You should never take a signal from an amplifier direct into a mixer. You will either fry the channel or the power supply in your mixer.

Remember, all good direct boxes have ground lift switches and there are a few units that have an automatic grounding system. Make sure that your direct box has this feature.

Line Matching Transformer

Another common method of connecting low level electronics to a sound system is by using a line matching transformer. The transformer is usually mounted in a barrel type connector with a ¼ inch-tip sleeve connector at one end and an XLR three pin connector on the other end. The whole unit is often about 4 inches long. There are only a few manufacturers of these products and they seem to work.

Radio Shack, EV and other mic companies has two types and churches tend to buy these because they are so visible and easy to get. One converts low level line outputs to mic levels. This unit with the ¼” female to male XLR can handle a lot of power but, there is a major penalty when you drive this transformer to hard. In bench measurements, when the sign was greater than 2 volts, it introduced distortion. At 3 volts there was 10% distortion. At 5 volts there was about 20% distortion. On a guitar this may be desirable or in a noisy night club show where you won’t hear the distortion, but in a church, the distortion can be very unpleasant. As long as the sign stays below 2 volts, this transformer will do a reasonable job.

The other unit converts Mic Levels to Line Levels. The performance of these units were bench tested with a MLSSA (a computerized audio and acoustical testing system) and the performance was surprisingly very good. The limiting factor is voltage. The unit with the Female XLR to Male ¼ inch connectors can not handle a load much higher that 1 volt of power. At 1 volt the transformer saturates and it sound horrible. Any signal below 1 volt will have a frequency response from 10 hertz to 20,000 hertz ±1.5dB. The transformer is down 6dB at 3 hertz. From 50 hertz to 15,000 hertz the unit is ± .25dB. In my books, this is an excellent performance for most smaller church needs. The best function for this transformer is in trapping RF signals for mixers that do not have good quality electronically balanced inputs (Some mixers have transformer inputs which traps RF.)

Update 1997.

Recently on the news groups, there was some mis-information being shared which I feel should be corrected. A person posted the question, “Can an active DI boost the signal from -20dB to +0dB. I want to boost the signal of my acoustic guitar pickup.”

The response to this question was remarkable. What was very surprising was when I saw who was answering the questions.

First of all, lets look at the question. – The request was to know if an active DI can boost an audio signal from -20dB to +0dB. First of all, we should know what -20dB means.

In HI-FI, -10 and -20dB is the standard used to connect from stereo equipment to equipment. Part of the reason for this standard is that a lower signal has few problems with noise from RF and HUMs and at that level, it is cheaper to provide RF protections at -10dB. However, this signal is too low to manipulate for editing without adding noise that is inherent of all audio equipment and signals – even digital signals.

In Pro Audio, we use +4 as a standard. Part of the reason (among other things) for this higher output is to boost the signal high enough for a greater signal to noise ratio. Let me explain. A line level to line level signal often already has a signal to noise ratio of 60dB or more. A microphone can have a signal that is from – 80dB to +10dB. That is 90dB of dynamic range. If the low level -80dB signal is clean – that is little or no noise, by boosting it to +4dB means that when you split the signal for monitors, effects and recording outputs, when you change the signal with the channel EQ and then send the signal out of the mixer, your original signal should be (almost) noise free. (If you have a cheep mic, that can often be a problem when micing a person’s voice at a distance.) In otherworldly, the hotter the signal, the better for Pro Audio- and all church sound system come under this label.

As a side bar. – Have you even connected a CD player directly to a Pro Amplifier and found that you could turn the CD up all the way without clipping the amplifier? It’s because the maximum output of most consumer CD player are .75 Volts – which is the maximum output of a HIFI product. For Pro Audio – many pro amplifier are 1.75 volts (+4dB) or 2.83 volts (+8dB). This voltage difference and signal difference is the main reason why you can not mix HIFI and Pro Audio equipment. (Note, some lower prices Pro audio amps have switches for .75 volts for consumer use.)

Back to the Question – Many active DI boxes have switches that can cut a signal down. Most Active DI boxes have 0dB, -10dB and -20dB. Some DI boxes also have -45dB. These are pads. Pads are loads created with resistors and other components to cut the signal down when the input voltage is too high. A passive DI box will loose between 3 to 6dB of signal. For many sound sources, this is OK. Also, passive DI use transformers. All transformers have a unique sound. If your church has an NC above 42dB, the sound of the DI will not be noticeable. If the church has an NC below 42dB, then everything counts.

Active DI boxes offer 0dB signal loss and since they don’t use transformers, they add far less coloration to the original sound. In order for a Direct Box to Boost a -20dB signal to +0dB, you need internal amplifiers like a mixer has. To the best of my knowledge, there are only a few Active DI boxes that have such abilities. Generally, they should be called Active DI with Preamps. Most of the common Active DI boxes do not have this ability.

These DI boxes with pre amps and gain controls built in require 24 volts or more to boost a signal. A full boost of signal can be achieved with a 48 volt phantom power supply as supplied in many pro quality mixers. Some of these DI’s can boost a signal to +20dB, but doing this without gain noise is remote. In a club with 55dB of background noise this probably isn’t a problem – in a church with 40dB of background noise and preamp noise will be a major issue.

The solution for the guitar player is to use a guitar foot pedal pre amp that can also add Bass, mid and treble tone controls – then go into a DI box. The signal will be boosted before going into the DI box – as it should.

For other low level signal, you can use a Guitar pre amp or- you can use a unit like the Symetrix 202. It is a two channel pre amp with phantom power. It can be used as a mixer by itself or to boost a low level signal. It can handle almost any kind of input and convert it to 600 ohm balanced load. You don’t need a DI box with this unit. it has a ground switch, a pad, a gain control and phase switch. Because it has two channels, you can mix two sounds, like a mic and guitar before sending it to the main mixer, or mix 2 acoustic guitars. The option is yours.

What prompted this writing is the fact that well known audio experts are either telling people that any active DI box can boost a signal, or they are accepting this info as fact. Yes, there are some active DI boxes that have a built in line amplifier to increase the signal which makes these unit more than a pure active DI and if you read the product label, it will tell you if there is a line amp included.

In summary, a DI box should always be used as your first choice when connecting an electronic instrument to a sound system where you are using mic cables over 50 feet to the mixer. Use the in line transformers sparingly, especially if your don’t know the output voltage. And yes, with practice, in 30 minutes you can connect up to 24 mic inputs with two people and finish a sound check. Check DI 1, DI 2, DI 3……

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DI Box FAQ

Question from those who search the web.

Can you use a DI box with a mic? Jan 2012

The short answer is – NO.

The long answer is – DI boxes are not pre amps or mic signal amplifiers. They are passive devices. Even an Active DI box is passive. All it does is give you better control of the input sign to prevent clipping of a hot signal. Di Boxes convert one type of signal to another. That said, there are a few expensive boxes that are suppose to work both as a DI box and as a preamp for line level signal. They can not be used to manage mic level signal whether balanced or unbalanced. DI boxes are 1/4 inch inputs and XLR and 1/4 inch outputs. When they say preamp/DI box, what they are saying is that they can change the bass, treble, mids and add sound effects to the hot signal and then send it to the mixer at mic level or line level for a Guitar amp.

If you are looking to boost a mic signal, you need a pre-amp and they are many phantom powered, battery powered, USB powered and DC/AC wall wart powered pre-amps.

Can you connect from a Mixer to an Amp Directly?

The Short Answer is – Yes

The Long Answer is – Amp inputs are line level. HIFI/Consumer products connect at -10dB. Pro products are setup for +4dB. The key here is to have the proper type of cable connections. It is best to run from XLR to XLR or TRS to TRS or TS to TS. If you have to go from XLR or TRS to TS, and you are having any hum issues then a DI box will help you out and correct the grounding issues.

What is the best way to connect from a computer or Laptop or Ipod/Iphone/Ipad to a mixer for music playback?

The proper way to take a headset signal output to a single mixer input is to connect with two Line Match Transformers. You need a transformer for both the Left and Right channel. Why? One of the sacred rules in audio is that you can split or “Y” an output signal to two devices but never combine or “Y” an input signal to the input of a mixer. In many churches there are Cassette players, MP3 players, CD players and other playback devices that have only one channel working. When you “Y” an output to a single connection, you are creating an improper load and that often leads to a Left or Right channel being burned out over time. There are summing boxes that you can use but they can be expensive. Better yet, if you have two free input channels or you have stereo input channel use them. If you only have 1 channel, the line match transformers will protect the mix and the playback device.

A good article to read is from Rane https://www.rane.com/note109.html

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Kingston Road United Church

Posted by jdbsound on May 25, 2012


Kingston Road United Church.

Location: Kingston Road, Toronto, Ontario Canada

Consulting Date March 2008
Completion Date by Church members – October 2008
Sound System installed by Westbury Sound – December 2008

  1. Seating capacity 500+
  2. Ceiling over 40 ft high
  3. Over 120 Cardboard Tubes custom made order and placed around the room in 8″ 12″ and 16″ half rounds.
  4. Between 120 to 800 hertz removed 18 to 22dB of excess energy.
  5. This change allowed a single speaker system to cover a whole room 134 ft long.
  6. Throw distances from speakers to back wall, 98 ft.
  7. Contractor who installed the system was surprised at how well this sound system worked and how much the room changed.
  8. Contractor suggested delayed speakers before the acoustical treatment was done.

If you wish to see additional photos of this project, visit my Flickr Photo Library.   Use this link to see them.   https://www.flickr.com/photos/jdbsound/sets/72157607243842820/

 

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Natural Acoustical Amplifiers

Posted by jdbsound on May 22, 2012


Walls are amplifiers of sound.
Outdoors – when you double the energy with amplifiers or speakers the sound levels increases 3dB.
Indoors – when you double the energy with amplifiers or speakers the sound level of certain frequencies can increase up to 9dB or cancel the sound 100%.

Example Below:

Armeanian Pentecotal Church Montreal

Before acoustical treatment, there would be 1dB loss at 10 ft and 2dB loss at 40 ft. without the sound system.

After acoustical treatment, there is 4dB loss at 10ft and 8dB loss at 40 ft. without the sound system.  Also, intelligibility changed from 79% at 40 ft to 92% after acoustical changes.  When you add the sound system the coverage with +/-3dB

This was in the middle of the acoustical transformation

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Microphones can be a health hazardous

Posted by jdbsound on May 21, 2012


If you have a chance, you should read my article about sharing tooth brushes.  I compare the sharing of microphones like sharing tooth brushes.  In the fall when it is Flue season, many performer pass on their cold to other performers by just simply sharing their microphones.  We don’t clean our microphones and the microphones are not made to be cleaned either.  Read the rest here.  Update includes suggestions for dealing Covid-19

Updated March 2020   microphones-are-hazardous-to-your-health

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