Church Acoustics

Solving Sound System problems only Acoustics can fix.

  • Sponsored by

    Ph # 519-582-4443
    email: jdb@jdbsound.com


    Successfully turning the most complicated, hostile and hardest acoustical spaces into the best sounding worship spaces in the world one church at a time.

  • Archives

  • Contact information of JdB Sound Acoustics qr code

    link to jdbsound.com

Posts Tagged ‘Sound’

What will give you the biggest bang for the buck in upgrading the Sound of your church?

Posted by jdbsound on May 2, 2018

This 300 seat church already had a reasonable high-quality sound system.  It was properly designed for the room and professionally installed. The acoustics were not that bad.  At least it was thought that the acoustics were not such a problem.  The outstanding issues they were trying to solve or improve were:

  1. Gain before feedback,
  2. Elimination of the few deadspots that were not solved from the previous sound system when the current new JBL speakers were installed
  3. Reduce sound spill from floor monitors,
  4. Better control of the drums (when using acoustic drums) and
  5. They wanted 3dB more bass from the Sub-woofer.

These are all reasonable reasons to upgrade the sound system.

Good Speaker System setup_s

The church was considered the following upgrades.

  1. Replacing the professionally designed and installed 12-year-old JBL sound system.
  2. They considered going for IEM (in-ear monitor) system for up to 8 people. (This would have included a new digital mixer)
  3. The church considered making an air-conditioned drum booth or get an electronic drum kit.
  4. They also wanted to add a second twin 15-inch sub-woofer.
  5. Estimated total cost, almost $26,000.00 installed.

This is what the church actually did. They changed the acoustics of the room.  They installed an acoustical Tube Radiator system.

What did they gain by doing this?

  1. The sonic quality of the existing JBL speaker system was greatly improved. The improvement was noticeable better regardless of how much equalization was added or when the EQ was bypassed. (Definite proof that the acoustics of the room changed the performance of the speaker system from the day they were installed.)
  2. All of the remaining deadspots were now gone. (This was never a speaker system problem as the right speaker system design was already installed.)
  3. The performance of the speaker system was such that picking up a person’s voice went from 12 inches to 35 inches with a Shure SM58 mic before feedback would show up. (Again, acoustics limits the performance of all sound system. Sure there are some very expensive gadgets that can improve gain before feedback, but such gadget can cost more than the material cost of the acoustical fix.)
  4. The floor monitors are now well behaved. No matter how loud the floor monitors get, you definitely need to and to add the front of house to hear clear sound. As it turns out, the overall stage mix dropped around 10dB without the performers even noticing as they were now able to hear the stage mix from the monitors so well at a lower volume. You could say that the monitor spill issue is eliminated.
  5. This eliminated the need for IEM’s.
  6. Since the drummer can hear himself now, he gradually started playing quieter after a few weeks. The need for a drum cage disappeared.
  7. The Single Sub-Woofer was now able to play 9dB louder without distortion. It would have taken 3 more sub-woofers to get the same loudness without distortion. That was equal to spending around $15,000.00. (Standing waves and bass buildup in the corners added air pressure onto the surface of the cones of the subs drivers. This added air pressure creates distortion. When the subs distort, the sound quality and maximum sound levels of what the sub is supposed to be able to do, can drop up to 15dB in many rooms.)

Aylmer EMC Church Pano 2017_ss

Other improvements

Congregation Singing.

  1. The participation of people singing went up from 30% to 75%. (When people can hear themselves and the other people around them, it encourages people to sing more.)  s a resulting, the congregation is singing 8 to 15dB louder. (The more people singing, the louder they will become.)
  2. No more distortion from the speaker system with playing louder which means the perception of loudness is greatly reduced. (Standing waves and bass buildup in the corners added air pressure onto the surface of the cones of the bass driver of full range speakers. This added air pressure creates distortion. When the bass drivers distort, the sound quality and maximum sound levels of what the full range speaker is supposed to be able to do, can drop up to 15dB in many rooms.)
  3. After two years, the congregation is starting to add harmonies to their singing. (That is what happens when people can hear each other.)
  4. Now when people stand up to give testimonies or prayer requests, people can hear them whenever they forget to use hand-held wireless audience microphone.
  5. The front of house stage mix is so much better. Now you can hear all of the performers without having to blast the sound system. (A well-diffused room can make the signal to noise ratio improve from 3dB to 25dB. As the signal to noise improves, the easier it is to settle into a high quality.)
  6. The worship space is now concert quality for any high SPL event, recitals, choirs or orchestral events.

The total cost of the acoustical system including painting the whole sanctuary. $1,400.00
Since this as a DIY project, the money saved went towards a better headset mic for the pastor and the new digital mixer. Total upgrade, $5,000.00. If the church contract out the installation of the Sono Tubes, add $5,200.00. That is still 60% of the cost of upgrading a perfectly good sound system if everything is contracted out or an 83% difference.

Conclusion

One can honestly say that fixing the acoustics had a far better return on investment versus just upgrading the speaker system alone. Upgrading the speaker system can never make the room sound better, improve congregational singing and it would have not been possible to delete the deadspots without adding more speakers on delays around the room. This transformation is typical of the new worship experience when a church gets the acoustics they are supposed to have. In the battle between acoustics vs sound systems, acoustics always wins. It’s Physics. Try moving a wall with air? You can’t. Change the wall and hear what happens!

 

Posted in Church Acoustics, Church Sound Systems, Photos of Church Projects | Tagged: , , , , , , , , , , , , , , , , , , , | Leave a Comment »

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

Posted in Church Acoustics | Tagged: , , , , , , , , , , , , , , , , , , , , | Leave a Comment »

Before and After results of a Real Multipurpose Hall

Posted by jdbsound on December 4, 2017

This is a before and after test results of a multipurpose room.  The room is a converter steel factory.  The purpose of the room is for multi use including banquets, acoustical and amplified musical performances, teaching and general meetings.  While the room has a fixed sound system, the  room performs equally well regardless of the orientation of the seating or event layout.

sandbox B-A results

From the graph, it shows the before and after.  Before the room had an average of 2.1 seconds of reverberation.  That said, at around 400 Hertz, the reverb time was 2.85 seconds. This made the room unacceptable for all uses.  It was hard to have a simple conversation with someone only 5 feet away.

The acoustical treatment in this case require 3 different acoustical system.  Tube Radiators were used for controlling sound from 200 to 2000 Hertz.  The tube radiators have only a profile depth of 4 and 6 inches and the idea that something so small can control sound down to 200 Hertz is amazing.  The tube radiators only covers 12% of the total wall space of the room.  

The second system was outround diffuser panels.  They covered another 10% of the available wall space.  These panels were used to manage sound from 100 to 500 Hertz.  By combining these two system with the limited wall space, we were able to cut the reverb time at 400 and 800 Hertz 1.8 seconds.  That is a massive amount considering that 400 Hertz is a wave length of about 33 inches long and 800 Hz is about 17 inches.

The third acoustical was a fiber absorber.  The fiber absorber covered 40% of the ceiling and 10% of the side walls.  The fiber panels covered the outrounds on the side walls.  It is rare to need absorption in such projects but when you have a concrete floor with no carpet, you have to replace the carpet with something similar.  Here is the thing about carpet.  Carpet, which is always within 4 to 7 feet of our ears works very efficiently.  The shallow angle of most sounds we hear in a large room event gives a 1/2 inch of carpet the acoustical performance of 2 inches of a typical wall panel absorber.  Since one of the requirements of this room is to include music that can reach 100dB, it was planned to have a reverb time of 1 second, +/- .2 tenths of a second.  That goal was met and the range it was met is typical of our acoustical fixes.  If you look at the before and after, the room now meets that goal from 150Hz to 4,000Hz.  Before, using the same criteria, the room had a average reverb time of 1.8 second with a +/- of 1.1 second variance.

percent alcons 4 sandbox

The critical question is, how does the room sound for speech, talking and for music.  For speech, the change was from 14% Alcon’s (rated as poor) to 4% Alcon’s.  At 4%, it means that you can talk to someone from end to end of the 55 ft long room with a slightly raise voice.  When you add a properly equalized sound system, you can better the speech intelligibility to 3.5%.  For talking across a table during banquet or social events is easy in this space.  You can talk to someone 15 ft away while the person next to you is talking to someone across the table without having to raise your voice to compete with other conversations.

As for music, so far, for the high energy high SPL events the room has been well received by musician and audience members.  That has meant fewer events with drum shields, fewer events with IEM (in ear monitors) and very little floor monitor spill that degrades the sound for the audience.

At the other end there have been a few recital type performances where the even was all acoustical.  One person who was a graduate of a royal conservatory of music remarked that the room was similar to recital rooms at a well known royal conservatory school in Toronto, Canada.  One violinist said that while she would have liked a longer reverb time, the quality of the sound of her expensive instrument was amazing.  The last time she heard her violin sound so great was at a high end recording studio that was  acoustical treated.  She was also stunned that it didn’t matter where in the room she performed, the violin sounded great.

There is one down side to the new room.  Since there is no carpet, when the room is empty, you do notice the reflection off the floor. This does make the room a little challenging for those who do rehearsals when the room empty and before any table and chairs are set up.  Once tables and chairs are setup, the room behaves well.

In the real world, there are a lot of rooms that are used as multi purposed spaces but perform poorly.  Most facility owners don’t worry about acoustics because they may have the only place in town that can accommodate such events.  That said, if they were to get 10 to 20% more bookings per year, they would recover the cost of investing in an acoustical fix in less than a year.  Furthermore, it would allow the facility owner to charge a hire fee if the place gets too busy.  There is no down side to having an acoustically friendly community center, convention hall, rental hall or banquet facility.

 

Posted in Non Church Projects | Tagged: , , , , , , , , , , , , , , , , | Comments Off on Before and After results of a Real Multipurpose Hall

Where are the Carboard Tubes

Posted by jdbsound on August 28, 2017

Churches use a lot of Cardboard Tubes in acoustical room fixes because they are very effective in getting the room performance they want and need.  Cardboard Tube not only outperform all other acoustical products in churches but they are also the most affordable.  There is nothing that can do what half round tubes can do, even at 40 times the cost.

Ok then, what if you don’t like the look of cardboard tubes around your worship space.  Here is an option some churches have been willing to spend a little extra for.

image10

These look like standard 5 inch deep absorbing panels.  They are not.  These are Sono Tubes mounted in a wooden frame and covered with cloth.

image9

The cloth was an added expense and it was worth it.  The fire rated cloth is expensive and before covering the panels, you want to make sure the acoustical system is going to work and work it did.  The church is very happy with the results and they are enjoying the room.

image8

This is what the installation looked like before it was covered.  The wooden frame has no effect on the performance of the half round tubes.  The cloth only affects frequencies above 10,000 Hertz which means they have no effect on speech or music.  In this installation three sizes of tubes were used.

image7

At the bottom is a huge video wall screen.  On the wall are the Sono Tubes.  Yes, the tubes will work behind a vinyl screen.  If you notice the pattern of the diffusers on the wall. that pattern was needed to control lower mids and bass sound energy.  This pattern was pretested in our test room.

northside church video wall

Here is the finished installation of the video system.  It takes three projectors for each screen.  The centre screen is a video wall.

Photos courtesy of Frederic Lachance of Northside Church in Coquitlam BC, 2017.

Posted in Church Acoustics, Photos of Church Projects | Tagged: , , , , , , , , , , , , , , , , , , , , , | Comments Off on Where are the Carboard Tubes

Church Ceiling Height Chart

Posted by jdbsound on May 26, 2017

Churches these days are building lower and lower building.  I guess when so many churches have experienced only poor quality acoustics, many wonder what is the point of building a taller worship space.  As it turns out, existing worship space acoustics is doing fine and a lot of churches are are getting their acoustics fixed, sounding better today than they ever did before.

When a church builds a low ceiling, it limits congregational singing and it makes you more dependant on technology, but guess what!  The same things that limits congregational singing is what also limits the performance of all sound systems.  So, instead of getting 100% out of your high quality over priced expensive sound system, your getting only 40 to 60% of the sound systems true performance abilities.  It is actually cheaper to build higher than the added cost of audio technology to make up the difference.   The chart below should clear the air as to the minimum height your next church should be.  Also, a taller worship space does not mean being stuck with longer reverb times. A higher ceiling means natural room reverberation is adjustable and tuneable.  With a taller ceiling you can change the frequency response of the whole room without needing a sound system or equalizer.

Minimum Church Ceiling height Chart.JPG

Church height is important for a worship space.  One of the biggest parts of worship is singing.  Congregational singing to be specific.  When singing as a group, several elements are required for a good and healthy worship experience.  There is chorusing, harmony, sound volume or loudness of the singing and being able to hear yourself as well as the people around you.  When all of these elements are in balance, the worship experience is like no other.  The majority of people get a lot of satisfaction from the singing experience during worshiping in rooms that have ceiling heights that matches the size of the seating capacity of the worship space. The above chart are minimum heights.  If you want to build higher, you can as the singing experience gets even better but the improvement is more subtle.
High ceilings allow better and less expensive sound systems to be used.  Higher ceiling permit better gain before feedback and it becomes easier to isolate drums and floor monitor. The performance of the sound system is much better too when that is coupled with a good quality acoustical management system.
There are economic advantages too.  The higher the ceiling, the cheaper it is to heat and cool when using a vertical displacement HVAC type system which is specifically designed for large gathering spaces for people.  Such systems cost less to install, they use smaller HVAC components and cost about 30 to 40% less to operate.  In addition, the cooling systems last 2 to 3 times longer before needing to be replaced.
Another thing to consider. If building new, don’t build a flat ceiling that is parallel to the floor. (and it doesn’t count of you put in a sloping floor.)  Many churches that are moving into commercial buildings are learning the hard way that flat ceilings limit the quality of live musical performances and congregational singing.  Sure, there are acoustical panels that can slightly improve the room for amplified sound, but the cost doesn’t justify the returns.  There is little that can help congregational singing even if you have the height. Vertical standing waves are hard to manage than horizontal standing wave. If you know what you are doing, horizontal standing waves can be controlled to create an outstanding room.  It is part of the formula for the almost perfect worship space.  Funny though, most concert musicians that perform in a church that I have fixed, they often make comments like, “I wish our concert hall sounded and performed as well.”  That is almost like saying, “concert halls make for lousy worship space but worship spaces can perform better than a concert hall.”
*Note* In any country that has freedom of religion laws, the worship space portion of a church building has no roof heights limits regardless of local city building height restrictions. 

**Note** The data is based on 2800 churches from North America, Europe, Philippines and Central America. 

Posted in Church Acoustics | Tagged: , , , , , , , , , , , | Comments Off on Church Ceiling Height Chart

How to Know if your Church has Good Acoustics – Part 1

Posted by jdbsound on February 3, 2016

Here is the first test you can do to know if you have good acoustics.  Have two people over 40 years of age standing 40 feet apart in the sanctuary.  Have one person on stage and the other anywhere in the audience.  With the room empty, the sound system off, with the lights on and whatever mechanical system that are on during worship, have the two people start a conversation.  The person in the audience area has to be understood by the person on stage equally as well as the person on stage to be understood by the person in the seating area.  This is important as all churches are used to hear and communicate from both ends of the worship space.

If the two people can converse for 5 minutes understanding each other, chances are your church is in good shape.  If hearing and understanding at 40 feet is not good, then move in closer until you do.  When speech becomes clear, that is the free field distance of the room.

If you can converse at 40 feet well, try moving further apart.  Keep moving apart until it become hard to understand or your up against the walls of the church.  If your able to increase the distance for understanding speech, then as you get further apart, the better the room most likely is.  This is step one.

Posted in Church Acoustics, Church Sound Systems | Tagged: , , , , , , , , | Comments Off on How to Know if your Church has Good Acoustics – Part 1

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/

Posted in Church Acoustics, Church Sound Systems, Photos of Church Projects | Tagged: , , , , , , , , , , , , , , , , , | Comments Off on Windermere United Church, Toronto, Ontario, Canada

Quote of the Day

Posted by jdbsound on January 10, 2013

If experiencing poor sound in church could be measured as pain and people are not complaining about it, it could be because they don’t consider taking 10 extra strength pain killers per worship service as overdosing.

by Joseph De Buglio Jan 2013

Posted in Church Acoustics, Church Sound Systems | Tagged: , , , , , , , , , , , , , | Comments Off on Quote of the Day

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

________________________________________

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……

________________________________________

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 http://www.rane.com/note109.html

Posted in Church Sound Systems | Tagged: , , , , , , , , , , , | Comments Off on Direct Boxes…..

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/

 

Posted in Church Acoustics, Church Sound Systems, Past Projects discussions | Tagged: , , , , , , , , , , , , , , , , , , , , , , , , , , , | Comments Off on Kingston Road United Church

Analog Mixer

Posted by jdbsound on May 22, 2012

If your church is using an Analog mixer, what make is it and how well does it meet your needs?

Posted in Church Sound Systems | Tagged: , , , , , , , , | Comments Off on Analog Mixer

Digital Mixers

Posted by jdbsound on May 22, 2012

If your church has a Digital Mixer, what make are you using and how well has it been working in your church?

Posted in Church Sound Systems | Tagged: , , , , , , , , , | Comments Off on Digital Mixers