CHURCH SOUND ADVICE - IITB 05.22

 

Chapter 5.22

Church Sound Advice

Traditional vs; Contemporary – Stereo vs; Monophonic - Audio Boards – Mirroring – Wired & Wireless Microphones – Speakers – Cue Systems – Meters – Foldback – Feedback - Resonant Frequencies – Phasing – Headroom – Wind screens - Distortion – Noise Gates – Peak Controller’s - Spectrum Analyzers – Notch Filters – Best Operating Practices

 

 

Early Audio

     You have heard the term “Cutting a Record”; in my early studio days we had record recorders which the stylus actually cut into the vinyl the commercial that the disc jockey would later play on the air.  The shavings looked like hair or whiskers as they peeled off behind the stylus.  They were fun to stick in your nose to “break up” the DJ while he was live on the Air.

     The process was called the “Hill and Dale” method for monophonic recordings, with the stylus moving up and down; later when two sources of sound presented itself, it was called “Binaural Sound” which later became known as stereo.  In addition to the Hill and Dale method of cutting a disc, the stylus would now also move laterally left and right to produce the second channel of audio. So now the magnetic phono pickup cartridge had to accommodate the stylus moving up and down as well as left and right.

     After a few passes of a record being played, scratches would appear and create high frequency noise in the sound; so the industry created a “pre-emphasis amplifier” that would record the music or commercial with the highs extremely increased and when the record was then played back it went back through a special “phono pre-amp” that de-emphasized the highs back down to normal levels.  Now when the record got scratches, those high frequency scratches were pushed way down; de-emphasized greatly and were not so noticeable.  That’s why a record player has its own special “Phono Pre-amp”. Later the bare needle was replaced with a diamond tip to reduce wear and scratches and a spray was developed to spray on to clean and “in effect” lubricate the stylus movement.

     Conclusion: Amplitude Modulated Noise has always been a problem for the audio engineer.  With today’s technology moving into the Digital format, unwanted noise has not just been reduced, but eliminated in recordings.  During pauses in passages you do not hear tape hiss or high frequency scratches; you hear “the Sound of Silence”.

     As a fun note: in the early years, most Radio station owners had both an AM & FM station. The first stereo radio transmissions where accomplished by sending the left audio signal to an AM radio station and the right channel signal to an FM radio station.  Folks at home at the advertised hour would place both AM & FM receivers on a table and then tune in both stations to the different frequencies and would sit back in amazement at the different sounds.  The first one I heard was “The Theme from Picnic” which has two different, but complementing themes running throughout the selection & presented on the separate speakers.

     The recording medium “standard” in the 50’s became vinyl tape coated with iron oxide.  As an Audio Engineer for Educational Radio and TV, my job was to edit audio tapes, taking out coughs, words pronounced wrong and unwanted sounds from the outside. To do so, you had to physically CUT THE TAPE and remove the unwanted section and then you re-inserted Room Tone back in its place, so that the passages would sound natural.

     ROOM TONE was recorded for two minutes after the recording session ended.  Everybody in the studio set silent the entire time.  This recorded room tone was then re-inserted into the tape so that you would not notice any change in the background sound; sometime it meant inserting only 3/8 inch of tape, if it was not enough, you took it out and added another 1/4 inch or so to it.

     This tedious time consuming job was not everybody’s cup of tea; you must love audio to put up with what some would call foolishness.  I call it pride, doing your work as into the Lord. 

 

Colossians 3:23 – The Book – Do your work as unto the Lord
²³ whatsoever ye do, work heartily, as unto the Lord; not unto men;

Audio Boards

     In the early days the audio boards contained tubes with the power supplies remotely located in a rack to reduce hum and was fan cooled; everything was hard wired into the board.  Every microphone or device passed through a patch panel bay first.  The only thing that could be plugged in was a microphone in the studio.  The audio consoles were made by GE or RCA and could do only three things.  1) Turn the mic off and on  2) Put the mic in audition /cue mode to hear it on a cue speaker and lastly, 3) vary the gain sent to the audio board with a rotary POTENTIOMETER which for short was called a ‘POT’”, with only one main VU meter.  (To some today, a POT is something you smoke.) 

     Today’s Audio Board inputs are not hard wired, but have balanced audio connectors with the “XLR“ being the most popular, but also 1/4 inch TRS jacks (Tip, Ring, Sleeve) as well as unbalanced RCA inputs.   Some have the inputs on the top of the console instead of the back for ease of setup and teardown.  A two conductor input is said to be “unbalanced” and is usually high impedance; and a three conductor is said to be “balanced” and has a low impedance.  The “balanced input” reduced amplitude modulated interference problems such as 60 cycle hum.

     VU is Volume Units and is measured in DB’s or decibels.  A db was the amount a human ear could detect a change.   An increase of 3db doubled the sound that the ear distinguished and a decrease of 3db cut the sound in half as the ear could detect.

     The Standard Reference Level was said to be “0”db which provided an adequate feed to recording devices, amplifiers and transmitters.  Later this standard would move to +8db which was much better concerning pushing down noise on transmissions lines such as was provided by the telephone company that connected the studio to the transmitter site.

     Level Matching became the challenge for the audio engineer.  If your standard reference level is 0db and you have a recorder that has a +4db output and another one that has a +8db output and cart machines that have 0db output, you must PAD down every device above 0db before they get to the audio board, making all levels the same at the point of  input.

     Modern Audio Boards do not have rotatory POTS, they have individual strips with sliders or faders which do the same thing, but each slider/fader is now on its own input, and have supporting “Pots” that can PAN the amount of signal sent into left and right stereo channels.  For “SWEETENING” they also have Frequency Band Equalizers, Reverbs, Rumble Filters, Routing Program switches, Noise Gates, as well as input attenuator TRIM Pots or PADS to bring the levels into your operating standard.  There is also auxiliary “Pre-fade” pots that send a feed to the performers fold back speaker or in-ear monitor.  This is independent of the house mix.

     A mixer used for simple remotes might have 6 channels where a night club might have 24 channels and a concert some 96 channels; a church might have 16 inputs which would be fine for a traditional service, but it would be pushing it for a Contemporary Service with a Praise Team, multiple guitars, base guitar, drums, keyboard, piano and special effect instruments.  Some Churches have two separate services; Traditional and Contemporary and two different audio board operators. It’s just two different sounds.

     The audio engineer can set all the faders to the mid position and then adjust the input attenuator for 100 percent modulation on its INDIVIDUAL VU METER which is a modern enhancement.  

Now a HOT input signal does not force you to run the fader at the bottom of its range and a WEAK signal does not force the fader to the top of its range.

     NOTE: Early Pots or faders were made of carbon and the actual audio passed through them and over time, the Pots would become noisy as you raised and lowered the level.  Today the fader can control a light with a photo cell or control a transistor’s output and are operational NOISE FREE.

 

Noise Gates

     Noise Gates are a preset threshold that a signal must exceed in order for the gate to open and allow the signal to pass.  When it is closed, you hear nothing.  The term “Noise” applies to any signal that is below the signal threshold.  Gates eliminate the background noise from “on stage” amplification systems, when a vocalist is not singing or an instrument is not in use. Noise gates can be “chained” so that one gate can cause other gates to open if desired.

     This is not a noise rejection circuit; if noise is present when the threshold gate is opened, the noise will also pass.  The adjustments are Attack, Hold and Release (fade out).  Noise gates can “chatter” (open and close) which is caused by spurious undesirable sound fluctuations A “Hysteresis” circuit in the more expensive audio consoles greatly reduces this “chatter”.

 

Subgroup Routing

     Specific inputs can be mixed on a subgroup channel and then inserted into the main mix.  For instance, drums in an enclosure could have a number of microphones with individual faders that are grouped on just one fader for insertion into the final house mix.  Instead of adjusting many faders for the drums, you would just adjust just one; same for the vocals.

 

Meters

     VU meters (with needles) indicate the levels for each channel; Peak Meters are often LED’s on each channel that light up different colors so that at a glance you can tell if the signal is too HOT and is clipping the audio.  Some systems use GREEN to indicate signal presence and YELLOW for a signal approaching clipping and RED to indicate clipping/distortion.

 

Cue Systems

     Early audio boards cue system was selected by rotating the pot all the way down until it clicked into the cue position which then could be heard on the control room cue speaker.  When the DJ opened the Control room mic, it would trip an “ON THE AIR” light outside the door and cut the cue speaker and send the cue signal to his headphones.  He could then cue up records as he talked live on the air.  When he opened a studio mic; the fold back speaker would be silenced in the studio and a “Quiet” or “On the Air” sign would light outside the studio doors.

     It was not unusual to see the audio board raised up about 5 inches to accommodate mercury switches below each pot that would turn on the appropriate TURN TABLES.  However, the most common method was to back cue the record 1/4 turn and then hold the “Platter” and let it “Slip” on the turntable felt until you were ready and then you just released it.

     Today’s cue system utilizes a PFL “Pre-Feed Listen” pot also known as a “Solo” pot or just simply “Cue”.  There is also a SIP “Solo in Place” button which literally mutes all other inputs so that you can only hear that specific audio input and troubleshoot it; CAUTION this function would be a disaster if depressed during a live performance.

     Talk-Back systems utilize a microphone at the audio console for the sound engineer to communicate with an announcer in a announce booth or a performer on stage which may be some distance away.  Talk-Back might utilize speaker monitors, or heard silently in headphones or an earpiece.  This can be observed on TV newscasts where the anchors wear an earpiece with a stretchable coil of wire located just behind their neck.

TEST TONE oscillators are on some audio consoles that are used for troubleshooting and testing channels during set up.  Many audio engineers prefer “Unity Gain” between pieces of electronic equipment; meaning the same level coming in is the same lever coming out.

 

Mirroring

     When mixing sound for a “Live” performance in an auditorium and also mixing sound for broadcast, some consoles can Mirror each other, making both consoles exact duplicates of each other.  The one for broadcast or recording can then be re-mixed as needed.

     In the event of hardware failure TV networks will have Mirror Audio Consoles so the listener never knows of a problem.  Many preamps have dual amplifiers, so that if one side fails the other continues and the audio only drops -3db which is only half the signal.  The audio engineer just raises the fader to increase the signal level back to normal.

 

Headroom

     Headroom simply stated is a term used for how much louder a signal can get above normal before distortion sets in.  For instance a 0db audio board may have 10db of head room which means that when a signal “over modulates” an amplifier, it can go as much as an additional 10db before distortion or clipping occurs.

     Wireless microphones have limited headroom because of the transmission “bandwidth” of the transmitter and receiver; so some hand held mics have selectable attenuators on the mic themselves.  Recording devices are also limited depending on the medium that it is being transferred to as well as Radio and Television Transmitters which have limited bandwidth.

     In the early days of Radio, broadcasting was on AM Amplitude Modulated frequencies and the owner of the station would want his station to sound louder than the other stations in the market.  The higher the signal pumped into the transmitter the more the Transmitter stayed at maximum power.  The results were the DJ would always have the audio pumping in the RED;  blowing it through. 

     The FCC Federal Communications Commission didn’t agree with that and would issues costly citations to the station for “Over Modulation”.   A television station’s CONSTRUCTION PERMIT PAPER would be worth one million dollars before anything had ever been purchased.  Fragrant “Over Modulation” violations could result in the loss of the station’s license to broadcast; so over modulation was a BIG DEAL.

     This resulted in the invention of “Peak Controllers” that would limit or push down the loudest audio signals to prevent over modulation.  This just gave the AM  radio stations the license to SIN; so they increased the audio levels even more making the Peak Controller work even harder.  It would suck up the lowest levels and then compress down the highest levels causing “Pumping” or “Sucking” of the audio.

     To the audio fanatic, which I am; being raised as a child on classical music in the 40’s and 50’s, this was JUST AWFUL because it destroyed the “Dynamic Range”; this is the range between soft passages and loud passages, THEY ARE JUST LOST.  Today audio pumping as well as distortion is injected as special effects into the music.

     Since the introduction of FM radio, the frequency is Modulated, not the Amplitude Modulated.  Therefore there is no need to SLAM the audio,  because it gets no louder, the power stays the same.  Today Radio and Television stations use an ALC Automatic Level Control at the studio that gently raises or lowers the base platform of the average signal plus or minus 10db.  The low passages of an old western movie would be gently and slowly raised as it was needed to the standard level.  Then at the transmitter site a “Peak Controller” or limiter would attack the high levels spikes of audio.

     Many stations use a five band loudness controller and limiter before the program audio is sent by the microwave STL (Studio Transmitter Link) to the Transmitter site.  This separates the audio into five discreet bands and attacks them individually leaving the other frequencies unaffected. Sweet

 

Microphones

     Microphones come in a variety of configurations, but the most common is the Omni-directional which picks up 360 degrees around the mic and the others are directional.  Some you see at football games pointing backward into a parabolic dish with filters that only pass the mid frequency range of the human voice.  It rejects or greatly reduces all the other sounds that are picked up “off axis” to what the operator is pointing at.  That’s how you can hear the calls of the players. (Today law enforcement can bounce a laser beam off your window pane and hear what is being said in the room, via the vibrations on the glass pane.)

     Phantom Power is power that is supplied to a condenser or capacitor microphone.  The mic cable is plugged into the power supply first then to the audio console.  A DC voltage is sent via the audio cable to the microphone to power it and the audio returns on the same cable.  Caution: this must be a dedicated line to that specific microphone.

     The one that is most used in churches would be the microphone that produces a cardioid pattern in one direction.  This greatly reduces the sounds originating on each side of the mic; it is a must for the audio operator whether it be a vocal or a violin.  Note; every microphone MUST be in phase with each other.  (see phasing)

     Microphones are additive; every time you add another mic you are increasing the sound that other microphones are also picking up, only at a reduced level, but additive none the less.  So the goal of the audio engineer is to make each mic invisible or dead to the other mics.  This is done through placement or proximity.  A vocalist who holds the microphone near their mouth aids in making their mic invisible to the vocalist beside them.

     The caveat is that the vocalist needs to know how to “Work the Mic”.  Every singer has a frequency range in which they are effective, and anything higher or lower than their range, their volume level falls off.   So the mic is moved in closer at the end of their range and further away in the middle of it.  Just a movement of an inch or two WILL have a profound effect at the audio board.  When the vocalist BELTS IT OUT, the microphone should be “worked” a good distance away.  This is a SECOND NATURE ART that must be learned and felt that only time can teach.  The audio operator will either smile or cringe.

     A base vocalist uses lots of air to produce a low note and is sung very soft otherwise he will run out of air; the results is that he needs to almost swallow the mic.  They CUP their hand from mouth to their ear just to hear themselves.  They may also be seen moving the mic rapidly in and out close to his mouth creating a vibrato sound.  A guitarist will do the same thing as he shakes his guitar on certain notes.

 

Presence

    Frequency Range is dependent upon the vocalist as well as the type of instrument being played; a tuba has a lower range than that of a flute and obviously vocalist by their very own nature find themselves singing as a soprano, alto, tenor or base; their voice ranges are just different.

     Presence is a term that is used to indicate that something is displaying additional quality of sound.  The Loudness Control on your stereo system ENHANCES THE LOWS while playing at low volume levels.  It does not make the overall sound louder, it just makes the frequency response “Fuller”. When a microphone is used close to the performer’s mouth, the lower frequencies are enhanced; they have a better “Presence”.  Lower frequencies are vocalized softer and require more AIR to get the sound waves moving.

     Wind screens are used inside and outside in order to prevent the explosive sounds that occur when a burst of air emits from the vocalist on certain sounds, particularly the “P” sound.

Wireless Microphones

     Wireless Microphones in their infancy were a joke.  You would be listening to the Pastor using his wireless mic and out of nowhere you would hear “10-4 Rubber Ducky… I’ll catch you on the Flip Flop”.   A wireless mic might only have a 1/4 watt transmitter and a Public Service Vehicle or an Armature Radio operator might have a 35 watt transmitter which is no match for the wireless receiver.

     Today wireless mics have their own FM frequency spectrum with squelches, filters and dual receiving antennas.   Sometimes a pastor wanders out in front of the speakers causing “Feedback”.  Technology today allows pastors to wear an invisible tube that conducts the sound to the pickup coil behind his ear.  The extreme proximity of the mic to the mouth allows the audio operator to lower the gain on his mic making it almost invisible to the auditorium speakers.  This can be a big deal concerning FEED BACK when the pastor moves around the stage area or even into the isles.

     Wireless receivers come equipped with a squelch that kicks in and shuts off the audio if the signal is too weak; otherwise it would blow white NOISE at a high level into the sound board.  This is noticed as the user’s audio cuts in and out; or it could be DEMONS in the audio board; maybe.

     Antenna placement can be troublesome in some rooms.  It is best to extend the antenna to the middle of the room in the ceiling or even under the podium so that when the user moves, he is always moving toward the antenna, not further from it.  I had to mic an Actor coming onto shore in a boat and then running down a beach for some 400 feet, so I buried a 400 foot wire in the sand all the way to the antenna on my receiver.  As she talked to the camera in the boat she was always moving closer to the antenna and then she ran on top of the wire; I never lost her signal once.

     Distortion is often noticed with wireless mics.  Let’s talk technically for a minute; the quiescent point of a transistor allows the amplifier to amplify the audio signal positive and negative equally at the same level.  When the batteries get low in the mic transmitter, the lower voltage causes the quiescent point to move downward, now the Positive swings are just fine, but the negative swings are clipped, squared off and we hear it as distortion.  It’s not the mic, it’s the batteries and it’s the audio operators fault.  You must be aware of the time on the batteries and when it’s time to change them. When in doubt start fresh.   It’s not the batteries fault; it’s your fault.

 

Phasing

     Phasing is very important in microphones as well as in speakers.  If one microphone is wired differently that the others, it would be said to be 180 degrees “Out of Phase” and therefore would “Cancel Out” the same sounds that the other microphones picked up. It is referred to as “Frequency Discrimination”.  This also occurs with MULTIPLE SPEAKERS.

     SPEAKERS A sound engineer would walk across the back of an auditorium and listen to the speakers; if the sound diminished or produced what is called “Dead Spots” on his walk, he knew he had a speaker or two that were “out of phase” and needed to be re-wired.  Speakers are color coded at the factory for “Plus & Minus” or Positive & Negative”.  There is actually no polarity in an “AC” circuit, but it just denotes the polarity for speaker phasing.

     NOTE: If the polarity of a speaker is not marked, you can take a 1 ½ volt battery with two clip leads and place on the two terminals of the speaker.  If the speaker pushes outward the terminal with the positive lead on it would be positive, if not, reverse the wires to get the outward movement for positive and then mark it.

     MICROPHONES A sound engineer doing microphone checks before a live concert would set all the mic’s at their mid-level on the sound board, then place his favorite microphone on a stand and began to speak into it.  As he spoke, he would bring in a second microphone alongside of it and speak into both of them, his assistant in the back of the auditorium would give a thumbs up if the sound “Increased” and a thumb down if the sound “Decreased”.   If the sound decreased, it would mean that the second microphone was wired backward; it was “Out of Phase” and needed to be rewired or a “Phasor” that reverses the wires be placed into the line to get it back “In Phase”.  This process would continue until all the Microphones were deemed “In Phase”.   In a 3 pin XLR connector, pin 1 is ALWAYS ground, pin 2 is red and pin 3 is black.  Pin 2 and Pin 3 may vary depending on the manufacturer.  Just make sure they are all wired the same. - (In the resistance color code, Red is always 2.)

     In the 50’s I worked as a sound engineer for Educational Radio and TV.   When running audio for baseball games, the crowd sounds were so loud that we could barely hear the announcer sitting in the announce booth speaking into a DESK mic. 

     My first attempt to correct the problem, was to put a smaller lavalier microphone on a coat hanger around his neck sticking up about an inch from his mouth.  Changing the proximity of the microphone allowed me to turn his volume down which essentially turned down the volume on the crowd noise.  My second attempt was to place a second microphone on the same coat hanger facing the opposite direction toward the crowd.  It was wired “Out of Phase” then reintroduced or mixed back into the sound board with just enough audio to “phase out” the “Crowd Noise”. Today we see announcers with headsets with microphones that almost touch their lips that have integrated voice canceling phasing technology built in.

     Far out FUN note: in the early days of stereo RECORDS; two microphones were set up to present separate left and right instrumental channels and the vocalist would be placed equally on both the left and right channel.  With that said, an audio engineer could take the phono preamp on the record player and reverse the wiring on the second channel, which when re-introduced into the sound board, would “Phase out” the vocalist; GONE, leaving only the music be heard.

     Conclusion; the reason you have a boat moving with two paddles synchronized “in phase” is so that you don’t wind up going in circles.  PHASING IS A BIG DEAL   

 

Speakers

     Just a word about speakers, we have already talked about phasing, so next to discuss is their power and impedance rating.  Speakers should have an impedance rating that matches the amplifier’s output impedance and have a power rating that matches or exceeds the amplifier’s power rating for each channel.  Often there is a desire to build your own speaker system and money becomes a big part of the decision on what you purchase.

     Example; You have a 100 watt stereo amplifier with 8 ohm outputs; that’s 50 watts of power for each channel, so each speaker must be able to handle 50 watts of power at 8 ohms to obtain maximum transfer of power without frequency discrimination.  You have found an awesome deal on some 8 ohm speakers with a FULL RANGE of 20 to 20,000 cycle’s frequency response, but they are only 12 watts each.

     So you figure you can connect four of these speakers for EACH channel; 12 watts times 4 speakers would handle 48 watts; a pretty good match for 50 watts per channel.  But the problem comes in, how do you wire the speakers, Parallel or Series?

     If you wire all 4 in parallel; the power is additive; you have 48w, but the impedance reduces; 8 ohms divided by 4 speakers, (8/4=2), the load would be just 2 ohms which would burn up the 8 ohm amplifier at maximum power.

     If you wire all 4 in series; the power is additive; you still have 48w. BUT the impedance adds (8+8+8+8=32) you would get 32 ohms and it would work, but you would not get the maximum transfer of power, plus you would get frequency discrimination. 

     Solution; Wire TWO SETS of two speakers in parallel (8 ohms divided by 2 speakers) that would give you a 4 ohm load for each set of two speakers.   Then wire the TWO SETS of parallel speakers in SERIES (4+4= 8 ohms) and now you get an 8 ohm load for each channel.  You now have a total of 8 speakers for both channels that can handle 96 watts of power.

     Constant voltage speaker systems are utilized when there are a number of speakers in a distribution system that are needed to send sound to church nurseries, overflow areas and hallways.

     There are 25, 50, 70 and 100 volt system.  I prefer the 70 volt system.  Each speaker has a 70 volt transformer with TAPS that can select the wattage the speaker uses.  The higher input voltage helps with signal loss on long runs as well as matches the impedance of the loaded speakers to the output of the amplifier for maximum signal transfer and optimum frequency response.  Since all lines are connected in parallel, the installation is made quite simple.  If an amplifier does not have a 70 volt output, an external step-up transformer can be purchased and connected to the 8 ohm output of an auxiliary amplifier.  You might be surprised, but typically a hallway speaker only uses ½ watt of power each.

     A 50 watt amplifier can handle 100 speakers connected at ½ watt each, or 50 speakers at 1 watt each, or 2 speakers at 10 watts each (20), plus 5 at 2 watts each (10), plus 15 at 1 watt each (15) and 10 at ½ watt each (5).   20 + 10 + 15 + 5 = 50 watts.   GET IT; its mix and match.

 

Speaker Placement

     Stereo or Mono speakers for a church sanctuary?  Depends on who you ask, there are argument on both sides of the fence.  The question becomes what is desired and what is required.  Mono cost less and gives a naturally better intelligibility system.  Stereo cost more, but most think it gives a better experience in the worship service.  But the wider the sanctuary, that experience is lost unless you duplicate the stereo speaker on each side and that introduces phasing problems throughout.

     Low Frequencies are not directional so they radiate out all sides of a speaker, therefore smaller churches have one MONO base speaker mounted in front, high and centered on staged area with the main Left and Right stereo speakers located angled down to the opposite corners of the auditorium.

     Half space loading occurs when a speaker is close to or touches a hard surface causing it to boost the low frequency energy.  Placing a speaker against the wall, the low frequencies are increased 6db and when placed in a corner it can be as much as 12db gain; so these two placements should be avoided for the flattest frequency response in the room.

     Sound originating at the speaker and arriving at the listener can be reduced or even cancelled out because of signals bouncing off the walls and arriving out of phase at the listener’s ear; likewise the signals can also be reinforced making specific sounds louder.

     Ideally the speakers are focused on the congregation avoiding the walls; a laser can be placed on the center top of a speaker to adjust the angle just as it hits the back row.

     In large auditoriums, more rows of speakers may be required and since sound travels faster in wires than in the air, the extra rows of speaker will need a delay system to make sure the listener hears the sound from the main and secondary speakers in phase, otherwise it can dampen the intelligibility of the sound. Some sound board mixers have a sub-group output delay just for this purpose; if not, a separate “add-on” processor can be purchased.

     Where balconies or extra rooms with a low ceiling exist, additional speakers must be added above and below these areas to prevent dead spaces and complaints.  Most will also need to be phased, delayed as well as have their own independent amplifier feed, so that the level can be adjusted.

 

Sound with a Twist

     Donald Leslie invented a device that would twist and flange “the sound of music”.  He sold the rights to CBS who then sold it to the Hammond Organ Company.

     The Hammond organ’s “Rotating Leslie” was a high frequency horn and a base speaker that rotated in a full circle, controlled with a motor at two different speeds to produce a vibrato much like a singer does when they sustain a note for a period of time.  This technique, if not overdone by the vocalist, is just more pleasant to listen to.

     The rotation made the sound waves twist and arrive at the ear going in and out of phase much like a vibrato, also mimicking the sound of a pipe organ.  The slow speed was known as choral and the fast speed tremolo.  The Rotating Leslie could be purchased separately as an “add on”.  Today there are electronic versions on the market that do the same thing.

     It’s also fun to know that the Allen Organ Company was the first ELECTRIC ORGAN Company to introduce an “air escape” sound when you pressed a key that mimicked the momentary sound that is first produced on an actual pipe organ as the large tubes filled with air.  The Allen electric organ sounded like a real pipe organ.

     In the early days of tape recording, on a Reel to Reel tape recorder, there was a distance of about an inch between the record head and the playback head.  During a live recording, the audio engineer could give a delayed echo to the original sound by injecting the sound picked up by the playback head into the audio board.  Running the tape deck at a speed of 7 1/2 inches per second gave a slow reverb and running it at 15 inches per second would give a faster reverb. Today electronic reverbs are used not only on vocals, but instruments such as guitars.

 

Impedance

     Impedance is resistance to the flow of electrons.  For something to have maximum signal transfer of power, the impedance is said to be “matched”.  For instance, if an audio amplifier has a speaker output of 8 ohms impedance then it is looking for a speaker that also has an 8 ohm impedance, this allow for the maximum transfer of power to be obtained as well as prevent frequency discrimination. 

     Mismatch: At maximum power; loading a 4 ohm speaker on an amplifier with an 8 ohm output could burn up the amplifier.  It is said to be “Loaded Down”.  However on the other hand, putting an 8 ohm speaker on an amplifier with a 4 ohm output works just fine, it said to be “Bridging” because the load of the impedance or resistance is higher than the amplifier.   In all cases the Load must be matched or be higher than the audio source.

     Audio lines come basically in two configurations, the first is composed of ONE WIRE inside a flexible shield said to be “high impedance” and used in economically low level devices such as microphones; the second is TWO WIRES that are also shielded and said to be low impedance and used with low level devices such as microphones as well as all high level devices.

     Belden Cable was the first to introduce audio cables that had aluminum “Z” foil folded around the wires which further reduced unwanted induced signals.  Multi Audio cable could be purchased with eight color coded audio lines in once cable.  The sound engineer would then make a 50-100 foot SNAKE with a box of EIGHT connectors on one end and EIGHT XLR plugs on the other.

     Loss & Noise; normally we have no concern for loss or noise until the audio lines start exceeding 100 feet in length.  Audio is Amplitude Modulated and so is noise as well as the common 60 cycle hum that is produced by electrical devices.  The longer the cable run the more loss of audio you have and the more chance of Hum, “Snap, Crackle and Pop” due to electrical devices being turned off and on and radiating into the cables.  Sometimes pre-amps are used to raise the audio source levels BEFORE it travels down the cables.     

     This not only gives a hotter signal, but it pushes any external noise generated down to where it is not noticed.  It also allows the microphone lines to be split so as to provide a feed to the live auditorium board as well as a separate feed to recording devices which in the best sense, should have a separate audio board for separate controlled results. Recording devices and Live speaker presentations are just two different ducks.  The larger churches will have two audio sound consoles.

     Have you ever noticed a POP when a projection screen is lowered or raised?  The switch radiates electrical energy when it “makes” and “breaks”.  It needs a non-polarized capacitor across the “End of Travel” limit switches to absorb the arc.

 

Foldback

     Foldback is a term used for sound which is currently being processed by the audio board and is sending it back into the studio or the stage area.  It is used as monitors on the stage for the performers, so they can hear themselves singing or playing their instruments.  The foldback speaker mix is different from the House speaker mix and can give the audio operator headaches as it also becomes part of the overall sound level in the auditorium or sanctuary.  The sound engineer’s job is to make sure the performers are HAPPY; so set them up first before optimizing the main mix.  Don’t be surprised that they want more “feed” once the room is running at its optimum level.

Caveat; this can contribute to FEEDBACK.

     Many performers have their own Foldback systems and are a MUST for their individual performance.  Just LOVE THEM and make sure they are happy before you start your house mix, because their foldback sound levels are additive to what is heard in the auditorium. 

     Caveat; an instrumentalist may hear their music just fine and NOT be heard at all in the overall mix.  It is the Audio operator’s responsibility to WORK THE BOARD and bring them forward, it’s not SET AND FORGET.

 

Feedback

     Audio Frequencies all travel at the same speed at the same temperature.  When traveling through Air at 68 degrees, they travel at 1,125 feet per second, but the wavelength of the frequencies vary. The length of a 1,000 cycle note is approximately 13 inches.  The “A” string on an instrument is 440 cycles/Hertz and the wave length is approximately 2 1/2 feet; 100 Hz is 11.25 feet and 50 Hz is a whopping 22 1/2 feet.

      The reason this matters is because the surfaces or materials the frequencies encounter either reflect or absorb the sound. Many churches have the seats padded so that they will all reflect or absorb the same whether they are “occupied” or not.

     Example: The 100 Hz bounces off a wall traveling right back along the same path bouncing off the other wall. A 100 Hz note will become excited if it encounters something else that is 11.25 feet or a multiple of that, reinforcing or adding to the sound.  Notch filters can help greatly with this… (See Resonant Frequencies)

     Automatic Feedback Suppression is accomplished by “Frequency Shifting”, “Adaptive Filtering”, “Automatic Notch Filtering” and “Delay”.  Most devices are invasive and noticeably COLOR the sound except for the Auto Notch technique which is the most popular method.

     Suicide Speakers are those located behind the stage presentation area limiting the amount of gain that can be utilized on a microphone before feedback starts to occur.  Church auditoriums are rectangular and many have the stage area constructed in ONE CORNER forming a “V”; thus reducing the reflection of sound off adjacent walls and complementing the sound distribution like a megaphone.

 

Resonant Frequencies

     A Resonant Frequency is the frequency of which a speaker or a room becomes sympathetic.  As a teenager, I would sit in a room at church with a bunch of other kids and I would hum at a certain frequency and the room would become sympathetic and would join in and the sound would reverberate and you could not tell where the sound was coming from.  I thought I was pretty funny until the teacher made me sit up front.

     Much though and engineering goes into the design of auditoriums and theaters, with angled walls and ceiling panels that reduce reflection and other panels to absorb sound, but rarely is a church sanctuary designed for sound; it is designed for the aesthetic appeal rather than acoustics.

     Church Auditoriums have a resonant frequency; most of the time two or three of them.   When music is displayed, the room enhances the sound at certain frequencies.  For the sound man this can be a nightmare of feedback.  NOTE:  A resonant frequency of 400 cycles has a sympathetic vibration at 800 cycles even though its reproduction sound level is greatly reduced and then again at 1600 cycles, etc. So killing the 400 cycle demon is the best solution.

     Solution:  Have a licensed and insured system integrator audio professional come out and “optimize” the auditorium. This is accomplished with a 32 or 64 set of notch filters.  White noise or Pink noise is injected into the sound system through any input, filling the room with a noise level much higher than normal.  A specially designed microphone is connected to a spectrum analyzer and it breaks down the white noise into 32 or 64 discrete frequencies and displays their levels on a display screen. Note; today you can get a spectrum analyzer application for your cell phone; some are free.

     By adjust the filters you can bring down the band of frequencies till they are all virtually at the same level, this is said to be a “Flat Response”.  Usually no more than eight filters would have to be purchased to optimize the house.  This compensates for the Audio Board, the Speakers as well as the Room imperfections.  Resonant frequencies would be vastly minimalized and the room would not “BOOM”; feedback tendencies would be greatly reduced making the Board operations much easier.

     Speakers have their own resonant frequency.  Try to select one that is below what the human ear can detect which is 20 to 20,000 cycles.  So if the speaker resonant frequency is 60 cycles, you have just bought a speaker that is sympathetic to the frequency of all AC powered devices which operate on 60 cycles… The not so technical term is called HUM….

 

Grooving

     Performer’s body motions in a church setting can be deemed EXCESSIVE AND SHOWY.  Point out to those that would complain, that performers feel their music and their emotions are transmitted to their body and that’s a good thing.  They are in “THEIR ZONE” praising God which is the ultimate end for which man was created.  SELAH

     A Praise and Worship Leader once told me that in the Psalms, the word SELAH is often used by the chief musician, indicating that when the foregoing passive is somber in thought, that you should in reverence “PONDER IT”, but when it’s joyful you should just Cut Loose and Do Your Thing. It’s in the Book

 

Psalm 30:12 – Our ultimate end is to offer praise to God
¹² To the end that my glory may sing praise to You and not be silent. O LORD my God, I will give thanks to You forever.

(NKJV)

 

Blending Vocals & Instruments

     The Blend you desire on vocals and instruments has a number of factors that enters into the equation.  As with the audio board you either have to RAISE all the LOW level vocals or instruments to 0db or LOWER the HIGH level devices to 0db. 

     The acoustical drums would probably rate as the highest level instrument, already being too loud when they are still being unpacked.  Don’t be surprised if the drummer wants a mic on the “high hat” to add in those high frequency sounds.  The mic should be positioned extremely close so that the input can be turned way down reducing the other drum sounds.

     The real solution is to put the drums in a glass enclosure to reduce their sound and then mic them independently.  IF NOT you must increase the levels of all the other instruments on stage to match the drum set.  Some considerate drummers put a pillow inside the base drum, others stick a little rubber mastic on the symbols and snare drums to help reduce some of the sound, while still others chunk the real drums and get electronic drums which introduce an irritating SMACK of the sticks on each device.

     Noise Gates can be used on drums with great success by reducing the “bleeding” between drum mics; making them almost invisible to each other. – (See Noise Gates)

 

Best Operating Practices

     There is a total “LOUDNESS” level of the room that varies depending on the operator, so sometime it is advisable to obtain a settable loudness meter so that a deacon or elder does not MESS WITH YOU about how loud it is; just point him to the meter.  A ship has only ONE CAPTAIN; find out who that captain is and that’s the one you please, hopefully it’s a performer who has wisdom as well as knowledge.

     Color coding should be used on all microphones on the stage.  Color Electrical Tape can be purchased at Lowe’s or Home Depot in the Electrical Department; place a strip of color on each microphone as well as a matching strip on the audio board.  It’s also a good practice on foldback speakers as well. 

     In case of a microphone failure; a spare color coded microphone, corded or wireless must be located in plain view as a “Stand by Mic.”  It’s the operator’s job to confirm its operational status as well as educate those on stage of its physical location.

     Wires should be dressed with PRIDE on all stands as well as along the floor to prevent accidents. To avoid HUM, power cords should NOT be dressed parallel to audio lines although they can be crossed without a problem.

     Seasoned operators can be seen using masking tape across the bottom of the audio console writing what’s on each channel.  Anybody can come in behind them and easily pick up the operation.  If your audio console does not have INPUT attenuators on each channel, then masking tape is recommended to place arrows for where the normal position of the fader should be.  You can then easily return to your “default value” setting whenever desired.

     Microphones that are not in use, should be left turned off so that if they are accidently bumped it will not be heard on the sound system.  Ease the sound up and down in making corrections.  When only one microphone is in use the majority of the time, all the others should be off.  My personal preference is to run the fader pots to the bottom so I can SNEAK them ON when I need them, not slam them on; then everybody knows you were late.

     When “hunting” a microphone don’t in frustration slam your fader or pot to the top of their range and then start turning on mics; you will blow out the audience when you find it.  With the attenuators set at their “default value”; then open the mics, find it, then adjust.

     Baby Grand Pianos can be a task to mic.  I find a pair of Omni-directional microphones placed 24 inches apart and about 10 inches above the strings and about 6 inches behind the hammers does an excellent job.  It is sent and mixed as a mono signal to the audio board.  If you get too close to the hammers you will hear the “attack” as the hammers hit the strings.

     As a compromise, one mic on a piano can also be utilized; since the low frequencies do not need as much help; place the mic on the floor near the right leg pointing up at the high frequency strings of the piano.  Caveat; you may hear the foot petals being depressed, which is very annoying.

     There are Piano mic systems (PianoMic) that use a compression pole to suspend two microphones above the strings that is designed to eliminate the ” Proximity” effect, allowing all the strings to sound equal.  Don’t get frustrated, at this writing there is no single STANDARD for mic placement on a piano. 

     Drums believe it or not, do need a mic on instruments that are used such as bongo drums, tambourines, cowbells, shakers, etc.  The audio operator’s job is easier if they are physically located away from the main drum set, and for balance, the single mic is placed further from the stronger instrument and closest to the weaker.

     An Announce mic is occasionally used on stage and sometimes you are surprised when it comes into use.  As a best practice it would normally be turned off.  A mic with a switch on it should be provided.   When it’s off, it adds nothing to the overall sound and when it is switched on and the fader is set at the default value, your job has already been done for you, the level is perfect and nobody is embarrassed.  “In line” switches that plug into the mic are also available as an “add on”.

     As a rule, Orchestras and large Choirs utilize a pair of directional microphones generally placed 13 feet up and 13 feet out and placed 13 feet apart.   In a church settings that have no orchestras, the microphones are placed much closer to the smaller choir.

     NOISE Caveat; Live microphones on stands transmit the sounds of walking on the floor as well as hands touching the stand.  Lavalier microphones on lanyards, rustle on clothes when they move. When clothes move on top of the microphone the sound becomes muffled.  If a lapel is chosen for a microphone, it should be placed on the side which the performer is most likely to be turned to.  Ideally the mic on the host that is most preferred for minimum sound level changes, is located on a tie or in the center of their apparel.

     Interesting Note; in “on stage performances”, four or more directional “SHOTGUN” mics are laid on the floor on foam rubber at the stage edge.  Some principal actors will wear wireless microphone with almost invisible clear tubes in their hair just above their forehead to provide “presence” to their presentation.  Stage actors PROJECT their voice anyway.

     It is your responsibility to tell your pastor, that his wireless mic must be considered HOT all the time, wherever he is, including the restroom. Did you notice that the POTUS does not wear a cordless mic?

If someone else can assist with the video presentations and audio recordings, you can do your job much more proficiently.

     One Omni directional microphone suspended in the rear center of the auditorium is great for adding in the overall sound produced as well as congregational or audience participation.  Some orchestra leaders want the feed in an ear piece to know which sections to get louder or softer.

     Hard of hearing church members can use wireless receivers and ear pieces to enjoy the sermon better.  It is the audio operator’s responsibility to check the levels being sent as well as the batteries; there is no “Do Over” to provide an Exceptional Worship Experience.  Remember low or weak battery voltage causes distortion in the ear piece.

     Taped Recordings are already limited by their band width, so ALC’s and peak controllers are recommended; while you are busy on your job on the audio console, the recordings are a SET AND FORGET operation.

 

Silent Servant

     Trying to balance vocals with the other instruments usually gets unsolicited HELP from those who think they know how to do your job, but won’t.  Be patient and LOVE them anyway; “Speak in Tongues” so they won’t know that you are frustrated.  A seasoned operator knows that as soon as the sanctuary or auditorium fills up, their clothing changes the acoustics, requiring many adjustments as the program proceeds.  That means the sound board is NOT PLUG AND PLAY, it requires continuously “Working the Board” to get the blend that the PERFORMERS DESERVE.

     In a studio or professional stage environment the audio engineer does this job every day and is super proficient.  But in a Church environment, audio is run by anybody who is willing to do it.  Some just “step in” at the last minute and have “enough going” to turn it Off & On.  Those who commit to running the board for long periods of time, give up one night during the week to practice, then give up Adult classes on Sunday morning to practice and then operate the board for the live service; some churches have two and three services.  This person is a SILENT SERVANT serving in the background.   It’s quite a commitment.  

     Andrew was one of the twelve Disciples, the only thing you know about him, was that he served God in the BACKGROUND, bringing people to meet Jesus.  He brought his brother Peter and 3,000 more people got saved.  The unnoticed Audio person makes a difference in lives.

    

John 6:8-9 – Andrew brings the boy with two sardines to Jesus

8 Another of his disciples, Andrew, Simon Peter's brother, spoke up, 9 "Here is a boy with five small barley loaves and two small fish, but how far will they go among so many?"  You are an Andrew; a Silent Servant

 

     It’s the Holy Spirit’s job to plant the seed; the Audio and Praise and Worship Team’s job is to water the seed, and it’s God’s job to harvest the seed.  We are only responsible for watering.  

Worship lets you get in on what God is doing; we “water” with our talents.

 

 

 

 

NOBODY WILL NOTICE WHEN YOU DO YOUR JOB RIGHT.

But just mess up one time and EVERYBODY will notice it.