VVCC Audio Ministry
Sound Reinforcement Audio Technician’s Guide
VVCC Sound Reinforcement Audio Technician’s Guide
This manual is for the training and reference of participants in the Audio Ministry at Valley View Christian Church. While the attempt has been made to be complete and accurate, some concepts presented have been simplified. In some cases, information presented here may be specific to VVCC and not necessarily applicable elsewhere. Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide Table of Contents VIBRATIONS AND THE GOAL ................................................................................................ 1 THE FRONT OF HOUSE (FOH) CONSOLE........................................................................... 2 INPUT CHANNEL ........................................................................................................................... 3 Input level meter ..................................................................................................................... 3 Phase ....................................................................................................................................... 3 Level adjustment..................................................................................................................... 3 -20 Button ............................................................................................................................... 3 High Pass Filter....................................................................................................................... 3 Equalization (EQ) ................................................................................................................... 4 HMID and LMID.................................................................................................................... 4 The EQ button......................................................................................................................... 4 Auxiliary buses ....................................................................................................................... 5 Routing and Pan...................................................................................................................... 6 The Mute Button ..................................................................................................................... 6 The Solo Button ...................................................................................................................... 6 Dir Pre..................................................................................................................................... 6 The Channel Fader.................................................................................................................. 6 THE MASTER SECTION ................................................................................................................. 7 The Auxiliary Outputs ............................................................................................................ 7 The Routing and Pan and........................................................................................................ 7 Master Faders.......................................................................................................................... 7 PFL.......................................................................................................................................... 7 Mute Groups ........................................................................................................................... 7 PLAYBACK .................................................................................................................................. 8 PLAYBACK SUB-MIXER ................................................................................................................ 8 CD ............................................................................................................................................... 8 To program a sequence of tracks: ........................................................................................... 9 TAPE .......................................................................................................................................... 10 Notes on recording:............................................................................................................... 10 IN-EAR MONITORING.............................................................................................................. 12 CONCEPTS OF IN-EAR MONITORING ........................................................................................... 12 THE AVIOM SYSTEM .................................................................................................................. 13 RESPONSIBILITIES OF THE AUDIO TECHNICIAN: ........................................................ 14 THE 8:00 SETUP ......................................................................................................................... 14 THE 8:00 WORSHIP .................................................................................................................... 16 THE 9:30 WORSHIP .................................................................................................................... 17 THE 11:00 WORSHIP .................................................................................................................. 18 EQUIPMENT AND SIGNAL PATH OVERVIEW ................................................................ 19 CONNECTIONS ............................................................................................................................ 20 SIGNAL CHARACTERISTICS ........................................................................................................ 21 DECIBELS ................................................................................................................................... 22 Sound Reinforcement Guide 2005 10 16.doc
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Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide AUDIO MIXING CONSOLE .......................................................................................................... 22 Pre- and Post-EQ ............................................................................................................... 23 Pre- and Post-Fader .......................................................................................................... 23 PHANTOM POWER ...................................................................................................................... 23 POWERING UP............................................................................................................................. 24 POWERING DOWN ...................................................................................................................... 24 MAKING CONNECTIONS .............................................................................................................. 24 SETTING LEVELS..................................................................................................................... 25 GAIN .......................................................................................................................................... 25 FEEDBACK ................................................................................................................................. 26 AMPLIFIERS ............................................................................................................................... 27 MICROPHONES ........................................................................................................................... 27 Choir mics............................................................................................................................. 27 Hand-held mics ..................................................................................................................... 27 TECHNICAL NOTES................................................................................................................. 28 PSYCHO-ACOUSTICS .................................................................................................................. 29 SOUND AND EQUALIZATION (EQ).............................................................................................. 30 EQUIPMENT NOTES .................................................................................................................... 33 TROUBLESHOOTING.............................................................................................................. 35 THE OVER AND UNDER METHOD OF COILING CABLE ............................................... 36 CREDITS & BIBLIOGRAPHY ................................................................................................. 37
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
Vibrations and the Goal Sound is all about vibrations. Drums make vibrations. Instruments make vibrations. Our voices make vibrations. When we communicate orally, we’re making vibrations. Some vibrations are weak and others are strong. As Audio Equipment Operators, our goal is to raise the level of the vibrations that are weak and blend them with those that are strong in such a way as to present a pleasing, clear, and intelligible sound to the audience. People come into the VVCC auditorium to praise God. Our job is to help make that a pleasant and meaningful experience to all in attendance by helping everyone hear what is taking place without causing a distraction. In our role as Audio Technicians, we are most successful when the audience is unaware we are present.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
The Front of House (FOH) Console At Valley View Christian Church, the Front of House (FOH) console is a Soundcraft Series Two 32 Channel console with two additional stereo channels, four “return” channels, eight primary buses, two Matrix buses, and eight auxiliary buses. Generally speaking, a console consists of input channels, adjustments to each input channel, output from each channel, and output from the console to the amplifiers. The number of knobs and buttons may seem overwhelming, but once you learn the basic functions, many of the knobs and buttons are just doing the same thing at a different place.
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide
Input channel An input channel consists of an input jack, an input level adjustment, an equalization section, an auxiliary bus section, a signal routing section, mute, solo, and a main fader. Input level meter There is an LED strip at the top of each channel to indicate the input signal level. The lower nine LED’s on the meter are green, the tenth and eleventh are yellow, and the twelfth is red. The target input level is zero on the meter. Signals are allowed to peak at +6 on the meter, but when a signal reaches 9, (the first yellow LED) the input signal needs to be reduced. Phase We will not address the phase button in this document. Level adjustment You increase or decrease the input signal level by adjusting the SENS (Sensitivity) knob. This is sometimes called the Gain. The Sensitivity units indicate the amount of decibels below zero the channel has to reach in order to get the signal to zero as shown on the meter. In other words, a setting of –30 means the sensitivity has to reach down to –30 decibels to make the signal equivalent to zero. -20 Button This lets you adjust the range of control of the signal. If the Sensitivity level is set at the least sensitive portion of its range (turned counterclockwise), and it’s still too loud to make the proper adjustments, the input signal can be reduced by 20 decibels simply by pressing this button. High Pass Filter This feature is turned on or off by using the H/P button. When depressed, the feature allows you to determine the frequency below which signals will be removed. This is used for any channel that is not able to produce sound below a specific frequency. Voices for example rarely can produce sounds below 60 Hz, so to prevent low frequency hand and stage noise from entering the channel, the H/P filter knob can be set to 60 Hz.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide Equalization (EQ) The EQ section is like an expanded, detailed tone control, but similar to the tone controls on your home stereo. Instead of Treble and Bass, there is HF HMID LMID LF
High Frequency (12 kHz) High Mid, (550 Hz to 13 kHz) Low Mid, 80 Hz to 1.9 kHz), and Low Frequency (60 Hz).
The High and Low are known as “shelving” frequency bands. They raise or lower frequencies above or below a fixed frequency in a slope shape to the frequency specified by the knob and level them off like a shelf. HMID and LMID The HMID and LMID EQ controls consist of two knobs each, and allow you to adjust not only the peak or valley of the frequency curve, but also the center point of the curve. For example, if the signal in the HMID section was represented by a straight line — a flat response, and you wanted to increase the “tone” in that range, you would adjust the lower HF knob clockwise, and the change could be represented by a hill. Likewise, if you wanted to lower the “tone” in that range, you would turn the HF knob counter-clockwise, and the change could be represented by a valley. You could then adjust where the center of this hill or valley would be within the range specified by the upper knob of the HMID or LMID controls. The EQ button This allows you to turn on and off the adjustments made to the equalization of the signal with the press of a button. You can then tell whether or not you’ve improved on the original signal and whether further adjustments should be made.
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide Auxiliary buses Auxiliary buses are “outputs” for specific purposes. The respective knob controls the level of the signal to the Auxiliary output bus. This allows you to “mix” various channels together with different levels as desired. Today, we are using Aux 1 through Aux 6 as stage monitor mixes. Through these Aux buses, we can send the signals from specific channels to specific monitors (speakers) on the stage so the various musicians or singers can hear the sounds they need to hear in the relative proportions they would like to hear them. Aux 7 is being used to send the signal from selected channels to the Reverb processor to add fullness to the sound. Aux 8 is being used to send the signal from selected channels to the sub-woofer for amplification of very low sounds. There are five buttons to the right of the AUX knobs. The Pre=PREQ button, if pressed, sends the signals from the specific channel to each of the 8 buses without applying the adjustments made in the EQ section. The four PRE buttons are Pre-Fader buttons, and will affect the Aux buses in pairs to determine whether the channel fader will affect the signal. If the button is pressed, the channel fader will not affect the level of the signal to those two Aux buses. If it is not pressed, the channel fader will increase or decrease the signal to the two Aux buses.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide Routing and Pan The signal from each channel can be routed to any of eight output groups as well as directly to the Mix or to the Mono output buses. The group routing options are paired: 1-2, 3-4, 5-6, and 7-8. This means that if the button is pressed, the signal will be routed to both groups identified by the button unless the Pan knob is adjusted. For example, to send a signal only to group 1, the 1-2 button must be pressed, and the Pan knob must be set all the way to the right. The signal to the paired groups can also be adjusted proportionately, sending it more strongly to one group of the pair than to the other. This could be used to set instruments and vocalists in a “stereo field.” The signal can also be sent directly to the MIX or to Mono, but we do not do this for any channel at VVCC. We send signals to the Mono bus based on the group, as you will see later. The Mute Button The Mute button effectively turns the channel off. When you don’t want the signal from a channel to be heard by anyone, press the mute button for the channel. This will not mute the Direct Out of a channel if Dir Pre is pressed. The Solo Button The Solo button allows you to hear in the headphones only the signal from the channels that have the Solo button pressed. You can press them in any combination of channels, groups, or Aux’s. Be sure the Solo-In-Place button is not pressed or the signal you select will be sent exclusively to the main outputs. Dir Pre The Dir Pre button allows the input signal to pass out through the Direct-Out jack completely unaffected by anything set on the channel. This is appropriate for sending the signal to another console for processing in a different environment and is used to send each channel’s signal to the Recording Console, and to supply signal to the Aviom in-ear monitoring units. Note: the mute button will not affect the Direct Out signal if this button is pressed. The Channel Fader This is the primary output level control for the channel. We generally try to target 0 as the normal position.
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide The Master Section The Master Section contains many features we will not be discussing in this document. For now, we’re just going to discuss what you’ll need to use on a typical Sunday morning. The Auxiliary Outputs As we discussed before, there are eight Auxiliary buses that let you generate up to eight unique “mixes” of the input channels. Once you have decided what individual channels should be on each mix, you will want to send them some place. These will be the Auxiliary Outputs. Each one has a knob to set the output level and an AFL (After-Fade Listen) button to hear through the headphones what each particular mix sounds like. The Routing and Pan and Each Group can be sent to the Mono, Mix, and to the Group outputs directly. To send a group to the Mono output, press the MONO button. To send a group to the Mix, press the MIX button. Group signals are sent to the Group Outputs by default and are present there even when routed to Mono and Mix. The Mix output controls two signals. These can be used for Left and Right of a stereo image. At this time, the MIX is not used for anything. The Mono is a mono summation of the groups selected. This bus is used for the master house sound. Master Faders Each of the groups has a fader control; red ones for the Groups, a yellow one for the Mix, and a black one for Mono. The faders control the relative levels of the signals routed to the groups and send them to the destination you designate. Group 1 is used for Female vocals, Group 2 is Male Vocals, Group 3 is miscellaneous microphones, Groups 5 and six are playback signals. Groups 7 and 8 are used for sending the mix to the Console Tape deck. Group 4 is not in use. At this time, we are sending groups 1, 2, 3, 5, and 6 to the Mono (black) fader which controls the signal to the house speakers in the ceiling of the auditorium. PFL The Pre-Fade Listen buttons for the groups act as the Solo buttons on each of the channels, allowing you to hear the selected group or groups through the headphones. Mute Groups To the right of the master faders are Mute Groups that allow you to mute a preset selection of channels with the touch of a button.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
Playback The capability to play back external recorded sound sources through PA system is called Playback. We have routed several playback units through a sub-mixer which allows us to control the final output through only two channels on the FOH Console. At the present time, we have two CD players, and a Cassette tape player that has independent dual outputs through the playback mixer. The Computer and VCR signals from the balcony are also received through this mixer. The entire Playback mix is brought into the console through the ST1 channel.
Playback Sub-mixer The 12 channel (8 mono and 2 stereo) rack-mount mixer through which the playback signals are mixed is clearly labeled. Currently, they are CD1, CD2, Tape1, and Tape 2. The tape signals are on the stereo channels.
CD The primary CD players we have are the Denon DN-C630 and the DN-C635. There are some obvious differences, and some subtle differences between the two Denon units. The most notable difference is that the Play-Pause-Cue-Stop buttons are not the same. On the CD1, the DN-C630, Play and Pause share a green button, and the Cue is a red button to the left of it. On CD2, the DN-C635, the Play, Pause, and Cue all share independent buttons. Cue on the DN-C635 is where Stop is on the DN-C630, and Stop on the DN-C-635 is to the left of Cue.
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide To select a track other than track one, instead of pressing buttons like on most home CD players, you turn the “Track” knob to the desired track. (The knob is labeled “Push” on the DN-C635.) This is much faster than pressing buttons repeatedly. These CD players have two modes. While in the Single play mode, after playing the selected track the CD will automatically cue to the next track and wait. If in Continuous play mode, they will play the entire CD as normal CD players. You change modes by pressing the “Play Mode” button. One of the subtle differences between these CD players is that the DN-C630 calls the Continuous mode Total, while the DN-C635 calls the Continuous mode Cont. This normally works great for playback because you don’t have to worry about stopping the CD player when the song is finished. However, on some of the Choir CD’s, one song will span multiple tracks. You must play them in Continuous mode. At that point, you have two choices. Be prepared to stop the song when it is finished, or program the song’s tracks into the CD player. To program a sequence of tracks: Press “Prog In” Press the “Track” knob Turn it to a desired track Press the track knob again Do the above line for each track you want to program. Once all the tracks are selected, press “Prog In” again. Now, press “Prog Play On/Off” and you should see the programmed tracks listed in the display. To play the programmed tracks, simply press “Play.”
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
Tape The Cassette Tape device is a Denon DN-780R with completely independent tape wells and dual independent outputs. Unlike many dual-well tape units, with this unit, you can record on one tape well while you play a tape on the other. You may reset the counter at any time by pressing the RESET button for either well. This unit has a Memory Return feature. By pressing the MEMO button, the tape is able to rewind or fast forward to the point at which the tape counter was set to zero. This is ideal for re-queuing the tape for the next performance or taking the performer through a rehearsal run one more time. To play a tape, insert the tape into one of the wells, make sure the direction indicator is pointing to the right, and press Play. Make sure the gain and the fader for the respective channel on the sub mixer is turned up, and that the Playback channels on the FOH Console are ready. If there is a possibility you will want to return to the current starting point without having to cue the tape, press MEMO. If the direction indicator points to the left, press the > button for the respective tape well and the direction indicator will change to the right. In order to prepare for a performance of a song, you will need to cue the tape so it is just a couple seconds before the start of the music. Put the tape in one of the tape wells, reset the tape counter to zero, and press play. When the meters indicate the music has started, make a note of the tape counter. Rewind the tape to the beginning, and press play again. When the counter reaches two or three numbers less than the point at which the music begins, press stop. Press RESET and MEMO. You’re ready to replay the song as many times as the performer would like without having to spend a lot of time re-queuing. Notes on recording: To record a tape, once a tape is inserted into the deck, if you press the Record button (red dot), the deck is in record mode. If you press the Record button again, the tape will feed for seven seconds of silence and then stop. Do this twice to be certain the tape is set past the leader. Now when you’re ready to record, press play and recording will begin
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide To simultaneously record the same content on two tapes, put a tape in each well, press “Twin Rec,” and then when ready, press play on the Tape 1 side. Depending on the circumstances, sermons will either be recorded at FOH or in the Balcony. Before you use the tape device at the FOH for recording, be sure the gain and the channel fader on the Playback sub-mixer are turned off for the respective tape well. Record levels should be set so the signal reaches zero most of the time and does not peak over +3dB.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
In-ear Monitoring Concepts of In-ear Monitoring In order to successfully use in-ear monitoring, isolation earphones are optimal. This is due to the muffling of the ambient room sounds that can be heard as background when using normal headphones. There are generally two types of isolation ear phones available: General foam-insert earphones, and earphones with custom ear molds. The general foam-insert earphones provide less of a degree of isolation, but are usually adequate. These can range in price from $15.00 up to around $200.00. Earphones with custom ear molds start at around $200, and go up from there in price. They offer a higher degree of isolation as well as a greater degree of comfort to the wearer, since they are molded in the shape of the wearer’s ear and ear-canal. However, since they are molded to the wearer’s ear and ear-canal, they can only be used by the user for which they were molded. The higher degree of isolation is highly desirable because by isolating yourself from the potentially loud sounds in the room, you can listen to the monitors at much lower levels. Using an earphone in only one ear is not recommended because most people will turn up the in-ear monitor to compensate for the volume of the stage monitors and house sound at levels that can damage hearing. Normally, when using in-ear monitoring, a feed of ambient room and audience sounds is recommended for proper performer interaction. This adds a sense of space to an otherwise dry-room sound. Note: This ambient feed should not be sent to the FOH or monitor mixes. However, at VVCC, the vocal, and other open mics on stage proved sufficient ambient sound for most interaction, especially since in-ear monitoring channels are at a premium. The performer must resist the temptation to use the EQ on any monitoring device to adjust the sound of his or her own instrument in the monitoring device or an invalid sound will be potentially sent to console. Use it only to adjust the overall sound in the in-ear monitor.
Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide The Aviom System The AVIOM System is a digital in-ear monitoring system offering the performers up to 16 channels for them to mix independently to their tastes. The signals sent to the Aviom system are digitized and sent across Cat-5 style cable to its destination. The 16 channels sent to the Aviom provide the signals to both the on-stage in-ear monitoring, and to the recording desk in the balcony. At this time, the same set of 16 channels is present at both places. This requires us to take both functions into consideration when making modifications to the set of 16 channels sent to the Aviom. The signals sent to the Aviom units primarily make use of the Direct Out feature of the Mixing Console channels. (See p.6) We send them out as ”Dir Pre” (See p. 6) which means except for the input sensitivity, the signal that enters the Mixing Console is sent to the Aviom unaffected by any adjustments you make. The exceptions to this are the Miscellaneous Mics output which is sent to the Aviom through the Group 3 output, and the Playback (Trax) which is sent to the Aviom through the Aux 4 output. As a result, even when you mute an instrument’s channel, it is still live on the Aviom, and is still being sent to the stage and the Recording Mixer. Presently three Aviom units on the stage are powered from the backstage rack, and receive their signal set from Cat-5 style jacks in the floor pockets. The remaining three receive their power from outlets on the stage and the signal set through Cat-5 style cable daisy-chained from the third Aviom unit. We plan to change this in the future so they all will be powered from backstage, and receive their signal sets from the floor pocket Cat-5 style jacks. The Aviom signals sent to the Recording area in the balcony are converted back into analog signals and fed into 16 channels on the Recording Mixer. One thing to keep in mind is that when we adjust the input sensitivity on any channel that is also sent to the Aviom, we must make sure it doesn’t overdrive the Aviom system. You can tell whether a signal is too strong for the Aviom by the appearance of a red light on the channel when the signal from an instrument or voice is sent to it.
Sound Reinforcement Guide 2005 10 16.doc
Stephen M. Golden
Distribution Date: 01/06/09
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VVCC Sound Reinforcement Audio Technician’s Guide
Responsibilities of the Audio Technician: Remember: When powering up, turn amplifiers on last, and off first. The 8:00 Setup You should arrive no later than 07:15 to get things set up and to enable singers and instrumentalists to get sound checks before 07:45. Note: All sound checks must be completed by 7:45. No performance will be permitted if a sound check has not been made. First, turn on the power to the audio console desk by switching on the upper right switch at the top of the right-hand rack. If the equipment does not power on, turn on the switch immediately below it. Then turn on the power supply to the audio console at the bottom of the right rack. Mute all channels by pressing the “ALL” mute group. Ensure that Eva’s mic transmitter and the Lapel mic transmitter have new batteries. Open the pulpit mic channel, the Audience mic channel, each wireless mic channel, the Keyboard channel, and the Drum channel. Take the battery tester with you up to the stage. Test the batteries in the wireless mic transmitters on stage with the battery tester. Set the tester to the second position clockwise. The housing on the Telex (cylindrical) model unscrews to reveal the battery compartment. These models use 9v batteries. You do not need to remove these batteries from the unit to test them. If a 9 volt battery tests at 8.3 volts or less don’t use it. While it might work for now, it probably won’t make it through all three worship periods. The Shure wireless microphones each use 2 AA batteries. They have a built-in battery level indicator. Simply power up the mic and check the level. If the indicator does not read “three bars” remove the batteries and test them. Set the tester to the third position clockwise. If the batteries test at 1.30v or less, replace them. The Shure wireless microphone housing unscrews to reveal the battery compartment. Once you unscrew the housing on the bottom of these units, the retaining door opens from the top of the battery compartment and hinges at the bottom. Gently pull it toward the bottom of the microphone, and it will open. Turn on the power strips that lead to the Drum, Keyboard, and other equipment. There are three power strips you must turn on: One between the piano and the keyboard, and one on each side of the drum kit. Turn on the drum kit and the keyboard. After power is supplied to all the peripheral units, turn on the amplifier rack. To do this, open the back stage rack cabinet. At shoulder height or just below, there are two power related rack units: an Atlas unit and a Raxxess unit. You can turn them on in either order. The Atlas unit switch is a black toggle switch on the left, and Raxxess unit switch is a red toggle switch on the right. Once both are on, press the “Start” button on the Atlas unit and it will provide power to the amplifiers in a sequence. There should never be a need to touch the actual amplifier power switches. Sound Reinforcement Guide 2005 10 16.doc
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide Turn on and test the microphones by saying something into each one. The Telex and Sennheiser (Eva’s) wireless units are plug-on transmitters. The Telex mic transmitters each have a power switch and a mute switch. Turn on the power switch. The red light will blink once and go out. If the battery is low, the light will remain on. Now slide the mute switch in the same direction as the power switch, and test. The Sennheiser wireless units have a power button and a mute switch. Press the power button. The red light will stay on, and will flash if the battery is low. Slide the mute switch away from the word MUTE, and test. The Shure mic transmitters are integrated into the microphones. The Shure mics have a single button for power and mute. Press and hold the left button for one second, and it will power on. The indicator light will glow green. To mute the mic, press the left button briefly, and the indicator light will display orange. Press the same button briefly again and the indicator light will glow green again. Mute and turn off all the wireless mics. To turn off the Shure mics, press and hold the left button for more than one second, then release. To turn off the Telex mic transmitters, turn off the mute switch first, and then the power switch. To turn off the Sennheiser (Eva’s) transmitter, slide the mute switch, then press and hold the red button for one second. Test the drum kit, especially the high hat and kick drum to make sure they’re plugged in. Test the keyboard. Note: Each given channel must also be un-muted at the FOH console for you to hear sound. Re-coil the audience mic cable using the “over & under” method1 to prevent tangles. Position the pulpit mic so it is centered and pointed directly at the height of an average person’s mouth. Set up the choir mics if the choir will be singing. Return to the FOH console and test the lapel transmitter by turning it on and speaking into the lapel mic. Once everything passes the tests, mute all channels as appropriate. Get the specially marked copies of the program (bulletin) for the day from the lobby.
1
GSSW, p.161
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VVCC Sound Reinforcement Audio Technician’s Guide The 8:00 Worship All sermons are to be recorded. The 8:00 sermon is recorded only on Audio Cassette at this time. On the front side one cassette (when you hold the cassette in front of you, the tape should be on the left spindle) write “Sermon,” the date, and 8:00. Place the tape in one of the tape wells. It does not matter which. Make sure the tape direction indicator is pointing to the right on both tape wells. If not, press the correct direction “play” button, then press “Stop.” Ensure the Tape faders on the Alesis sub-mixer are all the way down for the wells that will be recording. Otherwise, you can potentially create an internal feedback loop. Press the record button. Press it again, and the deck will put 7 seconds of silence on the tape. Press it a third time for another 7 seconds of silence to ensure the tape is past the leader. When you’re ready to start recording, press Play If there are any special songs that will be sung using tape or CD, get them queued and ready in the playback deck(s) (tape or CD). Make sure the faders for the Alesis submixer are set at zero and the gain (the top knob) is set at the appropriate level for the LED’s to just reach the first yellow one while playing. At this point, you are ready to perform any sound checks necessary in preparation for worship (special music or other event). Open (un-mute) the Playback channels and perform the sound checks as needed. Write down any special settings used for the song or any other worship event. Before worship begins, you are requested to play some music from one of the CDs in the Audio Booth. Stay alert for things happening on stage. Open any microphone channels as needed. Start recording the sermon when the speaker says the “children are dismissed to junior church.” If the speaker forgets to say this, just start the recording when appropriate. If the special music used a tape, once completed, be sure to remove the tape and turn off the gain and fader for that tape channel on the Alesis sub-mixer. At the end of the sermon, rewind the 8:00 Sermon tape and remove it from the tape well. At the end of the worship, mute all microphone channels to prevent feedback and unwanted noise. Pass on any tips and anything you may have encountered during your Worship hour.
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Stephen M. Golden
Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide The 9:30 Worship The 9:30 Audio Technician should arrive in the audio booth before 9:15. You should speak with the 8:00 Audio Technician to get any information that might be helpful for the 9:30 worship. Be aware of any special settings used for the song or any other worship event. Also get any tips to pass on from the 8:00 audio person to the 11:00 audio person. When the praise team is ready to begin, open the instrument channels. Those using wireless mics are responsible for turning them on and off, so we generally leave their channels open. Be alert for things happening on stage. Note: You should be particularly alert in this worship period because it is more dynamic (changing) in style than the 8:00 Worship. When listening for the proper mix, it is important to make sure everyone can be heard and that no one source (voice or instrument) is too loud or soft. The voices should be clearly louder than the music. Often this means turning something down rather than the voices up. You are responsible for this balance. Try to make sure the overall sound is not too loud. Make sure the Tape faders and gain knobs on the Alesis rack mixer are all the way down for the wells that will be recording. Otherwise, you can potentially create an internal feedback loop. All sermons are to be recorded. Two copies of the 9:30 sermon are to be made. Place a tape marked 9:30 in each tape well. Make sure the tape direction indicator is pointing to the right on both tape wells. Press STOP for each tape well. For each deck, press the RECORD button. Press it again and the deck will put 7 seconds of silence on the tape. Press it a third time to ensure the tape is past the leader. Press STOP on both wells again. Press TWIN REC. This sets up both wells to record simultaneously. To start recording, press PLAY on the left-hand deck. Just before the sermon begins, start recording. At the end of the worship, mute all channels to prevent feedback and unwanted noise. There is a single mute group button for this. Pass on any tips from the 8:00 audio person as well as anything you may have encountered in your Worship hour.
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VVCC Sound Reinforcement Audio Technician’s Guide The 11:00 Worship The 11:00 Audio Technician should arrive in the audio booth around 10:45. You should speak with the 9:30 Audio Technician to get any information that might be helpful for the 11:00 worship. Be aware of any special settings used for the song or any other worship event. Mute all unused channels. Mute all instrument channels. When the praise team is ready to begin, open the instrument channels. Those using wireless mics are responsible for turning them on and off, so we generally leave their channels open. Be alert for things happening on stage. Note: You should be particularly alert in this worship period because it is more dynamic (changing) in style than the 8:00 Worship. When listening for the proper mix, it is important to make sure everyone can be heard and that no one source (voice or instrument) is too loud or soft. The voices should be clearly louder than the music. Often this means turning something down rather than the voices up. You are responsible for this balance. Try to make sure the overall sound is not too loud. However, by this time, the levels should be pretty well set. All sermons are to be recorded. Place the tape marked 11:00 in a tape well. (The 8:00 should be recorded on the back already.) Make sure the tape direction indicator is pointing to the right on each well. Make sure the 11:00 side of the tape is facing out and that it is properly wound to record on that side (the tape should be on the left spindle). Make sure the Tape faders and gain knobs on the Alesis rack mixer are all the way down for the wells that will be recording. Otherwise, you can potentially create an internal feedback loop. Press the RECORD button. Press it again and the deck will put 7 seconds of silence on the tape. Press it a third time to ensure the tape is past the leader. To start recording, press PLAY. Just before the sermon begins, start recording the sermon on the 11:00 sermon tape. At the end of worship, mute all channels to prevent feedback and unwanted noise. Insert some playback music, and open the playback channels. After nearly everyone has left the auditorium, turn the back-stage amplifiers off by pressing the “Start� button on the Atlas power unit. Once the amplifiers have sequenced off, turn off the Atlas power unit and the Raxxess power unit. Close and lock the rack cabinet. Turn off the power strips for the Drum, Keyboard, and other stage equipment. Turn off the console and the power strip under the audio desk. Cover the audio console with the vinyl cover
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VVCC Sound Reinforcement Audio Technician’s Guide
Equipment and Signal Path Overview The following is a quick overview of the basic equipment used in our Sound Reinforcement system and the path the signal makes from the source to the final output.
Mixing Console Source
Amplifier
DI Box
Speaker
Microphones (abbrev. Mic or Mics) - Pick up vibrations in air and convert them to electrical impulses -positive & negative, corresponding to the vibrations. Instruments - Produce vibrations either in the air or vibrations that are collected by specialized microphones called pickups, or both, or produce electronic signals that can be converted to vibrations later. Cables - Take the signal from the Mic or instrument to the audio mixer. Mics & Instruments use shielded cable. Some cables carry balanced signals, some carry unbalanced. The unbalanced signals should be converted to balanced signals in as short a length as practical. This cuts down on noise being induced into the system. Mixer - Combines the electrical impulses or signals into a single signal. Cables - Carry signals from the mixer to a signal processor or to an amplifier. These cables can be unbalanced and unshielded for short distances (<15’). For lengths greater than 10’ however, they should be both shielded and balanced. We run our mixed output for mains & monitors from the mixer to the stage through balanced and shielded cable (inside audio “snakes”) before we amplify it. Many amplifiers can accept either balanced or unbalanced signal. We use balanced because it dramatically reduces noise. Amplifier - Makes the electrical impulses or signals stronger. This signal is actually low voltage AC. You only connect amplified signal (amplified output) to speakers -- never to other components! Cables - Amplified signal is carried from the amplifier to the speakers through two conductor (14, 12, or 10 gauge wire), unshielded cable. These cables will have 1/4” TS plugs or SpeakOn connectors (discussed below). Speakers - produce vibration in air corresponding to the impulses they receive. These vibrations produce the amplified sound, which is our desired result.
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VVCC Sound Reinforcement Audio Technician’s Guide Connections Jacks, Plugs, & Cables Jacks are usually surface-mounted connectors complimentary to the connectors described below. Plugs are connectors found at the ends of cables. Cables are lengths of wire and insulation of various configurations usually having connectors on each end. We call them “cables,” not “cords” to eliminate confusion with “chords” instruments play. Snakes are a collection of two or more cables, almost always balanced, carrying multiple signals from one location to a common destination.
Common Cable types One-conductor & Shield Two-conductor & Shield Two-conductor - unshielded Conductors carry signal. Shield is either a foil wrapping or a wire mesh around the insulated conductor or conductors. Shield is used for ground. It also helps reduce noise such as AC hum and Radio Frequency Interference (RFI). Shielded cable should never be used to carry amplified signal to the speakers. Unshielded cable should never be used for line level (guitars, etc.), or microphone level signal. Connectors XLR “Cannon” - Balanced, low impedance (Z). Two conductors and a shield. Two varieties: Male & Female. TRS (Tip-Ring-Sleeve) - Balanced, high or low impedance. Two conductors and a shield, usually 1/4” plugs. Also used for “Insert” cables, and most commonly, for “stereo” connections such as headphones. TS (Tip-Sleeve) - Unbalanced, high impedance (Z). One conductor and a shield, usually 1/4” plugs. Used for guitars, keyboards, and other such equipment. Also called “phone plugs.” Or... TS - Two conductor to transmit amplified signal from the amplifier to the speakers. Speak-On - Two conductor, as TS above, but have the advantage of locking in place to prevent accidental disconnection. To connect, line up notches, insert, and turn clockwise. To disconnect, pull back silver tab, turn counterclockwise and remove from jack. (The Speak-On connectors we use can also support four conductors for “bi-amping” the speakers, but we don’t employ that amplification method at this time. Details about this method are beyond the scope of this training.)
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VVCC Sound Reinforcement Audio Technician’s Guide RCA connectors - Unbalanced, high impedance (Z). Commonly seen on home stereo equipment. Two varieties: Male & Female (usually as jacks, not plugs). Also called “Phono plugs.” DI Box - Direct Insertion Box or Direct Injection Box. This box transforms unbalanced, high impedance signal to balanced, low impedance signal. There are basically two types: active and passive. Active DI boxes use a supplemental power source such as a battery, power supply, or phantom power, to transform the signal. Passive DI boxes use the signal itself as the means of transformation. There is much discussion as to which is better. DI Box
Signal Characteristics Three signal characteristics we need to discuss are Balanced/Unbalanced, Impedance (resistance), and Level. Balanced - Cable type: Two-conductor & shield. Good for carrying signals well beyond 200’. The normal signal (+e) is sent through one conductor and a signal 180° out of phase (-e) is sent through the other. Both conductors are wrapped inside the shield. At the receiving end, the out-of-phase (-e) signal is transformed back to normal inphase signal (+e) and added to the original signal (+e) to yield double the signal strength (+2e). Any noise picked up along the way is canceled out. Here’s how: The same noise is induced into the both the normal and out-of-phase signals. Positive (+) noise is induced into the normal signal (+e) and the out-of-phase signal (-e). But when the transformer converts the out-of-phase signal (-e) back to normal signal (+e) it also transforms the positive (+) noise in the out of phase signal (-e) to negative (-) noise. When we add +e and +e, we get +2e, but when we add positive noise to negative noise, we get zero noise. Unbalanced - Cable type: commonly one-conductor & shield. +e and ground. Should not exceed 20’ in length. Susceptible to noise: AC hum and Radio Frequency Interference (RFI). Low Impedance - Refers to the resistance at the source of the signal: 150 ohm or less. Describes the signal in conjunction with balanced or unbalanced. High Impedance - Refers to the resistance at the source of the signal: 25k ohm or more. Describes the signal in conjunction with balanced or unbalanced. Microphone level - very low-level signal - less than -20dBu (77.5mV) Line level - medium level signal - -20dBu (77.5mV) to +30dBu (24.5 V) Amplified/Speaker level - (power signal) - This is the AC signal sent to the speakers that makes the sound in the room. +30dBu (24.5 V) and above.
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VVCC Sound Reinforcement Audio Technician’s Guide Decibels The concept of decibels (dB) is complicated and has many nuances. The deci-Bel literally means a tenth of a Bel, a unit of measurement defined by Alexander Graham Bell. GSSW, p.27; SRH, p.19
It represents a ratio between two quantities or values. It only has meaning when used in a comparison relationship. By itself, it has no meaning. The term Decibels takes many forms, and we will not go into great detail here. But be aware, different dB designations mean different things. If comparing specifications between components, make sure the dB designation is the same. The dB reference most applicable to our use is dBu and we use it to describe relative levels of signal through the sound reinforcement system. We’re comparing the level of the original signal with the level at each stage of signal processing, and ultimately with the final output. Increasing and decreasing the levels will often be described in dB’s. (For descriptions of various dB terms, see “Decibel Terms” in the Technical section below.) “Zero dB does not mean ‘nothing,’ it means “no difference from the reference wattage (or voltage).” The signal is the same level coming out of the device or sequence of devices as it was going into it. In other words, if a singer’s voice after passing through a system produces 0 dB, the output would be the same loudness as the singer’s unamplified voice. GSSW, p.28
One Bel, ten decibels, is perceived as twice as loud.
GSSW, p.28
One decibel is the smallest difference between two sounds most people can detect. GSSW, p.28
In order for the average listener to detect a difference in loudness, the watts must be doubled. That’s slightly more than the minimum detectable difference. LSR, p.35 Doubling power increases the level by 3 dB. In other words, to get an increase of 3 dB of sound you must double the amplifier power. GSSW, p.28 Doubling distance from source drops sound level (pressure) by 6dB. GSSW, p.28
Audio Mixing Console The audio mixing console is the control center of the sound reinforcement system. All source signals are sent to the console, mixed and modified as desired, and sent out either for amplification or to a recording device. After amplification, the signal is sent to speakers for sound reproduction in air. The mixing console consists of a channel section with multiple individual channels, and a master section. The master section allows adjustments to be made to the entire mix and controls the final output signals. Sound Reinforcement Guide 2005 10 16.doc
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VVCC Sound Reinforcement Audio Technicianâ&#x20AC;&#x2122;s Guide Each signal source, whether microphone or instrument, connects to the console on its own channel. Usually, balanced low impedance connections are used through male XLR connectors into corresponding female XLR connectors on the console. Most consoles also have jacks that accommodate balanced and unbalanced high impedance connectors as well. Typically, each channel has the following: Gain -to set the maximum input level EQ -to tailor the tone of the sound Auxiliary outputs (Aux) - to allow different mixes of sounds to go to different performers, or to send it out to another component Pan or balance -to place the sound of that channel into the â&#x20AC;&#x153;stereo field,â&#x20AC;? or to group the sound with specific other sounds in a submix Fader to control the relative output of the channel to the house (speakers) Pre- and Post-EQ Sometimes, a monitor or Aux will be designated as either pre- or post-EQ. If designated as pre-EQ, the monitor or Aux signal will be unaffected by adjustments to the EQ settings. If designated as post-EQ, the monitor or Aux will be affected by adjustments to the EQ settings. Pre- and Post-Fader Sometimes, a monitor, EQ, or Aux will be designated as either pre- or post-Fader. If something on the channel is designated as pre-Fader, the signal for that feature will be unaffected by adjustments to the Fader. If designated as post-Fader, the signal for that feature will be affected by adjustments to the Fader: that is, if the fader level is increased, the feature level will be increased accordingly.
Phantom Power This is a means of providing voltage to system components (9 to 48v.) directly from the mixing console. It is most commonly used to enable condenser microphones, which require voltage across their diaphragms, to work. Phantom power is also used by other components designed to take advantage of it. It is more reliable than using batteries, and more convenient than using AC to DC power transformers (wall warts). Phantom Power is only possible with balanced connections as the voltage is applied to the +e and -e conductors equally and therefore is canceled out from a signal standpoint. When using phantom power, you must be careful to not send voltages through sensitive equipment. This is done by properly connecting the equipment before power is turned on.
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VVCC Sound Reinforcement Audio Technician’s Guide Powering up First, make sure everything is connected the way it should be. It’s best to not make connections after the system is powered up. If everything is connected, turn on any equipment that is to be connected to the mixing console (CD/Tape players, etc.). Then turn on the console. Turn on the amplifiers last. They should be the last components turned on and the first components turned off. This avoids loud “pops” that can damage system components.
Powering Down Turn off the amplifiers first! Then turn off the other equipment.
Making connections Ideally, when making connections to the sound reinforcement system, all components should be turned off. However, sometimes this is impractical. Even so, the following should be noted: 1. When making any connections or disconnections to the mixing console, make sure the channel is muted. 2. When connecting to or disconnecting from the mixing console line level jacks, first turn off the phantom power. Failure to do so will send a 48v. surge through the respective component. This is not good. 3. When connecting or disconnecting equipment on stage to the respective insert point (stage box or DI box, which will allow it to be connected to the mixing console), or when the musicians are doing so, make sure the channel is muted, or if the line is equipped with a mute switch (Cough Drop), the musician should make sure it is muted.
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VVCC Sound Reinforcement Audio Technician’s Guide
Setting levels “Gain,” “clipping,” “feedback,” and how to set proper levels
Gain The whole point of an amplification system is to increase the level of a signal. In other words, we want to make a person’s voice louder than his or her normal speaking voice, or allow an instrument to produce a louder sound than it normally produces. The relative increase above normal is called the “gain.” Gain can be achieved at various stages along the signal path. Total gain is the difference between the normal sound of the source to the sound coming out the speakers Electrical gain is the difference between the input signal level and the output signal level. Maximizing Gain Rule to follow: Take as much gain as possible as early in the signal path as possible. This will keep the signal to noise ratio at an optimal level. The typical VU meter is designed to have a 10dB meter lag.2 A zero VU meter level typically corresponds to a +4dBu peak level. These two facts combined mean that for sharp attack sounds, the actual signal could be as hot as +14dB greater than the meter shows. Noise All electronic audio components introduce some amount of noise into the signal, usually in the form of hiss. Clipping Clipping occurs when the signal at some point in the path is stronger than a given audio component can handle. This results in a distorted (fuzzy or scratchy) sound, and can damage components. Other related terms are “overload” and “peak.” The difference between the background noise level and clipping/overload/distortion of the signal is called the dynamic range. The difference between the average sound level and clipping/overload/distortion of the signal is called headroom. A proper gain structure will allow a greater amount of dynamic range and headroom.3
2
Meters on newer mixers are much more responsive and usually do not have as much of a lag. Probably not more than a 6dB lag. See Alesis Studio 12R manual, p.34. 3 SRH, p.35 Sound Reinforcement Guide 2005 10 16.doc
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VVCC Sound Reinforcement Audio Technician’s Guide Feedback Feedback is a phenomenon that happens whenever an amplified signal is returned, or “fed back,” into the component that amplified it. Feedback is most often characterized by an unpleasant ringing or swelling sound usually produced at painful loudness levels. At the lowest stages of feedback, a slight ringing sound can be heard when a microphone is used, or an instrument is played. The ringing fades when the signal stops because the feedback ringing is not quite strong enough to be picked up and amplified a second time. Feedback overload or a feedback loop occurs when the amplified signal is picked up, fed back and amplified again, picked up, fed back and amplified again, picked up, fed back and amplified again... and so on. How do you stop feedback? You can’t stop feedback by covering the mic with your hand. That creates a hollow resonant cavity and makes the problem worse. So how do you stop feedback? Turn down the level of signal — either at the channel, or at the master section. If you know the channel causing the feedback, simply lower the gain on that channel. It will usually be related to something you just changed or something out of the ordinary. In an emergency situation when you have feedback and you don’t know the source, drop the main fader, then turn down all monitor output controls Slowly turn them up one at a time to isolate the source of the problem. Once you’ve identified the feedback source to one of these locations, observe what is connected in that path and turn down the levels accordingly. The best way to prevent feedback is to minimize the distance from the mic to the source of the offending sound, and maximize the distance from the mic to the speakers. LSR, p.82 How to set levels The objective is to get the highest gain potential without clipping or feedback. We want to set the signal levels as high as possible as early in the signal chain as possible so we amplify the strong signal instead of noise. The higher the signal level is above the baseline noise of the electronic component, the quieter the system will seem to be. 1. On the channel for which you wish to set the level, set all output levels (monitors & mains) to off. 2. Set all EQ to nominal (0). 3. Have the singer/player play the loudest he or she is going to sing or play. 4. Adjust the gain to the point where the signal is reaching 0 dB. That will be the gain setting for that channel. 5. Next, set the monitor levels to the taste of the people using the monitors. 6. Finally set the mains level. Sound Reinforcement Guide 2005 10 16.doc
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VVCC Sound Reinforcement Audio Technician’s Guide 7. Do this for each channel.
Amplifiers Be careful! Amplifiers should be turned on LAST and turned off FIRST. This prevents damaging noise, clicks and pops, from reaching the speakers.
Microphones Microphone placement: The distance between any two microphones should be no less than 3 times the distance between the mic & the nearest voice. This is known as the Burroughs 3-to-1 rule.4 Every time the number of open mics doubles, the system gain before feedback is reduced by 3 dB.5 Choir mics: Use as few as you can. Usually one microphone every 20 to 30 feet is adequate. However, we use two, and angle them slightly away from each other. Choir mic positioning: Height: 1-2’ above the heads of the singers in the last row and 2-3’ in front of the heads of the singers in the first row. Aim the mics at the mouths of the singers in back row.6 Feeding choir mic signal into choir monitors is asking for trouble. Any time the Sound Pressure Level (SPL) is equal to the SPL of the source at the mic, a feedback loop will start. Even before that occurs, any spill from the monitors being picked up by the choir mics can create phase cancellation and result in a hollow, unnatural sound over the house system.7 Nevertheless, we are often asked to do this very thing. Hand-held mics: Proximity Effect The hand-held microphones we use here at VVCC are directional microphones. That is, they have a stronger pick-up capability at the front of the microphone than at the back or sides. A particular notable feature of directional microphones is called the proximity effect.8 When a directional microphone is held two inches or closer to the source of the sound (usually a person’s mouth), there is boost in the lower frequencies. Conversely, when the same microphone is held farther from the source, the sound may seem lacking in the lower frequencies. You may need to adjust the lower frequencies on the console channel to account for this difference.
4
GSSW, p.52;LSR, .90,232 GSSW, p.56 6 GSSW, p.53 7 LSR, p.90,232; GSSW. p.153 8 GSSW, p.51 5
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VVCC Sound Reinforcement Audio Technician’s Guide
Technical Notes Fundamentals & Harmonics The lowest frequency produced by an instrument when making a given sound is the Fundamental. A sine wave is a pure fundamental tone. Harmonics are frequencies produced in addition to the fundamental. The harmonics of an instrument make the sound distinct. If it weren’t for harmonics, all instruments would sound alike. Harmonics produced by an instrument occur at various frequencies throughout the musical spectrum and include vibrations well above the range one might expect for the resultant sound. The sum of all the odd harmonics produces a square wave.9 The sum of all the harmonics produces a saw tooth wave.10
Decibel Terms11 dBu -expresses input or output voltage. This is the designation we will use most of the time. The “u” stands for unloaded, as if it were on an open circuit or into an insignificant load, as found with typical high impedance inputs of modern audio equipment. It is equivalent to dBm only if derived with a 600 ohm load. dBm -measure of electrical power level referenced to 1 milliwatt. No direct relationship to voltage or impedance. Equivalent to dBu only when dBu is applied to a 600 ohm load. dBV -Old designation where 0dBV=1 volt rms. Used mostly in consumer audio. As long as you’re dealing with voltage, not power, dBV can be converted to dBu by adding 2.2dB to the dBV value. dBv -Old designation similar to dBV, but with a different zero reference. This term is identical with dBu however dBu is the preferred usage today. 0dBv = 0.775 volts. For example: +4 dBv = 1.27 v. RMS while +4 dBV = 1.6 v. RMS dBW -Selectively used by a few sources to describe large power output of multihundred watt power amplifiers. 0dBU = 1 watt. A 100-watt power amplifier is a 20 dBW amplifier. (10 log (100) =20) dB SPL -used to describe speaker efficiency in terms of sound pressure levels. If a given SPL is twice another, it is 6 dB greater. dB PWL -describes acoustic power levels. Used mostly to calculate the reverb decay time of an enclosed space.
9
LSR, p.31 LSR, p.32 11 SRH, pp.19-26 10
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VVCC Sound Reinforcement Audio Technician’s Guide Psycho-Acoustics Some comments on how the ear and the mind perceive music. Beats: two notes very close together producing an in-phase and out-of-phase relationship that the ear hears as a “beat.” 12 Difference tone: This is a tone that is heard but is not really present. It its produced by two notes sufficiently far apart (usually a 40-50 Hz separation) producing a beat rapid enough for the ear to hear a lower note that is not there.13 Missing fundamental: When whole number harmonics of a fundamental are produced simultaneously, a listener will hear the fundamental of a note even if it is absent. This is how a telephone earpiece reproduces a recognizable voice.14 Precedence Effect: The human ear gives precedence to the sound that arrives to it first when determining the source of the sound, in spite of the loudness level of any reflections. Sounds, either from supplementary speakers or from reflections, arriving within the first 25 ms of the direct sound are perceived as the direct sound itself. Delayed sounds (up to 25 ms) can be as much as 6dB louder than the direct sound and the listener will still perceive the source as emanating from the direct sound.15 (Also see Speaker delay formula below.) Effective Acoustic Difference (EAD):16 This is the perceived difference between the person speaking and the actual distance to a point in the audience. Half the distance +6dB One fourth the distance +12dB One eighth the distance +18dB
12
LSR, p.44 LSR, p.44 14 LSR, p.45 15 LSR, p.50 16 LSR, p.217 13
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VVCC Sound Reinforcement Audio Technician’s Guide Sound and Equalization (EQ) Wavelength = 1130 (speed of sound) / frequency Frequency = measured in cycles per second or Hertz (Hz). Wavelengths (approximate): Frequency Wavelength17 Frequency Wavelength 25-31.5 Hz ~40’ 50-63 Hz ~20’ 100-125 Hz ~10’ 200-250 Hz ~5’ 400-500 Hz ~30” 500-800 Hz ~24” 800-1 kHz ~16” 1 - 1.6 kHz ~12” 1.6 - 2 kHz ~8” 2 - 3 kHz ~6” 3 - 4 kHz ~4” 4 - 6 kHz ~3” 6 - 8 kHz ~2” 12 - 16 kHz ~1” The audio spectrum spans roughly 10 octaves. Each octave doubles in frequency. This represents a 2:1 ratio. Each doubling in frequency covers the same length on the scale. The doubling in frequency is a logarithmic relationship. The middle of the audio spectrum is not numerically half way between 20 & 20,000 Hz, rather it is half the number of octaves, which is approximately 640 Hz. The audio spectrum can be divided into three “decades” roughly corresponding to the ranges covered by typical speaker components. Low: 20Hz-200Hz, Med: 200Hz-2000Hz, High: 2000-20000Hz.18 The long-term average frequency for male voices centers at about 750Hz. The long-term average frequency for female voices centers at about 1kHz.19 Why 1/3 octave EQ works: There is a minimum detectable difference in sine waves by the human ear. In order for the human ear to hear the difference between two sine wave tones as distinct notes, the tones must be at least 1/3 octave apart. (This is not to be confused with tones played on an instrument.) Minor variations (3dB or less) in frequency response (volume peaks or troughs) within 1/3 octave of each other will have little impact on perceived sound quality. 20
17
LSR, p.185 LSR, pp.19-20 19 LSR, p.215-216 20 LSR, p.44 18
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VVCC Sound Reinforcement Audio Technician’s Guide Frequency/loudness warp: At high levels it is possible for a 110 Hz tone to sound like it is out of tune with its 220 Hz counterpart and even further out of tune with its 880 counterpart.21 Frequency associations:22 ooh (whispered) 125-300 Hz uh (whispered) 160-400 Hz aahh (whispered) 200-500 Hz K (no vowel) 500-2 kHz (w/energy above & below) CH (no vowel) 2k-6 kHz (w/energy below) S (no vowel) 4k-12 kHz (w/energy below) —————— OOOH, deep U 100-250 Hz O 200-400 Hz AAH 300-600 Hz A 500-1000 Hz E 800-2 kHz eeee (chipmunky) 1.6 kHz and up Frequency-related (subjective) Qualities:23 Note: e = energy Less than 40Hz Generally heard only in special effects. Difficult for most sound systems to reproduce at substantial levels. 40-100Hz Too much e in 40-100Hz range: murky, muddy. Too much in 80-100Hz: boomy 100-250Hz Too much e: boomy, muffled, too thick. Too little: trebles lack depth. 250-630Hz Too much e: cloudy, boxy, opaque. Too little: empty, lacking fullness 500-800Hz Too much e: “megaphone-like” 800-1200Hz Too much: excessively hard, “telephone-like” Too little: lacking solidness. 1200-2kHz Too much: blary Too little: lack of clarity 2-4kHz Too much: tinny, trebly, brash Too little: lack of clarity or “bite” (4k) 4-6kHz Too much: sharp, brash Too little: lack of distinctive edge 6.3kHz and above Too much: excessive or annoying sibilance Too little: the sibilants “s z & t” lack zip (6.3k) or sweetness (8k+) 16kHz This is the extreme limit of hearing for adults with very good hearing. Note: While the human ear cannot hear fundamentals or harmonics above 20,000 Hz, newer research has demonstrated it can detect the presence of harmonics at such high frequencies. This is represented by an improvement in sound quality itself.
21
LSR, p.46 LSR, p.104 23 LSR, p.109 22
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VVCC Sound Reinforcement Audio Technician’s Guide Attenuation (reduction) of sound in air per 100’:24 Sorted by kHz: 12kHz at 20% Humidity, sound level drops by 10dB for each 100 feet 12kHz at 90% Humidity, sound level drops by 4.5dB for each 100 feet 8kHz at 20% Humidity, sound level drops by 6dB for each 100 feet 8kHz at 90% Humidity, sound level drops by 2.3dB for each 100 feet 4kHz at 20% Humidity, sound level drops by 3dB for each 100 feet 4kHz at 90% Humidity, sound level drops by 1dB for each 100 feet 2kHz at 20% Humidity, sound level drops by 2dB for each 100 feet 2kHz at 90% Humidity, sound level drops by 0.3dB for each 100 feet 1kHz at 20% Humidity, sound level drops by 1dB for each 100 feet Sorted by percent: 12kHz at 90% Humidity, sound level drops by 4.5dB for each 100 feet 8kHz at 90% Humidity, sound level drops by 2.3dB for each 100 feet 4kHz at 90% Humidity, sound level drops by 1dB for each 100 feet 2kHz at 90% Humidity, sound level drops by 0.3dB for each 100 feet 12kHz at 20% Humidity, sound level drops by 10dB for each 100 feet 8kHz at 20% Humidity, sound level drops by 6dB for each 100 feet 4kHz at 20% Humidity, sound level drops by 3dB for each 100 feet 2kHz at 20% Humidity, sound level drops by 2dB for each 100 feet 1kHz at 20% Humidity, sound level drops by 1dB for each 100 feet
24
LSR, p.54
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VVCC Sound Reinforcement Audio Technician’s Guide Equipment Notes Microphones Microphone sensitivity: 25 -65dBu/Pa is fairly low output -40dBu/Pa is a very “hot” mic Microphone impedance:26 Low impedance 150 ohm or less High impedance (including guitar) 25k ohm or more Microphones [and other signal generating equipment] should be connected to a load with input impedance that is roughly ten times the impedance of the microphone (low input impedance: 1000-1500 ohms, high input impedance: >250 k ohms).27 Amplifiers: Impedance ratings of amplifiers and speakers are nominal values. That is, they just call it that because that’s the closest average of impedances for the amplifier or speaker. Actual impedance varies greatly according to frequency. Typically the impedance in the low range can be up to 3 times greater than mid range (typical derivation of the nominal rating), and rising up to 3 times higher as the frequencies approach 10kHz. This impedance rise in the low frequencies is one reason the amplifier’s power rating should exceed the speaker’s power rating on low frequency components.28 Levels:29 Microphone: Low level, less than -20dBu (77.5mV). Line: Medium level, -20dBu (77.5mV) to +30dBu (24.5 V) For equipment, usually 10dBu (245mV) (non-pro) or +4dBu (1.23 V) (pro). Speaker: High level, +30dBu (24.5 V) and above. Speaker delay formula:30 Delay (milliseconds)= 1000(Distance/1130) (and up to 20 ms more) An estimate of this is 88.5 ms / 100’. The delayed sound must arrive within 30 ms (preferably between 5 and 25 ms) or it will be perceived as a separate event. For a distributed system there should be a delay zone every 20 feet. Speaker impedance formulas:31 In seriesZ=Z1+Z2+Z3 In parallelZ=1/((1/Z1)+(1/Z2)+...(1/Zn)) 25 26 27 28 29 30 31
LSR, p.93 GSSW, p.51 GSSW, p.51 LSR, p.196 GSSW, p.120 GSSW, p.81;LSR, p.226 GSSW, p.89
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VVCC Sound Reinforcement Audio Technician’s Guide Speaker cable:32 Prefer many fine strands rather fewer coarse strands. Load Z <100’ >100’ 8 ohms Minimum 14 ga. Minimum 12 ga. 4 ohms Minimum 12 ga. Minimum 10 ga. Placing speaker cable in close proximity to mic or line level cables risks cross-talk. For best results, to minimize cross-talk, run mic level signals & line level signals in different snakes. Never run lines to the stage monitors in the same snake as mic lines from the stage. Keep loudspeaker level lines as far as possible from lower-level cables.33 Connections: Never connect stereo outputs together with a “Y” cable to achieve a mono signal. At best, this is a poor way to mix signals; at worst, it can cause distortion and may overtax the outputs. Never use a “Y” cable to combine signals. Use a “Y” only to split a signal into two outputs.34 Even though an amplifier’s impedance load can be met with variations of multiple series/parallel speaker combinations, the practical limit to the number of speakers that should be connected to any given amplifier is based on the power output of the amplifier vs. the rating of the speakers. The wattage to each speaker (amp output wattage for the ohm load divided by the number of speakers) should exceed the speaker ratings. Ideally, speakers connected to a channel of an amplifier should be matched speakers.
32
GSSW, p.126 GSSW, p.126 34 GSSW, p.65 33
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Distribution Date: 01/06/09
VVCC Sound Reinforcement Audio Technician’s Guide
Troubleshooting Where you begin to troubleshoot depends on the problem you’re having. Generally, start from one end and work to the other. Follow the path. Don’t jump around. Test one thing at a time. For example, the CD player is not producing any sound. You can start at either end. Does anything else produce sound? If not, investigate that. If so, keep looking. Does the CD player indicate activity? If not, investigate that. If so, keep looking. Are the cables in back of the CD player plugged in? If not, plug them in. If so, follow them to the other end. Are they plugged in? -- to the correct place? And so on. Another example: No sound is coming from the guitar. First, check the obvious: Do you see a signal on the meter for the guitar channel? If no, the signal is not reaching the Console. Most likely the guitar is unplugged at or near the source. Can sound be heard from other sources? If no, is the amplifier on? Is the other equipment on? If yes, proceed. Is the channel turned on? If no, turn it on. If yes, turn the channel off, and starting from either the mixing console or the guitar itself, check all the connections. (Sometimes the guitar will have a volume control. Make sure it is turned up. Some guitars require a 9v. battery. Make sure it is fresh.) After you have followed all the connections from one end to the other and have verified they are all secure, turn the channel back on. You should now have guitar sound. If still no sound, try swapping out various components: cables, DI Boxes, entire channel paths, etc. Turn off the guitar channel and any channels connected to the components you are going to swap. Make the swap, turn on the guitar channel and test for sound. Keep doing this systematically, one component at a time until the problem is resolved.
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VVCC Sound Reinforcement Audio Technicianâ&#x20AC;&#x2122;s Guide
The Over and Under Method of coiling cable Hold the microphone (female) end of the cable in your left hand with the sockets facing you. The cable should trail off the far side of your left hand and away from you. With your right hand, reach about two feet down the cable, grab the cable and lay it in the palm of your left hand, adding a half twist to the left in the process. Reach down the cable again with your right hand, but this time, take the cable in your palm, reaching underneath and grabbing it from the left side. Lift it up so that both of your hands are side by side, palms facing up. This will twist the cable to the right in the processs. Lay the cable in your left hand. Repeat this process until the cable is completely coiled.35
35
GSSW, p.161
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VVCC Sound Reinforcement Audio Technician’s Guide
Credits & Bibliography Significant portions of this training manual were taken from: 1. Live Sound Reinforcement (LSR), by Scott Hunter Stark,©1996 Mix Books 2. Guide to Sound Systems for Worship (GSSW), by Jon F. Eiche, ©1990 Yamaha Corporation of America 3. Sound Reinforcement Handbook (SRH), by Gary Davis & Ralph Jones, ©1990 Yamaha Corporation of America and Gary Davis & Associates
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VVCC Sound Reinforcement Audio Technicianâ&#x20AC;&#x2122;s Guide
Index 1
D
1/3 Octave EQ........................................... 30 11:00 Worship........................................... 18
dBm........................................................... 28 dBu............................................................ 28 dBv............................................................ 28 dBV ........................................................... 28 dBW .......................................................... 28 Decibels............................................... 22, 28 dBm....................................................... 28 dBu........................................................ 28 dBv........................................................ 28 dBV ....................................................... 28 dBW ...................................................... 28 Denon DN-770R............................................... 10 DN-C630................................................. 8 DN-C635................................................. 8 DI Box....................................................... 21 Difference tone.......................................... 29 Dir Pre......................................................... 6
8 8:00 Setup ................................................. 14 8:00 Worship............................................. 16 9 9:30 Worship............................................. 17 A Amplifiers ..................................... 19, 27, 33 Attenuation................................................ 32 Audio spectrum......................................... 30 Aux.............................................................. 5 Aux buses.................................................... 5 Auxiliary outputs ........................................ 7 B Balanced.................................................... 21 Beats.......................................................... 29 C Cables........................................................ 19 Types..................................................... 20 CD ............................................................... 8 Cue .......................................................... 8 Programming........................................... 9 Choir mics................................................. 27 Clipping..................................................... 25 Connections......................................... 20, 34 Connectors Cannon .................................................. 20 DI Box................................................... 21 RCA ...................................................... 21 Speak-On............................................... 20 TRS ....................................................... 20 TS.......................................................... 20 XLR....................................................... 20 Console ................................................. 2, 22 FOH......................................................... 2 Cue ........................................................ 8, 10 CD ........................................................... 8 Tape....................................................... 10
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E Effective Acoustic Difference................... 29 EQ ......................................................... 4, 30 Equalization .......................................... 4, 30 1/3 Octave ............................................. 30 F Fader ....................................................... 6, 7 Feedback ................................................... 26 FOH............................................................. 2 Frequency.................................................. 30 Associations .......................................... 31 Qualities ................................................ 31 Front of House ............................................ 2 Fundamentals ............................................ 28 G Gain........................................................... 25 Groups......................................................... 6 H Hand-held mics ......................................... 27 Harmonics ................................................. 28 High Impadance ........................................ 21 High pass..................................................... 3
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VVCC Sound Reinforcement Audio Technicianâ&#x20AC;&#x2122;s Guide I
R
Input ............................................................ 3 Instruments................................................ 19
Recording................................ 10, 16, 17, 18 Routing.................................................... 6, 7
L
S
Levels .................................................. 25, 33 Loudness warp .......................................... 31 Low Impedance......................................... 21
Setting levels ............................................. 25 Shelving ...................................................... 4 Signal Amplified .............................................. 21 Balanced................................................ 21 High Impedance .................................... 21 Line level .............................................. 21 Low Impedance..................................... 21 Mic level ............................................... 21 Unbalanced ........................................... 21 Solo ......................................................... 6, 7 Solo-In-Place............................................... 6 Sound checks ............................................ 14 Speakers .................................................... 19 Cable ..................................................... 34 Delay ..................................................... 33 Impedance ............................................. 33 Ohms ..................................................... 33 Submixer ............................................... 8, 16
M Memory..................................................... 10 Microphones ................................. 19, 27, 33 Placement.............................................. 27 Missing fundamental................................. 29 Mixer......................................................... 19 Mute ...................................................... 6, 18 Mute groups ................................................ 7 P PFL.............................................................. 7 Phantom power ......................................... 23 Playback...................................................... 8 submixer.................................................. 8 Power Down............................................... 18, 24 Phantom ................................................ 23 Up.................................................... 14, 24 Powering down ................................... 18, 24 Powering up ........................................ 14, 24 Pre and Post............................................... 23 Precedence effect ...................................... 29 Pre-EQ......................................................... 5 Pre-Fade Listen ........................................... 7 Pre-Fader..................................................... 5 Proximity effect ........................................ 27 Psycho-Acoustics...................................... 29 Beats...................................................... 29 Difference tone...................................... 29 Effective Acoustic Difference............... 29 Missing fundamental............................. 29 Precedence effect .................................. 29
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T Tape........................................................... 10 Cue ........................................................ 10 Direction ................................... 16, 17, 18 Memory................................................. 10 Recording.................................. 10, 16, 17 Twin Rec............................................... 17 Tape Recording......................................... 18 Troubleshooting ........................................ 35 Twin Rec................................................... 17 U Unbalanced ............................................... 21 W Wavelength ............................................... 30
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VVCC Sound Reinforcement Audio Technicianâ&#x20AC;&#x2122;s Guide
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