Theatre Sound

Information paper for schools using sound reinforcement for school theatrical productions

Presented by: Paul Johansen. MD Stage Sound End Ltd Ph: 09 444 8776

The following information has been compiled with our compliments for the use of teachers and amateur production managers who are actively involved in school theatrical or musical productions such as operetta.

It is hoped that by following the various suggestions herein that substantial improvements can be made to these types of shows as my experience has shown me that very little basic and to the point information is available for this purpose. This information is offered in good faith and its use is at the readers own risk. It does not contain anything more than basic safety operational advice and care should be taken to consult any OSH regulations that may well apply when hanging such objects as loudspeakers from a height or running mains cabling in the areas where people are likely to walk. We accept no responsibility whatsoever for the correct or incorrect use of the information contained in this article. Please do not attempt to read and use the information offered on the fly as it were. It is intended for private study in an uninterrupted atmosphere as the writer is attempting to install a way of thinking in the reader that should become instinctive and intuitive with the passing of time and experience. Hence it is hoped the reader will actually absorb the meaning of what is being talked about rather than merely reading the words and following it like a map.

A Basic Overview.

The way an audio reinforcement application is approached varies depending on the type of show one is doing. For example if we were doing a full on rock opera we would never get a satisfactory result from the singers if we tried doing this with lapel mics because they are usually clipped on too far away from the mouth to allow enough volume before they feedback. Similarly if we were doing a play or drama production using a headmic would be absurd to say the least. To begin with they tend to look hideous and invisible lapels will work just fine in the same application.

The object of the exercise is as follows: We are trying to cover as much of the seated area as we can with good clear audio with as little hum, hiss or feedback as possible and the minimum of visual interference of the performers. We need to be far more concerned with the people seated near the rear of the hall than we do about those seated in say the first three rows of seats. This is because the people near the stage will be receiving a reasonable level of unamplified sound directly from the performers themselves. The exception to this rule is when we need to get the vocal level above the sound from the band or orchestra but in this case feedback is far less of a worry because we should be using a headmic and this means we can place the loudspeakers closer to the stage itself. If we were using lapels we should ideally have a situation where we did not have to compete with the sound pressure coming from a loud band. To put this another way the further down the side aisle we can place the loudspeakers the better those people at the rear will here but we should be careful not to move them to far back because then we may be compromising those sitting near the front. So it is a balancing act.

The systems used for a rock opera need to be far more substantial than a system being specked for a drama production. This is because we have the problem of creating impact and we must also attempt to get the vocals well up in level to be audible over the band. In my experience we are seldom offered the budget to provide an ideal sound system for a large ambitious production and we often end up making serious compromises in order to satisfy the schools financial limitations.

The Audio System Setup Arrangement.

The setup of the reinforcement system can make or break a show. If you go the extra mile with this it can make a huge difference to the audio quality and hence the audiences enjoyment of the event. Remember it is not only the kids that are on display here. The audience will probably think that the sound production was not the domain of the performers and will assume that a teacher has taken responsibility for this increment.

Sometimes the system available will be very substandard indeed and not much to work with at all. This of course is most unfortunate but many schools can afford little else so you may well have to work with what is available rather than ringing me with a non-existent budget of $4000 for hire gear.

This article assumes some basic knowledge of sound equipment but is by no means intended to be a full tutorial on audio engineering. If you want this then please ask me about my book and I will let you know how this is going.

Equipment Placement

I will attempt to describe the set up of a very basic system first and then grade it upwards by adding the increments of a more substantial system as we go.

 The best place to mix from by far is out front. Ideally right out in front of the stage about two thirds of the way back. This is seldom possible because it will tend to clash with an optimal seating layout. If you have to move to one side then that is all there is to it. You will not however be able to get the best stereo image if you are aiming for this. You may also need a riser to see clearly over the heads of the audience but using one may very well block the view of those seated to the rear of you. If you only have a powered mixer then you will need some long speaker cables to run down the sides of the hall to reach your mix position. You may need to hire these but the $20 to $30 it will cost you is worth every cent to enable you to work from this ideal position.

The next consideration is where to place the loudspeakers and this is also crucial to a good outcome. If the speakers are fixed to the wall at each side of the front bulkhead this may not be ideal if you are using wireless lapel mics as they may be to close and therefore prone to feedback and not loud enough to give you any noticeable increase in vocal level. Remember you are always battling this evil. Feedback is the single biggest problem anyone attempting to use wireless lapels has to face. Let’s assume the property officer has agreed to let you shift the speakers.

Lets also assume that you only have one pair of composite speakers and that you can place them on stands. Bring them down the side of the hall about three to six pews back and set the stands as high as you can ensuring that they cannot topple over and damage someone’s head. This setup is still not ideal. If you can secure them up at the window level, lashed to a laminated arch or steel RSJ then you are going to get the maximum positional location from them. You should attempt to point them at a seated person around two thirds of the way back towards the center of the hall. For a single pair of composite speakers this is about as good as it gets. The only better position is usually impossible to achieve and that would be directly above the Center of the stage about over the front row of seats perhaps hung from a lighting truss. They would need to be touching each other and angled slightly outwards from each other pointing towards the half way back mark at the floor on the left and right hand sides equally. This is considered as close to perfection as is normally possible but getting them up there may be a serious challenge and you need to run cables to them as well. This means all speech will be mixed in mono but this is a small price to pay for a top-notch result. Keep in mind that it really requires an experienced eye to set up the central speakers. It is important that they are correctly located to provide the optimum results. If they are too far forward or to far back or not angled correctly they will not work properly and the result will be uneven coverage or a dead spot.

For those who would like a semi technical explanation of why this concept works so well I will attempt to be brief. Speakers spread apart cause the sound coming from them to reach a person’s ears who is seated off center at slightly different times. This causes an aberration known as phase shift. This in turn results in a substantial loss of clarity. The other big plus is that it improves the front to back ratio meaning that the people near the front do not get overpowered by the sound level and the people at the rear of the hall do not have their sound blocked by the people sitting in front of them. In other words they get a direct 'line if sight' as we call it to the loudspeakers. All in all, a most desirable situation indeed.

If we have the opportunity to do things in this way the next big improvement we can make, assuming we have the equipment to make this possible, is to have the best of both worlds, i.e. a pair of speakers for the vocals only up top and in the centre and another pair at the left and right sides as described earlier for the music so it can be performed in true stereo sound. To have the music in stereo obviously we need to have the speakers to the left and right but to get the best from speech performances to maintain the highest quality we need them in one place above the stage and in the Centre.

Going one stage further, if we were doing a rock opera we would ideally like to add a pair of subwoofers to the system and we would locate these in the front of the stage walls on the left and the right sides. This would also usually require an amplifier rack which we would normally locate in the stage wings or under the stage and well out of sight of the audience.

Fold back or Side Fill Speakers.

Fold back is used in slightly more sophisticated systems to enable the singers to hear themselves above the band or backing music. This makes it far easier for them to sing in tune. Floor wedges are most commonly used but these cause a visual distraction so if possible a pair of side fill speakers is preferable. These are usually hidden by the stage wings or the curtains and out of sight of the audience which makes them visually preferable to floor monitors.

If fold back is to be used in either form care must be taken with feedback. It is generally not possible to use a fold back system in conjunction with radio lapel mics. Even the very best soundmen find this extremely difficult to do successfully. Also remember that doing musicals with lapel mics tends to be very tricky due in the main to the fact that they are usually located at chest height and quite a long way from the singer’s mouth. Taping them down the side of the vocalists face can work a lot better, but even so a good graphic equaliser well adjusted is essential in order to achieve a reasonable result using this technique. The same can be said for side fills as while it is great to have monitoring for the vocalists feedback will be an issue needing special treatment to avoid.

The Multi core.

If you are mixing from in front of the stage you will definitely need a multi core cable. If this is to be installed permanently it will require a cable trunk or conduit that has been previously installed. Sometimes a multi core can be run underneath the hall floor, over the ceiling or along the central RSJ at the apex and held in place with ties, brackets or glue. A permanently mounted stage box should be attached to a stage cavity wall.

This allows you to combine all the microphone way lines in to one cable similar in size to a garden hose. In non-permanent situations this is usually run down the side of the hall or strung along up at window height and held in place using gaffer tape or nylon ties.

You can use a multi core in conjunction with a powered mixer but more often they are used to feed a separate mixing console with the amplification stored in a rack at the front as described above. They have a stage box with female XLR microphone sockets mounted in a metal case called the stage box. The mic cables are usually run along the floor at the front or rear of the stage and held in place with gaffer tape.

Setting Up the Microphones.

If we are going to get the best out of our sound system we are going to have to pay careful attention to how we choose the microphones and how we place them.

There is a lot of myth surrounding these devices and this has been going on since they were invented. There are good and poor quality microphones. Microphones best suited to percussion use and microphones best suited to vocal use. Microphones suited for musical instrument use and microphones suited for long range or distant mincing. Some are best used on the floor and some on a table or lectern and so it goes on and on, or so we are told. In my experience any good quality cardioids (directional) microphone, either of the dynamic or condenser variety can be used to work well almost anywhere if used correctly with the equalisation set intelligently. The rest is mainly hype and I have yet to see this proven otherwise.

If something is too quiet you are going to need to close mic it to get over the volume level of the band so it can be heard. If you are having serious problems achieving this even with a close up mic you are going to have to ask the band to turn down. If they cannot or will not do this, you only have two other choices. You either record them and get them to mime the music or you place them in another room out the back. Once they are presented with these two choices they will generally turn down. This can be a big ask for a highly dynamic band especially one with a heavy acoustic drummer. A drummer using an electronic drum kit can be turned down with a volume control on his controller unit. A microphone used to raise the level of a voice or acoustic instrument such as a flute or bongo drum needs to be placed as close as possible to the noise source in general. Other techniques are often used by experts but this is beyond the scope of this article. If you can hide the mic stand by stealth or use tape to secure it so it is not visible to the audience then this is highly desirable indeed. Small microphones such as lapels can also be used as these are very subtle visually and easily hidden. Try to point any directional microphones away from the loudspeakers or in the opposite direction as this can greatly help in the elimination of feedback. Do not allow any mechanical contact to occur between the microphone and any object that may have some movement or you will get a loud rattling sound occurring and you do not want this to happen. If you can place any mic stands on carpet or soft matting this will help foot noise vibrating the mic stands during quiet passages or speaking parts. There are many ways to hide microphones such as plants or taped to a shelf or broom handle. You can place one microphone on a table with six people spread around it and you will be amazed at just how much lift you can get provided you have set the speakers up as outlined above. Shotgun mics are best used at the front of the stage just poking over the stage edge. This method helps eliminate the floor reflection and also helps reduce foot noise. These are best used to raise the overall spoken parts and are not likely to give you any perceptible vocal lift over an electric band. A vocal group or chorus can be group milked with say one mic to every three singers or more in most situations. If you can’t hear them over the band then the band is too loud. Ask them to drop the level or get another job. Always remember, they are there for the singers not the other way around. They are not the key part but they can badly compromise the key parts if they will not co-operate here. Don’t stand for any nonsense or you will waste a lot of valuable rehearsal time getting nowhere.

If you need to mic up an acoustic band then you may need to mic each instrument individually as acoustic instruments will usually not cut it in a large hall especially if they are in front of the stage and close to the loudspeakers. Light percussion such as small bells etc do not have much natural volume and will need some assistance. If you need to mic an electric guitar band which is most unlikely, then try using a single microphone or two at the most above and angled downwards a metre or two away from them. Headmics are a great way of getting vocalists over a band in level. They always sit very close to the mouth and never cause feedback problems. The trouble is they tend to look rather obvious and the small invisible ones are extremely expensive and can also be a bit fragile as well. The other advantage is their sound quality. They usually sound almost as good as a hand held and they eliminate another problem called weaving. This occurs when a singer does not hold the mic steady in one position which results in seriously fluctuating vocal sound.

Boundary microphones are another option for speaking parts. They sit on the floor and in some situations they can work better than shotgun mics because the actor can often get closer to them. They are Omni directional or 360 degree sensitive so they can also be prone to feedback. There are two enemies, feedback and a loud band so you may be working against both of these in some cases. As you can see by the above dialog it is a question of fine tuning things and playing around with what you have in order to get the best results. You may have two chaps leaning on a bar top talking to each other using one mic sitting amongst some fruit on a plate that is also sitting on the bar. No one in the audience will know to look for it at all. It’s as though it’s not there.

There is no one magic Centre and often trial and error is this only way to get things to work. Having done a lot of this I can generally see what is going to be successful as soon as I get the gist of what is going on. Clever techniques of concealing small microphones is often the way to go if you have enough of them to go around all the scenes and personal. If you have scene changes with closed curtains you can always move the mics around of course. Some microphones will pick up the sound all the way around them and some highly innovative engineers, such as myself, have connected these to lapel transmitters and these can be carried around by the actors like a pack of fags and placed on tables and shelves etc. Doing this can save several microphones in some cases. I tried this out at Wailuku College in 2003 and it worked a treat. It was amazing how much lift was achieved when compared to the actors speaking without any reinforcement at all. It more than doubled the volume level.

Placing the Microphone Radio Receivers.

This can be very important. The mic receivers are like a transistor radio but are working with a much smaller transmitter. Just a few Milli watts instead of the hundreds of watts coming from a radio station. This means we must allow them to receive as strong a signal as we can give them if we want them to pick up all of what is meant for them. If we place these receivers out front at the mixer position to save on cable and speed things up we may be making a serious compromise that will not become apparent until the hall fills up with hundreds of people. Once the show has begun and we are getting drop out all over the place there will be absolutely nothing we can do about it until the end of our first opening night show. How embarrassing.

It is simple, don’t take the chance. It’s just not worth it. I have seen this one cause more calamities than I care to remember.

The best place to put the receivers is on a platform along the side of the stage wall on either side (which ever causes the least congestion) so that the transmitter antennas and the receiver antennas get a clear view of each other. This is called 'line of sight'.

Even using this technique is no guarantee that you will not experience drop out but it certainly helps. Drop out can also be caused by a nasty logy called RF absorption. This is caused mainly by the steel work in a buildings construction. There are a few potential remedies the first being to relocate the receiver and the second being to change to another frequency.

If this is not practical and the drop out is only happening in one or two places on the stage, you can place a mark on the floor using masking tape so that the performer wearing the problematic mic knows not to stand on that point.

Direct Inject Boxes.

These natty little devices normally called DI boxes are used to replace microphones when electronic instruments need to be fed into a PA system. They are plugged into the output of such items as keyboards or drum machines and they convert a phone jack output to match a mic cable thereby by balancing it electronically to be fed into a mixer. If they can be used then they are far preferable to a microphone as they do not pick up spill from other instruments close by.

Some Mixing Techniques.

The person doing the mixing has the unenviable task of concentrating non-stop throughout the entire performance. His job is to set the volume levels of each mic to suit the scene in question with each mic balanced to each other mic with no feedback and a nice sounding equalisation setting. Any mic channel that is not in use should be closed immediately the actor leaves the stage. We have heard some hilarious stories about people who have finished their part and then gone to the toilet still wearing their lapel mic when the engineer has forgotten to turn down the volume or mute the channel. The less said about that one the better.

Setting up a sophisticated mixing console is beyond the scope of this article and here again if you want to read about this in depth ask me about my upcoming book and you will find all the answers there. Suffice is to say that mixing is both a natural and acquired art so attend all the rehearsals and strive for a natural sound. Remember also that things will change for the better as far as the acoustics in your hall are concerned with the reverberation disappearing almost completely (in a full hall) and the volume also dropping radically as well. You will need to be ready with your fingers wrapped around the master volume control when things start up for the first time because you will definitely need to raise the level substantially. It is a good idea to mark the operating position of the volume slide pot with removable adhesive paper. Do not use an ink marker or felt tip pen directly onto the control surface as this is often permanent and you will not be to popular with the sound company when you hand back their badly soiled mixing console. If the mixer has mute buttons fitted it is far better to use these rather than moving the channel fader up and down all the time between scenes. Run a length of masking tape along the front edge of the mixer and use this to write the names of the characters associated with that channel underneath the volume fader.

If you have different scenes then use more than one strip of tape and remove them as the scenes change so you know exactly what is going on all the time. You can also write little notes on this tape to remind you of things that may change during that scene. Make sure you have sufficient light and ensure that it is aiming downwards onto the mixer and not in the audience’s eyes. Nothing is worse than this. If you are using pre recorded sound cues or music try to avoid using a solenoid-activated cassette deck as these make far too much mechanical noise. Where possible a mini disc or PC should be used. These are completely silent and don’t interfere with the show in any way. Set your sound cues up so that they are nose to tail in the order that they are going to be used and on separate tracks with their numbers recorded on your cue sheet. If you get the record level correct you won’t even need to re-adjust the volume control for each sound effect you use.

Use a communication system or intercom if you can justify the cost. This will keep you in touch with the stage and help sort out any problems if they occur without leaving you in the dark as it were. It is also a good idea to allow the lighting mixer to sit alongside the audio mixer so they can work in conjunction with each other. Try to keep the dimmer pack well away from the audio system and on a separate mains earth if at all possible. This can greatly help reduce the unpleasant buzzing that is caused by mains interference from the dimmer pack. If this is not possible you can create an artificial earth by driving metal rod into the ground outside the hall and earthling the dimmer pack to this. Make sure you water the earth rod for better conduction. I would check the OSH regulations on this one as well.

Effects Processors and Their Uses.

This information is included to whet the appetite of those who are dedicated to doing things really well and who would like to move to the next level of sound production. As separate articles could be written on each and every one of the following items please do not expect too much from this section. Here again I can offer you a far more advanced version of this document if you would care to contact me directly.

Graphic Equalisers.

These are a wonderful tool in the right hands or a dangerous weapon in the wrong hands. They have two main purposes with the emphasis being on the first. Their prime purpose is to correct aberrations in the overall frequency response of a sound system in a given environment and this includes the loudspeakers. Because different halls or venues have their own personality or sound characteristics we cannot expect a sound system to perform in an identical manner in every area. Ideally we would say we are looking for a flat frequency response which means all the notes in an eight or ten-octave scale should be heard at the same volume. We do not want any loud or quiet notes as this would not be considered musically accurate. A third octave equalizer has three separate volume controls for each octave. This means we have quite a lot of control over the sound pressure level at all frequencies. By adjusting the boost and or cut at the various points across the audio spectrum we can trim out the vast majority of peaks or dips that may be occurring. This is done in one of two ways. We can either use our ears or we can opt to use an electronic device called a spectrum analyser. A spectrum analyser uses a microphone to pick up the sound coming from a loudspeaker and displays its level relative to a flat response on a graphical display that usually uses lads or a fluorescent bar graph. The display alters as the graphic equalizer is adjusted and this gives a visual indication to the engineer as he alters the frequency response of the audio system. This method unfortunately only works where the microphone is located unless several microphones are placed in various locations, the accuracy of doing this is highly questionable. The other method entails good taste and a lot of experience and this is done by listening to a piece of very familiar music and setting up the system by ear. Both methods have their strengths and weaknesses but I prefer to listen to the system, move around the whole area and try to get a smooth sound on average across the floor space. The second purpose an equalizer has is to compete with the feedback menace. This is done by picking the offending frequency and reducing the volume level at exactly that point. We can force the issue at a point where we think ringing is going to occur by gradually raising a selected fader at the offending frequency and then dropping it back down very quickly to correct it. This should not be done by inexperienced persons or damage to horn diaphragms will result in major repair costs. It is fair to say that when equalizing an FOH (front of house) or main speaker system that feedback should not be an issue unless we are using lapel mics. Most feedback is caused by a fold back system that needs to be set to a very loud level.

Compressors.

Compressors have one purpose only and any one that tells you otherwise has fallen victim to myth. They were designed to help compensate for poor mic technique. Their chief function is to automatically reduce the volume in order to overcome some of the effects of weaving. Unless a vocalist knows how to move the mic away from his mouth when he sings loudly and then bring it in again when he sings softly he will most likely be in need of the help of a compressor. The big downside of these devices which do nothing whatever to improve the tone quality of an audio system is that they tend to destroy the natural dynamic content of a performance unless they are used carefully and with subtlety. An in depth description is beyond the scope of this article but readers would be wise to make note of the existence of these devices because they can come in very handy with young would be rock opera singers.

Electronic Reverbs and Echo Units.

These devices do as their names suggest. They add reverberation or echo to a performance. Here again they should be used with intelligence and care by someone who knows what he is doing. Many times I have seen a so called engineer dialing in reverb when the clown is working in a highly reverberant room. Whatever for!

Noise Gates.

These are really useful devices when they actually work as intended. They automatically block the sound going to a mic channel when the minced up item is not

Being used therefore to stop any so-called 'spill' sound from entering that channel. The problem here is that if the spill they are meant to be stopping is loud enough the gate opens again making its inclusion in the chain less than useless. Used properly however they can be quite useful and do tend to improve the sound quality.

Helpful Hints and Useful Tricks.

• Isolation is quite important in many instances on order to keep things from spilling sound into microphones where it is not wanted.
• Point microphones at an angle that is away from other noisy sources of sound so that they are less likely to pick up the sound generated from the adjacent items. It is also important to try to point them away from fold back speakers to keep feedback under control.
• If you are using an acoustic drum kit try to set it up on a large square of carpet. This helps to stop the stands from moving around on the smooth floor and also reduces the vibrations traveling in either direction through the drum stands. Placing the drum kits mic stands on the carpet also helps eliminate mechanical spill as well.
• Never let any of the stands come in contact with the side of a drum frame. Make sure the kick drum mic is up close to the head contact point but not touching anything other than perhaps the edge of the hole in the front skin.
• Sometimes a very good result can be obtained by mincing up a drum kit using only two microphones. These should be placed on stands set high with one at each side of the kit about half a metre above the cymbals and angled downwards and inwards slightly. This will work well on a stage where sheer volume is not needed from the band.
• Use gaffer tape to hold any mic in place that may be likely to move or fall off the stand during a performance.
• Do not over tighten the mic stand clutches as this can easily cause permanent damage to the tension screws.
• Tape any loose mic leads to the floor to stop performers tripping over them during a performance. This is very important and not worth the risk of overlooking.
• Always keep mains cabling away from mic cables especially if they are unbalanced or use phone jacks instead of XLRs
• A small coin or an ignition key can be most useful for tightening up loose mic clips or freeing up a stuck thread adaptor if you don’t have a large screw driver handy.
• If you have a serious cable mismatch and you know what wires need to go where cut the connectors of the cable ends using a pair of side cutters or a Stanley knife and twist the relevant wires together and separate them using sell tape. This can get you out of a serious jam if you are running out of time. It is only a five minute job to undo the temper damage done by doing this later on in a technical workshop.
• If you ever need to lift an earth to prevent an annoying 50 Hz hum it is not wise to lift the mains earth. Remove the screen braid at the output end of the cable not the input end. Remember hum usually indicates that something is being earthed twice.
• Using a mic on a cable can be a great way of finding a break in the signal chain and this will even work when plugged into the input of a power amplifier. If you lose sound and you need to find out where it has dropped out start at the power amps and work backwards to the mixer. You will not get any sound if you plug a mic into a speaker socket however as it does not generate enough current to drive a speaker.
• If you lose one channel of an amplifier, as long as this has not been caused by a faulty speaker lead, you may well be able to run both speakers off one side of the amp provided you do not exceed the output load rating e.g. it may be 4 ohms max.
• When using lapel or headmics always has a careful student attach and remove them from the performers. This is very important and can save a lot of damage to the delicate cables that connect the microphone to the transmitter or body pack. When fitting them try to ensure that these cables cannot be snared on anything by running them inside clothing or using tape or rubber bands to hold them in close to the performer’s body.
• Always keep a good supply of spare batteries close by as well. So called fresh batteries will often do only one long performance before getting too low in voltage to make it through a second show. Bear in mind that batteries do not have a very long shelf life so the ones you just purchased may be almost flat and may not go the distance. Be sure to turn the mics off before you remove them and make sure the sound man knows to close the associated channel before this is done. If you must leave them turned on then use their mute position on the body pack to stop any interference that they may well cause when sitting idle. If you are using rechargeable batteries be sure to have more than one spare per mic and plenty of chargers available or you may be caught short.
• For any further information on this or other blog topics please call Paul Johansen on Ph: 444 8776