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A BRIEF GUIDE TO STAGE SOUND

Funny old stuff, sound. Its around us all the time and its pretty vital to our understanding and enjoyment of most live entertainment.
Before the advent of 'sound equipment' in theatres and halls the performers used technique and skill to make the audience hear and understand them. Musicians played acoustic instruments, and achieved a balance by playing louder or softer to suit. Sound effects were produced live by a series of ingenious means.
Performance venues were designed and built so that the sound on stage carried clearly to all parts of the auditorium. (The acoustics in Matcham designed theatres are infinitely superior to those in all (that's ALL) modern theatre buildings.
Greater and greater reliance on electric sound reproduction and re-inforcement has bred a generation of lazy performers. Higher and higher sound levels from TV, radio and 'in car entertainment' has produced audiences that cannot listen.
The ambient noise level in auditoriums is creeping back up as more and more members of the audience treat a live performance as if it were TV. Audiences now think nothing of talking during a show, rustling sweet wrappers and so on.
These general trends mean that even in tiny village halls the reliance on the sound department is higher than ever.

Unfortunately sound is an area which has for many years been the poor relation in live entertainment.
This situation is changing in the big professional venues so in a few years the small scale and amateur world will start to see things improving.

There are, basically, two general forms of sound in venues. Re-inforcement, where the performer's voice is amplified to increase audibility. This amplification is done very subtly, and at its best is so gently done that the audience is actually unaware that any sound system is in use at all.
P.A. (public address) is much more blatant, and ranges from an amplifier & speaker arrangement to play music and sound effects, through tannoy style horns on outdoor events for announcements to seriously big kit for musical events and rock concerts.

Much of the success or failure of sound is a subjective matter of opinion. I spent 6 months on tour as the sound engineer with a major touring production of 'Sound of Music' many years ago. I got the re-inforcement to a level of subtlety where even we professionals had to concentrate really hard to tell what was live and what was re-inforced. Venues loved it. The management at Bradford Alhambra said it was the best sound they had ever had. The producers of the tour didn't like it, because they had paid a lot of money for the equipment and couldn't tell whether they were getting their money's worth.

On the P.A. front life is much easier. But even here the divergence of opinions is staggering. Some like it loud, some like it soft. And within the mix everyone has personal preferences.....but we are getting ahead of ourselves.

Look at an old record closely and you will see little wiggles in the grooves. These wiggles are the physical manifestation of sound waves. If you make a noise down a microphone the mic converts this noise into tiny electical impulses.
These tiny electrical impulses can be amplified and fed to a loudspeaker. There they are used to make the speaker cone move back and forth. This movement compresses and stretches the air and recreates the original noise.

Within our industry this basic principle is at the heart of most stage audio. The world of digital sound exists alongside this, and involves changing the electrical wiggle to a series of on/off digital pulses early in the system, recording, treating, storing or whatever these on/off digital pulses, and then converting them back to electical wiggles just before the amp-speaker stage.

Taking all this back to front: the digital methods of recording offer major advantages over analogue ones (that's basic electrical wiggles) as digital signals are not subject to any degradation, and can be treated in various different ways very successfully. The digital recording methods are at the heart of CD, MP3 and mini-disc. Within the small stage world more and more amateur and small scale performance companies are turning to these methods of recording for both music and sound effects replay at live performances.

The CD enables you to find individual tracks quite quickly, and start them fairly accurately on cue. Most amateurs, however, do not have access to facilities to edit CDs (you can do this by using your CD writer of course). MP3 and similar files can be manipulated on the hard drive, and instant replay achieved by using a PC in the control room to run sound cues. (set up the various cues as desktop icons and click when required). The best option however, in the absence of PC facilities, and the one that allows editing, track numbering and naming, etc. is probably the mini-disc.

If none of these recording formats are available most amateurs rely on cassettes. It is notoriously difficult to cue up a cassette. (reel to reel tape is vastly superior in every respect if you still have that facility), and the best way to proceed is to record each cue at the start of a separate (short) cassette.

Speaker positioning is an area that causes major headaches for the small user. Instinct makes most people put one speaker each side of a conventional stage. While this may work for simple background music replay and some occasional effects throughout a play the technique is fraught with problems.
Generally such speaker positioning will result in the extreme ends of 'A' row of the auditorium receiving a higher sound pressure level than the back rows of the house. This means that the levels you set will be a compromise and will probably satisfy no-one. Where possible for small scale shows we are now recommending a simple centre cluster of speakers flown just above the middle of the proscenium arch. This sacrifices stereo, (although an image position can be achieved by the addition of a pair of small speakers in the conventional left/right places to provide a 'pan' position without using high level output.) but gives a much more even coverage of the auditorium seating and avoids many of the feedback problems that arise from having speakers in the same plane as the microphones where these are in use.
(Feedback (not to be confused with foldback) is what the Americans call howlround, and is the unpleasant scream caused by a microphone or microphones 'hearing' the speaker output and sending that sound back round the system again and again)
(Foldback (not to be confused with feedback) is sound sent to the performers onstage...as opposed to that sent to the audience. Generally this will only be done on musical events, and may be as simple as the replay of recorded music for a dance show (to keep the dancers in step) or may be some or all of the instruments and/or voices involved in a musical performance. Bigger musical events may have several different foldback sends running simultaneously, where diferent artists want to hear different things, and of late much foldback is sent to IEM (in ear monitoring) cutting down on the sound levels and numbers of speakers onstage)
With outdoor PA for announcements and so on we now do our best to do this business of keeping the speakers high up in the air. (we do mast based systems for outdoor PA at fetes, carnivals etc.) this allows us to run relatively high sound pressure levels at the PA horns to carry over a wide area without the punters cringing with earache as they pass close to the system.

Where the show requires microphones several choices need to be made. Microphones fall into various different categories.
'Omni-directional' these mics pick up sound from all directions. Mostly best avoided on stage due to feedback problems (you can't point them away from the speakers to cure this!) You will find that the 'tie-clip' mic on that kind of radio mic system is an omni.....that's why you will have feedback problems with those!
'Uni-directional' sometimes known as 'cardioid' because of the heart shaped graph of the pick-up field. These mics reject sound from behind them. Most vocal mics are cardiod.
'Hyper-cardiod' these are like a cardiod mic...but with greater rejection of the noise coming at them from the side too. Sometimes, rather inaccurately known as 'rifle mics' they do not pick up sound from further away, as commonly supposed, they just let you put a bit more gain into the system before feedback breaks in.
'PZM' or 'pressure-zone-microphone', a small capsule that is laid on a hard flat surface (floor, table or wall) and picks up broadly in a hemisphere. Some of these come with a metal sound plate attached (British police use this type in interview rooms for recording). While these are physically discreet (which may be an advantage when trying to do re-inforcement) you would probably do as well to use a cardiod mic on a stand pointing down at the front edge of the stage fixed about half an inch off the stage surface. (Yes I know that sounds odd...but it really is a good technique to try for re-inforcement)

A live (close miked) music event is probably easier to deal with than re-inforcement because if the performers have any sort of mic technique (and that starts with pointing the wretched thing at their mouths) a pretty good sound pressure level will be arriving at the microphone capsule. This means that the system can be run with much lower gain, and therefore the risk of feedback is significantly reduced. The sound bod can therefore spend his time concentrating on what the show sounds like...rather than battling on the edge of unpleasant noises all the time.

Of course re-inforcement is the most difficult thing to do. It is really really really difficult to amplify the feeble voice of an actor. Usually what happens anyway is that a director realises at the last minute that his cast cannot project properly (that's a bit like taking on a window-cleaner who can't climb a ladder) and decides on adding sound gear at the last minute. The cast sees the gear arrive, and immediately assumes that it doesn't have to try any more, the sound level drops, and the audience still can't hear the script. The best answer (why should I tell you this.....we hire equipment!) is to make your cast speak up.

Some sort of equipment is needed to 'mix' the various signals together. In very simple set ups mixer and amplifier are combined in one box as a 'mixer-amp'. In most cases these will have a knob for each channel and a 'master' knob to control the overall level. This is the very simplest arrangement, and, frankly, less than satisfactory for anything but the crudest of control.

More suitable for our stage purposes is a proper mixer. This will have, for each channel:
A gain control:-
this is used to adjust the level of the incoming signal, whether it be mic level or 'line' level from a deck or similar, to suit the internal circuitry of the desk. Generally we want to bring the signal up to 0db, line level, (about three-quarters of a volt) before treating it in any way. Mics produce minute electrical levels which need to be amplified as soon as possible in the chain, decks (such as CDs, mini-discs, tape decks etc) are probably producing line level already and need no amplification at the input stage. The setting of the input gain on a mixer is very much a matter of using your ears and your experience. We want to ensure that peaks in the sound level coming into the channel input do not distort the circuit, and equally that the low levels are not so low that any noise on the system is intrusive. In addition you will want to establish a level that gives you the maximum travel on the actual channel fader (see below).

An equalisation section:-
This will consist of at least three controls (treble, middle and bass/ top, mid, bass). They are more sophisticated versions of the tone control you find on your domestic stereo. On some desks the 'mid' control will also have a frequency sweep to allow the engineer to select the frequency at which the 'mid' control operates. Tone controls/equalisation can be used to correct for inadequacies in the sound signal arriving at the desk, although if you really have a problem of this sort it is likely that you are not using good enough mics, you have a mis-match or the mic positioning is wrong. Where you have feedback problems it may be possible to roll off a little of the top (or maybe upper mid) to help introduce a bit of headroom. From an effects point of view you can change the sound quite dramatically. Bored sound engineers may like to try interfering with a drum break by doing some extreme boosting of the mid on the snare mic, and then sweeping the signal left-right on the pan pot, while at the same time frequency sweeping the boosted mid gain! Your drummer may like it or loath it...but I guarentee you'll get a reaction.

Auxilliary sends:-
There will be at least two of these, hopefully more. These allow you to tap off a bit of signal and send it to places other than the main (PA) mix. Possible destinations for such signal include foldback or effects treatments like echo. Aux sends are either 'pre-fade' or 'post-fade. Pre-fade sends are unaffected by the channel fader. Post-fade sends have their level controlled by the channel fader.

Pan:-
This control sends the signal to the left or right output proportionally, depending on where you set it,

Grouping:-
On bigger desks the signal can be sent to output 'groups' and from there to the main output. Most desks will have 8 output groups. One advantage of this arrangenet is that you can group whole sections of a big mix and control them separately. For example you could have the string section on one pair of groups, brass on another, vocalists on a thrid pair...This would mean that if you wanted to change the balance between the brass and the strings in an orchestra you could do so with a couple of adjacent faders, rather than having to rummage around in among dozens of individual channels.

PFL:-
'pre fade listen' allows you to route the channel signal to your monitor headphones so that you can listen to what's going on on a particular channel.

Main Channel Fader:-
And nearest to you..the volume control for each channel!

The desk output gets connected to an amplifier or amplifiers. The siganl going into the amp from the desk will be at 'line level'. The speaker output is, naturally, connected to the speakers.
Beware of all this plugging.
Mic level is in the order of a few millivolts (thousanths of a volt), Line level is, as we explained, about three-quarters of a volt, Speaker level is likely to be at least thrity volts.....and may be as high as a hundred volts (on a 100V Line system) Make sure you don't get these confused! things will go bang and stop working if you do.

Additional 'nuts & bolts' pages here will give you specific details of pin configurations etc.

If you're already all clued up on this sort of thing please excuse the simplistic view of the world we are offering here. If you need specific help email me and I will do my best to answer your question(s).