A GUIDE TO

SOUND FOR THE SCHOOL SHOW

This Guide has 13 pages.

(Introduction)

Although schools (and amateur theatres for that matter) often use quite sophisticated lighting rigs and plots, sound remains somewhere in the dark ages, with the odd microphone or two run through a simple amplifier which drives a couple of fairly basic speakers. Feedback squeals are not uncommon and the only quality that the finished result has is loudness. The techniques of Sound Reinforcement which the professional theatre has developed over the last twenty or so years have been largely ignored by schools, partially because of the expense of the equipment involved and partially because of ignorance.

(Acoustics)

To understand stage sound properly, you need some knowledge of the science of Acoustics so that you can work out what equipment you will need and what that equipment does to the sound.

First of all, sound is merely vibrating air. Of course, vibrations can occur at different speeds: the faster the vibration, the higher-pitched the sound. We count the number of times a sound vibrates in one second and call this the frequency of the sound. Frequency is measured in Herz (pronounced like "hurts"), abbreviated to Hz, and kHz (kiloherz, i.e. 1000Hz). Frequencies are usually divided into high (above 10kHz), mid-range, and low (below 100Hz).

High frequencies are directional: that is, they tend to move in the direction in which the source is pointed. If a loudspeaker is pushing out high frequencies you hear the sound best in front of the speaker, less well to either side, and poorly, if at all, behind. Low frequencies, however, are omni-directional: that is, they tend to spread equally in all directions. So if you are listening to a rock group, you will hear the bass guitar almost as well if you are behind the speaker as you would if you were in front.

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(Equipment)

The next stage in the chain is the Mixer, in which the sound from the various mics (and other sources such as musical instruments, tape decks, and so on) are mixed together to achieve the right balance. Inputs to mixers for stage use are normally in multiples of four, and eight is the lowest number worth getting. The highly regarded and popular Allen and Heath desks offer 8, 12, 16 and 24 inputs.

Each input should have the following controls:

Gain
This adjusts the sensitivity of the input. You may have to contend with a singer with a loud voice who holds the mic up against the mouth and another with a quiet voice who holds the mic a foot or more away both at the same time. The gain control (a kind of coarse volume control) will enable you to bring the input levels closer together. Some mixers have an additional control (a "pad") which automatically cuts the input by 12dB or so when the channel begins to overload.

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(Operating the System)

There's just one further point to be made: the best equipment in the world will be useless in the hands of an insensitive operator, so it is worth setting up an operating system which will get the best out of the equipment, even in the hands of an inexperienced operator. Here are some suggestions.

First of all, your sound operator must hear the same sound as the audience. He should not be in a sealed control room because, even if he has the best monitors in the world, he won't hear the sound that the audience hears. The best place - and the place where I always put our operator - is at the centre back of the hall (towards the front of the back-stalls in a real theatre!). Incidentally, for the same reason he should not use headphones. Their only use in a theatre context is to line up tapes or check that mics are live when you have a pre-fade listen capability on the mixer.

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Then it is time to start working on the settings for the input channels. These will be very variable, depending upon the sound you are reproducing (usually the voice of the singer/speaker) and the frequency response of the mic you're using. For each singer or instrument you are using you must adjust gain and input equalizer controls to get an attractive sound. Gain comes first, then I prefer to adjust the mid-range control next. The human voice has a comparatively limited frequency range, most of which falls in the mid-range band of a three band equalizer.

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One final point (I think this is actually about the third final point!): any sound system has a lot of trailing cables, often running through the audience - they'll certainly be running through the audience if you position your sound desk in the auditorium - and this can be dangerous: you could be in for a very expensive claim if a member of the audience trips over a trailing cable and injures himself. Don't just run cables under mats! It's very tempting, I know, but dangerous, even though the cables carry very little current. It is possible to buy half-trunking which fastens to the floor and has a kind of tunnel through which the cable runs, but it is very expensive, albeit the best solution. The cheapest is gaffer tape. This can be put down on all kinds of floors and will stick firmly, yet it will come off quite easily when you want it to without leaving any mark even on the most delicate floors. It's normally available in silver-grey or black. Use the silver which it is more visible, so audience members see it and are more likely to mind their feet. Actually, it's worth always having a roll in stock. I always intend to but forget and so the day before a show we're rushing round trying to buy some!

And by the way, you always use more than you think you will! I reckon we use 2-3 rolls per production - and that's apart from what the caretaker pinches when we're not looking!

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