Simon Baker

Sound System Basics

Some theatres have a “house system” other theatre’s are empty and everything needs to be brought in. All require thought. You have to work out a way in which the audience are going to hear the show, the actors and the music, be it live or recorded as well as the sound effects. The whole thing needs to be one sonic picture. This could mean microphones on actors, musicians, playback system...it will always mean loudspeakers.

Lets take a musical in a west end theatre. The work scales up or down depending on the size of the show and budget but the fundamentals are constant. First off, west end theaters are empty except for the seats and on Broadway not even that. The 1st thing that has to be drawn up is the bid list. A list of all the sound equipment the production needs - not just sound equipment but also communication equipment. A long way away from the fun of making sound effects. So thats first bit of my job. What do we need?

I start with the loudspeaker system as that's what we will all be listening too. I look at the all the drawings of the theatre and often sit quietly in it for a while trying to imagine. My job here is to ensure that each seat is covered by a loudspeaker. To expand on that I need to understand how sound travels through air, I need to have an understanding of acoustics and detail physco-acoustic theory (ie how we perceive sound).

Some basics - don’t worry about them just bear them in mind; it will help. Sound travels at a constant speed (768 miles per hour)
, sound is a logarithmic scale and the higher the frequency of sound the more directional it becomes, that solid objects reflect sound and soft objects absorb it. Also know that speakers are just paper cones with magnets at the end of them being driven by electrical impulses that vibrates the paper cone that moves the air. Knowing these basics helps more than anyone ever realises. I’ll explain why as I go. Maybe...

Speakers, surprisingly, do develop in technology. In fact everything in sound does. One of my jobs is to stay up-to-date. In fact the technology in sound is an ever changing thing. There are many different types, functions, shape and sizes of speaker. The job is to pick the right system that will work in the space. Its also a major part of my job to get the speakers into the right place. Quite often scenic designers, directors or producers will ask you to move speakers. This is always annoying. There are very few placements for speakers and their positioning is crucial. Putting a speaker too high means that the sound image will be to high and not connected to the stage, to far off and the image gets wide and the first few rows wont hear. How can you tell? Well speakers work like a maths puzzle. They have a vertical sound dispersion as well as a horizontal one. Or at least they all used to until a few years ago. So in the olden days you knew that a speaker was 60º horizontal coverage and 90º vertical. It was pretty simple to work out where the best place was. Modern loudspeakers - the banana shaped boxes you now often see work in slightly different way. These speakers cover only the width of the box vertically but are 100º (usually) horizontal. They offer much more power and are much more accurate. However they are not a cure all solution. For a start you need lots of them and they are bigger than conventional systems - and of course more expensive. Working out which speaker to use is key and then finding the best position is next.

There are lots of audio prediction bits of software where you can virtually model the auditorium and work out how the speaker will react in it. They are helpful but due to manufactories ambitious claims they not that accurate and judgement and luck play a huge part. I use them on the big shows as they are great for rough calculations and also as a visual aid when talking through a placement issue with a producer or designer.

Of course there’s not just the main proscenium system to manage. There are lots of other speakers to deal with. A modern musical like MATILDA has around 140 speakers on the rig all doing different jobs.

Trying to squeeze quality sound under balconies in west end theaters is always a challenge. The main proscenium speakers may not “see” all the way to the back of the stalls so you need to use a fill speaker. This is a smaller speaker just to fill in the audio in the back few rows - same in the circle and balcony. Now remember the notes from the top about the speed of sound. This is where the knowledge has a real world application.

If Im stood on stage and talk to you, you know I’m there - shut your eyes and you can still locate me. Our visual relationship to the world relies on our hearing, as does our balance. If I talk to you on stage wearing a radio mic and you hear my voice from a speaker the ears tell the eyes where I must be - where the speaker is. Now if you are sat at the back at the auditorium your hearing my natural acoustic voice, my voice coming from the pros loudspeakers and another coming from the fill speaker under the circle ledge. Thats just confusing and a bit like an echo. If you’ve ever left the radio on in a bedroom and then put the same channel on the radio in the kitchen you'll hear what I mean.

However you can cure it, just by understanding that sound travels at a certain speed. This is what is meant by delaying sound. I would delay the sound of the Pros speaker back to the actor standing on stage (it will only be a few milliseconds but the ear is quite discerning and I can certainly hear the change of delay in half millisecond steps - we all can we just haven't worried about it before. I would then delay the fill speaker (you can see why they are called delay speakers now) back to the actor - probably quite a bit. Its maths and judgement. We know that sound sound travels at 768 miles per hour - or about a foot a millisecond. The further the speaker the longer the delay.

Ok so thats a simplified version of it as it doesn't account for temperature or latency in audio equipment or any of those things but it does explain it a bit. Now imagine 120 speakers all need there own time calculated back to one spot in order to deliver a coherent system. Thats one of the reasons the sound designer gets cross when someone one wants to move one as it doesn't just effect that speaker it effects the relationship to all the others.

So there you go - speaker system design. Lots of speakers all doing a job to deliver one harmonious sound into the auditorium. After that you have Sub bass speakers, foldback speakers - so actors can hear the band or themselves as well as effect loudspeakers, speakers built into props - some cabled and some wireless. All need to be designed, chosen, ordered and put into practice.

The next bit, along side the delay process is the EQ process. EQ is equalization. A bit of a misleading term to be honest. It suggest that every thing across the sound frequency range should be equal - and it shouldn't. What you are looking for and listening for is not equal but clear.

Sound that we hear works across a range of 20Hz to 20Khz. 20Hz is low and 20Khz is very high, really high in fact. A mains buzz is around 60Hz - the frequency of mains in this country. An old TV buzzing is 11Khz. A whistling kettle is about 3Khz. Some frequencies on the ear seem fine others harsh, others feel too loud. A flat sound, ie all frequencies at the same level would be pretty ugly. Thats the problem with letting technology EQ a system. What you want is warm and clear and for me that means losing all the annoying nasal, harshness, pushing the low end and pushing the very top end to add some sparkle. Everyone has their own taste but mine is based on what I like to hear and comes from a memory of listening to The Beatles Abbey Road LP on Dancette.

In the EQ process you are also looking to clear out any standing waves that the architecture of the building is causing. Earlier I said that solid surfaces reflect sound. A building with lots of sharp corners will cause the sound to roll around at certain frequencies so we use parametric equalizers to reduce these frequencies. You cant cure everything with EQ - getting the speaker in the right place in the first instance is the proper approach.

Also remember that all our hearing is very different, from the age of 3 our hearing has already started to deteriorate. Babies can hear dog whistles really clearly.

Oh yes one other thing. Scenic Designers, Directors and Producers love hiding loudspeakers. To be honest I like not seeing them also - I like the technology hidden. However I do accept their existence and need. Quite often complex negotiations have to be done with the other design departments about what is covering the proscenium. This is often tricky and requires lots of 3D rendering and complex technical drawings. This is often, and should be done, early in the process.

The bit you need to know is that for loudspeakers to sound best should have nothing between them and the audience they are pointing at. Anything on front of them has a detrimental effect.

So with the speaker system designed you need to be able to control the signals going to it. This means using a combination of amplifiers, EQ systems, time correction systems and fun things such as cross point level and delay matrixes. Don't worry about them but they are all there. They just change size with the size of systems. I tend to use a complex Matrix unit that handles all this work. I can design a system that means that I can accurately control the EQ and delay of each loudspeaker in the system and also control the amount of level going to that loudspeaker depending on what its source is. For example you may want less vocals from the ensemble cast in the stalls than you do in the front of the circle. You may not want much Drum or Percussion in the delays but lots of strings. Some designers will do this at the desk but I prefer to do it away from the desk. I also like to have the software that does all this on a tablet computer so I can sit in amongst the audience and work with the system as the audience are hearing it. On a musical the main body of the work can only occur when an audience are in.

After or before - depending on your point of view is the mixing desk or console. Again one needs to be specc’d that suits the show and the budget. They come in all shapes and some shows may have multiple desk doing different jobs. Im not keen on this method unless you need a dedicated desk for foldback. Desk size is determined by how many things you want to plug into it and how many things have to come out of it. A small play may only have 12 inputs and 8 outputs so a small desk, musicals often have in excess or 200 inputs and a 60 plus outputs. Running out of inputs and outputs is often a common issue and sometimes why the sound designer looks stressed when a director asks for just that extra instrument or extra effect speaker to be added. Its not the problem of doing it, its the fact that there is know where to plug it in.

Im not a big fan of comparing sound to lighting - the 2 disciplines are so different. However if you try and make a comparison to lighting bear this in mind - lighting have to deal with output only. Mains voltage going to a lamp - the net result is brightness. Of course modern lighting system are much more complex but its still focussed on output. So that’s like amplifiers - voltage to move air - loudness. Lighting don't have to trouble themselves with input. If, for example the incoming mains was random and from 200 plus sources and it all had to be manipulated live then a comparison to lighting is fair. Which it probably wont ever be. In short adding a lamp is about an available dimmer. Sound has 2 things to consider - whats it's source and where is it going.

These days desks are digital. This means that they can be smaller. Not all digital desks sound the same though. They all offer better manipulation of sound and make sound operation easier (to a certain extent). I haven't done a show on an analogue desk for years. However, having started in the analogue world means that at least I understand what I am doing. Much of the terminology in sound has its DNA in the old analogue and tape machine world - it must be so confusing to newcomers who never had to learn what a VCA
was.

Once you have the output (speakers) and the control (Desk and Matrixes) next up is the input. To capture and amplify a live sound you need a microphone. There are 1000s of them. For now lets assume there are 2 main categories. Wired and Wireless.

Wired mics can be the standard mic on a stand that a performer sings at and the shape we recognise as microphone is the Shure SM58. Its been in use for 30 years and has never really changed. But there are lots of choice here and selecting the right one is again based on use, preference and budget. Microphones have pick up patterns and are called strange things; cardioid (the pattern is similar to a heart shape), hyper-cardioid, omnidirectional, directional. All have uses. A vocal mic needs to be cardioid in most environments but in high feed back environments a hyper cardioid might be better. Again lots of choosing to do here. Instrument mics are very specific. Most equipment used in theatre is rarely built for theatre but built for studio use. This often clashes with the stresses live work puts equipment under. Mics on instruments tend to be very expensive when you are looking for premium quality and decent flute mic for example might be around the £1500 mark. A sprung Neumann Mic (the big brother of all mics) can set you back around £3000. This is why sound people get upset when they get dropped. They are delicate. Some mics use very thin ribbon to pick up the sound and even putting them away if you slam the lid on the mic box can destroy them. (Done that before). Every instrument has multiple choices when it comes to mics. I learnt the old school way having been taught by mainly old-school teachers with beards. The lesson is that with the right mic with the right cable and with the correct amount of gain applied, being played out of the right speakers in the right position there should be no need for EQ or any other tricks we now regularly rely on. It should just work, and be as transparent as it can be.

Footnotes