The Birth of the Array Part One – Concert Sound Overview
The mechanics and conventions of the big gig
Three days earlier this was an empty paddock (see picture above). A day after the show finishes it will be an empty field again. There is a long history of show production that has produced a number of technologies and conventions that made it possible
The purpose of live concert engineering
The concert sound industry is about amplifying a small sound source to cover a large number of people with a realistic and intelligible duplication of that minor sound source. Whether it is done with a megaphone, architectural design or a mega PA, we are making something small sound big.
This engineering approach is the opposite of the recording engineer, who has to make something big, (a band or orchestra), sound realistic through a six-inch speaker in a small room. The recording engineer is distilling down to an essence; the sound reinforcement engineer is making something bigger than it really is.
There were concerts long before this millennium, how were the performers heard?
In the early days, knowledge of acoustics and building design did the job. A concert, theatre performance, and an assortment of live spectacles could be effectively staged to an auditorium full of people. The word Auditorium is a Latin word meaning ‘a place of hearing’.
Today we use specialist microphones, mixing consoles, signal processors, system controllers, amplifiers and sophisticated speaker systems to achieve the same result.
The audio concert sound industry, as we know it today is a relatively new industry. There has been endless theorising and experimenting on how it should be approached and as a result, you have heard great concerts, ok concerts, and plenty of bad concerts that were just a mush of unintelligible noise. The ‘book’ is constantly being re-written as long held opinions are replaced by facts.
There are a number of reasons why it can all go wrong. Theatre, live music and public speaking addresses to the masses are not new. Live shows attended by large multitudes have been around for at least 5000 years and the theatrical engineers of each age have developed their own solutions with the tools available.
“Roman Amphitheatre Seating 80,000 Spectators”
An understanding of the basic principles of acoustics, and understanding technical expertise with the audio tools available is the key to consistent good results. Every sound guy who gets results understands the tools of his trade, how they work and the acoustic environment they must work in.
The number one issue for any person planning a live production where sound propagation and duplication is required will be the acoustic characteristics of the proposed venue. This applies to any age and technological level.
“A sound guy at the dud gig looking for somewhere to hide?”
If the sound system is working against the environment, get ready for a ‘dud gig’ and you, as the sound guy will be the most unpopular person around.
The mechanics and conventions of the big gig: an historical perspective.
People have been working on understanding and handling this problem of large scale sound coverage for a long time. To understand and apply the latest developments in professional audio, it helps to get some history on why certain technical directions were pursued and how and why many of the present day conventions were established.
A 1920’s horn loudspeaker: It sounded like somebody shouting down a drain pipe but at least you could hear it.
When was the first recorded published work on acoustics for the purpose of understanding the propagation of sound waves?
1657. The book Magiae Universalis by Gaspare P Schotto. (1608 – 1666) Written in Latin and published in Germany. If you can find an earlier work, let me know.
What do we know about this early sound guy?
Gaspare was one of the few early researchers on acoustics whose work is still around today. He was the first recorded person since the early Greeks to consider sound behaviour and distribution as a largely geometric problem.
Illustration of reflections and sound wave behaviour within a semicircular reflective environment such as under a dome or within a parabolic stone wall.
Whether a person shouting or an amplified speaker, the sound waves will behave the same and the reflective surfaces will greatly affect the sound. Especially if the listener is in a position where they hear more reflected sound than direct sound from the source.
A graphic representation of the rules regarding reflective sound expressed as a geometric problem.
Applying the principles he had developed, Gaspare looked for practical applications. He even developed listening devices for ‘spying’. His ‘bugging’ device was a horn and reflector that would be rather hard to hide.
A post-medieval mechanical sound transmission, and amplification system featuring a large horn to direct and amplify speech and music.
Goths versus Greeks
Staying with the history of venue acoustics for a moment lets look at how the purpose of the building and the style of the performance affected the acoustics at the design stage. This is a competition between the Goths and the Greeks – the acoustic principles of the Greek theatre versus the Gothic Cathedral (600AD ~ 1950AD).
The Greek Gig
Speaking of the Greeks and geometry, who ever designed the Greek amphitheatre, really understood the problem of staying awake during his maths classes, (a far more complex problem than drawing circles). This fixation with geometry and sound is a continuous thread that reaches its zenith in the year 2002 but for the moment lets look BC.
Definition: Just for the record, geometry is the branch of maths that measures and compares lines, angles, surfaces and solids in space. It is especially used for the definition, comparison and measurement of circles, cones, cubes and spheres. It comes from a Greek word Geo (earth) and Metron, (to measure). It is used for everything from navigation to ballistics.
The Greek Amphitheatre (XXX BC?)
The semicircular Greek amphitheatre acts as a natural acoustic amplifier; in the way it directs and controls sonic reflections in a way that intelligible speech and music can be conveyed to a large number of people. The early Greeks developed and could apply geometry and this knowledge applied to sound propagation has been rediscovered many times over the centuries.
What is missing in this artist’s impression is the tent like cover that was suspended over the audience (according to old pictures found on walls and pottery). The cover was not just a sunshade; it reflected sound back down to the seated masses. Even the Roman Coliseum had such a system for both shade and sonic distribution.
But there’s more…
The Gothic Gig
The worst acoustic environment to set up a sound system or have intelligible natural voice is probably the Gothic Cathedral. (A stone wall reflects 98% @ 1K). It was originally designed for the Catholic Latin Mass that was chanted rather than spoken. The high ceilings and long reflective stone surfaces generated multi second reverberation times to create a hallowed atmosphere. Long reverb times are the enemy of clear speech reproduction, but more about that later.
The construction of Cologne Cathedral commenced in about AD 1250 and completed 500 years later, (a government job?). It was renovated by the RAF in 1943-4, but has again been restored to its former three-second reverb time.
That was then, this is now
Theatre and ecclesiastical architectural acoustics parted ways around 600 AD and were not to converge again until the 21st century.
From the Stone Age to ‘Queens of the Stone Age’
Moving to the present era, what lessons are there from the old pre electronic days? Will we learn them or if learnt, have many live performers forgotten them today.
Here come some self evident clichés:
When western man encounters an obstacle, he is more likely to invent a machine rather than fix the source problem. This generally leads to the original problem being buried in complex solutions. This really applies to audio at every level.
Rule Number One:
A microphone is not a substitute for good vocal technique. Every singer and public speaker should write this line out five hundred times.
Here comes another rule that won’t make you popular with inexperienced performers.
Rule Number Two:
Twenty sends of (loud) foldback will not make up for a band’s inability to listen to each other or work together. Acoustic big bands and large brass sections learn this one quickly. Amplified musicians take much longer.
A famous monitor engineer getting ready to impose discipline. Rod Matherson (mixing Silverchair) has heard them all, from; “We need everything louder than everything else, in every wedge and we want it now!” to “Have you seen my guitar lead anywhere?”
In the engine room it gets hot
Silverchair show out the front. At this level of the business in 2005, you had better know what you are doing if you want to have a continuing career.
A large number of technical conventions have been established over the years through trial and error. A trip down memory lane might demystify the present and make the rules easier to remember. Follow The Birth of the Array in next month’s issue of Filter, where we take a look at the last 100 years of concert sound.
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