A live concert at an iconic music venue is nothing without a solid PA system. An amplified electric guitar riff, pulsating drum beat and vocal vibrato is something concert-goers have been accustomed to for years.
Great things have humble beginnings, however. Although top PA systems are now associated with the Super Bowl half-time show, or a sell-out gig at Wembley, it started out as simply a moving coil loudspeaker with a 34-inch horn!
In this article, we explore how the PA system was invented, where it was first used and how it has evolved over time.
The ‘bellowing telephone’ and co.
PA stands for ‘public address’, which reflects the most common applications of a PA system – whether it be train stations, sports stadiums, shops, hospitals, airports or hotels. The three core components of a PA system are – the microphone, which captures sound vibrations and converts them into an electrical signal; the amplifier, which increases and controls electrical signals, and the loudspeaker, which converts an electrical audio signal into vibrations and broadcasts them as a sound.
Up until the late 19th century, all forms of public address were done using architectural acoustics – there was no viable alternative to improve speech comprehension. However, the first step towards completely changing how people perceived sound came in 1875, when British-American inventor and music professor David Edward Hughes invented the carbon microphone.
This was the first device which enabled proper voice transmission and was built by Hughes using toy boxes, sealing wax and wires in the drawing room of his home. The carbon microphone contained two metal plates and worked by sound waves striking its diaphragm, causing the carbon granules contained inside to vibrate (allow Google to demonstrate!)
The higher the pressure on these granules, the lower their resistance and the closer they are pushed together, resulting in a sound current being passed between the plates. Hughes coined the term ‘microphone’ to describe his invention, as he saw it as the audio equivalent of the microscope. Thus, the first component of a modern-day PA system was born.
A couple of decades later, the world’s first experimental moving coil loudspeaker was invented by British physicist Oliver Lodge. Known as the ‘bellowing telephone’, this invention contained the same basic features as today’s loudspeakers – a diaphragm vibrated by a voice coil, the sound of which was then amplified by a flared horn.
The final piece of the PA system puzzle came in 1906, when American inventor Lee DeForest invented the Audion – the first device capable of amplifying an electrical signal. This amplification was made possible by the device’s three electrodes, which are a heated filament, a grid and a plate.
The PA system pioneers
Once these three components had been invented, the quest to peace them together for the purposes of sound production began.
Edwin Jensen and Peter Pridham, engineers from the American electronics company Magnavox, were among the early pioneers of sound reproduction and amplification. During a series of tests in their laboratory from 1911 to 1915, they connected a microphone and loudspeaker to a 12-volt battery, resulting in the first ever occurrence of acoustic feedback.
Through their research, Jensen and Pridham developed the ‘Magnavox’, the world’s first electric PA system used to amplify speech. This was a dynamic moving coil loudspeaker featuring a one-inch voice coil, a three-inch corrugated diaphragm and a 34-inch horn. The Magnavox system was publicly unveiled at San Francisco City Hall on December 24, 1915, with 100,000 people turning up to listen to the broadcasting of Christmas music and speeches.
In the years that followed, Jensen and Pridham continued developing PA systems, one of which was used by US President Woodrow Wilson to address a 75,000-strong crowd in San Diego – the first time a President used such a system to address the public.
Another key PA system pioneer was the British telecommunications company Marconi. Throughout the 1920’s, Marconi manufactured a high volume of PA systems to meet the growing demands of this emerging market. Such was their popularity, that a Marconi PA was used by King George V to address 90,000 people during the British Empire Exhibition at Wembley in 1925.
World War Two, The Beatles and beyond
The PA system underwent rapid redevelopment during World War Two, due to an increased expectation for more efficient methods of amplified communication. Amplifiers became so big that they used radio transmitter valves to feed output into loudspeakers.
However, commercial PA systems were yet to catch on. Up until the 1950’s, the output levels of such systems did not exceed 25 watts (W) – it was the advent of the electric guitar and rock ‘n’ roll music which kickstarted an upsurge in amplification levels.
Suddenly, musicians were performing live using 50-100W valve PA amplifiers, pushing PA systems into distortion to achieve the sound they wanted. By the 1960’s, live bands were taking their own PA systems on tour – although these were relatively small systems and most bands still relied on house PA systems at the venue in which they were performing.
A watershed moment in the history of PA systems came in August 1965, when The Beatles played at Shea Stadium in New York. In preparation for this unique event, four Altec 1570 amplifiers, each giving 175W of sound, were distributed around the stadium. At the time, such levels of power output were virtually unheard of for a live concert.
The idea didn’t go to plan, however, as the crowd of 42,000 screaming girls completely drowned out the PA systems. It’s estimated that the noise coming from the crowd was 135 decibels (dB) – more than double the output coming from The Beatles’ sound equipment.
A little over a year later, the Fab Four had ceased from touring, so in many ways this concert can be viewed as a live music disaster. However, if nothing else, it was a catalyst for change.
The bigger, the better
If bands were going to play live shows, they needed a bigger sound to (literally and figuratively) stand out from the crowd and make their gigs a memorable experience. As touched on earlier, The Beatles’ Shea Stadium performance left little to be desired and bands largely relied on outdated house PA systems.
In the words of British audio engineer Charlie Watkins: “They were bloody awful – they were terrible! It was usually horrible old war-surplus equipment with 12-inch hard-cone speakers with boxes spread all round the hall. I don’t know why it went on so long.”
Watkins is labelled the ‘British father of PA’ and was peripheral in redefining live music production. It was he who championed the mixer-to-power-amp-to-speaker arrangement that still figures in most contemporary PA systems.
At the Windsor Jazz & Blues Festival in 1967, Watkins unveiled his Slave PA system, which was capable of generating 1,000W of power. A little-known band called Fleetwood Mac made their first live music appearance at the festival and their sound was engineered using Watkins’ system, only he wasn’t present to enjoy it – because he was arrested for disturbing the peace. From this moment on, kilowatt PA systems became the norm at British music festivals.
Then there was the 70’s – the decade in which modern-day sound amplification was created. In February 1970, American sound engineer Bob Hall was tasked with building a sound system for rock band The Grateful Dead, ahead of their gig at the Fox Theatre in Missouri, United States. The result was a 20,000W system which broke world records – some advancement from the ‘bellowing telephone’ (just for the record, we don’t want to encourage hearing damage – we just think these statistics are amazing!). The Who and Deep Purple later battled it out for the title of ‘world’s loudest band’, with The Who coming out on top for their 1976 gig at The Valley in London, which reached 126 dB.
An array of sound
Loudspeaker capability continued to develop into the 1980’s and 90’s, with a growing number of audio manufacturers moving into the concert market to take advantage of this trend. Among them were American manufacturer Easter Acoustic Works, which made its name by developing the KF580 loudspeaker system in 1985. A 3-way ‘arrayable’ loudspeaker, this system was the benchmark for live sound for many years. To this day, it is included in more technical specifications for live performances than any other loudspeaker.
Over in France, Dr Christian Heil and his team of sound engineers at the manufacturer ‘L’Acoustics’ revolutionised modern sound production by developing the modern line source array loudspeaker in 1993. This system overcame the interferences caused by closely aligned loudspeakers and helped push sound energy further, with a more even frequency response. Line arrays are very much a product of the computer age and today, nearly every professional audio loudspeaker manufacturer adopts the line array model for their premier touring systems. As such, Heil is widely recognised as the ‘father of the modern line array’.
To use a completely unintentional pun… we’re out (insert mic dropping sound). Hopefully you found this an interesting read!
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