Live Sound — December 2015
Change Language:
Andy Coules

Marking a milestone that leads to where we are today.

BACK IN 1915, the first World War was raging across Europe, Charlie Chaplin’s film “The Tramp” was released, Babe Ruth hit his first career home run, the one millionth Ford car rolled off the assembly line, the first stop sign appeared in Detroit (that can’t be a coincidence), and Billie Holiday, Orson Welles, Les Paul, and Frank Sinatra were all born.

Towards the end of the year, on December 24, a Magnavox PA system was deployed to amplify a Christmas carol concert on the steps of San Francisco City Hall for an estimated audience of 100,000 people, the first recorded example of an electric PA system being used to amplify a musical concert. That was exactly 100 years ago this month.

In geological terms 100 years is a blink of the eye, but in modern history a lot can happen technologically and socially in that time frame. Back in 1915 about 15 percent of the world population lived in cities, whereas we’ve recently reached the point where half of the world population now lives in cities, for the first time in human history.


The development of PA systems didn’t happen because of any overriding need to amplify music, that drive simply didn’t exist at the time. Music was invariably written to be performed in a particular space with a specific ensemble that augmented specific instrument groupings to achieve the appropriate volume and mix. The birth of public address was driven more by the need to amplify the human voice and enable the addressing of larger crowds – the clue is in the name.

Prior to this point public speaking was an area of serious discussion and study by academics, thinkers and even future presidents – John Quincy Adams published his book “Lectures on Rhetoric and Oratory” in 1810. By the middle of the nineteenth century, elocution books were popular to the extent that almost every middle class home would contain at least one volume. Aside from advocating chastity, temperance and religion, these books also included physical and breathing exercises as well as vocal exercises designed to increase the volume of the voice. It’s no coincidence that the devices invented to convey sound at high volume became known as “loud speakers.”

Pretty much all of the technology utilized in those early PA systems was invented for a different purpose. The microphone was invented for use with the telephone, the vacuum tubes that powered the early amplifiers were developed to amplify radio signals, and while various loudspeaker-like devices existed on the telephone, the phonograph and the gramophone, the true moving coil loudspeaker was developed for wireless telegraphy (i.e., Morse code transmitted by radio).

Our understanding of how the ear works has changed a lot in the last 100 years. In 1915 we had a pretty good understanding of the mechanism of the ear, thanks to various scientists (most notably Alfonso Corti and Hermann von Helmholtz) but we didn’t have a very firm grasp of how we hear.

It took Hungarian biophysicist Georg von Békésy to get to the bottom of this great mystery. He developed a method for dissecting the inner ear of human cadavers which left the cochlea intact and enabled him, via strobe photography, to observe the basilar membrane moving like a surface wave when stimulated by sound. From this he was able to discern that different frequencies excited different sections of the membrane, thus stimulating different nerve fibers in a way that was registered by the brain and perceived as sound. This discovery lead to him being awarded the Nobel Prize in Physiology or Medicine in 1961.

The first research on how the ear hears different frequencies at different levels was conducted by Harvey Fletcher and Wilden A. Munson and published in their 1933 paper “Loudness, It’s Definition, Measurement and Calculation.” In 1937 they created the first equal loudness curves, which were subsequently updated by D.W. Robinson and R.S. Dadson in 1956 and became the ISO 226 standard (which was updated again in 2003).


But by far the biggest change in live sound in the last 100 years is the PA system itself; today’s systems are light years ahead of those early efforts in every respect.

The Magnavox system in San Francisco for Christmas Eve in 1915 used a rudimentary carbon microphone connected to an amplifier powered by a handful of vacuum tubes that generated about 10 watts of power. This certainly wouldn’t have been enough power to address a crowd of 100,000 people were it not for the fact that the loudspeakers exploited the acoustic amplification afforded by a flared horn.

It’s interesting to ponder what it must have felt like for that crowd, being able to experience a concert that was so far away. Prior to that point, you would expect to be in close proximity to a musical ensemble in order to hear them. The newspapers reported that the concert was heard “with absolute distinctness,” and considering the gramophone and radio were both relatively new inventions, this must have been quite a unique experience for those present.

The people behind that ground-breaking system were Edwin Jensen and Peter Pridham, who would go on to form the Magnavox company in 1917. The company still exists today and is famous for bringing us the very first home video game console – the Odyssey, introduced in 1972.

But back in 1915 Magnavox was just the name of the PA system that Jensen and Pridham built as a result of a series of experiments in their Napa laboratory. (The name comes from Latin and means “great voice.”) One of their first experiments involved connecting a carbon microphone to a 12-volt battery, resulting in the first instance of acoustic feedback, a phenomenon that sound engineers have been dealing with ever since. They got around this rudimentary problem by mounting the loudspeaker on the roof of their laboratory, claiming that the amplified human voice could be heard one mile away (which must have been quite odd for their neighbors in that pre-amplification age).

The duo demonstrated their fledgling sound system by connecting it to a phonograph and playing pre-recorded music at their laboratory, as well as at the Pan Pacific Exposition and at Golden Gate Park throughout December. After the seminal Christmas Eve concert, another first quickly followed the next week with the amplification of the first outside broadcast on December 30. California governor Hiram Johnson was due to give a speech at the Civic Auditorium in San Francisco but was too ill to attend, so Jensen and Pridham connected a carbon microphone at Johnson’s home a few miles away to the system in the auditorium, enabling him to deliver his speech as a disembodied voice.


Advances in sound system design and size were incremental through the first half of the 20th century; the main obstacle was amplification and the limitation of vacuum tubes. Jensen and Pridham built a 25-watt amplifier in 1919, and amps didn’t really start to get any bigger until the mid 1950s.

The invention of the transistor in 1947 promised a whole new era of smaller, more powerful amplifiers. but it took a while for them to usurp the valve behemoths. Part of the problem was the prohibitive expense of those early silicon transistors; germanium ones were much cheaper but had an annoying tendency to burn out, especially when presented with an unpredictable load.

Then, in 1967, a tape deck company produced one of the first truly reliable and powerful solid state amplifiers: the Crown DC300. It provided 150 watts per channel and offered low distortion and low noise thanks to it’s direct coupled DC operation. The success of the DC300 was aided by it’s size – at 7 inches tall and weighing just 45 pounds, it was less than a quarter the size and weight of an equivalently powered tube amplifier.

Using amps like the DC300, various pioneers developed perceptually louder sound systems by using crossovers to bi-, tri- and quad-amplify systems, enabling them to more efficiently amplify different frequency bands. Then along came Bob Carver with the Phase Linear 700, a power amp that promised 350 watts per channel and invariably delivered.

The 1970s also heralded the birth of the mixing desk. Various “home brew” models existed previously, but production consoles started to appear both in the studio and on the road that helped establish the analog paradigm and push forward the possibilities of mixing. In 1974, Midas developed the PRO4 console, which was soon out on the road with Supertramp, while Soundcraft brought out the Series 1 and Yamaha unveiled the PM1000. In 1977, Clair Brothers debuted the CBA32, the first live console to have parametric EQ.


Advances in amplification throughout the 1980s meant that sound systems could fill out arenas and stadiums with dynamic sound, enabling a whole new generation of bands to develop bigger and bolder shows.

By the 1990s, we saw the first digital desks, sparking the (still ongoing) analog versus digital debate and exciting engineers with the possibilities of total recall. And in 1993, Christian Heil and his team at L-Acoustics ushered in the modern line array era with the introduction of the V-DOSC system.

No two key developments typify the world of modern live sound and underline just how far we’ve come since those early PA systems than the digital console and the line array. Both utilize the latest computer technology in design and utilization to push the boundaries of what’s possible in live sound. We’ve certainly come a long way in the last 100 years.

ANDY COULES ( is a sound engineer and audio educator who has toured the world with a diverse array of acts in a wide range of genres.