Editing Public address system (section)

==Early systems==
===Megaphone===

[[File:MOHAI - firefighter's speaking trumpet 01A.jpg|thumb|A late 19th-century [[speaking trumpet]] used by [[firefighter]]s]]
[[File:HPIM0145 megaphone.jpg|thumb|A small sports megaphone for cheering at sporting events, next to a {{Convert|3|in|cm|0|abbr=on}} cigarette lighter for scale]]

From the Ancient Greek era to the nineteenth century, before the invention of electric loudspeakers and amplifiers, [[megaphone]] cones were used by people speaking to a large audience, to make their voice project more to a large space or group. Megaphones are typically portable, usually hand-held, cone-shaped [[horn (acoustic)|acoustic horn]]s used to [[amplifier|amplify]] a person's voice or other [[sound]]s and direct it towards a given direction. The sound is introduced into the narrow end of the megaphone, by holding it up to the face and speaking into it. The sound projects out the wide end of the cone. The user can direct the sound by pointing the wide end of the cone in a specific direction. In the 2020s, [[cheerleading]] is one of the few fields where a nineteenth century-style cone is still used to project the voice. The device is also called "speaking-trumpet", "bullhorn" or "loud hailer".

===Automatic Enunciator===

In 1910, the [[Automatic Electric|Automatic Electric Company]] of Chicago, Illinois, already a major supplier of automatic telephone switchboards, announced it had developed a loudspeaker, which it marketed under the name of the ''Automatic Enunciator''. Company president Joseph Harris foresaw multiple potential uses, and the original publicity stressed the value of the invention as a hotel public address system, allowing people in all public rooms to hear announcements.<ref>[http://chroniclingamerica.loc.gov/lccn/sn85053089/1910-07-22/ed-1/seq-6/ "Replaces Bell Boy"], ''The (Culbertson, Montana) Searchlight'', July 22, 1910, page 6.</ref> In June 1910, an initial "semi-public" demonstration was given to newspaper reporters at the Automatic Electric Company building, where a speaker's voice was transmitted to loudspeakers placed in a dozen locations "all over the building".<ref>"Hear Sermon, Enjoy Pipe", ''The (Ottawa Kansas) Evening Herald'', June 25, 1910, page 4.</ref>

A short time later, the Automatic Enunciator Company formed in Chicago order to market the new device, and a series of promotional installations followed.<ref name="formed">''Robert D. Fisher Manual of Valuable and Worthless Securities: Volume 6'' (1938), page 75.</ref> In August 1912 a large outdoor installation was made at a water carnival held in Chicago by the Associated Yacht and Power Boat Clubs of America. Seventy-two loudspeakers were strung in pairs at forty-foot (12 meter) intervals along the docks, spanning a total of one-half mile (800 meters) of grandstands. The system was used to announce race reports and descriptions, carry a series of speeches about "The Chicago Plan", and provide music between races.<ref>[https://books.google.com/books?id=qUo_AQAAMAAJ&dq=%22Automatic+Telephone+and+Enunciator+Carnival+Features%22&pg=PA246 "Automatic Telephone and Enunciator Carnival Features"], ''Telephony'', August 24, 1912, pages 246–247.</ref>

In 1913, multiple units were installed throughout the [[Comiskey Park]] baseball stadium in Chicago, both to make announcements and to provide musical interludes,<ref>"Loud-Speaking Telephone Enunciators in Baseball Grand Stand", ''Electrical World'', August 2, 1913, page 251.</ref> with Charles A. Comiskey quoted as saying: "The day of the megaphone man has passed at our park." The company also set up an experimental service, called the [[Musolaphone]], that was used to transmitted news and entertainment programming to home and business subscribers in south-side Chicago,<ref>[https://books.google.com/books?id=WwXnAAAAMAAJ&dq=%22Increasing+the+Revenue+Producing+Efficiency+of+a+Plant%22&pg=PA196 "Increasing the Revenue Producing Efficiency of a Plant"] by Stanley R. Edwards, ''Telephony'', October 11, 1913, pages 21–23.</ref> but this effort was short-lived. The company continued to market the enunciators for making announcements in establishments such as hospitals, department stores, factories, and railroad stations, although the Automatic Enunciator Company was dissolved in 1926.<ref name="formed" />

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===Magnavox===

[[File:Early vacuum tube public address system.jpg|thumb|upright=1.8|Early public-address system from around 1920 using a Magnavox speaker.  The microphone had a metal reflector that concentrated the sound waves, allowing the speaker to stand back so it would not obscure his or her face.  The early [[vacuum tube]]s could not produce much [[Gain (electronics)|gain]], and even with six tubes the amplifier had low power. To produce enough volume, the system used a [[horn loudspeaker]].  The cylindrical [[compression driver|driver]] unit under the horn contained the diaphragm, which the voice coil vibrated to produce sound through a flaring [[horn (acoustic)|horn]]. It produced far more volume from a given amplifier than a cone speaker.  Horns were used in virtually all early PA systems, and are still used in most systems, at least for the high-range tweeters.]]

Peter Jensen and Edwin Pridham of [[Magnavox]] began experimenting with sound reproduction in the 1910s. Working from a laboratory in [[Napa, California]], they filed the first patent for a [[moving coil loudspeaker]] in 1911.<ref name="Yaxley 2002a">{{cite web|author=Yaxleys Sound Systems|title=The First Outside Broadcast 1915|year=2002|url=http://www.historyofpa.co.uk/pages/history.htm|work=History of PA|publisher=History of PA Charity Trust|access-date=25 November 2011 |archive-url=https://web.archive.org/web/20150318074636/http://www.historyofpa.co.uk/pages/history.htm |archive-date=2015-03-18 |url-status=dead}}</ref> Four years later, in 1915, they built a dynamic loudspeaker with a {{convert|1|in|cm|adj=on}} [[voice coil]], a {{convert|3|in|cm|adj=on}} corrugated [[Diaphragm (acoustics)|diaphragm]] and a [[Horn (acoustic)|horn]] measuring {{convert|34|in|cm}} with a {{convert|22|in|cm|adj=on}} aperture. The [[electromagnet]] created a flux field of approximately 11,000 [[Gauss (unit)|Gauss]].<ref name="Yaxley 2002a" />

Their first experiment used a [[carbon microphone]].  When the 12 V battery was connected to the system, they experienced one of the first examples of [[acoustic feedback]],<ref name="Yaxley 2002a" /> a typically unwanted effect often characterized by high-pitched sounds. They then placed the loudspeaker on the laboratory's roof, and claims say that the amplified human voice could be heard {{convert|1|mi|km}} away.<ref name="Yaxley 2002a" /> Jensen and Pridham refined the system and connected a [[phonograph]] to the loudspeaker so it could broadcast recorded music.<ref name="Shepherd 1986">{{cite web|last=Shepherd|first=Gerald A|title=When the President Spoke at Balboa Stadium|year=1986|url=http://www.sandiegohistory.org/journal/86spring/president.htm|publisher=The Journal of San Diego History|access-date=25 November 2011}}</ref> They did this on a number of occasions, including once at the Napa laboratory, at the [[Panama–Pacific International Exposition]],<ref name="Yaxley 2002a" /> and on December 24, 1915, at [[San Francisco City Hall]] alongside [[Mayor of San Francisco|Mayor]] [[James Rolph]].<ref name="Shepherd 1986" /> This demonstration was official presentation of the working system, and approximately 100,000 people gathered to hear Christmas music and speeches "with absolute distinctness".<ref name="Yaxley 2002a" />

The first [[outside broadcast]] was made one week later, again supervised by Jensen and Pridham.<ref name=paorsr /><ref name="Crow Bozeman 1998 145">{{cite book|last=Crow|first=Michael M|title=Limited by design: R&D laboratories in the U.S. national innovation system|year=1998|publisher=Columbia University Press|location=New York City, NY|isbn=0231109822|page=145}}</ref> On December 30, when [[Governor of California]] [[Hiram Johnson]] was too ill to give a speech in person, loudspeakers were installed at the [[Bill Graham Civic Auditorium|Civic Auditorium]] in [[San Francisco]], connected to Johnson's house some miles away by cable and a microphone, from where he delivered his speech.<ref name="Yaxley 2002a" /> Jensen oversaw the governor using the microphone while Pridham operated the loudspeaker.

The following year, Jensen and Pridham applied for a patent for what they called their "Sound Magnifying Phonograph". Over the next two years they developed their first valve amplifier.  In 1919 this was standardized as a 3-stage 25 watt amplifier.<ref name="Yaxley 2002a" />

This system was used by former US president [[William Howard Taft]] at a speech in [[Grant Park (Chicago)|Grant Park]], [[Chicago]], and first used by a current president when [[Woodrow Wilson]] addressed 50,000 people in [[San Diego, California]].<ref name="Crow Bozeman 1998 145" /><ref>{{cite book|last1=Hogan|first1=Michael|title=Woodrow Wilson's Western Tour: Rhetoric, Public Opinion, And the League of Nations|date=2006|publisher=Texas A&M University Press|isbn=9781585445332|page=10|url=https://books.google.com/books?id=P1jqotqWvd4C&q=Woodrow+Wilson+san+diego+1919+50.000+crowd&pg=PP10|access-date=16 November 2015}}</ref> Wilson's speech was part of his nationwide tour to promote the establishment of the [[League of Nations]].<ref name="Schoenherr 2001">{{cite web|last=Schoenherr|first=Steven|title=Woodrow Wilson in San Diego 1919|year=2001|url=http://homepage.mac.com/oldtownman/recording/wilson.html|publisher=Recording Technology History Notes|access-date=25 November 2011|url-status=dead|archive-url=https://web.archive.org/web/20120113015655/http://homepage.mac.com/oldtownman/recording/wilson.html|archive-date=13 January 2012}}</ref> It was held on September 9, 1919, at [[Balboa Stadium|City Stadium]]. As with the San Francisco installation, Jensen supervised the microphone and Pridham the loudspeakers. Wilson spoke into two large horns mounted on his platform, which channelled his voice into the microphone.<ref name="Schoenherr 2001" /> Similar systems were used in the following years by [[Warren G. Harding]] and [[Franklin D. Roosevelt]].<ref name="Yaxley 2002a" />

===Marconi===

By the early 1920s, [[Marconi Company|Marconi]] had established a department dedicated to public address and began producing loudspeakers and amplifiers to match a growing demand.<ref name="Yaxley 2002a" /> In 1925, [[George V]] used such a system at the [[British Empire Exhibition]], addressing 90,000 via six long-range loudspeakers.<ref name="Yaxley 2002a" /> This public use of loudspeakers brought attention to the possibilities of such technology.  The 1925 Royal Air Force Pageant at [[Hendon Aerodrome]] used a Marconi system to allow the announcer to address the crowds, as well as amplify the band.<ref name="Yaxley 2002a" />  In 1929, the [[Schneider Trophy]] race at [[Calshot Spit]] used a public address system that had 200 horns, weighing a total of 20 [[ton]]s.<ref name="Yaxley 2002a" />

===Late 1920s–1930s===
Engineers invented the first loud, powerful amplifier and speaker systems for public address systems and [[movie theater]]s. These large PA systems and movie theatre sound systems were very large and very expensive, and so they could not be used by most touring musicians. After 1927, smaller, portable AC mains-powered PA systems that could be plugged into a regular wall socket "quickly became popular with musicians"; indeed, "... [[Leon McAuliffe]] (with [[Bob Wills]]) still used a carbon mic and a portable PA as late as 1935." During the late 1920s to mid-1930s, small portable PA systems and guitar combo amplifiers were fairly similar. These early amps had a "single volume control and one or two input jacks, field coil speakers" and thin wooden cabinets; remarkably, these early amps did not have tone controls or even an on-off switch.<ref name="vintageguitar.com">{{Cite web|url=https://www.vintageguitar.com/1804/antique-guitar-amps-1928-1934|title = Antique Guitar Amps 1928-1934 &#124; Vintage Guitar® magazine| date=5 September 2002 }}</ref> Portable PA systems that could be plugged into wall sockets appeared in the early 1930s, when the introduction of electrolytic capacitors and rectifier tubes enabled economical built-in power supplies that could plug into wall outlets. Previously, amplifiers required heavy multiple battery packs.<ref>{{Citation needed|date=August 2024}}</ref>

===Electric megaphone===
[[File:"Geração à Rasca" Demonstration.jpg|thumb|right|209px|A woman using a small handheld electric megaphone at a demonstration in Portugal. Electric megaphones use a type of [[horn loudspeaker]] called a ''reflex'' or ''reentrant horn''. ]]
In the 1960s, an electric-amplified version of the megaphone, which used a loudspeaker, amplifier and a folded horn, largely replaced the basic cone-style megaphone. Small handheld, battery-powered electric megaphones are used by fire and rescue personnel, police, protesters, and people addressing outdoor audiences. With many small handheld models, the microphone is mounted at the back end of the device, and the user holds the megaphone in front of her/his mouth to use it, and presses a trigger to turn on the amplifier and loudspeaker. Larger electric megaphones may have a microphone attached by a cable, which enables a person to speak without having their face obscured by the flared horn.