Early_systems Public_address_system

1 systems

1.1 megaphone
1.2 automatic enunciator
1.3 magnavox
1.4 marconi
1.5 late 1920s-1930s
1.6 electric megaphone

early systems
megaphone

a late 19th-century speaking trumpet used firefighters.



a small sports megaphone cheering @ sporting events, next 3 in. cigarette lighter scale

from ancient greek era nineteenth century, before invention of electric loudspeakers , amplifiers, megaphone cones used people speaking large audience, make voice project more large space or group. megaphones typically portable, hand-held, cone-shaped acoustic horns used amplify person’s voice or other sounds , direct towards given direction. sound introduced narrow end of megaphone, holding face , speaking it. sound projects out wide end of cone. user can direct sound pointing wide end of cone in specific direction. in 2010s, cheerleading 1 of few fields nineteenth century-style cone still used project voice. device called “speaking-trumpet”, “bullhorn” or “loud hailer”.

automatic enunciator

in 1910, automatic electric company of chicago, illinois, major supplier of automatic telephone switchboards, announced had developed loudspeaker, marketed under name of automatic enunciator. company president joseph harris foresaw multiple potential uses, , original publicity stressed value of invention hotel public address system, allowing people in public rooms hear announcements. in june 1910, initial semi-public demonstration given newspaper reporters @ automatic electric company building, speaker s voice transmitted loudspeakers placed in dozen locations on building .

a short time later, automatic enunciator company formed in chicago order market new device, , series of promotional installations followed. in august 1912 large outdoor installation made @ water carnival held in chicago associated yacht , power boat clubs of america. seventy-two loudspeakers strung in pairs @ forty-foot (12 meter) intervals along docks, spanning total of one-half mile (800 meters) of grandstands. system used announce race reports , descriptions, carry series of speeches chicago plan , , provide music between races.

in 1913, multiple units installed throughout comiskey park baseball stadium in chicago, both make announcements , provide musical interludes, charles a. comiskey quoted saying: day of megaphone man has passed @ our park. company set experimental service, called musolaphone, used transmitted news , entertainment programming home , business subscribers in south-side chicago, effort short-lived. company continued market enunciators making announcements in establishments such hospitals, department stores, factories, , railroad stations, although automatic enunciator company dissolved in 1926.

magnavox

early public-address system around 1920 using magnavox speaker. microphone had metal reflector concentrated sound waves, allowing speaker stand wouldn t obscure or face. vacuum tubes couldn t produce gain, , 6 tubes amplifier had low power. produce enough volume, system used horn loudspeaker. cylindrical driver unit under horn contained diaphragm, voice coil vibrated produce sound through flaring horn. produced far more volume given amplifier cone speaker. horns used in virtually pa systems, , still used in 2010s in systems, @ least high-range tweeters.

edwin jensen , peter pridham of magnavox began experimenting sound reproduction in 1910s. working laboratory in napa, california, filed first patent moving coil loudspeaker in 1911. 4 years later, in 1915, built dynamic loudspeaker 1-inch (2.5 cm) voice coil, 3-inch (7.6 cm) corrugated diaphragm , horn measuring 34 inches (86 cm) 22-inch (56 cm) aperture. electromagnet created flux field of approximately 11,000 gauss.

their first experiment used carbon microphone. when 12 v battery connected system, experienced 1 of first examples of acoustic feedback, typically unwanted effect characterized high-pitched sounds. placed loudspeaker on laboratory s roof, , claims amplified human voice heard 1 mile (1.6 km) away. jensen , pridham refined system , connected phonograph loudspeaker broadcast recorded music. did on number of occasions, including once @ napa laboratory, @ panama–pacific international exposition, , on december 24, 1915 @ san francisco city hall alongside mayor james rolph. demonstration official presentation of working system, , approximately 100,000 people gathered hear christmas music , speeches absolute distinctness .

the first outside broadcast made 1 week later, again supervised jensen , pridham. on december 30, when governor of california hiram johnson ill give speech in person, loudspeakers installed @ civic auditorium in san francisco, connected johnson s house miles away cable , microphone, delivered speech. jensen oversaw governor using microphone while pridham operated loudspeaker.

the following year, jensen , pridham applied patent called sound magnifying phonograph . on next 2 years developed first valve amplifier. in 1919 standardized 3-stage 25 watt amplifier.

this system used former president william howard taft @ speech in grant park, chicago, , first used current president when woodrow wilson addressed 50,000 people in san diego, california. wilson s speech part of nationwide tour promote establishment of league of nations. held on september 9, 1919 @ city stadium. san francisco installation, jensen supervised microphone , pridham loudspeakers. wilson spoke 2 large horns mounted on platform, channelled voice microphone. similar systems used in following years warren g. harding , franklin d. roosevelt.

marconi

by 1920s, marconi had established department dedicated public address , began producing loudspeakers , amplifiers match growing demand. in 1925, george v used such system @ british empire exhibition, addressing 90,000 via 6 long-range loudspeakers. public use of loudspeakers brought attention possibilities of such technology. 1925 royal air force pageant @ hendon aerodrome used marconi system allow announcer address crowds, amplify band. in 1929, schneider trophy race @ calshot spit used public address system had 200 horns, weighing total of 20 tons.

late 1920s-1930s

engineers invented first loud, powerful amplifier , speaker systems public address systems , movie theaters. these large pa systems , movie theatre sound systems large , expensive, , not used touring musicians. after 1927, smaller, portable ac mains-powered pa systems plugged regular wall socket became popular musicians ; indeed, ...leon mcauliffe (with bob wills) still used carbon mic , portable pa late 1935. during late 1920s mid-1930s, small portable pa systems , guitar combo amplifiers similar. these amps had single volume control , 1 or 2 input jacks, field coil speakers , thin wooden cabinets; remarkably, these amps did not have tone controls or on-off switch. portable pa systems plug wall sockets appeared in 1930s when introduction of electrolytic capacitors , rectifier tubes enabled economical built-in power supplies plug wall outlets. previously, amplifiers required heavy multiple battery packs.

electric megaphone

a woman using small handheld electric megaphone @ demonstration in portugal. electric megaphones use type of horn loudspeaker called reflex or reentrant horn.

in 1960s, electric-amplified version of megaphone, used loudspeaker, amplifier , folded horn, largely replaced basic cone-style megaphone. small handheld, battery-powered electric megaphones used fire , rescue personnel, police, protesters, , people addressing outdoor audiences. many small handheld models, microphone mounted @ end of device, , user holds megaphone in front of her/his mouth use it, , presses trigger turn on amplifier , loudspeaker. larger electric megaphones may have microphone attached cable, enables person speak without having face obscured flared horn.