Editing Loudspeaker (section)

===Moving-coil===
The first experimental moving-coil (also called ''dynamic'') loudspeaker was invented by [[Oliver Lodge]] in 1898.<ref>{{cite web |url=https://www.aes-media.org/historical/html/recording.technology.history/loudspeaker.html |title=Loudspeaker History |access-date=January 20, 2019 }}</ref> The first practical moving-coil loudspeakers were manufactured by Danish engineer [[Peter L. Jensen]] and Edwin Pridham in 1915, in [[Napa, California]].<ref>{{cite news |last=Kornum |first=Rene |url=http://ing.dk/artikel/hoejttaleren-fylder-100-aar-og-foedselaren-er-dansk-179868 |title=The Loudspeaker Is 100 Years Old |work=[[Ingeniøren]] |date=November 4, 2015 }}</ref>  Like previous loudspeakers these used horns to amplify the sound produced by a small diaphragm.  Jensen was denied patents. Being unsuccessful in selling their product to telephone companies, in 1915 they changed their target market to radios and [[public address system]]s, and named their product [[Magnavox]]. Jensen was, for years after the invention of the loudspeaker, a part owner of The Magnavox Company.<ref>{{cite web |url=https://www.aes-media.org/historical/html/recording.technology.history/jensen.html |title=Jensen History |access-date=January 20, 2019 }}</ref>

[[File:Edward Kellogg & Chester Rice with cone speaker 1925.jpg|thumb|[[Edward W. Kellogg|Kellogg]] and [[Chester W. Rice|Rice]] in 1925 holding the large driver of the first moving-coil cone loudspeaker]]
{{Multiple image
| align = right
| direction = horizontal
| image1   = Rice Kellogg loudspeaker 1.jpg
| caption1 = Prototype moving-coil cone loudspeaker by Kellogg and Rice in 1925, with electromagnet pulled back, showing voice coil attached to cone
| width1   = 150
| image2   = Rice Kellogg loudspeaker 2.jpg
| caption2 = The first commercial version of the speaker, sold with the RCA Radiola receiver, had only a six-inch cone. In 1926 it sold for $250, equivalent to about $3000 today.
| width2   = 250
}}

The moving-coil principle commonly used today in speakers was patented in 1925 by [[Edward W. Kellogg]] and [[Chester W. Rice]]. The key difference between previous attempts and the patent by Rice and Kellogg is the adjustment of mechanical parameters to provide a reasonably flat [[frequency response]].<ref>{{cite journal |journal=Journal of the Audio Engineering Society |volume=52 |issue=4 |date=2004 |pages=412–432 (p. 416) |url=http://www.aes.org/journal/online/JAES_V52/jaes.cfm?file=JAES_V52_4/JAES_V52_4_PG412.pdf |quote=The key difference in the Rice and Kellogg design was the adjustment of mechanical parameters so that the fundamental resonance of the moving system took place at a lower frequency than that at which the cone's radiation impedance had become uniform. Over this range, the motion of the cone was mass controlled, and the cone looked into a rising radiation impedance. This in effect provided a significant frequency region of flat power response for the design. |author1-link=John M. Eargle |first1=John M. |last1=Eargle |first2=M. |last2=Gander |title=Historical Perspectives and Technology Overview of Loudspeakers for Sound Reinforcement }}</ref>

These first loudspeakers used [[electromagnet]]s, because large, powerful [[permanent magnet]]s were generally not available at a reasonable price. The coil of an electromagnet, called a field coil, was energized by a current through a second pair of connections to the driver. This winding usually served a dual role, acting also as a [[choke coil]], filtering the [[power supply]] of the [[audio power amplifier|amplifier]] that the loudspeaker was connected to.<ref>{{cite book |first=Henry B.O. |last=Davis |title=Electrical and Electronic Technologies: A Chronology of Events and Inventors from 1900 to 1940 |publisher=Scarecrow Press |date=1983 |isbn=0810815907 |page=75 }}</ref> AC ripple in the current was attenuated by the action of passing through the choke coil. However, AC line frequencies tended to modulate the audio signal going to the voice coil and added to the audible hum. In 1930 Jensen introduced the first commercial fixed-magnet loudspeaker; however, the large, heavy iron magnets of the day were impractical and field-coil speakers remained predominant until the widespread availability of lightweight [[alnico]] magnets after World War II.