History and Types of Loudspeakers
The standard dyanmic loudspeaker that we know of today was developed in the 1920's, however there are more kinds of speakers: Horn Loudspeakers, Piezoelectric speakers, Magnetostrictive speakers, Electrostatic Loudspeakers, Ribbon and Planar Magnetic Loudspeakers, Bending Wave Loudspeakers, Flat Panel Loudspeakers, Heil Airl Motion Transducers, Plasma Arc Speakers, and Digital Loudspeakers.
The dynamic loudspeaker in the photo above out-performs many other types of speakers, and is lower cost to produce. For these reasons it is the most popular. We will outline some other types in this page.
Horns were the earliest form of amplification. Horns do not use electricity. Thomas Edison, Magnavox, and Victrola all developed advanced and well-performing horns from 1880 to the 1920's. The problem with horns is that they could not amplify the sound very much. With the use of electrical amplification in the future loud sound could be generated to fill large public spaces. Horns remain a novelty for collectors today.
See the bottom of this page for photos of horns.
What is an electrodynamic loudspeaker? A: This is a device that uses an electromagnetic coil and diaphragm to create sound. This is the most common type of speaker in the world today.
1877 - The idea of the electromagnetic coil driven speaker is formulated by Werner Von Siemens, he used it with input signals of DC transients and telegraphic signals. He had no way to amplify sound to create a useful speaker, but he theorized that this could eventually be done.
1877-1921 - Various inventors and engineers played with the idea of the electrodynamic loudspeaker but could only create rough distorted sounds. There was no way to electrically amplify the signal to create very loud sounds. The industry continued to rely on more advanced horns to create amplification.
1921
The development of the electrodynamic loudspeaker:
C.W. Rice of General Electric and E.W. Kellogg of AT&T worked together in Schenectady, New York to develop the modern speaker and first electric amplification system. They created a working prototype in 1921. In 1925 they filed for patents and made a speech in St. Louis to the AIEE. After several years of work they perfected it as the first commercial product of it's kind called the Radiola Loudspeaker #104. It sold in 1926 for $ 250 (about $3000 in todays USD) and was produced under the name of RCA.
Watch the video below to see the first prototype:
Flat Panel Speakers use voice coils mounted to flat panels to act as the source of sound. The flat panel acts as a diaphragm. Below are some examples of different designs. Different materials can be used as a diaphragm, from vinyl to sterofoam. This is different from a diaphragm speaker in that the moving voice coil is not wrapped around the same material as the flat panel. The panel part is adhered to the coil assembly.
 |
 |
 |
 |
___ |
 |
 |
|
Diaphragm
Speakers
|
Diaphragm Speakers This is a speaker that has the coil directly mounted on the diaphragm. Below is an example of a flat panel style diaphragm speaker. The copper coils have been wrapped around the base of the clear plastic bulges in the photos below. The entire clear plastic sheet below moves to create sound. See the diagram below. This is a heavier speaker than the flat panel speakers above.
 |
 |
The Horn: Used until the 1920's
Below are photos of various horns:
This webpage is under construction, come back again later to see more.
Sources:
Technical Research - Steve Normandin
Photos and Graphics - M. Whelan
copyright 2010 Edison Tech Center
