Make Electronics

What Next? 243

Experiment 27: Loudspeaker Destruction

BAckground

Origins of loudspeakers

Loudspeakers utilize the fact that if you run a varying electrical current through
a coil situated in a magnetic field, the coil will move in response to the current.
This idea was introduced in 1874 by Ernst Siemens, a prolific German inven-
tor. (He also built the world’s first electrically powered elevator in 1880.) Today,
Siemens AG is one of the largest electronics companies in the world.

When Alexander Graham Bell patented the telephone in 1876, he used Siemen’s
concept to create audible frequencies in the earpiece. From that point on,
sound-reproduction devices gradually increased in quality and power, until
Chester Rice and Edward Kellogg at General Electric published a paper in 1925
establishing basic principles that are still used in loudspeaker design today.

At http://www.radiolaguy.com/Showcase/Gallery-HornSpkr.htm you’ll find
photographs of very beautiful early loudspeakers, which used a horn design
to maximize efficiency. As sound amplifiers became more powerful, speaker
efficiency became less important compared with quality reproduction and low
manufacturing costs. Today’s loudspeakers convert only about 1% of electrical
energy into acoustical energy.

Figure 5-28. This beautiful Amplion AR-114x illustrates the efforts of early design-
ers to maximize efficiency in an era when the power of audio amplifiers was very
limited. Photos by “Sonny, the RadiolaGuy.” Many early speakers are illustrated at
http://www.radiolaguy.com. Some are for sale.