Zoom October 2011

At its essence, a loudspeaker translates electrical energy into mechanical/acoustic energy. The most common, seen in audio and/or visual electronics, is known as a “dynamic driver,” and magnetism is at the core of its function. First the voice coil interacts with the permanent magnet. The voice coil is an electromagnet, copper wire magnetized by electricity, which is wrapped around a form and nestled in the hole of the doughnut-shaped permanent magnet. When alternating electrical current enters the speaker through terminals, the dual magnetic fields cause the voice coil to move. Sound is produced when air moves through a cone-shaped diaphragm called, appropriately enough, the cone, usually made of paper, plastic or metal and mounted on a cast aluminum frame. This is the part of the speaker that actually moves air and produces sound. Depending on the polarity of the AC current, the speaker either moves forward or backward from the rest position tightly maintained by brackets called spiders. The development of the telephone spurred the development of the loudspeaker, and despite what you learned in school, the first telephone was created by Italian inventor Antonio Meucci at least 25 years before Alexander Graham Bell. Meucci happened upon the possibility of transmitting the human voice over wires by accident in 1849. He was attempting to cure illnesses with electric shocks, so, to this end, he possessed copper wires attached to a battery. About to shock a friend in the next room, he suddenly heard the friend’s voice through the copper wires. This led to his invention of the “Teletrefono.” The dynamic driver design, created by British physicist Oliver Lodge in 1898, turned out to be the best of a litany of subsequent designs, and took off in the marketplace when it was refined to the point of high fidelity in 1921 by Chester Rice and Edward Kellogg, scientists working for General Electric.

michael isenbek

Michael Isenbek, Associate Editor, dabbles in both fiction and nonfiction writing, coordinates the Pulse event listings and writes the text for "Zoom," among other editorial tasks. He has a Master's Degree in Liberal Studies and a Bachelor's Degree in Cultural Studies with a concentration in Journalism from SUNY Empire State College.