Headphones
Ian SinclairNot all sound reaches us through loudspeakers, and the advent of the Sony Walkman has
led many listeners back to headphone stereo. In this chapter, Ian Sinclair shows the very
different type of problems and their solutions as applied to this alternative form of listening.
25.1 A Brief History......................................................................................................
The history of modern headphones can be traced back to the distant fi rst days of the
telephone and telegraph. Then, headphone transducers for both telephone and radio
worked on the same moving-iron principle—a crude technique compared to today’s
sophistication, but one which served so well that they are still to be found in modern
telephone receivers.
Moving-iron headphones suffered from a severely restricted frequency response by
today’s standards, but they were ideal. These sensitive headphones could run directly
from a “ cat’s whisker ” of wire judiciously placed on a chunk of galena crystal. Radio
could not have become such a success so early in its development without them.
As “ cat’s whiskers ” bristled around the world, these sensitive headphones crackled to
the sound of the early radio stations and headphones became as much a part of affl uent
living as the gramophone. But the invention of sensitive moving-iron loudspeakers was
the thin end of the wedge for headphones. Although little more than a telephone earpiece
with a horn or radiating cone tagged on (with developments like the balanced armature to
increase sensitivity and reduce distortion), they freed individuals or even whole families
from the inconvenience of having to sit immobile.
Later, in the 1930s, with the invention of the then revolutionary but insensitive moving-coil
loudspeaker and the development of more powerful amplifi ers to drive them, headphones
CHAPTER 25