ABSTRACT
Although the original moving-coil, cone loudspeaker of Rice and Kellogg was the first true loudspeaker of a type that we know today, it was, itself, a development of ideas which had gone before, principally relating to the design of telephone earpieces, which were not very loud speakers. The moving coil direct radiator, along with amplifiers as great as 15 watts output – which was then huge – soon opened a door to room-filling sound levels, and, within only a couple of years, talking pictures at the cinema. The need to fill larger and larger theatres with sound led to horn designs, and the need for greater bandwidth led to the separation of the drive units into frequency ranges where they could operate more efficiently. Thus began a refinement and specialisation of designs which continues to this day, with ever more ideas, magnet materials, diaphragm materials and radiator concepts all designed essentially to do the same thing – convert electrical energy into sound waves. What follows in this chapter is a discussion of some of the various ways in which this conversion can be made to take place, and the strengths and weaknesses of the various approaches.
