CHAPTER 12 Diversity of Design Loudspeakers by Philip Newell and Keith Holland 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 theaters with sound led to horn designs, and the need for greater band- width led to the separation of the drive units into frequency ranges where they could operate more effi-