Radial catenoidal horn in loudspeaking telephony

One of the adverse factors going against designing the loudspeaking telephone set powered solely via the telephone line has been the critical shortage of power to drive the loudspeaker adequately. A folded radial catenoidal horn of moderate size has been designed as a means of boosting the efficiency of the small, therefore inherently inefficient, loudspeaker used in the desk‐top model loudspeaking telephone set. Based on the classical plane wave horn theory, the catenoidal horn had been selected as most suitable for this purpose. With the aid of a computer, the horn parameters had been optimized to the particular driver loudspeaker parameters. The folding and the bell portions had been rigorously calculated and build based on these parameters optimized through the iteration method. Test results showed that the horn boosted the radiation efficiency of the loudspeaker 12 ± 5 dB over the frequency range 300–1500 Hz, where most of the speech energy is stored.