Abstracts of technical articles from bell system sources

An Efficient Loud Speaker at the Higher Audible Frequencies¹ L. G. Bostwick. This paper describes a loud speaker designed for use as an adjunct to existing types for the purpose of extending the range of efficient performance to 11,000 or 12,000 cycles. A moving coil piston diaphragm structure is used in conjunction with a 2000-cycle cutoff exponential horn having a mouth diameter of about 2 inches. Motional impedance measurements on this loud speaker indicate an average absolute efficiency of about 20 per cent within the frequency range from 3000 to 11,000 cycles. The variation in response within this band does not exceed 5 db. By using a high-frequency loud speaker of this type the efficiency and power capacity of the associated low-frequency loud speaker can be improved and a uniform response-frequency curve from 50 to 12,000 cycles can be obtained.