Horn-Type Loud Speakers-A Quantitative Discussion of Some Fundamental Requirements in Their Design

Horn loud speakers have found widespread commercial application due to their practical possibility of maintaining high efficiency over a relatively wide frequency range. The inherent limitations of such speakers are not generally recognized, however, as neither are the specific relations that must be satisfied in the choice of constants in the electrodynamic system. This paper discusses the limitations of a single speaker to cover the entire range of reproduction. It shows the quantitative relations that must be maintained between the components of the vibrating system in order to secure maximum efficiency at all frequencies. It also demonstrates that certain definite relations must be satisfied if one is to gain by the use of aluminum-wire voice coils. Unless these are satisfied, a loss in efficiency may occur by using aluminum instead of copper. The paper also describes various means that have been employed to avoid the limitations of the single-horn speaker to cover a wide range of reproduction, and concludes with a description of a new experimentally developed speaker employing two entirely separate driving elements mounted on a common magnetic structure; each cone feeding a separate horn. The composite structure takes the approximate form of a cylinder five feet in diameter, two feet deep, and weighs under 100 pounds.