A New Family of Horns

Abstract

An examination of the properties of practical horns indicates that the throat admittance of a horn with finite expansion cannot be a positive real at all frequencies. The nearest approach to this characteristic is a conductance (real part of the admittance) constant for all frequencies above a minimum or cut-off frequency. It is possible to generalize Webster's plane wave horn theory to yield a relation between horn shape and the conductance. When the condition that a constant value of this conductance be reached shortly above the cut-off frequency is specified a new family of horns results. With certain of these horns it is possible for the throat resistance to rise more rapidly to the asymptotic value than in the exponential type. As a result horns having optimum conductance and susceptance characteristics for practical electromechanical driving units may be readily selected.