Electro-Acoustic Phase Shift in Loudspeakers

Abstract

Direct measurements of envelope delay (dβ/dω) have been obtained for a series of commercial and experimental loudspeakers. The modulation phase shift method of Nyquist and Brand has been adapted for direct indication of envelope delay by utilizing a direct-reading electronic phase meter. By suitable choice of modulating frequency, the phase shift of the modulation envelope (between electrical input and sound pressure on the loudspeaker axis) in degrees gives the envelope delay directly in milliseconds. Pressure-amplitude curves measured under the same conditions provide data for a preliminary attempt to interpret the correlation between delay response and pressure response.