Frequency-Modulation Distortion in Loudspeakers

As the frequency-response-range of a sound-reproducing system is extended, the necessity for minimizing all forms of distortion is correspondingly increased. The part which the loudspeaker can contribute to the over-all distortion of a reproducing system has been frequently considered. A type of loudspeaker distortion which has not received general consideration is described. This distortion is a result of the Doppler effect and produces frequency modulation in loudspeakers reproducing complex tones. Equations for this type of distortion are given. Measurements which confirm the calculated distortion in several loudspeakers are shown. The first Appendix giving the derivation of the equations is included.