A New Approach to Simulating the Leslie Speaker

I NTRODUCT IONThe Leslie speaker [11 is an electromechanical device which imparts some of the spatial characteristics of a pipe organ to the tone of an electronic organ.This is achieved by rotating horn -like mechanism which deflect the sound emanating from enclosed loudspeakers.In effect a directional sound source rotates about a vertical axis, and the organ tone is modulated in both phase and amplitude.In the current terminology animation is added, In order to cut the cost, improve reliability and produce a more compact device, there have been many attempts to emulate this modulation electronically.'Some of those described in the popular electronics press [2,3] tend to oversimplify the problem.whilst some more sophisticated examples may be found amongst recent patents [4,5], but generally it is the author's opinion that the resultant sound lacks depth when compared with a real Leslie speaker, especially when heard 'live' as opposed to through a p.a. system or via a recording.In this paper an expression is given for the acoustic field of a Leslie speaker in free -field conditions.and then the effects of echoes and reverberation are considered.A phenomenon is found which suggests that to reproduce the Leslie