From jukefox@jukejoynt.com Tue Nov 20 22:28:44 2012
Subject:Re: Speaker placement

Speaker placement is always an interesting question because of the physics involved. For instance, for a static, monaural signal channeled through two separate transducers (dual mono, as opposed to "stereo"), frequencies of like footage can cancel one another at points of opposing phase. Bass frequencies typically take up to 16' to fully propagate in the air and careless cabinet placement can result in bass disappearing at points, or being excessively "rumbly" in others.

Clonewheel organs exhibit frequency behaviors that can be affected by all of these considerations, yet their ideal speaker placements in avoidance of such may well be detrimental to sounds emanating from synthesizers, electric pianos, clavinets, romplers and other instruments commonly found in a multi-keyboardist's rig.

For sound reinforcement of a stereo rotary sim, consider that the length of one Leslie horn is approximately 10". The travel of the mouth of that horn through 180 degrees (one side of rotation to the opposite) places audio emission extremes at some 20" apart. Coincidentally (or probably not), that is the amount of separation between the centers of the left and right speakers in my Motion Sound KBR-3D, with the unit's stationary horns set out another 6" or so to the outsides (extended horizontal throw, perhaps).

I would propose that, if one is using on-stage sound as the primary clonewheel sound source in any given venue (as opposed to a front of house mains/in-ear monitor system with no onstage sound reinforcement), either a self-contained stereo keyboard amplifier or a stereo pair of speakers (be they active or passive) aimed between 22 and 45 degrees outward with cone centers spaced at around 20" separation would serve to help generate the most authentic possible rotary simulation, while providing an adequate enough stereo-field to be convincing throughout most of the venue (depending upon stage position in the room and speaker placement on-stage) and resulting in minimal possibilities for phase cancellation anomalies.

This sounds like a solution fairly similar to what Bruce describes here, and would seem more-or-less ideal for small-to-medium size venues. My belief is that paper tweeters may actually be preferable in any such setup, as the V-21 Jensen drivers are already considered in the models and paper should reproduce that portion of the model quite accurately, while avoiding adding harshness inherent in bullet tweeters and peizos found in many cabinets common at the cabaret level.

Or, you could just carry a Leslie and fuggetaboudit.

Peace,
Fox