Crossover network for a multi-element electrostatic loudspeaker system

DETAILED DESCRIPTION The present invention relates to an electrostatic speaker system having a plurality of driver elements which are designed to operate over different audio frequency ranges, and more specifically, to an improved crossover network for such a speaker system.
As is well known in the art, electrostatic drivers include a pair of fixed conductive plates which are spaced apart on opposite sides of an insulating diaphragm element.
Recognizing that such an electrostatic driver is essentially a capacitor of relatively fixed value, the present invention contemplates a crossover network in which a parallel resonant circuit is formed by the electrostatic driver and the secondary winding of a step-up transformer to which it is connected.
Each parallel resonant circuit thus formed is tuned to a frequency that is within the operating range of its associated driver.
More specifically, in a loudspeaker system according to the present invention the plates of a first electrostatic driver designed to operate over one frequency range are connected to the secondary winding of a first step-up transformer having a primary winding connected to an audio signal source, and the plates of a second electrostatic driver designed to operate over another frequency range are connected to the secondary winding of a second step-up transformer which has a primary winding also connected to the audio signal source.
The secondary winding of each step-up transformer forms a parallel L-C circuit, or tank circuit, with the driver to which it connects, and the inductance of each step-up transformer secondary winding is selected to tune each tank circuit to a frequency within the designed operating range of its associated electrostatic driver.
As a result of the "tuned" secondary circuits on each step-up transformer, the impedance reflected into its primary winding increases substantially for frequencies within the operating range of its associated driver.
The primary windings of the step-up transformers are connected together in series with an impedance device across the audio signal source