The idea of broadening the directivity pattern of a push-pull electrostatic loudspeaker by partitioning the stators into concentric annular rings, which are connected to tappings along a delay line, isn't new. However, the delay line has traditionally been attenuated to avoid response irregularities due to the finite size of the membrane. An alternative approach is presented here whereby a constant-impedance delay line is configured to imitate an oscillating sphere, which is an ideal constant-directivity dipole source that needs no attenuation. Walker's equation for the on-axis pressure does not account for the effect of the delay line without taking the vector sum of the currents though all the rings, so a simple alternative that does is presented here.
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