The Isodynamic Principle
The moving coil loudspeaker is simple in design, rugged, and requires no external power supply but suffers from breakup modes due to the fact that it is made up of several moving parts which must be matched carefully. The cone needs to be rigid and hence relatively heavy. In the electrostatic loudspeaker, the force is applied evenly over the whole diaphragm but it requires a separate power supply and transformer. To obtain the good transient response of the electrostatic but retain the electromagnetic drive and simplicity a transducer of the type described below has been designed. This type of transducer has a long history but suffers from the disadvantage of low efficiency. Gamzon describes a similar transducer.
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