Thermal protection of electro dynamic transducers used in loudspeaker systems

Abstract

Electro dynamic transducers can fail due to either excessive voice coil excursion, causing mechanical clipping, or by overheating of the voice coil causing degradation of the materials. The disclosed invention relates to protection against excess voice coil temperature in such transducers. The current through the transducer voice coil and the voltage across its terminals, are measured. The resistive part of the impedance of the transducer is then estimated based on the measurements of current and voltage. When the resistive impedance for the given type of transducer is well known at one temperature it is then possible to calculate the temperature when the resistive impedance changes. The estimated voice coil temperature is then fed to a signal attenuator or controller, which attenuates the output signal to the transducer.

Dependencies are inferred from the claim text.