Loudspeakers are devices that accumulate heat during their transduction process. The rise of temperature is potentially harmful for the voice-coil and must be countered by the active heat control (AHC) process when other passive and mechanical dissipation schemes become inefficient. Known AHC aim at limiting the voice-coil temperature through a closed-loop approach and may lead to oscillations and audio artifacts when temperature measurements are available with latency. This paper establishes that an open-loop AHC relying on a dynamic range compressor configured as a brick-wall limiter whose threshold is modulated by the temperature of the magnetic components insures a bounded voice-coil temperature. The temperature of the magnetic assembly and the driving force of the loudspeaker can be both estimated in real-time, respectively by a linear quadratic observer (a Kalman filter) and by an envelope follower. The new AHC scheme is demonstrated and compared to closed-loop AHC on a simulation example.
https://www.aes.org/e-lib/browse.cfm?elib=17206
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