Generating sufficient acoustical output with smaller loudspeakers requires maximum voice coil excursion, thereby exploiting the available mechanical resources of the motor and suspension. Digital preprocessing of audio input signals can be used to prevent a mechanical or thermal overload, which would generate excessive distortion and eventually damage the transducer. The most important characteristics of the protection algorithm are the measurement or adaptation error for the critical state variables, overshoot and undershoot of the activation control system, and latency added by the protection system. An inexpensive adaptive protection scheme can be realized by monitoring the voltage and current at the transducer terminals without using a mechanical sensor. The adaptive nonlinear control generates not only the largest AC amplitude and maximum output but also reduces the nonlinear distortion. The active linearization and stabilization of the transducer also needs a reliable mechanical protection system because overshooting the protection limits will cause an undesired increase of the nonlinear compensation signal, and that would require power amplifiers to provide a higher peak voltage.
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