Abstract: The invention relates to an arrangement for converting an electric input signal into an acoustic or a mechanical output signal comprising a transducer 19, a controller 15 and a parameter detector 17. The output 23 of the controller is connected via the parameter detector to the terminals of the transducer. The controller has a parameter vector input 24 to change the linear or nonlinear transfer characteristic of the controller between its control input 13 and control output 23. The parameter detector comprises an error circuit 31 and update circuit 33. The error circuit 31 measures an electric signal at the terminals of the transducer and generates an error signal e(t) which describes the difference between the measured electric signal and an estimated electric signal derived from the output signal or other state signals of the controller. The update circuit 33 estimates transducer parameters by minimizing the amplitude of the error signal.