An audio controller for use with a loudspeaker that generates sound in dependence upon a loudspeaker signal is disclosed. The loudspeaker includes a voice coil. The audio controller includes a monitor to monitor an electric response of the voice coil to the loudspeaker signal and a signal generator to generate an evaluation signal. The evaluation signal comprises a signal having an evaluation frequency that is below resonant frequency of the loudspeaker. A processing unit is included to generate, based on the monitored electric response, the loudspeaker signal from an input sound signal. The processing unit is configured to combine the evaluation signal with the input sound signal to generate the loudspeaker signal.