Apparatus and method for filtering a signal to match a loudspeaker

A signal-processing circuit for the generation of a loudspeaker signal, comprising:

• an input for the feeding of a digital, time-discrete input signal;
• a digital equalizer filter that is coupled to the input and has at least one first recursive filter of second order that is defined by a first adjustable set of coefficients;
• an amplification device coupled to the equalizer filter, said amplification device comprises a digital-analog converter and an amplifier and is configured to generate the loudspeaker signal as a function of the filtered input signal and to output on an output terminal;
• a current measurement device that is coupled to the amplification device and is configured to output a digital, time-discrete measurement signal that represents a current of the loudspeaker signal;
• a digital filter block that is configured to generate, through filtering, an estimate signal as a function of the measurement signal, wherein for this purpose the digital filter block has at least one second recursive filter of second order that is defined by a second adjustable set of coefficients;
• and
• a matching block that is configured to determine a new set of coefficients as a function of the measurement signal, the estimate signal, and the filtered input signal and to use the newly determined coefficients in the first and second adjustable set of coefficients such that the resulting transfer functions (HEQ(Z), HRES(Z)) of the at least one first recursive filter and the at least one second recursive filter are inverse relative to each other.