The method comprises the determination of an observation vector that comprises only electrical measurements of the voltage (Umes) at the loudspeaker terminals and of the current (i) passing through the loudspeaker, and a state vector (X) whose components comprise: values of linear parameters of the loudspeaker response such as the electrical (Re) and mechanical (Req) resistance, and polynomial coefficients of nonlinear parameters such as the force factor (BI), the equivalent stiffness (Keq) and the electrical inductance (Le). The voltage and current measurements are applied to an estimator with a predictive filter of the extended Kalman filter incorporating a representation of a dynamic model of the loudspeaker. This filter operates a prediction of the state vector (X) and readjusts this prediction by calculation of an estimate (Uest) of the voltage based on the state vector and on the measured current and comparison of this estimate with the measurement (Umes) of the voltage.