The nonlinear characteristics of a loudspeaker system, often derived by combining those of each subcomponent estimated by lumped-parameter modeling and harmonic excitations, are identified simply by fitting the NARMAX model to one set of stationary random input voltages into the driving coil and the corresponding output displacement of the cone. Nonlinearities in the amplitude domain as well as in the frequency domain are obtained at once by generating the generalized frequency response functions and are compared with those measured separately by harmonic excitations.