Modeling nonlinearities and thermal effects in moving coil speakers

Simple explanations of moving coil speaker behavior assume that the magnetic force factor, the mechanical spring stiffness and the coil electrical inductance are all constants of the design. The work of Klippel identifies all of these as varying with speaker cone displacement. The electrical resistance also varies with temperature, which varies because of electrical heating in the coil. Methods of measuring these nonlinearities are available in commercial equipment. Using this data to model speaker performance requires a model that considers behavior I the electrical, mechanical, thermal and acoustical domains. This paper describes an open source method to use the measured nonlinear parameters to calculate the time waveform of radiated pressure with large signal excitation for speakers.