Total harmonic distortion improvement for elliptical miniature loudspeaker based on suspension stiffness nonlinearity

This article reports the effect of geometric modification of diaphragm on the total harmonic distortion (THD) for an elliptical miniature loudspeaker by systematically investigating and modifying suspension stiffness. Three diaphragms, typified by different track patterns on the concave ring are simulated and experimented. Initially, the prototype specimens were tested for stiffness curves and electroacoustic parameters by laser vibrometry. Further, the stiffness curves for three sample designs were numerically modeled using finite element analysis (FEA). The loudspeaker is also modeled using equivalent circuit method (ECM) for simulating THD. As a result of employing Runge- Kutta method for the solution of a coupled system of ordinary differential equations, THD was calculated and subsequently presented as a function of frequency. In addition, their THD was measured in a standard anechoic chamber and compared with simulations. It is found that the effect of track patterns on the sound pressure level is absolutely insignificant. On contrary, effect on THD is observable and leads to the conclusion that the diaphragm with curved tracks outperforms other diaphragms (partial straight and straight tracks). The reliability of simulation and its confirmation with the measurement has assured the possibility of simulating THD by FEA and analytical method for design optimization of track patterns.