Loudspeaker Rocking Modes (Part 1: Modeling)

The rocking of the loudspeaker diaphragm is a severe problem in headphones, micro-speakers and other kinds of loudspeakers causing voice coil rubbing which limits the maximum acoustical output at low frequencies. The root causes of this problem are small irregularities in the circumferential distribution of the stiffness, mass and magnetic field in the gap. A dynamic model describing the mechanism governing rocking modes is presented and a suitable structure for the separation and quantification of the three root causes exciting the rocking modes is developed. The model is validated experimentally for the three root causes and the responses are discussed conforming a basic diagnostics analysis.