Rocking Modes (Part 2: Diagnostics)

摘要

The rocking behavior of the 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 imbalances in the distribution of the stiffness, mass and force factor in the gap. Based on lumped parameter modeling, modal decomposition and signal flow charts presented in a previous paper (Part 1) this paper here focusses on the practical measurement using laser vibrometry, parameter identification and root cause analysis. New characteristics are presented which simplify the interpretation of the identified parameters. The new technique has been validated by numerical simulations and systematic modifications of a real transducer. The diagnostic value of the new measurement technique has been illustrated on a transducer used in headphones.