Jump phenomena in electrodynamic loudspeaker
In very low frequency range, the loudspeaker can be treated as a lumped-parameter system, a simple mass-spring system. Therefore, its vibration can be described by an ordinary differential equation. The nonlinearity of loudspeaker at low frequencies comes mostly from two factors-nonlinearity of suspension stiffness and nonhomogeneity of magnetic field in the air gap, with the former resulting in a nonlinear restoring force, and the latter causing a nonlinear driving force and a nonlinear damping. These factors appear because the displacement of vibration is large at low frequencies. By taking both factors into account, the jump phenomenon was theoretically and experimentally studied in this paper. The results show that: (1) for a loudspeaker with magnetic nonlinearity only, the jump phenomenon will not occur; (2) for a loudspeaker with the restoring force nonlinearity only, the jump phenomenon can occur, if the loudspeaker is subjected to a large enough driving voltage; (3) for a system with large damping, the occurrence of the jump phenomenon is much more sensitive to the change of the damping than to the change of the driving force; (4) the jump phenomenon occurs more easily in the loudspeaker with both nonlinearities of restoring force and magnetic field than in the loudspeaker only with restoring force nonlinearity. Experiments were performed for three types of loudspeakers-with both restoring force nonlinearity and magnetic nonlinearity, with restoring force nonlinearity only and with magnetic nonlinearity only. The jump phenomenon was observed only in the loudspeaker of the first type. To prevent the occurrence of the jump phenomenon in loudspeakers, an effective method is to increase the value of the Bl product.
Zhi-liang Zhang Chang-jun Cheng
Department of Physics, Zhejiang Normal University, Junhua 321004, Zhejiang Province, China Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China
国际会议
The 5th International Conference on Nonlinear Mechanics(第五届国际非线性力学会议)
上海
英文
1440-1443
2007-06-11（万方平台首次上网日期，不代表论文的发表时间）