| Nowadays,loudspeaker system has been widely used in many devices,such as mobile phones,computers,headphones,speakers and so on.The main function of loudspeaker system is to reproduce the sound.The reproducibility of the existing sound is an important criterion for evaluating the quality of a loudspeaker system.The ability to reproduce,however,is progressed slowly at low frequencies.At present,the bass enhancement technology can be divided into two categories: digital virtual bass enhancement technology and hardware bass enhancement technology.The physical level of hardware bass enhancement technology has great challenges,but it is very important for bass reproduction.Therefore,this paper proposes a mechatronic passive diaphragm loudspeaker system and Analyses it.The advantages of adjustable acoustic impedance of electromechanical passive membrane are utilized to enhance the low frequency response capability of the system at the physical level.Electromechanical passive vibration diaphragm is the core of the new loudspeaker system.Based on the principle of electromagnetic coupling,the coil is viscous on one side of the mechanical diaphragm.The outer circuit of the coil contains a negative impedance converter(NIC),which enlarges the adjustable range of the circuit parameters.The coil is immersed in the magnetic field and designed as a passive electromechanical diaphragm.Through coupling,the acoustic impedance of the diaphragm can be adjusted by the coil circuit parameters.A mathematical model of the acoustic impedance of electromechanical passive diaphragm is established.The influence of additional circuit parameters on the acoustic impedance of electromechanical passive diaphragm is analyzed.A mechanical passive diaphragm loudspeaker system is designed by combining mechanical and electrical passive diaphragm,and the mathematical model of system frequency response is established.The influence of three parameters of electromechanical passive diaphragm additional passive circuit on system frequency response is studied respectively.According to the mathematical model of system frequency response,the optimization model with the minimum cut-off frequency of bass as the optimization objective is established.The calculation results show that the bass cut-off frequency of the mechanical passive diaphragm loudspeaker system is obviously lower than that of the conventional mechanical passive diaphragm loudspeaker system and the conventional closed-box loudspeaker system.In order to verify the rationality of the theoretical calculation,a prototype of the electromechanical passive diaphragm loudspeaker system is made.The TS parameter measurement experiment and frequency response measurement experiment of the loudspeaker system based on the laser vibrometer are designed.The influence of three parameters of the electromechanical passive diaphragm additional circuit on the frequency response curve of the system is carried out,and the parameters are given.Finally,parameter optimization verification experiments were carried out.In the experiment,the results show that the three parameters of the additional circuit have the same effect on the trend of the system frequency response curve as the calculation results.The optimization of the parameters reduces the cut-off frequency of the system bass and improves the enhancement ability of the system low-frequency acoustic radiation significantly. |
