Effect of Voice-Coil and Surround on Vibration and Sound Pressure Response of Loudspeaker Cones
The numerical analysis of the vibrational behavior and the sound pressure response of cone loudspeakers is discussed. The finite-element method is used to calculate the changes in eigenfrequencies, the shapes of the normal modes, and the displacements due to forced vibration of the conical cone resulting from the attachment of the voice coil and the outer surround. The sound pressure response is calculated using the displacements due to forced vibration. The same calculations are performed for the convex and the concave cones. For the conical cone the attachment of the voice coil causes a change in the peak sound pressure level corresponding to the normal modes of the cone. A large increase was calculated in the sound pressure level for the first- and second-order, a slight decrease for the third orde,r and a large decrease for the fourth and higher order normal modes. The attachment of the surround also causes a change in the peak sound pressure level, namely, a large decrease for the first order, a slight increase for the second order, and a slight decrease for the third and higher order normal modes. For the convex cone the attachment of the voice coil causes a slight increase, while the attachment of the surround causes a decrease in the peak sound pressure level corresponding to the normal modes. In the concave cone the attachment of the voice coil causes a large decrease in the eigenfrequency but little change in the large peak level of the sound pressure in the first-order normal mode, yet a decrease in the peak sound pressure level in the second and higher order normal modes was observed. The attachment of the surround causes little decrease in the eigenfrequency and in the sound pressure level of the first-order normal mode. These results show that the convex cone is strongly affected by the surround, yet virtually unaffected by the voice coil, and the concave cone is strongly affected by the voice coil, but virtually unaffected by the surround.
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