Abstract
In a dynamic speaker, a particular supporting piece is used for positioning of the moving coil. Actual structure of this supporting piece is variously devised in practice to decrease the stiffness and to prevent generation of non-linear strain. In order to satisfy these two essential requirements, the length of the supporting piece in the radial direction is inevitably increased to a certain degree. Then, the frequency characteristic of vibration of the cone diaphragm gets more complicated because of an obstruction caused by higher mode of vibration above the second resonance of the supporting piece itself. Taking these possible problems into consideration, the vibration characteristic of the vibration system composed of the moving coil and the supporting piece has been analyzed to estimate the degree of this obstruction. Contrary to our previous expectation, it has been found that the obstruction from the higher mode of vibration is actually eliminated, if the weight of the moving coil (including the vibrating plate) is more than ten times that of the supporting piece. It has been made clear that the whole system is approximated as a simple resonant system of one-freedom. Therefore, it is apparent that a considerably long supporting piece can be used practically without any trouble.
