| 摘要 |
PURPOSE:To increase a range where displacement amplitude is not vibratory, by varying the viscous resistance of air with displacement, by fitting an annular flat plate on the bobbin inside wall of a bobbin coil. CONSTITUTION:When a signal is inputted to a voice coil 20, an annular flat plate 60 is displaced, so pressure in space 82 varies. The pressure variations pass through the inside and outside of a bobbin 21, and are branched to the 1st path passing through pores of a spider 50, gaps between the flat plate 60 and buffer bodies 71 and 72 and the 2nd path passing through a hole to be released. The viscous resistance of air in the 2nd path varies with the vibratory displacement of the flat plate 60, so the range where the displacement amplitude is not vibratory is increased. |
