| 摘要 |
PURPOSE:To improve the degree of freedom for designing of a magnetic circuit as well as a voice coil bobbin, etc., by forming a flat plate through connecting plural porous foamed body having different levels of apparent density and thus obtaining a desired density distribution. CONSTITUTION:A porous foamed body 1a is conical in shape, and a porous foamed body 1b is conical with hole. Such foamed bodies 1a and 1b are connected together with an adhesive and formed into a disk having such a section as shown in the diagram. The surface is fixed in the ordinary way. Then the density of the foamed body 1a is set higher than that of the foamed body 1b. As a result, the density at the center part of the disk becomes higher than that at the outer circumference part. Accordingly the position of a nodal ring caused under such conditions is shifted toward the center of the disk in comparison with the case of the even density. As a result, the drive diameter of a disk-shaped diaphragm becomes smaller than the ordinary case. |
