PURPOSE: To make a titled diaphragm have high rigidity, to reduce its distortion, and also to raise its input resistance, by packing foamed resin between a surface material and a skeletal member.
CONSTITUTION: A skeletal member 12 is formed by bending a rectangular kraft paper material in a zigzag shape, and developing it like a ring so that its one side part and the other side part become the inside circumferential face and the outside circumferential face, respectively. A surface material 11 consists of aluminum, and is made to adhere to both faces of the skeletal member 12. Subsequently, the hollow part formed by the surface material 11 and the skeletal member 12 is packed with foamed polyurethane resin 13. An auxiliary diaphragm 14 obtained by heating and forming like a dome a sheet which is obtained by using polyethylene synthetic pulp as a base material, and mixing a carbon fiber is joined to the center part of this diaphragm.
MARUNO YOSHIAKI
TAKAYAMA SATOSHI
MURATA KOUSAKU
