| 摘要 |
PROBLEM TO BE SOLVED: To enhance the stiffness, the withstanding temperature, a large input capability and a thin profile by foaming a resin that is a mixture of a modified polyphenylene oxide and resin and a polystyrene resin filled in metallic dies, making a center hole to fit a voice coil, forming a groove for connection tinsel and forming the outer circumference of the speaker to be nearly circular. SOLUTION: Prescribed amounts of the modified polyphenylene oxide and resin and the polystyrene resin are mixed, the mixture is foamed preliminarily, the mixture resin is filled in metallic dies. Foaming is implemented by using vapor and annealing is applied to the foamed resin in the metallic dies. A speaker diaphragm 11 of a flat plate shape obtained thereby has a cylindrical center hole 11a to which a voice coil is fitted, a step 11b to which a dust cap is fitted, a groove 11c and a throughhole 11d for positioning tinsel. Furthermore, a gate port for resin filling at forming is formed on the speaker diaphragm 11 at an outer circumferential side in the vicinity of the rear side of the groove 11c. Thus, the speaker with high tensile strength, compression hardness and heat deformation temperature and excellent sound pressure frequency characteristic can be obtained.
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