PURPOSE: To attain light weight and high rigidity of a speaker by constituting a core member where paper-tablet form rib pieces are arranged radially.

CONSTITUTION: A skin member 22 and a rib member 23 of desired form are obtained by mechanical rolling and cutting process when beryllium or its alloy is used as the constituting member. On the other hand, in using boron, its alloy or composite member, flat film (foil) is formed by means of a vopor deposition technology such as a vacuum deposition method. The skin member 23 is formed by means of an electron beam vapor deposition method by putting a titanium base plete 11 covered with a mask member 12 into a DC ion plating device 13. The rib member is formed by cutting the boron film made with the same condition as the skin member into the desired shape by means of a laser cutter.