Abstract: In an electroacoustic converter, center pole and top plate which constitute a magnetic circuit are mechanically abutted against each other by interposing an air gap defining member therebetween. The air gap defining member is a projection provided on the center pole or top plate, otherwise non-magnetic ring-like sleeve covered on the center pole or top plate. An air gap in the magnetic circuit can be precisely defined by the air gap defining member without using any alignment tool in its assemble process.

Abstract: A method of forming diamond-like carbon layer which is advantageously adaptable as a coating layer on acoustic diaphragms. In the method, carbon vaporized out of solid carbon source is deposited onto the surface of the diaphragm as the coating layer in the atmosphere of catalystic gas, for instance, H.sub.2 +Ar or H.sub.2 of about 10.sup.-4 Torr. The deposited carbon layer on the surface of the diaphragm is an amorphous carbon of inclusion of hybridized orbital SP.sup.2 bond and hybridized orbital SP.sup.3 bond and crystalline carbon particles of hybridized orbital SP.sup.3 bond dispersed in the amorphous carbon, or an amorphous carbon of inclusion of hybridized orbital SP.sup.2 bond and hybridized orbital SP.sup.3 bond.

Abstract: A modacrylic fiber comprising a copolymer containing acrylonitrile, at least one of vinyl chloride and vinylidene chloride, and a sulfo group-containing vinyl monomer having a relative reactivity of at least 1 to acrylonitrile, in a specific ratio. The copolymer is prepared by polymerizing the monomers, while adding the sulfo group-containing vinyl monomer to the polymerization system under the following condition:16<Y-X<83wherein X and Y are percentages of the amount of a polymer produced at the time of starting the addition and the amount of a polymer produced at the time of finishing the addition, respectively, based on the amount of the whole polymer to be produced. The fiber has an excellent flame resistance and an excellent devitrification preventing property.

Abstract: An acrylonitrile polymer comprising acrylonitrile, at least one of vinyl chloride and vinylidene chloride, a sulfo group-containing vinyl monomer having a higher reactivity ratio than acrylonitrile and a methallyl sulfonic acid monomer, which is prepared by conducting a polymerization in a manner such that at least half amount of the methallyl sulfonic acid monomer to be used is added to the polymerization system in a substantial period of adding the sulfo group-containing vinyl monomer having a higher reactivity ratio than acrylonitrile to the system. The acrylonitrile polymer is suitable for the preparation of a modacrylic synthetic fiber, and the modacrylic fiber prepared therefrom has excellent flame resistance, devitrification preventing property and dyeing affinity.

Abstract: A bass-reflex type speaker system having a cabinet including a front baffle board, a back panel and two side panels and a speaker mounted on the front panel. A port is disposed in either the back panel or in one of the side panels and a duct is in communication with the port. The back panel may be flat or have a generally triangular cross-sectional configuration where the apex of the triangle is directed toward the speaker. Further, the speaker may be positioned in the approximate center of the front baffle board and the port positioned at the apex of the back panel. A beam may be provided extending across and spaced from the port, the beam having a triangular shaped tip directed toward and spaced from the port.

Abstract: A method of producing an acrylonitrile copolymer of 40 to 65 weight percent acrylonitrile and mainly vinyl chloride and vinylidene chloride in amounts within the range102.8 <A+B+1.29C<107.4,wherein, A is a mixture of olefinic monomers excluding B and C, in weight percents, mainly comprising acrylonitrile; B is vinyl chloride in weight percents; and C is vinylidene chloride in weight percents; wherein the polymerization is carried out in an aqueous solution of 45 to 65 weight percent dimethyl formamide; and in the presence of 0.2 to 8.0 weight percent of at least one of vinyl benzyl sulfonic acid, derivatives of vinyl benzyl sulfonic acid or salts thereof. The polymer has excellent non-inflammable properties.