Abstract: An electroacoustic transducer has a magnetic circuit unit including a plate-shaped yoke, first and second magnets juxtaposed on the yoke, and first and second top plates mounted on the respective tops of the first and second magnets. One end of the first magnet is magnetized to one of north and south poles. The other end of the first magnet is opposite in polarity to the one end. The second magnet is magnetized to polarities opposite to those of the first magnet. A magnetic gap is formed between the first and second top plates.

Abstract: An electromagnetic exciter includes a first suspension having a cylindrical side wall portion coaxial with respect to a cylindrical wall of a yoke of a magnetic circuit assembly, and a spring portion integrally formed at the lower end of the cylindrical side wall portion to support the lower end of the magnetic circuit assembly so that the magnetic circuit assembly is vibratable. An annular support member is secured to the inner peripheral surface of the upper end opening of the cylindrical side wall portion of the first suspension. A printed wiring board that supports a voice coil is supported on the annular support member. A protector has a cylindrical portion installed to cover the outer peripheral surface of the cylindrical side wall portion of the first suspension, and a caulking portion that is bent radially inward over the upper end edge of the cylindrical side wall portion of the first suspension to clamp the printed wiring board between itself and the annular support member.

Abstract: An electroacoustic transducer has a magnetic circuit unit including a plate-shaped yoke, first and second magnets juxtaposed on the yoke, and first and second top plates mounted on the respective tops of the first and second magnets. One end of the first magnet is magnetized to one of north and south poles. The other end of the first magnet is opposite in polarity to the one end. The second magnet is magnetized to polarities opposite to those of the first magnet. A magnetic gap is formed between the first and second top plates.

Abstract: An electroacoustic transducer includes a magnetic circuit unit having a yoke, a magnet secured to the top of the bottom wall portion of the yoke, and a top plate secured to the top of the magnet. An annular magnetic gap is defined between the peripheral wall portion of the yoke and the top plate. A voice coil is disposed in the magnetic gap of the magnetic circuit unit. A diaphragm is secured to the voice coil, and a space is formed between the diaphragm and the top plate. The outside of the transducer and the space are communicated with each other through mutually communicated through-holes formed in the bottom wall portion of the yoke, the magnet and the top plate, respectively. The through-hole of the yoke has an inner diameter larger than the inner diameter of the through-hole of the magnet. A filter is disposed in the through-hole of the yoke and bonded to the magnet, thereby preventing entry of contamination into the space from the outside of the electroacoustic transducer.

Abstract: An electromagnetic exciter includes a first suspension having a cylindrical side wall portion coaxial with respect to a cylindrical wall of a yoke of a magnetic circuit assembly, and a spring portion integrally formed at the lower end of the cylindrical side wall portion to support the lower end of the magnetic circuit assembly so that the magnetic circuit assembly is vibratable. An annular support member is secured to the inner peripheral surface of the upper end opening of the cylindrical side wall portion of the first suspension. A printed wiring board that supports a voice coil is supported on the annular support member. A protector has a cylindrical portion installed to cover the outer peripheral surface of the cylindrical side wall portion of the first suspension, and a caulking portion that is bent radially inward over the upper end edge of the cylindrical side wall portion of the first suspension to clamp the printed wiring board between itself and the annular support member.

Abstract: A vibrating assembly comprises a yoke having a center pole and a peripheral flange, an annular permanent magnet secured to the flange, and an annular top plate secured to the permanent magnet. A supporting plate is provided for resiliently supporting the vibrating assembly in the frame. A preventing means is provided for preventing the vibrating assembly from moving in a radial direction of the vibrating assembly.

Abstract: A vibrating assembly comprises a yoke having a center pole and a peripheral flange, an annular permanent magnet secured to the flange, and an annular top plate secured to the permanent magnet. A supporting plate is provided for resiliently supporting the vibrating assembly in the frame. A preventing means is provided for preventing the vibrating assembly from moving in a radial direction of the vibrating assembly.

Abstract: A magnetic direction detecting apparatus has a magnetic sensor head composed of a magnetic core, an exciting coil wound around the core and a pair of detection coils diametrically wound around the core perpendicularly to each other; an oscillator for supplying a rectangular current wave of a single polarity to the exciting coil; and a switching gate openable synchronously with the rectangular wave for permitting only peaks of the same polarity to pass therethrough. The detection of a magnetic direction by using this apparatus does not suffer from restrictions in switching gate-opening timing.

Abstract: A process for producing a phenolic resin comprising condensing a phenol component and an aldehyde component, characterized in that the phenol component comprises (high-molecular-weight phenolic compounds which are left after bisphenol A-containing by-products formed in the production of bisphenol A by condensing acetone and phenol in the presence of an acid catalyst are treated at a high temperature of at least 150.degree. C. in the presence of an alkaline catalyst to remove low-boiling components therefrom.

Abstract: Unsaturated dimers which contain 2,4-diphenyl-4-methyl-1-pentene as their main component (i.e., in an amount of greater than 95%) are produced by reacting an .alpha.-methylstyrene at a temperature of from 20.degree. to 100.degree.C. in the presence of a sulfonic acid type cation-exchange resin catalyst and in the further presence of a primary or secondary monohydric alcohol containing from 2 to 5 carbon atoms. By this reaction, side products including a saturated dimer of 1,1,3-trimethyl-3-phenylindane, trimers and higher polymers are produced only in an extremely small amount. The unsaturated dimers are very useful as a molecular weight modifier when employed, instead of dodecylmercaptans, for the production of polymers such as an ABS resin, an AS resin, and the like.