Matsushita Electric Industrial Co., Ltd.

Kazuhiro Ohyama

Masayuki Wakamiya

Kiyoshi Kojima

Hiroshi Ueda

Shizuo Furuyama

A magnetic circuit unit for a loud-speaker is provided, in which an adhesion step can be reduced or omitted, magnetic properties can be improved through enhancement of magnetic efficiency, and a durable anti-corrosive treatment can be performed at low price, so that higher performance and lower cost of the loud-speaker can be attained. A method of manufacturing the same is also provided. A top plate has a conical, columnar, truncated conical, or partially spherical hollow part formed on one side whose inner surface is integrated with an anisotropic Nd--Fe--B system magnet under a forming pressure of 100 to 200 kgf/cm.sup.2 through Joule heating by passing a current under compression. The forming die is cooled to a temperature below 100.degree. C. while maintaining the pressure, and the compact is then taken out from the forming die. This integrated compact is adhered to an outer yoke, and a looped yoke and a loop anisotropic Nd--Fe--B system magnet are also adhered thereon to fabricate a magnetic circuit unit. Subsequently, this magnet circuit unit is dipped in acrylic resin emulsion, and a coating of 7 to 15 .mu.m thick is formed by using a rotary coating device.

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Osaka, Japan

Kazuhiro Ohyama