PURPOSE: To realize a magnetic circuit for an acoustic transducer having a magnetic gap with a high magnetic flux density, light weight and less leakage magnetic flux by providing a support member made of an antimagnetic substance supporting the magnetic circuit in a magnetic-resistance cover.

CONSTITUTION: Since a support member 21 made of a antimagnetic substance supporting the magnetic circuit in a magnetic-resistance cover 6 is provided to the magnetic circuit, the magnetic reluctance via the magnetic-resistance cover 6 is far larger than the magnetic reluctance via a magnetic gap 8. Thus, the leakage magnetic flux is reduced by the magnetic-resistance cover 6 and the reduction in the magnetic flux density of the magnetic gap 8 is suppressed. Then no use of repulsion magnet is required and the weight of the magnetic circuit is reduced.