Patent ID: 8280096

Claim:
An electrodynamic transducer ( 1 ) with a diaphragm ( 2 ), comprising an electrodynamic motor in a frame ( 7 ) and in which can move a moving coil ( 6 ) fastened to a mandrel ( 3 ) integral with the diaphragm, the mandrel and the moving coil and the diaphragm forming a moving unit, the mandrel being a shape generated by a generally linear generatrix, the moving coil being arranged in an air gap of a vertical free space in which it can move and which is delimited, toward the transducer's centre, by an internal magnetic structure ( 4 ), and toward the transducer's periphery by an external magnetic structure ( 5 ), at least one of the magnetic structures generating a static magnetic field, the transducer comprising no peripheral suspension and no internal suspension, the peripheral suspension being a suspension between the diaphragm's periphery and the frame, the internal suspension being a suspension between the diaphragm or the mandrel and the frame, guidance of the moving unit and pneumatic sealing between the front and rear faces of the diaphragm being provided by a ferrofluid, characterized in that the mandrel is held in the air gap by a ferrofluid spread on at least one of the two faces of the mandrel and said ferrofluid completely fills the air gap over all the corresponding at least one face of the mandrel.