Patent ID: 8131005

Claim:
An electrodynamic transducer ( 1 ) with a diaphragm ( 2 ), comprising: an electrodynamic motor in a yoke ( 7 ) and in which can move a coil ( 6 ) borne by a mandrel ( 3 ) integral with the diaphragm, the mandrel having a shape generated by a globally linear generating line, the coil being placed in an air gap of a vertical free space in which the coil can move and which is defined, toward the center of the transducer, by an internal magnetic construction ( 4 ), and toward a periphery of the transducer, by an external magnetic construction ( 5 ), characterized in that the transducer comprises neither peripheral suspension nor internal suspension, the peripheral suspension being a suspension between a periphery of the diaphragm and the yoke, the internal suspension being a suspension between the diaphragm or the mandrel and the yoke, and in that the transducer comprises, in the vertical free space, at least two areas of concentrated magnetic field ( 11 ) in order to form, by way of a ferromagnetic liquid, at least two ferrofluidic seals ( 12 , 13 , 14 ) stepped in the vertical free space, fulfilling at least a double guidance of the coil and the pneumatic tightness between front and rear faces of the diaphragm, at least one of the at least two ferrofluidic seals being continuous.