An electrodynamic transducer with a membrane includes an electrodynamic motor in a carcass in which a coil held by a mandrel connected to the membrane is capable of movement. The mandrel has a shape generated by an essentially linear generatrix, the coil being arranged in an air gap of a vertical free space where it is capable of movement and defined, towards the center of the transducer, by an inner magnetic structure and, towards the periphery of the transducer, by an outer magnetic structure, at least one of the magnetic structures generating a static magnetic field, wherein the transducer does not include any peripheral nor inner suspension and the guiding of the mobile equipment and the pneumatic tightness between the front and rear faces of the membrane being ensured by a ferrofluid. The mandrel is maintained in the air gap by the ferrofluid applied on at least one of the two faces of the mandrel and entirely filling the air gap.