The invention relates to an electrodynamic transducer (1) with a dome type diaphragm (2), comprising an electrodynamic motor with a coil (6) borne by a mandrel (3) integral with the diaphragm suspended to a yoke (7), the coil being placed in an air gap of a vertical free space in which it can move and which is defined, toward the center, by an internal magnetic construction (4), and toward the periphery, by an external magnetic construction (5), wherein the suspension comprises neither peripheral suspension nor internal suspension, the transducer comprises at least two magnetic field confinement means (11) in the air gap in order to form by mean of a ferromagnetic liquid at least two ferrofluidic seals (12, 13, 14) stepped in the air gap, fulfilling at least the guidance of the coil and the pneumatic tightness between the front and rear faces of the diaphragm, at least one of the ferrofluidic seals being continuous. Application to loudspeakers.