Electrodynamic transducer having a yoke and in which at least one electrical coil placed in a static magnetic field can move about a rest position in an excursion range of a vertical free space, the coil(s) being wound and fixed on a segment of circular or elliptical cross-sectioned vertical straight cylinder forming a mandrel, a return mean enabling the mandrel bearing the coil(s) to be returned to the rest position in the absence of an external bias, the straight cylinder defining an internal volume toward the inside of said cylinder and defining an external volume toward the outside of said cylinder, characterized in that the magnetic field is produced by an external magnetic construction comprising at least one ring-shaped fixed permanent magnet arranged in the external volume as well as an internal magnetic construction comprising at least one ring-shaped or pellet-shaped fixed permanent magnet arranged in the internal volume, the external and internal magnetic constructions being substantially in a face to face relation on either side of the vertical free space, said motor comprising no ferromagnetic or magnetic part extending between the external volume and the internal volume, no ferromagnetic part being arranged in the volume defined by the horizontal planes passing through the ends of the coil(s) at a rest position, the yoke, at least in the part thereof that holds the magnets in a fixed position, being made of a non-ferromagnetic and non-magnetic material, and in that the ratio R of the inductance value L p of the coil at the rest position and blocked in the transducer to the inductance value L l of the same coil when free and isolated in the space, namely R=L p /L l, is a value comprised between 0.9 and 1.1 in the useful frequency band of the transducer, and in that it comprises on each side of the vertical free space, arranged in a face to face relation, a fixed intermediate magnet (15, 18, 39, 67, 70, 82), and above said intermediate magnet, an upper magnet (6,7, 6', 7', 14, 17, 38, 64, 66, 69, 81), and under said intermediate magnet, a lower magnet (10, 11, 10', 11', 16, 19, 40, 57, 60, 65, 68, 71, 83), and in that the intermediate magnets on either side of the vertical free space have a same horizontal direction of internal field and in that the upper and lower magnets on either side of the vertical free space have: - either vertical internal fields and with opposed directions for both a same side of the vertical free space and for the upper magnets on either side of the vertical free space and for the lower magnets on either side of the vertical free space, in such a manner that the intermediate magnetic field in the vertical free space be of opposed direction to the directions of the two upper and lower magnetic fields of said vertical free space for a maximal loopback of the field lines, - either horizontal internal fields and all of same direction of internal fields opposed to the direction of the internal fields of the intermediate magnets. - either vertical internal fields and with opposed directions for both a same side of the vertical free space and for the upper magnets on either side of the vertical free space and for the lower magnets on either side of the vertical free space, in such a manner that the intermediate magnetic field in the vertical free space be of opposed direction to the directions of the two upper and lower magnetic fields of said vertical free space for a maximal loopback of the field lines, - either horizontal internal fields and all of same direction of internal fields opposed to the direction of the internal fields of the intermediate magnets.