Performances and Design of Ironless Loudspeaker Motor Structures

1 This paper presents several kinds of structures of ironless loudspeaker motors. The proposed devices 2 go from simple structures, in terms of manufacturing process, to structures in which the magnet rings 3 can be stacked, with different magnetization directions or values. The structures are studied and compared 4 according to their created induction level and uniformity across the coil displacement range, which are 5 directly linked to the loudspeaker performances (force factor). The model used is the coulombian model 6 of magnets to calculate the magnetic field created, therefore all the calculations are analytical. The paper 7 shows that no structure is universal when it comes to the loudspeaker design: some are well adapted to 8 micro displacements of the coil while other structures are adapted to large displacements. 9