Patent ID: 8055010

Claim:
Magnetic structure ( 5 , 5 ′, 5 ″, 10 ) generating a magnetic field for an ironless motor of an electrodynamic loudspeaker ( 1 ) having a mobile coil ( 2 ), wherein the magnetic structure generates a magnetic field in a gap in which the coil is arranged, said magnetic structure consisting of a stack of three magnets corresponding to one intermediate magnet ( 8 , 8 ′, 8 ″) and two top and bottom covering magnets ( 7 , 9 ) ( 7 ′, 9 ′) ( 7 ″, 9 ″) ( 11 , 12 ), the gap-circumscribing edges of said magnets being aligned and forming a straight gap border, said magnets being further located side by side, the intermediate magnet having a radial magnetic polarization, the covering magnets having the same magnetic polarization and substantially identical remanent magnetizations, characterized in that the covering magnets have a radial ( 7 , 9 ) ( 7 ′, 9 ′) ( 7 ″, 9 ″) or axial ( 11 , 12 ) magnetic polarization and in that, when magnetic polarization of the covering magnets is radial, remanent magnetization of each covering magnet is higher than remanent magnetization of the intermediate magnet, and in that when magnetic polarization of the covering magnets is axial, remanent magnetization of each covering magnet is lower than remanent magnetization of the intermediate magnet.