Fecha de publicación: 12/12/1929 Fuente: WIPO "miel" 322,622. Rothermel, R. A. Nov. 13, 1928. Magnetic instruments.-In a moving coil loud-speaker, the vibratory system is provided with a centring arrangement comprising two supports c, d one on each side of the moving coil b. The inner support d comprises a concentric ring fixed at its outer rim to the casing of the instrument.