Electromagnetic loudspeaker structure - has coil moving in permanent magnet gap, immersed in low viscosity ferromagnetic liquid

摘要

The electro acoustic convertor, such as a loudspeaker, has a permanent magnet construction giving an annular liquid gap. The movable part of the convertor is a calotte shaped membrane (1) and is connected to the spool (3). The gap is partially filled with a ferromagnetic fluid (9) and the spool is partially immersed. The fluid contains ferromagnetic particles and has a low viscosity. The circular gap (4) is between a central circular permanent magnet pole (5) and a pole surface (6) which is covered with a coaxial ring shaped pole piece (7).