| 摘要 |
PURPOSE:To obtain inexpensively a speaker with less external leakage magnetic field possible for large input by connecting a sub-magnetic and a yoke cover to a main field section. CONSTITUTION:A size Lv of a step provided with a ribbed plate 12 of a magnetic field section of speaker for preventing magnetic leakage ensures a bottom depth size Lb and it is not required to thick the thickness Lm' of the main magnet 8. The magnetic flux of the N pole of the magnet 8 reaches the N pole of a gap (g) at the upper part of the center pole through the plate section of the plate 12 and the magnetic flux of the N pole of the sub-magnet 4 reaches the N pole of the gap (g) through a rib 11 of the plate 12. On the other hand, the magnetic flux of the S pole of the magnet 8 reaches the S pole of the gap (g) through the upper plate 1 and the magnetic flux of the S pole of the magnet 4 takes a route reaching the plate 1 through a yoke cover 3. Thus, the entire outside of the magnetic field section is magnetized to the S pole, the magnetic potential difference around the magnetic field is decreased and externally leaked magnetic flux is reduced. |
