| 摘要 |
PROBLEM TO BE SOLVED: To improve heat radiation, to miniaturize a speaker and to increase the magnetic flux density at the magnetic gap part to obtain the speaker of high performance. SOLUTION: The magnetic circuit of the speaker has a magnet 1, an upper end face plate 2 and a lower end face plate 3, which are arranged at an upper end face and a lower end face, which form both magnetic poles of the magnet 1 and an outer ring 4 which surrounds the magnet 1 to which the upper end face plate 2 and the lower end face plate 3 are jointed and is arranged to form magnetic gaps G1 and G2 in a part facing the outer peripheral faces of the plates 2 and 3. A magnetic path passing the magnetic gap G1 from the magnet 1 through the upper end face plate 2, passing the outer ring 4, passing the other magnetic gap G2 and returning to the magnet 1 through the lower end face plate 3 is formed in the circuit structure. A plurality of holes 21 are formed on a side wall facing the magnet 1 of the outer ring 4.
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