| 摘要 |
PROBLEM TO BE SOLVED: To enlarge sound power of a speaker and to suppress vibration of a speaker box by disposing a movable body of a foamable synthetic resin or rubber and a vibrator composed of a weight to a speaker or a speaker box. SOLUTION: A vibrator 26 is joined to a bottom part of a yoke 3 composing a magnetic circuit by way of an adhesive material. A movable body 27 of a foamable synthetic resin, a rubber or the like molded in an almost cylindrical shape is joined to a rear side of the yoke 3 by way of the adhesive material so that the vibrator 26 faces the center pole 3a of the yoke 3. Also, a weight 28 consisting of a cylindrical-shaped non-magnetic material and the like is joined to a top part of the movable part 27 by way of the adhesive material, to constitute the vibrator 26 which gives an equivalent mass M2 and an accelerationα2. In this case, the movable body 27 is selected so that a specified stiffness (nature of spring) is added so as to constitute the vibrator 26. Thus, reactive force-F1 against the sound power F1 of a vibration plate 7 and reactive force F2 of the vibrator 26 acting on the movable body 27 and the weight 28 are mutually offset or attenuated.
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