| 摘要 |
PURPOSE:To improve a directivity to a high pitched tone area by dividing a voice coil every band, connecting respective division networks, weighting a driving force to execute a multiplex driving and applying a sound pressure frequency characteristic good and plane in the directivity in a middle and high pitched tone band. CONSTITUTION:A part of a diaphragm 1 enclosed by broken lines is considered to be a diaphragm 8 for a middle and high frequency band and is formed by a double layer voice coil 2 and a double layer voice coil 7 for the middle and high frequency band. When oscillating the low pitched tone, the entire of the diaphragm 1 (including the diaphragm 8 for the middle and high frequency band) is driven and when oscillating the middle and high pitched tone, only the diaphragm for the middle and high frequency band is driven. The diaphragm 8 for the middle and high frequency band is a part of the diaphragm 1, thinner than it in thickness, driven highly efficiently by a small electric input signal and small is an area. Further, since the diaphragm 8 for the middle and high frequency band is driven highly efficiently and enhances the sound quality, an edge may be constituted in the periphery (shown by broken lines). Thereby, an input signal frequency is changed and a suitable oscillating part can be driven, so that the directively throughout all the bands is improved.
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