| 摘要 |
PURPOSE:To maintain the balance of diaphragm and suppress the increase in distortions by providing the diaphragm provided with a dielectric on the surface side opposing to the electret fixing pole at least on the negative charge side. CONSTITUTION:Since the surface of a diaphragm 23 opposing to the electret fixing pole 21 on the negative charge side is formed of a dielectric 231 such as high molecular film or the like, the dielectric 231 is charged as a whole with negative charges. Then, the gaps (d) on both sides of the diaphragm 23 are approximately equal and even if the absolute values of the voltages of the electret fixing poles 21, 22 having a pair of negative and positive different code charges are made equal, the potential difference for the electret fixing pole on that negative charge side is decreased and therefore the balances on both sides are maintained without being strongly attracted to the electret fixing plate on the negative charge side, whereby increasing distortions may be suppressed and ideal push-pull effect may be accomplished. |
