Poly was melt-spun at 200\xb0 C. And on oxide basis, it comprises 1-50 wt % Group VIII metals, 1-50 wt % divalent metals, and 5-60 wt % two Group VIB metals. of a solution obtained by dissolving 0. The wedge is adapted to wedge two electrical conductors against respective opposing inner sides of the shell. The invention can be applied to e. By utilizing the directivity, a difference in sound pressure levels based on a difference in attenuation of sound in distances to two left and right channels is corrected and a listening range providing excellent stereophonic feeling can be enlarged.