PURPOSE: To reduce parts number and raise a productivity by fixing and holding a square shape diaphragm by an opposing face of a square rod shape permanent magnet through spacer provided on upper and lower surfaces of both ends of a plate like suspension protruding from a short side of the square shape plate with respective magnetic gaps from an exciting section maintained.

CONSTITUTION: Square shape diaphragm having steps 45, 46 have steps on surfaces opposing to permanent magnets 36, 37, 38, 39 and fixed and held through spacers 41, 42, 43, 44 by means of screws 51, 52 so as to keep magnetic gaps 47, 48, 49, 50 equal to an exciting section. An electric signal is applied to exciting coils 34, 35, and then a magnetic fordce operating on square shape diaphragms 45, 46 is changed and a driving force is generated. In structure, they are absolutely symmetrical, a symmetrical driving force is generated to the square shape diaphragms 45, 46 and from a front panel 3 an acoustic reproducing according to the electric signal to the exciting coils 34, 35 are realized.