An edge damper frame 18b is disposed in between a part of an outer
peripheral surface 20a of a frame-cover 20 and a leveling
surface 14c-1 of a frame 14. A slope 18e
of a diaphragm 15 is extended from the edge damper frame 18b
toward the frame 14 and provided alongside an outer side surface 14c-2
of a convex portion 14c of the frame 14.