PURPOSE: To increase the sound of a low frequency range generated from the titled speaker and to miniaturize an enclosure by comparing the amplitude of an opposite side part to the fulcrum of a diaphragm with the amplitude of the coupling part of a diaphragm driving mechanism and expanding the former amplitude.

CONSTITUTION: A diaphragm 3 is provided in a freely rockable manner with a fulcrum provided at one side part of the side wall of an enclosure 1 as a center in the enclosure 1. A diaphragm driving mechanism 16, which rocks and vibrates the diaphragm 3 in accordance with a given electric signal, is coupled to the fulcrum side part away from the middle between the edge on the fulcrum side of this diaphragm and the other edge of the opposite side. The amplitude of the opposite side part to the fulcrum of the diaphragm 3 is compared with the amplitude of the diaphragm driving mechanism 16, expanded, and a sound size generated from the other edge part side go to larger.