The flat loudspeaker including an enclosure in the form of a support frame, a sound-emitting rectangular membrane attached to the frame, and an electrodynamic vibration exciter located opposite the membrane. Besides, the vibration exciter is attached with one of its ends to the membrane within a special line passing along the plane of the rectangular membrane, emerging from any vertex of the rectangular membrane, and ending at a point on the opposite vertex of the membrane's horizontal side located at a distance of ⅔ of the membrane's opposite side from the top horizontally.