A stiffening part (25) arranged to be integrated into the interior of a casing (12) of an audio speaker (11) in order to stiffen said casing, the audio speaker also being capable of comprising at least one loudspeaker (18a) mounted on a first face (14) of the casing, the stiffening part comprising a connecting portion, at least one damping support defining a receiving space arranged to receive a damping device (40a) for intended to limit vibrations of the loudspeaker, wherein the damping support comprises a plurality of ribs (34) distributed around the receiving space (31), each rib extending in a distinct plane parallel to a depth of the receiving space, the stiffening part being arranged such that, when the enclosure (11) is assembled, the connecting portion interconnects inner walls of a second (15) of the casing and a third face (16) of the casing opposite each other and both perpendicular to the first face (14), the damping device being positioned in the receiving space, and a rear portion of the loudspeaker abutting the damping device.