A loudspeaker comprising: a voice coil; and a diaphragm attached to the voice coil, the diaphragm having a generally rectangular outer shape and comprising: an outer rim area having an outer edge and an inner edge, the diaphragm being fixed in position at the outer edge; and an inner section surrounded by the outer rim area, the inner section comprising: an outermost area adjacent to the outer rim area and coupled to the voice coil, the outermost area having the same generally rectangular outer shape as the diaphragm; and an inner area surrounded by the outermost area, the inner area comprising a rectangular central rib area (A01 p) having a plurality of ribs in a periodic pattern, the ribs being oriented parallel to the shorter sides of the inner area; and a first lateral transition area (A01c) disposed between an edge of the central rib area (A01 p) and one of the shorter side edges of the outermost area, and a second lateral transition area (A01c) disposed between an opposite edge of the central rib area (A01 p) and the other shorter side edge of the outermost area. a voice coil; and a diaphragm attached to the voice coil, the diaphragm having a generally rectangular outer shape and comprising: an outer rim area having an outer edge and an inner edge, the diaphragm being fixed in position at the outer edge; and an inner section surrounded by the outer rim area, the inner section comprising: an outermost area adjacent to the outer rim area and coupled to the voice coil, the outermost area having the same generally rectangular outer shape as the diaphragm; and an inner area surrounded by the outermost area, the inner area comprising a rectangular central rib area (A01 p) having a plurality of ribs in a periodic pattern, the ribs being oriented parallel to the shorter sides of the inner area; and a first lateral transition area (A01c) disposed between an edge of the central rib area (A01 p) and one of the shorter side edges of the outermost area, and a second lateral transition area (A01c) disposed between an opposite edge of the central rib area (A01 p) and the other shorter side edge of the outermost area. an outer rim area having an outer edge and an inner edge, the diaphragm being fixed in position at the outer edge; and an inner section surrounded by the outer rim area, the inner section comprising: an outermost area adjacent to the outer rim area and coupled to the voice coil, the outermost area having the same generally rectangular outer shape as the diaphragm; and an inner area surrounded by the outermost area, the inner area comprising a rectangular central rib area (A01 p) having a plurality of ribs in a periodic pattern, the ribs being oriented parallel to the shorter sides of the inner area; and a first lateral transition area (A01c) disposed between an edge of the central rib area (A01 p) and one of the shorter side edges of the outermost area, and a second lateral transition area (A01c) disposed between an opposite edge of the central rib area (A01 p) and the other shorter side edge of the outermost area. an outermost area adjacent to the outer rim area and coupled to the voice coil, the outermost area having the same generally rectangular outer shape as the diaphragm; and an inner area surrounded by the outermost area, the inner area comprising a rectangular central rib area (A01 p) having a plurality of ribs in a periodic pattern, the ribs being oriented parallel to the shorter sides of the inner area; and a first lateral transition area (A01c) disposed between an edge of the central rib area (A01 p) and one of the shorter side edges of the outermost area, and a second lateral transition area (A01c) disposed between an opposite edge of the central rib area (A01 p) and the other shorter side edge of the outermost area. a rectangular central rib area (A01 p) having a plurality of ribs in a periodic pattern, the ribs being oriented parallel to the shorter sides of the inner area; and a first lateral transition area (A01c) disposed between an edge of the central rib area (A01 p) and one of the shorter side edges of the outermost area, and a second lateral transition area (A01c) disposed between an opposite edge of the central rib area (A01 p) and the other shorter side edge of the outermost area.