A diaphragm for use is a loudspeaker is described. This diaphragm may include a housing with an elongated shape having a length along a first axis that is longer than a width along a second axis. Moreover, the housing may include: an outer surface and an inner surface; an outer opening defined by an outer edge and an inner opening defined by an inner edge; and regions having heights relative to the inner surface, where the regions are grouped in pairs that are positioned equidistant and symmetrically about the inner opening along the first axis. Furthermore, the regions may have a second length along the first axis, and the second length may be less than a distance along the first axis between the outer edge and the inner edge. Note that the regions may increase a stiffness of the diaphragm relative to a stiffness of a material in the diaphragm.