An acoustic passive radiator that controls “rocking mode” vibration. An acoustic passive radiator includes a diaphragm for radiating acoustic energy. The diaphragm has a perimeter portion and a central portion. The perimeter portion is thicker than the central portion. The passive radiator further includes a passive radiator suspension. The suspension includes a skin element encasing the diaphragm. The skin element comprises a surround for physically coupling the passive radiator to an acoustic enclosure, pneumatically sealing the diaphragm and the enclosure. The surround has a non-uniform width. The passive radiator a non-pneumatically sealing, non-surround, non-spider suspension element. The non-surround suspension element and the surround coact to control the motion of the diaphragm and to support the weight of the diaphragm.