Diaphragms for lousdspeaker drive units or microphones

A diaphragm (14) for a loudspeaker drive unit or for a microphone comprise a rigid dome-shaped member having a thickness that varies from a first thicker thickness at a first location (region 30) at the periphery of the dome-shaped member to a second thinner thickness at a second location (region 40), which is nearer to the centre of the dome-shaped member. There is a step-wise change in thickness at a location (boundary 50) between the first location and the second location. Having greater thickness at the periphery of the dome-shaped member may improve stiffness of the diaphragm and may allow for an increased break-up frequency (Fig. 6). Having thinner material elsewhere in the dome-shaped member may allow the mass of the diaphragm to be kept low and may result in better acoustic sensitivity.