An inertial exciter (40) for an acoustic radiator (42), and a loudspeaker incorporating an acoustic radiator and such an exciter. The exciter has a massive member (44); a coupler (56) adapted for attachment to the acoustic radiator (42) and adapted for relative movement with respect to the massive member (44); a motor for effecting relative movement of the coupler with respect to the massive member; and a suspension (60) for supporting the massive member relative to the coupler. The suspension (60) acts in a plane generally passing through the center of mass of the massive member, thereby reducing any moment acting on the suspension.Also disclosed is a loudspeaker exciter assembly (70) that has a base plate (86) for attachment to an acoustic radiator in a non-repeatedly engageable manner, and an exciter (40) attached to the base plate (86) in a repeatedly engageable manner; and a loudspeaker incorporating such an exciter assembly.