A loudspeaker driver that includes a suspended diaphragm and a plurality of voice coils each suspended in a magnetic field and coupled to the diaphragm. The safety cover plate, and most of the assembly being made of non-conductive material. The first signal portion is representative of the radial deformation to which a first tread area portion of the tire is subjected during passage of the first tread area portion through a contact region between the tire and the rolling surface.