A hydraulic mount apparatus for supporting a vibration source on a base; a housing extending about and along a first axis and defining a housing chamber, a flexible body made of an elastic material at least partially disposed in said housing chamber extending radially about and along said first axis for deforming elastically in response to movement of the vibration source relative to the base, a diaphragm made of an elastic material disposed in said housing chamber and spaced axially from said flexible body, a partition assembly disposed in said housing chamber between said flexible body and said diaphragm for dividing said housing chamber into a pumping chamber between said flexible body and said partition assembly and a receiving chamber between said partition assembly and said diaphragm with the volume of each of said chambers (64, 66) being changed by deformation of said flexible body and said diaphragm in response to an external excitation, at least one sensor disposed on at least one of the hydraulic mount apparatus and the vibration source and the base for measuring a vibration condition of the vibration source in response to the external excitation and producing a corresponding signal, a fluid contained within said pumping and receiving chambers (64, 66) and being responsive to a magnetic field to modify its shear properties, said partition assembly defining a fluid passage extending axially between said pumping chamber and said receiving chamber to fluidly connect said pumping chamber and said receiving chamber for passing said fluid between said pumping and receiving chambers in response to deformation of said flexible body and said diaphragm, said partition assembly including at least one electromagnet coil disposed adjacent to said fluid passage for variably generating a magnetic flux across said fluid passage for modifying the shear resistance of said fluid passing through said fluid passage to variably change the damping stiffness of said mount in response to said signal from said sensor when the measured vibratory frequency is at low frequencies, characterized in that it comprises an actuator assembly including an actuator at least partially of a piezoelectric material extending at least partially into said pumping chamber for moving within said pumping chamber for varying the volume of said pumping chamber to prevent a pressure increase in said pressure chamber to cancel the external excitation when the measured vibratory frequency is at high frequencies, said actuator assembly further includes a moving member operatively engaging said actuator for axially moving with said actuator within said pumping chamber for varying the volume of said pumping chamber, said moving member is a plunger member having a generally disc shape, said partition assembly defines a partition bore extending between said pumping and receiving chambers (64, 66) and said actuator extends from outside of said housing into said housing chamber and at least partially through said partition bore, and said partition assembly further includes a plunger support ring disposed radially about and spaced from said partition bore and the edge of said plunger member sealingly engages said plunger support ring to seal said partition bore, said actuator further includes an actuator casing and an actuator piston slideably extending from inside said actuator casing and in engagement with said moving member.