An electromechanical transducer apparatus for converting between mechanical energy and electrical energy, the apparatus comprising: a housing; a static portion substantially immobilized within the housing, the static portion comprising: a magnetic flux generator operable to generate a magnetic flux; a pair of pole pieces (130, 132) operable to couple magnetic flux generated by the magnetic flux generator through at least one of a first magnetic circuit and a second magnetic circuit, at least one coil (190, 192) operable to carry an electric current and being disposed to electromagnetically interact with at least one of the first and second magnetic circuits; the static portion being rigidly connected to the base of the housing to provide a low thermal resistance path between the static portion and the housing to permit removal of heat generated during operation of the transducer; a movable portion comprising: a first closing piece completing the first magnetic circuit and separated from the pair of pole pieces by first gaps (200a, 200b); and a second closing piece completing the second magnetic circuit and separated from the pair of pole pieces by second gaps (202a, 202b); the first and second closing pieces being mechanically coupled and supported to permit reciprocating motion with respect to the pair of pole pieces about an equilibrium position, the reciprocating motion being operable to vary the first gaps (200a, 200b) and second gaps (202a, 202b) such that an increase in the first gaps (200a, 200b) causes a corresponding decrease in the second gaps (202a, 202b), the variation of the first and second gaps causing a variation in magnetic reluctance in each of the first and second magnetic circuits. a housing; a static portion substantially immobilized within the housing, the static portion comprising: a magnetic flux generator operable to generate a magnetic flux; a pair of pole pieces (130, 132) operable to couple magnetic flux generated by the magnetic flux generator through at least one of a first magnetic circuit and a second magnetic circuit, at least one coil (190, 192) operable to carry an electric current and being disposed to electromagnetically interact with at least one of the first and second magnetic circuits; a magnetic flux generator operable to generate a magnetic flux; a pair of pole pieces (130, 132) operable to couple magnetic flux generated by the magnetic flux generator through at least one of a first magnetic circuit and a second magnetic circuit, at least one coil (190, 192) operable to carry an electric current and being disposed to electromagnetically interact with at least one of the first and second magnetic circuits; the static portion being rigidly connected to the base of the housing to provide a low thermal resistance path between the static portion and the housing to permit removal of heat generated during operation of the transducer; a movable portion comprising: a first closing piece completing the first magnetic circuit and separated from the pair of pole pieces by first gaps (200a, 200b); and a second closing piece completing the second magnetic circuit and separated from the pair of pole pieces by second gaps (202a, 202b); a first closing piece completing the first magnetic circuit and separated from the pair of pole pieces by first gaps (200a, 200b); and a second closing piece completing the second magnetic circuit and separated from the pair of pole pieces by second gaps (202a, 202b); the first and second closing pieces being mechanically coupled and supported to permit reciprocating motion with respect to the pair of pole pieces about an equilibrium position, the reciprocating motion being operable to vary the first gaps (200a, 200b) and second gaps (202a, 202b) such that an increase in the first gaps (200a, 200b) causes a corresponding decrease in the second gaps (202a, 202b), the variation of the first and second gaps causing a variation in magnetic reluctance in each of the first and second magnetic circuits.