An electromagnetic transducer apparatus (10) includes a core (30, 31) providing a pair of yokes (34, 35) between which there is an air gap (38, 39), at least one coil (32) disposed about the core (30, 31), an armature (14) moveable in the air gap (38, 39) in response to the coil (32) being energised, the armature (14) being mounted between a pair of suspension springs (22, 23), and characterized in that the armature (14) includes a cylinder (14) in which is disposed a piston (12) which is immovable relative to the core (30, 31).