Electroacoustic transducer unit with reduced resonant frequency and mechanical spring with negative stiffness, preferably used in such a transducer unit

An electroacoustic tranducer unit comprises an electroacoustic transducer including a diaphragm. This may be for example an electrodynamic transducer with a diaphragm (1), a magnet system (2) with an air gap (3), a voice-coil former (4) such a voice coil (5) arranged on this coil former in the air gap (3) of the magnet system (2). The transducer unit comprises means for reducing the resonant frequency of the transducer in the form of mechanical springs with negative spring stiffness (9 and 10), which springs are each coupled between a stationary part (11 or 8 respectively) of the transducer unit and movable part, for example the voice-coil former (4) or the diaphragm (1) of the transducer (Figure 1b). Further, the transducer unit comprises a control device (42) for correcting the position of the diaphragm (1) under the influence of a control signal (43) generated by the control device (Figure 4).The mechanical spring with negative spring stiffness comprises two blade springs of which both ends are coupled to each other and which, underthe influence of a compressive force F which acts in a direction along an imaginary line through both ends of the mechanical spring, are each bent in one or two opposite directions (Figures 2a en 2b). Such springs may also be employed for different purposes.