Digitally driven combination coils for electrodynamic acoustic

Abstract

An electrodynamic acoustic transducer (54) having two voice coils (50, 52), the coils being addressed by amplified digital signals. The system (12, 60, 54) utilizes a preamplified analog input signal (10) which is supplied to a bifurcated network, one such signal being processed by an inverter (18). The analog signals (42, 44) are compared with triangular waves (38, 40) to effect switched signals (46, 48) that are pulse width modulated signals. The signals (46, 48) are then amplified through impedances (76, 78) and high speed, high current semiconductor switch means (80, 82) so that the amplified digital signals serve as driver means communicated to the separately addressable coilds (50, 52). There is a dynamic balance achieved by separate energization of the coils (50, 52) whereby the diaphragm (97) is positively located in both axial driving directions and is disposed in equilibrium positions by the energization and balancing of the respective coils (50, 52). As a result, the dynamic range, clarity, cleaness, and response time is substantially improved. An important aspect of this invention is the direct addressing of two distinct coils (50, 52) by amplified pulse trains which are of digital characteristic. The speaker (54) does not require mechanical restoring means but instead the suspension of the diaphragm (97) has a high compliance and serves only to maintain concentric relationship of the voice coils (50, 52) with the gap (92).