Velocity Feedback Compensation of Electromechanical Speakers for Acoustic Applications

Electromechanical speakers are commonly used as actuators in acoustic control applications and have non-constant velocity frequency response making them poor actuators. Velocity feedback compensation designed to minimize magnitude and phase variations in speaker velocity response is developed in this work. A proportional feedback compensator acting on the error between desired velocity input and measured speaker velocity is used to drive the speaker. Speaker cone velocity is sensed using velocity induced voltage in a secondary speaker coil. Laboratory tests on a dual-wound coil subwoofer are presented to demonstrate the performance of sensor and feedback compensation. As the compensation gain is increased, the compensated speaker velocity response magnitude and phase variations are reduced. The compensated speaker velocity accurately follows any desired velocity input from 4 Hz to over 400 Hz and makes feedback compensated speakers effective acoustic control actuators.