On the Use of Motion Feedback as Used in 4th Order Systems
Class D amplification allows the design of compact very high power amplifiers with a high efficiency. Those amplifiers are an excellent candidate for being used in compact high powered subwoofers. The drawback of compact subwoofers is the non-linear compression of the air inside the (acoustically) small box. 4th order systems are beneficial over second order systems due to their increased efficiency. To combine the best of both worlds, 4th order design and acoustically small enclosures, a feedback mechanism has been developed to reduce the non-linear distortion found in compact high-powered subwoofers. Acceleration feedback on woofer systems is traditionally used in 2nd order systems. This paper discusses the use of an acceleration and velocity feedback system applied to a 4th order system.
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