并请注意文章发表的年份(这才知道作为扬声器大国的生力军的我们,竟落后了多少年)。
Compensation for Nonlinear Distortion of Horn Loudspeakers by Digital Signal Processing
Author(s): Klippel, Wolfgang
Publication: JASE Volume 44 Number 11 pp. 964-972; November 1996
Abstract: Nonlinear distortion of horn loudspeakers can be compensated by prefiltering the electrical input signal inversely. A new filter architecture is derived from the results of nonlinear loudspeaker modeling using static nonlinear and dynamic linear subsystems. This special structure requires less computational effort and less memory than other generic architectures and allows complete compensation for the modeled nonlinear mechanisms. In practice, simplified versions of this filter can be implemented to compensate for dominant nonlinearities only. System identification performed on a particular horn loudspeaker provides valuable information about the dominant nonlinearity and allows adjustment of the free filter parameters. The implementation of an adequate filter structure for a professional loudspeaker in a DSP56000 is discussed, and results of the distortion reduction are presented.
Direct Feedback Linearization of Nonlinear Loudspeaker Systems
Author(s): Klippel, W.
Publication: Preprint 4439; AES Convention 102; March 1997
Abstract: The control law used in regular static-state feedback is expressed in a novel direct form which is advantageous for the linearization of loudspeaker systems. Compared with the straightforward integrator-decoupled form, the direct form increases the computational efficiency, requires less loudspeaker parameter, and can be easily implemented on signal processors working with a fixed-point format. The control law in the direct form can be applied to loudspeaker systems with different acoustic radiation aids (closed-box system, vented-box system) and dispenses with measurement of the internal states and full identification of the acoustic parameters. The relationship between feedback linearization and feedforward filter techniques (Volterra filter, mirror filter) is discussed.
Adaptive Adjustment of Nonlinear Filters Used for Loudspeaker Linearization
Author(s): Klippel, Wolfgang J.
Publication: Preprint 4646; AES Convention 104; May 1998
Abstract: Signal distortions caused by loudspeaker nonlinearities can be compensated by inverse nonlinear processing of the electric driving signal. This concept is based on an adequate control architecture having free control parameters adjusted to the particular loudspeaker. Optimal performance requires a self-tuning (adaptive) system to compensate for variations of loudspeaker parameters due to the effect of heating and aging while reproducing the audio signal. Straightforward adaptive controllers use an additional nonlinear filter for modeling the loudspeaker and for transforming the identified parameters into control parameters. This approach is susceptible to systematic errors and cannot be implemented in available DSP-systems at low costs. This paper presents a novel technique for direct updating of the control parameters which makes separate system identification superfluous.
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