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EP-3785451-B1 - NONLINEAR CONTROL OF LOUDSPEAKER SYSTEMS WITH CURRENT SOURCE AMPLIFIER

EP3785451B1EP 3785451 B1EP3785451 B1EP 3785451B1EP-3785451-B1

Inventors

  • LAZAR, JAMES F.
  • BRUNET, PASCAL M.

Dates

Publication Date
20260506
Application Date
20190125

Claims (7)

  1. A system for nonlinear control of a loudspeaker, the system comprising: a current source amplifier connected to the loudspeaker; and a controller connected to the current source amplifier, wherein the controller is configured to: determine a target displacement of a diaphragm of a speaker driver of the loudspeaker based on a source signal of the current source amplifier for reproduction via the loudspeaker and a first physical model of the loudspeaker, wherein the first physical model is a linear state space model; determine a control current based on the target displacement of the diaphragm and a second physical model of the loudspeaker, wherein the second physical model is a nonlinear state space model; and transmit a control current signal specifying the control current to the current source amplifier, wherein a state of the loudspeaker of both the linear state space model and the nonlinear state space model is described by a state vector representation X(t) = [x, ẋ] T , where x is the displacement of the diaphragm and x is a velocity of the diaphragm, and wherein the current source amplifier is configured to output the control current to drive the speaker driver based on the control current signal, and wherein an actual displacement of the diaphragm during the reproduction of the source signal is controlled based on the control current, via the control current signal.
  2. The system of claim 1, wherein the controller is configured to determine the target displacement of the diaphragm based on a target sound pressure for the system to deliver during the reproduction of the source signal and the first physical model of the loudspeaker.
  3. The system of claim 1, wherein the current source amplifier is configured to drive the speaker driver by amplifying the source signal based on the control current.
  4. The system of claim 1, wherein a system transfer function of the system is independent of one or more of the following nonlinear impedances: an electrical resistance of a driver voice coil of the speaker driver, or an inductance of the driver voice coil.
  5. The system of claim 1, wherein a mechanical force applied on the diaphragm is based on an actual current output by the current source amplifier, the actual current based on the control current, and the actual current independent of one or more of the following nonlinear impedances: an electrical resistance of a driver voice coil of the speaker driver, or an inductance of the driver voice coil.
  6. A method for nonlinear control of a loudspeaker, the method comprising: determining a target displacement of a diaphragm of a speaker driver of the loudspeaker based on a source signal of the current source amplifier for reproduction via the loudspeaker and a first physical model of the loudspeaker, wherein the first physical model is a linear state space model; determining a control current based on the target displacement of the diaphragm and a second physical model of the loudspeaker, wherein the second physical model is a nonlinear state space model; and transmitting a control current signal specifying the control current to the current source amplifier connected to the loudspeaker, wherein the current source amplifier outputs the control current to drive the speaker driver based on the control current signal, and wherein an actual displacement of the diaphragm during the reproduction of the source signal is controlled based on the control current, via the control current signal, wherein a state of the loudspeaker of both the linear state space model and the nonlinear state space model is described by a state vector representation X(t) = [x, ẋ ] T , where x is the displacement of the diaphragm and x is a velocity of the diaphragm.
  7. The method of claim 6, wherein a mechanical force applied on the diaphragm is based on an actual current output by the current source amplifier, the actual current based on the control current, and the actual current independent of one or more of the following nonlinear impedances: an electrical resistance of a driver voice coil of the speaker driver, or an inductance of the driver voice coil.

Description

[Technical Field] One or more embodiments relate generally to loudspeakers, and in particular, a method and system for nonlinear control of loudspeaker systems with current source amplifier. [Background Art] A loudspeaker produces sound when connected to an integrated amplifier, a television (TV) set, a radio, a music player, an electronic sound producing device (e.g., a smartphone, a computer), a video player, etc. [Disclosure] [Description of Drawings] FIG. 1 illustrates a cross section of an example speaker driver;FIG. 2 illustrates an example loudspeaker device driven by a voltage source amplifier;FIG. 3 illustrates an example electroacoustic model for the loudspeaker device in FIG. 2;FIG. 4 is an example graph illustrating nonlinear characteristics of different large signal loudspeaker parameters for the loudspeaker device in FIG. 2;FIG. 5A illustrates an example linear system representing a linear state-space model of the loudspeaker device in FIG. 2;FIG. 5B illustrates an example nonlinear system representing a nonlinear state-space physical model of the loudspeaker device in FIG. 2;FIG. 6 illustrates an example loudspeaker control system for nonlinear control of a loudspeaker device with a current source amplifier, in accordance with an embodiment;FIG. 7 illustrates an example electroacoustic model for the loudspeaker device in FIG. 6, in accordance with an embodiment;FIG. 8A illustrates an example linear system representing a linear state-space model of the loudspeaker device in FIG. 6, in accordance with an embodiment;FIG. 8B illustrates an example nonlinear system representing a nonlinear state-space model of the loudspeaker device in FIG. 6, in accordance with an embodiment;FIG. 9 illustrates an example controller for the loudspeaker device in FIG. 6, in accordance with an embodiment;FIG. 10 illustrates another example controller for the loudspeaker device in FIG. 6, in accordance with an embodiment;FIG. 11 is an example graph comparing frequency responses of a loudspeaker device with nonlinear control and a different loudspeaker device without nonlinear control, in accordance with an embodiment;FIG. 12A is an example graph illustrating a frequency spectrum of a loudspeaker device without nonlinear control for correction of audio distortion (i.e., without anti-distortion);FIG. 12B is an example graph illustrating a frequency spectrum of a loudspeaker device with nonlinear control for correction of audio distortion (i.e., with anti-distortion), in accordance with an embodiment;FIG. 13 is an example flowchart of a process for implementing nonlinear control of a loudspeaker device with a current source amplifier, in accordance with an embodiment; andFIG. 14 is a high-level block diagram showing an information processing system comprising a computer system useful for implementing various disclosed embodiments. [Mode for Invention] A first aspect of the invention provides a system for nonlinear control of a loudspeaker. The system comprises the set of features as defined in claim 1. A second aspect of the invention provides a method for nonlinear control of a loudspeaker. The method comprises the sequence of steps as defined in claim 6. Preferred embodiments are set out in the dependent claims. These and other features, aspects and advantages of the one or more embodiments will become understood with reference to the following description, appended claims, and accompanying figures. The following description is made for the purpose of illustrating the general principles of one or more embodiments and is not meant to limit the inventive concepts claimed herein. Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. For expository purposes, the terms "loudspeaker", "loudspeaker device" and "loudspeaker system" may be used interchangeably in this specification. For expository purposes, the terms "displacement" and "excursion" may be used interchangeably in this specification. A conventional loudspeaker is nonlinear by design and produces harmonics, intermodulation components, and modulation noise. Nonlinear audio distortion (i.e., audible distortion) impairs sound quality of audio produced by the loudspeaker (e.g., audio quality and speech intelligibility). In recent times, industrial design constraints often require loudspeaker systems to be smaller-sized for portability and compactness. Such design constraints, however, trade size and portability for sound quality, resulting in increased audio distortion. As such, an anti-distortion system for reducing/removing audio distortion is needed, in particular for obtaining a more pronounced/bigger bass sound from smaller-sized loudspeaker systems. A loudspeaker device includes at least one speaker driver for reproducing sound. FIG. 1 illustrates a