ACOUSTIC APPROXIMATION FOR DETERMINING DEFLECTION LIMITS IN LOUDSPEAKERS

Abstract

Loudspeaker system comprising: a loudspeaker excursion characterization system (200; 300; 400) for a loudspeaker (126) with a signal generator (210) configured to generate a signal with several different amplitudes;and an inverse displacement filter (214) having an inverse displacement filter response, receiving the signal, applying the inverse displacement filter response, and having an output in communication with an amplifier circuit (112) of the loudspeaker (126), wherein the amplifier circuit (112) includes an input for receiving an output of the inverse displacement filter (214), a delay circuit (118) for receiving an input into the amplifier circuit (112), and a variable amplifier (122) having a variable gain factor and an input that receives an output of the delay circuit (118), wherein the inverse displacement filter response is an inverse of a displacement filter response of a displacement filter (114) in the amplifier circuit (112) of the loudspeaker (126).

Description

CROSS-REFERENCE TO RELATED REGISTRATIONS

[0001] This application claims the benefits of the preliminary US application No. 62 / 902,476, filed on September 19, 2019. All disclosures of the above-referenced application are hereby incorporated by reference. TECHNICAL AREA

[0002] The present disclosure relates to loudspeakers and in particular systems and methods for determining deflection limits for loudspeakers. BACKGROUND

[0003] The background information provided here serves the purpose of a general presentation of the context of the disclosure. Works of the inventors mentioned herein, to the extent described in this background section, as well as aspects of the description that might not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly included as prior art with regard to the present disclosure.

[0004] Mobile devices, such as smartphones, laptops, and tablets, incorporate relatively small speakers. Designers must strike a balance between the desire for a larger sound, better sound quality, lower power consumption, and improved reliability, and the increasingly smaller size of the speakers. Electromagnetic speakers contain a permanent magnet and a voice coil. The voice coil is attached to a diaphragm that pushes air to produce sound. The speaker is typically enclosed in a protective housing that provides a rear air volume for the speaker to press against and project sound. However, these types of speakers are usually not very loud, lack bass response, and are prone to damage. Furthermore, these speakers can be overdriven to the point of distortion and / or damage.

[0005] Excursion refers to how far a loudspeaker cone moves linearly from its resting position. If a loudspeaker is driven beyond its physical limits, overextension can occur and the loudspeaker can be damaged. SUMMARY

[0006] A loudspeaker excursion characterization system includes a signal generator designed to produce a signal at several different amplitudes. An inverse excursion filter has an inverse excursion filter response, receives the signal, applies the inverse excursion filter response, and has an output that communicates with an amplifier circuit of the loudspeaker. The inverse excursion filter response is the inverse of an excursion filter response of an excursion filter in the loudspeaker's amplifier circuit.

[0007] In other cases, the signal is generated at multiple frequencies. The signal includes a sweep signal. The signal generator includes a sweep signal generator.

[0008] In other configurations, the signal generator produces a sine wave signal. A microphone picks up the output from the loudspeaker. A control circuit is designed to increase the signal's amplitude and selectively identify distortion in response to feedback from the microphone.

[0009] Other features of a loudspeaker system include the loudspeaker excursion characterization system, an amplifier circuit, and the loudspeaker. The amplifier circuit includes an input to receive an output from the inverse excursion filter. The loudspeaker receives an output from the amplifier circuit.

[0010] In other cases, the amplifier circuit includes a delay circuit for receiving an input to the amplifier circuit. A variable amplifier has a variable gain and an input that receives an output from the delay circuit.

[0011] In other features, the amplifier circuit includes a deflection filter to receive the input to the amplifier circuit. A gain-factor control amplifier has a first input that receives an output from the deflection filter, a second input that receives a voltage threshold, and an output configured to control the variable gain of the variable amplifier based on the voltage threshold and the output of the deflection filter.

[0012] A loudspeaker excursion characterization system for a loudspeaker includes a signal generator configured to produce a signal with a specified frequency. An envelope generator circuit is configured to produce an envelope signal based on the signal's frequency and / or a time interval since the signal was initiated. A multiplier is configured to receive the signal and the envelope signal and output the product to an amplifier circuit of the loudspeaker.

[0013] In other cases, the signal is generated at multiple frequencies. The signal includes a sweep signal. The signal generator includes a sweep signal generator.

[0014] In other configurations, the signal generator produces a sine wave signal. A microphone captures an output from the loudspeaker. A control circuit is designed to vary the amplitude of the envelope generation circuit and to identify distortion based on feedback from the microphone.

[0015] A loudspeaker system includes the loudspeaker excursion characterization system. An amplifier circuit includes an input configured to receive an output from the multiplier and an output. A loudspeaker receives an output from the amplifier circuit.

[0016] In other cases, the amplifier circuit includes a delay circuit for receiving an input to the amplifier circuit. A variable amplifier has a variable gain and an input that receives an output from the delay circuit.

[0017] In other features, the amplifier circuit includes a deflection filter for receiving the input to the amplifier circuit. A gain-factor control amplifier has a first input that receives an output from the deflection filter, a second input that receives a voltage threshold, and an output configured to control the variable gain of the variable amplifier.

[0018] A converter displacement characterization system for a converter includes a signal generator configured to produce a signal at several different amplitudes. An inverse displacement filter has an inverse displacement filter response, receives the signal, applies the inverse displacement filter response, and has an output that communicates with an amplifier circuit of a first converter. The inverse displacement filter response is the inverse of a displacement filter response of a displacement filter in the amplifier circuit of the first converter.

[0019] In other features, a second transducer captures an output from the first transducer. A control circuit is designed to increase the signal amplitude and selectively identify distortion in response to feedback from the second transducer.

[0020] In other cases, the signal is generated at multiple frequencies. The signal includes a sweep signal. The signal generator includes a sweep signal generator.

[0021] For other characteristics, the signal generator produces a sine-wave signal.

[0022] Further applications of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are provided for illustrative purposes only and are not intended to limit the scope of protection of the disclosure. List of characters

[0023] The present revelation is better and more fully understood with the help of the detailed description and the accompanying drawings, whereby the following applies: Fig. Figure 1 is a functional block diagram of an example of an amplifier circuit and a loudspeaker; Fig. Figure 2 is a graph illustrating an example of a filter response of a displacement filter; Fig. Figure 3 is a functional block diagram of an example of a loudspeaker excursion characterization system according to the present disclosure; Fig. Figure 4 is a graph of an example of a signal; Fig. Figure 5A is a graph of an example of a filter response of an inverse displacement filter according to the present disclosure; Fig. Figure 5B shows a deflection response using the inverse deflection filter according to the present embodiment; Fig. Figure 6 is a flowchart of an example of a method for characterizing a loudspeaker deflection according to the present disclosure; Fig. Figure 7 is a functional block diagram of another example of a loudspeaker excursion characterization system according to the present disclosure; Fig. Figure 8 is a functional block diagram of another example of a loudspeaker excursion characterization system according to the present disclosure; and Fig. Figure 9 is a graph of an example of an envelope generation circuit according to the present disclosure.

[0024] Reference numbers can be reused in the drawings to identify similar and / or identical elements. DETAILED DESCRIPTION

[0025] Excursion protection is an important aspect of a loudspeaker protection strategy. Typically, a loudspeaker excursion threshold is determined. This threshold is usually determined using excursion calibration equipment, which includes a laser that directs a laser beam onto the loudspeaker's diaphragm. As the diaphragm moves, the laser reads the physical excursion. When the diaphragm begins to approach a physical maximum excursion limit, the loudspeaker starts to produce various audible artifacts. The excursion calibration equipment identifies the maximum physical excursion at the excursion limit.

[0026] The mass deployment of loudspeaker protection systems necessitates the mass deployment of excursion calibration equipment and / or other accompanying instruments that aid in calibrating these systems. This approach tends to be very expensive, as the excursion calibration equipment is costly, the process is time-consuming, and specialized training is required.

[0027] The systems and methods described here provide an alternative to expensive excursion calibration equipment. Instead of using the laser and associated components, the systems and methods according to this disclosure generate audible signals at various excursion limits to determine the physical excursion limit of the loudspeaker under test. This helps customers to tune their audio systems more quickly without needing the more expensive excursion calibration equipment.

[0028] Systems and methods according to the present disclosure generate a signal at successively increasing amplitudes. In other words, the amplitude is increased until distortion is audible (or measurable via a microphone). The distortion indicates a collision between moving and static parts of the loudspeaker, meaning that the excursion range is exceeded at the current amplitude.

[0029] An inverse sweep filter receives the signal and compensates for the frequency response of a sweep filter located in the loudspeaker's amplifier circuit. If the signal's amplitude causes detectable distortion, a voltage threshold is set by the amplifier circuit based on the signal's amplitude at which the distortion is detected. This voltage threshold serves as a reference for determining when to reduce the amplifier circuit's gain for the loudspeaker. In some examples, the signal might be a sweep generated by the signal generator. In other examples, the sweep might be a sine sweep.

[0030] Now, with reference to Fig. 1 and Fig. 2 includes an audio system 100 an amplifier circuit 112 and a speaker 126Although the figures contain a loudspeaker 126 As shown, the present application is not for the loudspeaker shown. 126 limited and 126 can include a transducer including, for example, among others, a dynamic driver, a voice coil driver, a balanced armature driver, a planar magnetic driver, an electrostatic driver, and a magnetoresistive driver. The amplifier circuit 112 includes a deflection filter 114 , which receives an audio signal. The amplifier filter 112 It also includes a gain factor control amplifier. 116 . An input of the gain factor control amplifier 116 is equipped with a reference voltage threshold V T connected. Another input of the gain control amplifier. 116 is connected to an output of the deflection filter 114 tied together.

[0031] The audio signal is also fed into a delay circuit. 118 Entered. An output of the delay circuit. 118 is fed into an amplifier 122 entered with a variable gain factor. The amplifier 122 with variable gain factor has a gain factor control input which is used to control the gain factor of the amplifier. 122 The gain can be varied by adjusting the gain factor. Increasing the gain factor increases the amplification of the input signal, while decreasing the gain factor decreases the amplification of the input signal.

[0032] One output of the gain factor control amplifier 116 is equipped with a gain factor control input of the amplifier 122 connected with a variable gain factor. One output of the amplifier. 122 with variable amplification factor is combined with a moving element of the loudspeaker 126(e.g., a coil, a voice coil, or other drive structure). When the input is connected to the gain control amplifier 116 relative to V T As the current increases, the gain factor of the amplifier also increases. 122 with variable amplification factor reduced and vice versa.

[0033] In Fig. Figure 2 shows an example of a displacement filter's response. The graph shows the displacement as a function of frequency at constant voltage. In this example, the filter response is a low-pass response with frequency fo and Q. Although a low-pass filter response is shown, other filter responses can be used. The displacement filter 114The transfer function H(z) = Y(z) / X(z) is defined, where Y(z) and X(z) are z-transformations of the filter output and filter input, respectively. Numerator roots of the transfer function H(z) define zeros, and denominator roots of the transfer function H(z) define poles. The filter response of the displacement filter... 114 is determined by the poles and zeros of the transfer function H(z).

[0034] Now, with reference to Fig. 3 to Fig. 5 is a loudspeaker excursion characterization system 200 shown. In Fig. 3 includes the loudspeaker excursion characterization system 200 a signal generator 210 , which generates a signal. The amplitude of the signal can increase manually or automatically after each iteration (or after S iterations, where S is an integer greater than or equal to 1).

[0035] In some examples, the signal has a constant amplitude and a monotonically increasing (or decreasing) frequency during each iteration. In some examples, the amplitude of a sweep signal can increase manually or automatically after each iteration (or after S iterations, where S is an integer greater than or equal to 1). In some examples, the frequency range of the signal generator is 210 across the entire audible frequency range from 20 Hz to 20,000 Hz, or a portion thereof. An output of the signal generator. 210 is fed into an inverse deflection filter 214 entered.

[0036] In Fig. Figure 4 shows an example of a signal at the output of the signal generator. In some examples, the signal includes a sine sweep, although other types of signals can be used. The sine sweep has a constant amplitude and an increasing (or decreasing) frequency during each iteration. The amplitude of the sweep is increased after one or more iterations until distortion is detected.

[0037] In Fig. 5A represents the inverse deflection filter 214 an inverse of a response from the deflection filter 114 in the amplifier circuit 112 Ready. The graph shows voltage as a function of frequency. In some examples, the poles and zeros of the transfer function H(z) of the displacement filter are shown. 114 swapped to give an inverse answer (as in Fig. 5A shown) in the inverse deflection filter 214to provide. In other words, the poles and zeros of the deflection filter correspond to each other. 114 the zeros or poles of the inverse deflection filter 214 An output of the inverse deflection filter 214 is fed into the amplifier circuit 112 entered, which sends a signal to the speaker 126 outputs. In some examples, an amplitude of the signal generator is used. 210 The amplitude of the signal generator is set by an input voltage. 210 The gain factor is increased manually or automatically during characterization until distortion is detected. The threshold of the gain factor control amplifier... 116 is based on the amplitude of the signal generator 210 , is set when a distortion is detected. In Fig. Figure 5B shows the displacement for one of the passes. The inverse displacement filter flattens the displacement as a function of frequency.

[0038] Now, with reference to Fig. Figure 6 shows a method for characterizing loudspeaker excursion. 218 will f c and Q of the loudspeaker 126 definitely. At 222 A response from the displacement filter and / or the inverse displacement filter will be based on f c and Q of the loudspeaker 126 definitely. At 226 A signal with an amplitude is generated. 230 The procedure determines whether distortion occurs. In some examples, an output from the loudspeaker is... 126 by a microphone or other type of transducer designed to receive audio output (e.g. changes in air pressure or sound pressure level (SPL)) transmitted through the loudspeaker 126In one example, a signal is generated, and a control system is used to detect distortion. In other examples, an operator listens to the loudspeaker to identify distortion.

[0039] If no distortion is detected at 230, the amplitude at 234 increased and reverses the process 226 back. In some examples, the amplitude is monotonically increased from one level to another, although a different approach could be used. If distortion is detected at 230, the threshold voltage for the loudspeaker V is set. T The setting is based on the amplitude when a distortion is detected or heard by the operator.

[0040] Now, with reference to Fig. 7 is a loudspeaker excursion characterization system 300 shown. The loudspeaker excursion characterization system 300 It also includes a control system. 310 and a microphone 320The control 310 initiates the signal generator 210 and determines the amplitude. The control 310 The signal generator is triggered using a specified amplitude value. If no distortion is detected, the controller increases or otherwise adjusts the amplitude and checks again for distortion. This process is repeated until the controller or operator detects distortion. The microphone 320 receives audio output from the speaker 126 and generates a feedback signal for the control system. 310 .

[0041] Now, with reference to Fig. 8 and Fig. 9 is a loudspeaker excursion characterization system 400 shown. The input of the amplifier circuit. 112 It can be generated in other ways without using the inverse deflection filter. For example, a signal generator 410a signal that reflects the current frequency of the signal generator 410 represents an envelope generation circuit. 420 It generates an amplitude signal based on a desired amplitude of the signal as a function of the current frequency. In some examples, the envelope generation circuit can... 420 Use a lookup table, a formula, or another approach to generate the envelope as a function of the sweep signal's frequency. Alternatively, the envelope generation circuit can be used. 420 generate the envelope based on a period of time that has elapsed since the signal was initiated.

[0042] The outputs of the signal generator 410 and the envelope generation circuit 420 are multiplied by a multiplier 430 multiplied and connected to an amplifier circuit 112Output. When the maximum frequency is reached, the envelope generation circuit activates. 420 the signal generator 410 It returns and increases the envelope signal relative to a previous iteration.

[0043] In Fig. 9 is a voltage output of the envelope generation circuit. 420 shown as a function of time. The voltage output is based on the inverse of the deflection filter's response. 114 .

[0044] The preceding description is merely illustrative and is in no way intended to limit the disclosure, its application, or uses. The far-reaching teachings of the disclosure can be implemented in a variety of forms. Although this disclosure contains specific examples, the true scope of protection of the disclosure should therefore not be limited to these, since other modifications will become apparent upon review of the drawings, the specification, and the following claims. It is understood that one or more steps within a process may be carried out in a different order (or simultaneously) without altering the principles of the present disclosure.Furthermore, although each of the embodiments described above is characterized by certain features, one or more of these features described with respect to any embodiment of the disclosure can be implemented in features of any of the other embodiments and / or combined with them, even if this combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with each other remain within the scope of protection of this disclosure.

[0045] In this application, including in the definitions below, the term "module" or the term "controller" may be replaced by the term "circuit".The term "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combination logic circuit; a field-programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, as in a system-on-a-chip.

[0046] The module may include one or more interface circuits. In some examples, the interface circuits may include wired or wireless interfaces connected to a local area network (LAN), the internet, a wide area network (WAN), or a combination thereof. The functionality of a given module of this disclosure may be distributed among multiple modules connected via interface circuits. For example, multiple modules may enable load balancing. In another example, a server module (also known as a remote or cloud module) may perform some of the functionality for a client module.

[0047] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, data structures, and / or objects. The term "shared processor circuit" includes a single processor circuit that executes some or all of the code of multiple modules. The term "group processor circuit" includes a processor circuit that, in combination with additional processor circuits, executes some or all of the code of one or more modules. References to multiple processor circuits include multiple processor circuits on discrete dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above.The term shared memory circuit includes a single memory circuit that stores some or all of the code from multiple modules. The term group memory circuit includes a memory circuit that, in combination with additional memory, stores some or all of the code from one or more modules.

[0048] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not include volatile electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term computer-readable medium can therefore be regarded as tangible and non-transient.Non-restrictive examples of a non-transitory, tangible, computer-readable medium include non-volatile memory circuits (such as a flash memory circuit, a erasable programmable read-only memory circuit, or a mask read-only memory circuit), volatile memory circuits (such as a static random-access memory circuit or a dynamic random-access memory circuit), magnetic storage media (such as an analog or digital magnetic tape or a hard disk drive), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0049] The devices and methods described in this application can be implemented partially or completely by a specialized computer created by configuring a general-purpose computer to perform one or more specific functions implemented in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a qualified technician or programmer.

[0050] The computer programs contain processor-executable instructions stored on at least one non-transient, tangible, computer-readable medium. The computer programs may also contain or rely on stored data. The computer programs may include a BIOS (Basic Input / Output System) that interacts with hardware of the specialized computer, device drivers that interact with specific devices of the specialized computer, one or more operating systems, user applications, background services, background applications, etc.

[0051] The computer programs may include: (i) descriptive text to be parsed, such as HTML (Hypertext Markup Language), XML (Extensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code for execution by an interpreter; (v) source code for compilation and execution by a just-in-time compiler; and so on. For illustrative purposes only, source code may use syntax from languages ​​including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language, 5th version), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, and Lua. written in MATLAB, SIMULINK and Python®. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 62 / 902476

[0001]

Claims

[1] Loudspeaker excursion characterization system for a loudspeaker, comprising: a signal generator configured to generate a signal having a plurality of different amplitudes; and an inverse excursion filter having an inverse excursion filter response, receiving the signal, applying the inverse excursion filter response, and having an output in communication with an amplifier circuit of the loudspeaker, wherein the inverse excursion filter response is an inverse of an excursion filter response of an excursion filter in the amplifier circuit of the loudspeaker. [2] The loudspeaker excursion characterization system of claim 1, wherein the signal generator generates a sine sweep signal. [3] A loudspeaker excursion characterization system according to claim 1 or 2, further comprising: a microphone for detecting an output of the loudspeaker; and a controller configured to increase an amplitude of the signal and to selectively identify distortion in response to feedback from the microphone. [4] Loudspeaker system comprising: the loudspeaker excursion characterization system according to any one of claims 1 to 3; and the amplifier circuit, wherein the amplifier circuit includes an input for receiving an output of the inverse excursion filter. [5] The speaker system of claim 4, further comprising the speaker, the speaker receiving an output of the amplifier circuit. [6] A loudspeaker system according to claim 4 or 5, wherein the amplifier circuit includes: a delay circuit for receiving an input to the amplifier circuit; and a variable amplifier having a variable gain and an input receiving an output of the delay circuit. [7] A loudspeaker system according to claim 6, wherein the amplifier circuit includes: an excursion filter for receiving the input of the amplifier circuit; and a gain control amplifier having a first input receiving an output of the excursion filter, a second input receiving a voltage threshold, and an output configured to control the variable gain of the variable amplifier based on the voltage threshold and the output of the excursion filter. [8] Loudspeaker excursion characterization system for a loudspeaker, comprising: a signal generator configured to generate a signal having a frequency; an envelope generation circuit configured to generate an envelope signal based on the frequency of the signal and / or a period of time that has elapsed since the signal was initiated; and a multiplier configured to receive the signal and the envelope signal and output a product to an amplifier circuit of the loudspeaker. [9] The loudspeaker excursion characterization system of claim 8, wherein the signal generator generates a sine sweep signal. [10] A loudspeaker excursion characterization system according to claim 8 or 9, further comprising: a microphone for detecting an output of the loudspeaker; and a controller configured to vary an amplitude of the envelope generation circuit and to identify distortion based on feedback from the microphone. [11] Loudspeaker system comprising: the loudspeaker excursion characterization system according to any one of claims 8 to 10; and an amplifier circuit including an input configured to receive an output of the multiplier and an output. [12] The speaker system of claim 11, further comprising the speaker, the speaker receiving an output of the amplifier circuit. [13] A loudspeaker system according to claim 12, wherein the amplifier circuit includes: a delay circuit for receiving an input to the amplifier circuit; and a variable amplifier having a variable gain and an input receiving an output of the delay circuit. [14] A loudspeaker system according to claim 13, wherein the amplifier circuit includes: an excursion filter for receiving the input of the amplifier circuit; and a gain control amplifier having a first input receiving an output of the excursion filter, a second input receiving a voltage threshold, and an output configured to control the variable gain of the variable amplifier. [15] Transducer displacement characterization system for a transducer, comprising: a signal generator configured to generate a signal having a plurality of different amplitudes; and an inverse excursion filter having an inverse excursion filter response, receiving the signal and applying the inverse excursion filter response, and having an output in communication with an amplifier circuit of a first converter, wherein the inverse excursion filter response is an inverse of an excursion filter response of an excursion filter in the amplifier circuit of the first converter. [16] The transducer displacement characterization system of claim 15, further comprising: a second transducer for detecting an output of the first transducer; and a controller configured to increase an amplitude of the signal and to selectively identify distortion in response to feedback from the second transducer. [17] A transducer displacement characterization system according to claim 15 or 16, wherein the signal generator generates a sine sweep signal. [18] Loudspeaker excursion characterization system for a loudspeaker, comprising: a signal generator configured to generate a signal having multiple frequencies at multiple different amplitudes; and an inverse excursion filter having an inverse excursion filter response, receiving the signal, applying the inverse excursion filter response, and having an output in communication with an amplifier circuit of the loudspeaker, wherein the inverse excursion filter response is an inverse of an excursion filter response of an excursion filter in the amplifier circuit of the loudspeaker. [19] The loudspeaker excursion characterization system of claim 18, wherein the signal generator generates a sine sweep signal. [20] A loudspeaker excursion characterization system according to claim 18 or 19, wherein the signal generator comprises a sweep signal generator.