DE102020124461A1 - ACOUSTIC APPROXIMATION FOR DETERMINING DEFLECTION LIMITS IN SPEAKERS - Google Patents

Abstract

A loudspeaker displacement characterization system for a loudspeaker includes a signal generator which is configured to generate a signal at a plurality of different amplitudes. The signal can be generated at multiple frequencies. An inverse displacement filter has an inverse displacement filter response, receives the signal and applies the inverse displacement filter response, and has an output in communication with an amplifier circuit of the speaker. The inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the loudspeaker.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62 / 902,476 , filed September 19, 2019. The entire disclosures of the above referenced application are hereby incorporated by reference.

TECHNICAL AREA

The present disclosure relates to loudspeakers and, more particularly, to systems and methods for determining deflection limits for loudspeakers.

BACKGROUND

The background description provided here is for the purpose of generally presenting the context of the disclosure. Work by the present inventors to the extent described in this background section, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly incorporated as prior art with regard to the present disclosure.

Mobile devices such as smartphones, laptops, tablets, etc. incorporate relatively small speakers. Designers must find a balance for wanting bigger sound, better sound quality, lower power, and improved reliability against the increasingly smaller size of speakers. Electromagnetic speakers include a permanent magnet and a voice coil. The voice coil is attached to a diaphragm that pushes air away to create sound. The loudspeaker is typically enclosed in a protective box which provides a rear volume of air for the loudspeaker to press against and project sound. However, these types of speakers are typically not very loud, have no bass response, and break easily. Furthermore, these speakers can be overdriven to the point of distortion and / or damage.

Deflection refers to how far a loudspeaker cone moves linearly from its rest position. If a loudspeaker is driven beyond its physical limits, over-deflection can occur and the loudspeaker can be damaged.

SHORT VERSION

A loudspeaker displacement characterization system for a loudspeaker includes a signal generator which is configured to generate a signal at a plurality of 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 in communication with an amplifier circuit of the speaker. The inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the loudspeaker.

In other features, the signal is generated at multiple frequencies. The signal comprises a wobble signal. The signal generator includes a wobble signal generator.

In other features, the signal generator generates a sine wobble signal. A microphone detects an output from the speaker. A controller is configured to increase an amplitude of the signal and selectively identify distortion in response to feedback from the microphone.

In other features, a speaker system includes the speaker displacement characterization system, an amplifier circuit, and the speaker. The amplifier circuit includes an input for receiving an output of the inverse displacement filter. The speaker receives an output from the amplifier circuit.

In other features, 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 of the delay circuit.

In other features, the amplifier circuit includes a displacement filter for receiving input from the amplifier circuit. A gain control amplifier has a first input that receives an output of the excursion filter, a second input that receives a voltage threshold, and an output that is configured to control the variable gain of the variable amplifier based on the voltage threshold and the output of the excursion filter.

A loudspeaker displacement characterization system for a loudspeaker includes a signal generator which is configured to generate a signal having a frequency. On Envelope generation circuitry is designed 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. A multiplier is designed to receive the signal and the envelope signal and to output a product to an amplifier circuit of the loudspeaker.

In other features, the signal is generated at multiple frequencies. The signal comprises a wobble signal. The signal generator includes a wobble signal generator.

In other features, the signal generator generates a sine wobble signal. A microphone detects an output from the speaker. A controller is designed to vary an amplitude of the envelope generation circuit and to identify a distortion based on a feedback from the microphone.

A speaker system includes the speaker displacement characterization system. An amplifier circuit includes an input configured to receive an output of the multiplier and an output. A speaker receives an output from the amplifier circuit.

In other features, 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 of the delay circuit.

In other features, the amplifier circuit includes a displacement filter for receiving input from the amplifier circuit. A gain control amplifier has a first input that receives an output of the excursion filter, a second input that receives a voltage threshold, and an output that is designed to control the variable gain of the variable amplifier.

A transducer deflection characterization system for a transducer includes a signal generator configured to generate a signal at a plurality of different amplitudes. An inverse deflection filter has an inverse deflection filter response, receives the signal, applies the inverse deflection filter response, and has an output in communication with an amplifier circuit of a first transducer. The inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the first converter.

In other features, a second transducer detects an output from the first transducer. A controller is configured to increase an amplitude of the signal and selectively identify a distortion in response to feedback from the second transducer.

In other features, the signal is generated at multiple frequencies. The signal comprises a wobble signal. The signal generator includes a wobble signal generator.

In other features, the signal generator generates a sine wobble signal.

Further areas of application of the present disclosure will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the disclosure.

Figure list

• 1 ist ein funktionales Blockdiagramm eines Beispiels für einen Verstärkerschaltkreis und einen Lautsprecher;
• 2 ist ein Graph, der ein Beispiel für eine Filterantwort eines Auslenkungsfilters veranschaulicht;
• 3 ist ein funktionales Blockdiagramm eines Beispiels für ein Lautsprecherauslenkungscharakterisierungssystem gemäß der vorliegenden Offenbarung;
• 4 ist ein Graph eines Beispiels für ein Signal;
• 5A ist ein Graph eines Beispiels für eine Filterantwort eines Inversauslenkungsfilters gemäß der vorliegenden Offenbarung;
• 5B zeigt eine Auslenkungsantwort unter Verwendung des Inversauslenkungsfilters gemäß der vorliegenden Ausführungsform;
• 6 ist ein Flussdiagramm eines Beispiels für ein Verfahren zum Charakterisieren einer Lautsprecherauslenkung gemäß der vorliegenden Offenbarung;
• 7 ist ein funktionales Blockdiagramm eines anderen Beispiels für ein Lautsprecherauslenkungscharakterisierungssystem gemäß der vorliegenden Offenbarung;
• 8 ist ein funktionales Blockdiagramm eines anderen Beispiels für ein Lautsprecherauslenkungscharakterisierungssystem gemäß der vorliegenden Offenbarung; und
• 9 ist ein Graph eines Beispiels für einen Hüllkurvenerzeugungsschaltkreis gemäß der vorliegenden Offenbarung.

The present disclosure can be more fully understood from the detailed description and accompanying drawings, where:

• 1 Figure 3 is a functional block diagram of an example of an amplifier circuit and speaker;
• 2 Fig. 13 is a graph illustrating an example of a filter response of a displacement filter;
• 3rd Figure 3 is a functional block diagram of an example of a Speaker displacement characterization system according to the present disclosure;
• 4th Fig. 13 is a graph of an example of a signal;
• 5A Figure 3 is a graph of an example filter response of an inverse displacement filter in accordance with the present disclosure;
• 5B Fig. 13 shows a displacement response using the inverse displacement filter according to the present embodiment;
• 6th FIG. 3 is a flow diagram of an example of a method for characterizing speaker displacement in accordance with the present disclosure; FIG.
• 7th Figure 13 is a functional block diagram of another example of a speaker displacement characterization system in accordance with the present disclosure;
• 8th Figure 13 is a functional block diagram of another example of a speaker displacement characterization system in accordance with the present disclosure; and
• 9 Figure 13 is a graph of an example of an envelope generation circuit in accordance with the present disclosure.

In the drawings, reference numbers may be reused to identify similar and / or identical elements.

DETAILED DESCRIPTION

Deflection protection is an important aspect of a speaker protection strategy. A deflection threshold of the loudspeaker is typically determined. The deflection threshold is typically determined using deflection calibration equipment that includes a laser that directs a laser beam onto a diaphragm of the speaker. As the diaphragm moves, the laser reads the physical deflection. As the diaphragm begins to approach a maximum physical deflection limit, the loudspeaker begins to produce various audible artifacts. The deflection calibration equipment identifies the maximum physical deflection at the deflection limit.

The mass deployment of loudspeaker protection systems requires the mass deployment of deflection calibration equipment and / or other accompanying instruments that aid in the calibration of loudspeaker protection systems. This approach tends to be very expensive because the displacement calibration equipment is expensive and the process is time consuming and requires special training.

Systems and methods described herein provide an alternative to expensive deflection calibration equipment. Rather than using the laser and associated components, the systems and methods of the present disclosure generate audible signals at various deflection limits to determine the physical deflection limit of the speaker under test. This helps customers tune their audio systems faster without the need for the more expensive displacement calibration equipment.

Systems and methods in accordance with the present disclosure generate a signal at successively increasing amplitudes. In other words, the amplitude is increased until distortion can be heard (or measured using the microphone). The distortion indicates a collision between moving and static parts of the speaker, which means that the deflection range is exceeded at the current amplitude.

An inverse displacement filter receives the signal and compensates for a frequency response of a displacement filter located in an amplifier circuit of the loudspeaker. If the amplitude of the signal causes detectable distortion, a voltage threshold used by the amplifier circuit is established based on the amplitude of the signal when the distortion is detected. The voltage threshold is used as a reference to determine when to reduce the gain of the amplifier circuit for the loudspeaker. In some examples, the signal can be a wobble signal generated by the signal generator. In other examples, the wobble signal can be a sinusoidal wobble signal.

Now referring to 1 and 2 includes an audio system 100 an amplifier circuit 112 and a speaker 126 . Although a loudspeaker in the figures 126 is illustrated, the present application is not based on the illustrated speaker 126 and 126 may include a transducer including, for example, a dynamic driver, a voice coil driver, a balanced armature driver, a planar magnetic driver, an electrostatic driver, and a magnetoresistive driver, among others. The amplifier circuit 112 includes a displacement filter 114 receiving an audio signal. The amplifier filter 112 further includes a gain control amplifier 116 . An input of the gain control amplifier 116 is connected to a reference voltage threshold V _T. Another input of the gain control amplifier 116 is with an output of the displacement filter 114 connected.

The audio signal is also passed into a delay circuit 118 entered. An output of the delay circuit 118 gets into an amplifier 122 entered with variable gain factor. The amplifier 122 with variable gain has a gain control input for controlling a gain of the amplifier 122 can be varied with a variable gain factor. Increasing the gain increases the gain of the input signal, while reducing the gain decreases the gain of the input signal.

An output of the gain control amplifier 116 is connected to a gain control input of the amplifier 122 associated with variable gain. An output of the amplifier 122 with variable gain is with a moving element of the speaker 126 (e.g. a coil, a voice coil or other drive structure). When the input to the gain control amplifier 116 relative as V _T increases, the gain of the amplifier becomes 122 with a variable gain factor and vice versa.

In 2 an example of a filter response of a deflection filter is shown. The graph shows deflection as a function of frequency at constant voltage. In this example the filter response is a low pass response with a frequency fo and Q. Although a low pass filter response is shown, other filter responses can be used. The deflection filter 114 has a transfer function H (z) = Y (z) / X (z), where Y (z) and X (z) are z-transforms of the filter output and the filter input. 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).

Now referring to 3rd to 5 is a loudspeaker displacement characterization system 200 shown. In 3rd includes the loudspeaker deflection characterization system 200 a signal generator 210 generating a signal. An 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).

In some examples, the signal has a constant amplitude during each iteration and a monotonically increasing (or decreasing) frequency during each iteration. In some examples, an amplitude of a wobble signal may increase manually or automatically after each sweep (or after S sweeps, where S is an integer greater than or equal to 1). In some examples, the frequency range of the signal generator is 210 in the entire audible frequency range from 20 Hz to 20,000 Hz or part thereof. An output from the signal generator 210 becomes an inverse deflection filter 214 entered.

In 4th an example of a signal at the output of the signal generator is shown. In some examples, the signal includes a sine wave signal, although other types of signals can be used. The sine wobble signal has a constant amplitude during each sweep and an increasing (or decreasing) frequency during each sweep. The amplitude of the wobble signal is increased after one or more passes until a distortion is detected.

In 5A represents the inverse deflection filter 214 an inverse of a response of the displacement filter 114 in the amplifier circuit 112 ready. In the graph, voltage is shown as a function of frequency. In some examples, the poles and zeros of the transfer function are H (z) of the displacement filter 114 swapped to get an inverse answer (as in 5A shown) in the inverse displacement filter 214 provide. In other words, the poles and the zeros of the deflection filter correspond 114 the zeros or poles of the inverse deflection filter 214 . An output of the inverse displacement filter 214 becomes in the amplifier circuit 112 entered a signal to the speaker 126 issues. In some examples, an amplitude of the signal generator 210 set by an input voltage. The amplitude of the signal generator 210 is increased manually or automatically during characterization until distortion is detected. The threshold of the gain control amplifier 116 is based on the amplitude of the signal generator 210 when distortion is detected. In 5B a deflection for one of the runs is shown. The inverse deflection filter flattens the deflection as a function of frequency.

Now referring to 6th a method for characterizing loudspeaker deflection is shown. At 218 become f _c and Q of the speaker 126 certainly. At 222 be a response of the deflection filter and / or the inverse deflection filter based on f _c and Q of the speaker 126 certainly. At 226 a signal with an amplitude is generated. At 230 the procedure determines whether distortion occurs. In some examples, an output from the speaker 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)) produced by the loudspeaker 126 is generated, and a controller for detecting a distortion is sampled. In other examples, an operator listens to the speaker to identify distortion.

If no distortion is detected at 230, the amplitude will be at 234 increases and reverses the procedure 226 back. In some examples, the amplitude is monotonically increased from one level to another level, although a different approach can be used. If distortion is detected at 230, the threshold voltage for speaker V _T is adjusted based on the amplitude when distortion is detected or heard by the operator.

Now referring to 7th is a loudspeaker displacement characterization system 300 shown. The loudspeaker displacement characterization system 300 also includes a controller 310 and a microphone 320 . The control 310 initiates the signal generator 210 and determines the amplitude. The control 310 solves the Signal generator using a value for the amplitude. If no distortion is detected, the controller increases the amplitude or adjusts it in some other way and checks again for distortion. The process is repeated until the controller or the operator detects a distortion. The microphone 320 receives an audio output from the speaker 126 and generates a feedback signal for the controller 310 .

Now referring to 8th and 9 is a loudspeaker displacement characterization system 400 shown. The input of the amplifier circuit 112 can be generated in other ways without using the inverse displacement filter. For example there is a signal generator 410 a signal that is a current frequency of the signal generator 410 represents. An envelope generation circuit 420 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 420 use a look-up table, formula, or other approach to generate the envelope as a function of a frequency of the wobble signal. Alternatively, the envelope generation circuit 420 generate the envelope based on a time elapsed since the signal was initiated.

The outputs of the signal generator 410 and the envelope generation circuit 420 are through a multiplier 430 multiplied and to an amplifier circuit 112 issued. When the maximum frequency is reached, the envelope generation circuit resumes 420 the signal generator 410 back and increases the envelope signal relative to a previous iteration.

In 9 is a voltage output of the envelope generation circuit 420 shown as a function of time. The voltage output is based on an inverse of the filter response of the displacement filter 114 .

The preceding description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes specific examples, the true scope of the disclosure should not be limited thereto as 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 method can be performed in a different order (or simultaneously) without changing the principles of the present disclosure. Furthermore, while each of the embodiments is described above as having certain features, any one or more of these features described with respect to any embodiment of the disclosure can be implemented in and / or combined with features of any of the other embodiments, 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 one another remain within the scope of this disclosure.

In this application, including in the definitions below, the term “module” or the term “control” can 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 combinational 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 functionality described; or a combination of some or all of the above, such as in a system-on-chip.

The module can contain one or more interface circuits. In some examples, the interface circuitry 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 the present disclosure may be distributed among multiple modules that are interconnected via interface circuitry. For example, multiple modules can allow load balancing. In another example, a server module (also known as a remote or cloud module) can perform some of the functionality for a client module.

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 forms part of the executes all code from multiple modules. The term group processor circuit includes a processor circuit which, in combination with additional processor circuitry, 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 on a single processor circuit, multiple threads on 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 which, in combination with additional memories, stores some or all of the code from one or more modules.

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 viewed as tangible and non-transitory. Non-limiting examples of a non-transitory, tangible computer-readable medium are non-volatile memory circuits (such as a flash memory circuit, an 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 memory circuit). Random access memory circuitry, magnetic storage media (such as an analog or digital magnetic tape or hard disk drive), and optical storage media (such as a CD, DVD, or Blu-ray disc).

The devices and methods described in this application can be implemented in part or in whole by a special purpose computer created by configuring a general purpose computer to perform one or more special 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 by the routine work of a skilled technician or programmer.

The computer programs include processor-executable instructions that are stored on at least one non-transitory, tangible computer-readable medium. The computer programs can also contain stored data or be dependent on them. The computer programs may include a basic input / output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with special devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, and so on.

The computer programs may contain: (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, etc. By way of example only, source code using 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®, Lua, MATLAB, SIMULINK and Python®.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 62/902476 [0001]

Claims (20)

A loudspeaker displacement characterization system for a loudspeaker, comprising: a signal generator which is designed to generate a signal with 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 speaker; wherein the inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the loudspeaker. Loudspeaker deflection characterization system according to Claim 1 , wherein the signal generator generates a sinusoidal wobble signal. Loudspeaker deflection characterization system according to Claim 1 or 2 further comprising: a microphone for capturing an output of the speaker; and a controller configured to increase an amplitude of the signal and selectively identify distortion in response to feedback from the microphone. A loudspeaker system comprising: the loudspeaker displacement characterization system according to any one of Claims 1 to 3rd ; and the amplifier circuit, the amplifier circuit including an input for receiving an output of the inverse displacement filter. Speaker system according to Claim 4 further comprising the speaker, the speaker receiving an output of the amplifier circuit. Speaker 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. Speaker system according to Claim 6 wherein the amplifier circuit includes: a displacement filter for receiving the input of the amplifier circuit; and a gain control amplifier having a first input that receives an output of the excursion filter, a second input that receives a voltage threshold, and an output that is configured to control the variable gain of the variable amplifier based on the voltage threshold and the output of the excursion filter, having. A loudspeaker displacement 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 which is designed to receive the signal and the envelope signal and to output a product to an amplifier circuit of the loudspeaker. Loudspeaker deflection characterization system according to Claim 8 , wherein the signal generator generates a sinusoidal wobble signal. Loudspeaker deflection characterization system according to Claim 8 or 9 further comprising: a microphone for capturing an output of the speaker; and a controller configured to vary an amplitude of the envelope generation circuit and to identify a distortion based on feedback from the microphone. A loudspeaker system comprising: the loudspeaker displacement 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. Speaker system according to Claim 11 further comprising the speaker, the speaker receiving an output of the amplifier circuit. Speaker 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. Speaker system according to Claim 13 , wherein the amplifier circuit includes: a displacement filter for receiving input from the amplifier circuit; and a gain control amplifier having a first input that receives an output of the excursion filter, a second input that receives a voltage threshold, and an output that is configured to control the variable gain of the variable amplifier. A transducer displacement characterization system for a transducer comprising: a signal generator which is designed to generate a signal with a plurality of different amplitudes; and an inverse displacement filter having an inverse displacement filter response, receiving the signal and applying the inverse displacement filter response and having an output in communication with an amplifier circuit of a first transducer; wherein the inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the first converter. Converter deflection characterization system according to Claim 15 further comprising: a second transducer for sensing an output of the first transducer; and a controller configured to increase an amplitude of the signal and selectively identify distortion in response to feedback from the second transducer. Converter deflection characterization system according to Claim 15 or 16 , wherein the signal generator generates a sinusoidal wobble signal. A loudspeaker displacement characterization system for a loudspeaker, comprising: a signal generator which is designed to generate a signal having a plurality of frequencies at 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 speaker; wherein the inverse displacement filter response is an inverse of a displacement filter response of a displacement filter in the amplifier circuit of the loudspeaker. Loudspeaker deflection characterization system according to Claim 18 , wherein the signal generator generates a sinusoidal wobble signal. Loudspeaker deflection characterization system according to Claim 18 or 19th wherein the signal generator comprises a wobble signal generator.

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