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Compression of fundamental components

Characteristics:

KLIPPEL R&D System KLIPPEL QC System

Output amplitude versus input amplitude

 DIS, SIM  

Thermal power compression

 DIS, SIM, LSI, PWT MST

Nonlinear amplitude compression

 DIS, SIM MST

The SPL response of the fundamental component at high amplitudes differs from the response predicted by a linear model based on Thiele/Small parameters. The amplitude difference can be expressed by a compression factor in dB. The compression is caused by transducer nonlinearities and the increase of the resistance Re corresponding with the increased voice coil temperature due to dissipated electrical input power. Short-term and long-term measurements are recommended in standards to differentiate between the two mechanisms and to define the maximal acoustical output. Improving the linearity of a transducer usually requires a compromise in thermal power handling.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Transfer Function Module (TRF)

TRF provides a fast measurement of the fundamental component with minimal heating of the voice coil.

3D Distortion Module (DIS)

DIS module performs a steady-state distortion measurement using a single and two-tone signal and measures the amplitude of the fundamental and of the compression in dB. DIS stepwise increases the amplitude of the stimulus and protects the transducer under test if the voice coil temperature or the distortion exceed user defined limits. The pre-excitation time may be used to perform short-term or long-term measurements according to international standards.

Simulation (SIM)

SIM predicts the large signal performance considering the thermal and nonlinear parameters. It reveals the voice coil temperature and the maximal displacement which cause the compression of the fundamental and which limit the maximal acoustical output.

KLIPPEL QC SYSTEM (end-of-line testing)

Module

Comment

MST (Multistep Task), preview

MST performs a steady-state distortion measurement using a single or two-tone signal and measures the amplitude of the fundamental. It can stepwise modify the amplitude and frequency of the stimulus.

 

Example:

 


The figure above shows the amplitude of the voice coil displacement (fundamental component) versus terminal voltage. At low voltages (U < 2 Volt rms), there is almost a linear relationship between input and output amplitude as predicted by linear parameter modelling. At higher amplitudes, the nonlinearities in the motor and suspension system cause a soft limiting of the output amplitude which limits the maximal output but which also protects the voice coil former against bottoming at the back plate.

 


The figure above shows a short-term measurement by using the DIS module with a single-tone stimulus of 1s length. The voltage is increased in 3V steps but the measured acoustical fundamental is divided by the input amplitude. Therefore, all curves are identical as long as the system behaves linearly. At low frequencies, the loudspeaker nonlinearities reduce the acoustical output, but at the resonance frequency, the electrical damping due to force factor nonlinearity Bl(x) decreases and the loudspeaker produces 1 dB more output. At higher frequencies, the displacement is small and the fundamental component is not affected by loudspeaker nonlinearities.

 


The figure above shows the short-term measurement of the same loudspeaker, but the single-tone was replaced by a two-tone stimulus. The first tone f­1=20 Hz represents a bass signal. The frequency of the second tone f­2 is varied over the audio band. At higher voltages, the first tone generates high displacement and the loudspeaker nonlinearities reduce the output of the high-frequency tone f2 by 4 –10 dB at low and high frequencies. Only at the resonance the force factor nonlinearity Bl(x) reduces the electrical damping, and the acoustical output will be increased by 3 dB.

 

Templates of KLIPPEL products

Name of the Template

Application

DIS Compression Out(in)

Output amplitude versus input amplitude at four frequencies

DIS 3D Harmonics AN 9

Harmonic distortions versus frequency and voltage according Application Note AN 9

DIS 3D Intermodulation AN8

Intermodulation distortions versus frequency and voltage according Application Note AN 8

DIS Harmonics vs. Voltage

Harmonic distortion measurement versus amplitude

DIS X Fundamental, DC

Fundamental and DC component of displacement

SIM Compression Out(In)

Output amplitude versus input amplitude at four frequencies using large signal parameters imported from LSI; Simulated results are comparable with DIS Compression Out(In).

Diagnost. MIDRANGE Sp1

Comprehensive testing of midrange drivers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnost. SUBWOOFER (Sp1)

Comprehensive testing of subwoofers with a resonance 10 Hz < fs < 70 Hz using standard current sensor 1

Diagnostics MICROSPEAKER Sp2

Comprehensive testing of microspeakers with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics TWEETER (Sp2)

Comprehensive testing of tweeters with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics VENTED BOX SP1

Comprehensive testing of vented box systems using standard current sensor 1

Diagnostics WOOFER (Sp1)

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnostics WOOFER Sp1,2

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using current sensor 1 and 2

Thermal Parameters (woofer)

Analysis of heat transfer in woofers based on identified thermal woofer parameters

Thermal Parameters AN 18

Thermal Parameters measured by using PWT module according Application Note 18

Thermal Parameters AN 19

Thermal Parameters measured by using PWT module according Application Note 19

LSI Tweeter Nonlin. Para Sp2

Tweeters with fs > 400 Hz at sensitive current sensor 2

LSI Headphone Nonlin. P. Sp2

Nonlinear parameters of headphones with fs < 300 Hz at sensitive current sensor 2

LSI Woofer Nonl. P. Sp1

Nonlinear parameters of woofers with fs < 300 Hz at standard current sensor 1

LSI Woofer Nonl.+Therm. Sp1

Nonlinear and thermal parameters of woofers with fs < 300 Hz at standard current sensor Sp1

LSI Woofer+Box Nonl. P Sp1

Nonlinear parameters of woofers operated in free air, sealed or vented enclosure with a resonance frequency fs < 300 Hz at standard current sensor Sp1

LSI Microspeaker Nonl. P. Sp2

Nonlinear parameters of microspeakers with fs > 300 Hz at sensitive current sensor 2

TRF Equiv. Input Harm. (SPL)

Equivalent harmonic input distortion calculated by inverse filtering of the measured distortion

SIM Equiv. Input Harmonics

Equivalent input harmonic distortion using large signal parameters imported from LSI; Simulated results are comparable with TRF Equiv. Input Harm. (SPL).

SIM Therm. Analysis (1 tone)

Heat transfer based on thermal parameters imported from LSI using a single-tone stimulus

SIM Therm. Analysis (2 tone)

Heat transfer based on thermal parameters imported from LSI using a two-tone stimulus

SIM X Fundamental, DC

Maximal displacement, dc displacement, compression using large signal parameters imported from LSI; Results are comparable with DIS X Fundamental, DC.

PWT 8 Woofers Param. ID Noise

Parameter identification of woofers using internal test signal (no cycling, no stepping)

PWT EIA accelerated life test

Accelerated life testing according EIA 426 B A. 4 using any external signal to monitor temperature, power and resistance

PWT IEC Long term Voltage

Power test to determine long-term maximal voltage according IEC 60268-5 paragraph 17.3 without parameter measurement for one device monitoring voltage, resistance, temperature and power

PWT IEC Short term Voltage

Power test to determine short term maximal voltage according IEC 60268-5 paragraph 17.2 without parameter measurement applied to 1 DUT monitoring temperature, power and resistance

PWT Powtest (fast Temp.)

Power test for fast monitoring of temperature, power and resistance without parameter measurement using external continuous signal (noise) supplied to IN1

PWT Powtest EXT. GENER.

Power test for monitoring temperature, power and resistance using external continuous signal (noise) supplied to IN1

PWT Powtest LIMITS

Power test to find maximal input voltage, power and temperature limits without parameter measurement applied to 1 DUT

PWT Powtest MUSIC

Power test without parameter measurement monitoring temperature, power, voltage and resistance using any external signal

PWT Powtest SWEEP

Power test for measuring the thermal time constant of the voice coil using sweep signal with low crest factor

PWT Powtest TIME Const.

Power test for measuring time constant of voice coil using internal test signal with cycling (ON/OFF phase)

Standards:

  • IEC Standard IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
  • AES2-1984 AES Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement


Papers and Preprints:
W. Klippel, Tutorial “Loudspeaker Nonlinearities - Causes, Parameters, Symptoms,” J. of Audio Eng. Soc. 54, No. 10, pp. 907-939 (2006 Oct.).

W. Klippel, “Assessment of Voice-Coil Peak Displacement Xmax,” J. of Audio Eng. Soc. 51, Heft 5, pp. 307 - 323 (2003 May).

W. Klippel, “Nonlinear Large-Signal Behavior of Electrodynamic Loudspeakers at Low Frequencies,” J. of Audio Eng. Soc., Volume 40, pp. 483-496 (1992).

W. Klippel, “Prediction of Speaker Performance at High Amplitudes,” presented at 111th Convention of the Audio Eng. Soc., 2001 September 21–24, New York, NY, USA.

W. Klippel, “Nonlinear Modeling of the Heat Transfer in Loudspeakers,” J. of Audio Eng. Soc. 52, Volume 1, 2004 January.

C. Zuccatti, “Thermal Parameters and Power Ratings of Loudspeakers,” J. of Audio Eng. Soc., Volume 38, No. 1, 2, 1990 January/February.

K. M. Pedersen, “Thermal Overload Protection of High Frequency Loudspeakers,” Report of Final Year Dissertation at Salford University.

Henricksen, “Heat Transfer Mechanisms in Loudspeakers: Analysis, Measurement and Design,” J. of Audio Eng. Soc., Volume 35, No. 10, 1987 October.