Separated Loudspeaker Distortion
Characteristics: | KLIPPEL R&D System |
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Total distortion in a reproduced audio signal | PWT, SIM-AUR |
Distortion generated by force factor Bl(x) | LSI3, SIM, SIM-AUR |
Distortion generated by stiffness Kms(x) | LSI3, SIM, SIM-AUR |
Distortion generated by inductance Le(x) | LSI3, SIM, SIM-AUR |
Distortion generated by inductance Le(i) | LSI3, SIM, SIM-AUR |
Conventional distortion measurements use a special test signal with a sparse spectrum and identify all spectral components as distortions which are not excited by the stimulus. This technique cannot be applied to ordinary audio signals which usually have dense spectra. The nonlinear model developed for loudspeakers and other transducers makes it possible to calculate the large signal performance at high accuracy and to separate the distortion from the linear signal parts. This calculation requires the linear, nonlinear and thermal parameters of the loudspeaker and can be performed in real time using digital signal processing. Furthermore, for each dominant nonlinearity the corresponding distortion can be separated, and the spectrum and other signal characteristics (peak, rms-value, pdf) can be calculated.
Module | Comment |
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Using the identified large signal parameters, the LSI3 also predicts the peak ratio of the dominant nonlinear distortion versus measurement time. Distortion values depend on the spectral properties of the noise signal which is used as stimulus in the LSI. | |
SIM-AUR module calculates the internal loudspeaker states (displacement, temperature), the linear acoustical output and the distortion components of each nonlinearity. An arbitrary test signal or an ordinary audio signal can be used as stimulus, and the instantaneous distortion value is recorded in a history. | |
SIM module uses a two-tone stimulus and calculates the internal state variables, the acoustical output and the distortion by using a large signal model and the large signal parameters identified on the particular loudspeaker. The effect of a particular nonlinearity can be separately investigated by replacing the other nonlinearities by a constant parameter value. |
Example:
The figure above shows the peak ratio of the nonlinear distortion in percent of the total acoustical output versus measurement time. For each loudspeaker nonlinearity, the distortion is calculated separately. The force factor Bl(x) and the compliance Cms(x) are the dominant sources of nonlinear distortion compared with the small contribution of the inductance nonlinearity Le(x). The generated distortion highly depends on the total amplitude and spectral properties of the stimulus (bandwidth, bass enhancement).
Templates of KLIPPEL products
Name of the Template | Application |
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AUR auralization | Real-time auralization of the large signal performance |
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 |
SIM closed box analysis | Maximal displacement, dc displacement, compression, SPL, distortion using large signal parameters imported from LSI BOX |
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). |
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 IM Dist. (bass sweep) | Intermodulation distortion in current and sound pressure by using a variable bass tone fs/4 < f1 < 4fs and a fixed voice tone f2 >> fs; Simulated results are comparable with DIS IM Dist. (bass sweep). |
SIM IM Dist. (voice sweep) | Intermodulation distortion in current and sound pressure by using a fixed bass tone f2 < fs and a variable voice tone f1>> fs; Simulated results are comparable with DIS IM Dist. (voice sweep). |
SIM Motor Stability | Checking motor stability according Application Note AN 14; Simulated results are comparable with DIS Motor stability. |
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 vented box analysis | Maximal displacement, dc displacement, compression, SPL, harmonic distortion using large signal parameters imported from LSI BOX |
SIM X Fundamental, DC | Maximal displacement, dc displacement, compression using large signal parameters imported from LSI; Results are comparable with DIS X Fundamental, DC. |
SIM Separation AM Distortion | Amplitude modulation distortion according Application Note AN 10; Simulated results are comparable with DIS Separation AM Distortion. |
Standards
Audio Engineering Society
AES2 Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement
International Electrotechnical Commission
IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
Papers and Preprints
W. Klippel, “Speaker Auralization – Subjective Evaluation of Nonlinear Distortion,” presented at the 110th Convention of the Audio Eng. Soc., Amsterdam, May 12-15, 2001, Preprint 5310, J. of Audio Eng. Soc., Volume 49, No. 6, 2001 June, P. 526. (abstract)
W. Klippel, Tutorial “Loudspeaker Nonlinearities - Causes, Parameters, Symptoms,” J. of Audio Eng. Soc. 54, No. 10, pp. 907-939 (2006 Oct.).
W. Klippel, “Nonlinear Large-Signal Behavior of Electrodynamic Loudspeakers at Low Frequencies,” J. of Audio Eng. Soc., Volume 40, pp. 483-496 (1992).