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Separated loudspeaker distortion

Characteristics:

KLIPPEL R&D System

Total distortion in a reproduced audio signal

 PWT, AUR

Distortion generated by force factor Bl(x)

 LSI, AUR, SIM

Distortion generated by stiffness Kmx(x)

 LSI, AUR, SIM

Distortion generated by inductance Le(x)

 LSI, AUR, SIM

Distortion generated by inductance Le(i)

 LSI, AUR, SIM

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.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Large Signal Identification (LSI)

Using the identified large signal parameters, the LSI also predicts the peak ratio of the dominant nonlinear distortion versus measurement time. Distortion values depend on the spectral properties of the noise which are used as stimulus in the LSI.

Auralization (AUR)

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.

Large Signal Simulation (SIM)

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

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:

  • 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, “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).