|KLIPPEL R&D System||KLIPPEL QC System|
Multi-tone distortion spectrum
Multi-tone distortion (absolute, relative)
|Total multi-tone distortion ratio||MTON||MTD|
Multi-tone noise floor (absolute, relative)
Any nonlinear system such as a loudspeaker generates new spectral components which are not present in the stimulus. In addition to harmonics, the fundamental components interact with each other and generate difference- and summed-tone components in the output signal (intermodulation distortion) which can easily be identified in a two-tone signal.Using a multi-tone stimulus, the number of distortion products rises quickly with the number of excited tones. Therefore, the multi-tone stimulus has similar properties like the pink noise, the organ tone or other audio signals, but the distortion can be easily separated from the fundamental components by using Fourier analysis.
The figure to the left illustrates the interpretation of the multi-tone distortion generated by a woofer. The suspension generates distortion close to the resonance frequency fs. Force factor Bl(x) generates significant intermodulation throughout the audio band. The distortion generated by inductance nonlinearities L(x), L(i) and Doppler effect and cone vibration rise towards higher frequencies.
Although the distortion plots generated with sine sweep and multi-tone measurements cannot be compared directly for several reasons, some fundamental differences are visible. The plots to the left show the relative distortion results of both methods for a small Bluetooth® enabled speaker. While the green curve shows significant harmonic distortion only at low stimulus frequencies where the displacement is high, the distortion is dropping significantly at higher frequencies. But does that mean that at mid and high frequencies virtually distortion is generated?
The multi-tone distortion measurement uncovers a much more realistic picture here. Since the multi-tone stimulus frequencies are distributed over the full audio band, all distortion mechanisms (incl. intermodulation) are triggered. This is very similar to music playback, but neglected by pure sinusoidal THD tests.
|Multi-Tone Measurement (MTON)|
The MTON provides highly flexible and comprehensive measurements based on multi-tone stimuli for R&D applications.
While the Single Measurement mode performs a single multi-tone measurement, the Multiple Measurements mode offers an automatic test sequence to obtain the operation limits of the DUT related to mechanical and thermal compression as well as multi-tone distortion. This allows the MTON module to pinpoint the SPLmax according to IEC 60268-21 as well as the continuous max SPL (ANSI/CEA-2010-B and ANSI/CEA-2034) among other standard measurements.
Name of the Template
|MTON Rated Umax based on SPLmax @ SP1, IEC 60268-21||Rated maximum input value Umax according IEC 60268-21 §17.1.|
|MTON Max SPL @ SP1, fixed level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.1.2b.|
|MTON Max SPL @ SP1, increased level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.1.2b with increased stimulus level to determine SPLmax.|
|MTON Short term max SPL @ SP1, fixed level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.3.|
|MTON Short term max SPL @ SP1, increased level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.3 with increased stimulus level to determine SPLshort.|
|MTON Long term max SPL @ SP1, fixed level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.4.|
|MTON Long term max SPL @ SP1, increased level; IEC 60268-21||Rated maximum sound pressure according IEC 60268-21 §18.4 3 with increased stimulus level to determine SPLLong.|
|MTON SPL in stated frequency band @ SP1; IEC 60268-21||Sound pressure level in a stated frequency band IEC 60268-21 §18.6.|
|MTON Multitone @SP1; IEC 60268-21||Multitone Distortion according to IEC 60268-21 §23.|
|MTON Wireless Measurement AN16||Multi-Tone Distortion measurement of wireless devices (AN16)|
|QC Multi-tone Distortion (MTD)||Default operation template for multi-tone measurement for QC|
|System\Self-Powered\System Test (Multi-Tone)||Multi-tone test for self-powered speaker systems (QC Start test template)|
|System\Self-Powered\Mono (Multi-Tone)||Combined test with chirp and multi-tone signal for self-powered speakers (QC Start test template)|
|System\Passive\Mono (Multi-Tone)||Combined test with chirp and multi-tone signal for passive speakers (QC Start test template)|
Voishvillo, et. al. , “Graphing, Interpretation, and Comparison of Results of Loudspeaker Nonlinear Distortion Measurements,” J. Audio Eng. Society 52, No. 4 pp. 332-357 (Apr. 2004)
W. Klippel, Tutorial “Loudspeaker Nonlinearities - Causes, Parameters, Symptoms,” J. of Audio Eng. Soc. 54, No. 10, pp. 907-939 (2006 Oct.).
E. Czerwinski, et al., “Multitone Testing of Sound System Components' Some Results and Conclusions, Part 2: Modeling and Application,” J. of Audio Eng. Soc. Volume 49, 2001 December, pp. 1181 – 1192.
S. Temme, et al., “A New Method for Measuring Distortion Using a Multitone Stimulus and Noncoherence,” J. of Audio Eng. Soc., Volume 56, 2008 March, pp. 176 – 188.
W. Klippel, “Nonlinear Large-Signal Behavior of Electrodynamic Loudspeakers at Low Frequencies,” J. of Audio Eng. Soc., Volume 40, pp. 483-496 (1992).
A. Voishvillo, “Graphing, Interpretation, and Comparison of Results of Loudspeaker Nonlinear Distortion Measurements,” J. of Audio Eng. Soc., Volume 52, No. 4, pp. 332-357, April 2004.
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.