Single-valued Nonlinear Parameters
Characteristics: | KLIPPEL R&D System | KLIPPEL QC System |
---|---|---|
Voice coil offset Xoffset | LSI3, PWT | MSC |
Suspension asymmetry Ak | LSI3, PWT | MSC |
Maximal peak displacement Xmax | LSI3, PWT, MTON | MSC |
Force factor limited peak displacement XBl | LSI3, PWT | MSC |
Suspension limited peak displacement Xc | LSI3, PWT | MSC |
Inductance limited peak displacement XL | LSI3, PWT | |
Stiffness Kms(x=0) at the voice rest position | LSI3, PWT | MSC |
Force factor Bl(x=0) at the voice coil rest position | LSI3, PWT | MSC |
Effective stiffness related to effective resonance frequency | SPM, MSPM | |
Symmetry point xsym in force factor curve | LSI3, PWT | MSC |
In IEC standard 62458 single-valued parameters are derived from the nonlinear characteristics to simplify the interpretation and the data handling. For example, maximal peak displacement Xmax is limited by 10 % harmonic or intermodulation distortion generated by two-tone signal. For the motor and suspension nonlinearities Bl(x), Cms(x) and L(x) a corresponding displacement limit XBl, XC, XL can be derived from the shape of the nonlinear characteristic. The voice coil offset Xoffset is a single value derived from the symmetry point in the Bl(x) curve, expressed in mm. The suspension asymmetry describes the difference between the stiffness at positive and negative peak displacement referred to the mean value. All those values can be used for limit setting during end-of-line testing and for automatic control of the production process.
The symmetry point Xsym measured at the steep slopes of the Bl(x) characteristic (for xac > XBl) is a useful single-valued parameter describing the voice coil offset Xoffset≈Xsym.
Module | Comment |
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LSI3 primary measures the nonlinear characteristics and derives the single-valued parameters from the nonlinear curve shape. A noise signal is used as stimulus, and the bandwidth is adjusted automatically to ensure persistent excitation of the transducer. The permissible working range is automatically determined by using a protection system. An optional laser sensor may be used to check the orientation of the voice coil movement (coil in or out) and to calibrate the mechanical parameters. There are different versions of LSI3 dedicated to woofers, tweeters and loudspeaker systems (transducer mounted in enclosure). | |
PWT also provides full identification of the woofer’s lumped parameters using an arbitrary stimulus (music). In contrast to LSI, the voltage and the working range are determined by the user. | |
SPM measures the nonlinear stiffness and compliance of spiders, suspensions, drones and passive radiators. The stiffness asymmetry and the maximal peak displacement Xc limited by a decrease of the compliance down to 75% can be derived from the measured curves. | |
Micro Suspension Part Measurement (MSPM) | MSPM measures the moving mass, mechanical resistance as well as the nonlinear stiffness of micro suspension parts, usually used for micro speakers and headphones. The stiffness asymmetry and the maximal peak displacement Xc limited by a decrease of the compliance down to 75% can be derived from the measured curves. |
Multi-Tone Measurement (MTON) | MTON provides the maximal peak displacement measured if measurement is activated. |
Module | Comment |
---|---|
MSC determines the single-valued nonlinear parameters by using an ultra-short multi-tone stimulus (0.2 …2 s) and measuring voltage and current at the terminals giving relative parameters only. Importing the value Bl(x=0) or the moving mass Mms allows to express the mechanical parameters absolutely using SI units (m, N, kg). |
Example:
Application Notes
AN 1 Optimal Voice Coil Rest Position
AN 2 Separating Spider and Surround
AN 3 Adjusting the Mechanical Suspension
AN 5 Displacement Limits due to Driver Nonlinearities
AN 15 Checking for Compliance Asymmetry
AN 21 Reduce Distortion by Shifting Voice Coil
AN 24 Measuring Telecommunication Drivers
AN 26 Nonlinear Stiffness of Suspension Parts
Templates of KLIPPEL products
Name of the Template | Application |
---|---|
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 |
Diagnost. MIDRANGE Sp1 | Comprehensive testing of midrange drivers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1 |
Diagnost. RUB&BUZZ Sp1 | Batch of Rub & Buzz tests with increased voltage (applied to high power devices) |
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 |
Force - Deflection Curve | Using the results from LSI, the force -deflection curve is calculated. |
Separate suspension | Separated stiffness of surround and spider according to Application Note AN 2 |
SPM Suspension Part | Nonlinear stiffness of spiders and smaller cones based on ONE-SIGNAL Method |
SIM closed box analysis | Maximal displacement, dc displacement, compression, SPL, distortion using large signal parameters imported from LSI BOX |
SIM vented box analysis | Maximal displacement, dc displacement, compression, SPL, harmonic distortion using large signal parameters imported from LSI BOX |
PWT 8 Woofers Param. ID Noise | Parameter identification of woofers using internal test signal (no cycling, no stepping) |
PWT Woofer Param. ID MUSIC | Parameter Identification of Woofers using external test signal (no ON/OFF cycling, no stepping) |
PWT Woofer param. ID NOISE | Parameter Identification of Woofers using internal test signal (no ON/OFF cycling, no stepping) |
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
IEC 62458 Sound System Equipment – Electroacoustic Transducers - Measurement of Large Signal Parameters
IEC 62459 Sound System Equipment – Electroacoustic Transducers – Measurement of Suspension Parts
Papers and Preprints
W. Klippel, et al. “Fast Measurement of Motor and Suspension Nonlinearities in Loudspeaker Manufacturing,” presented at the 127th Convention of the Audio Eng. Soc., 2009 October 9-12, New York, NY, USA.
W. Klippel, “Dynamic Measurement of Loudspeaker Suspension Parts,” J. of Audio Eng. Soc. 55, No. 6, pp. 443-459 (2007 June).
D. Clark, “Precision Measurement of Loudspeaker Parameters,“ J. of Audio Eng. Soc., Volume 45, pp. 129 – 140, (1997 March).
W. Klippel, “Measurement of Large-Signal Parameters of Electro-dynamic Transducer,” presented at the 107th Convention of the Audio Eng. Soc., New York, September 24-27, 1999, Preprint 5008.
M. Dodd, et al., “Voice Coil Impedance as a Function of Frequency and Displacement,” presented at the 117th Convention of the Audio Eng. Soc., 2004 October 28–31, San Francisco, CA, USA.
R. H. Small, “Assessment of Nonlinearity in Loudspeakers Motors,” in IREECON Int. Convention Digest (1979 Aug.), pp. 78-80.
A. J. M. Kaizer, “Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by a Volterra Series Expansion,” J. of Audio Eng. Soc., Volume 35, pp. 421-433 (1987 June).
W. Klippel, “Dynamical Measurement of Non-Linear Parameters of Electro-dynamical Loudspeakers and their Interpretation”, J. of Audio Eng. Soc. 30 (12), pp. 944 - 955, (1990).
M. Knudsen, et al., “Determination of Loudspeaker Driver parameters Using a System Identification Technique,” J. of Audio Eng. Soc., Volume 37, No. 9.
W. Klippel, “Nonlinear Modeling of the Heat Transfer in Loudspeakers,” J. of Audio Eng. Soc. 52, Volume 1, 2004 January.