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Accelerated life and power testing

Characteristics:

KLIPPEL R&D System

Input power versus time

LSI, PWT

Displacement versus time

LSI, PWT, SPM

Voice coil temperature

LSI, PWT, DIS

Durability, endurance, reliability

LSI, PWT, SPM

Parameter variation over time (aging)

LSI, PWT, SPM

Long-term testing (usually called “power test”) is required to define maximal limit values (maximal displacement, power), to check the durability and reliability of the system and to investigate parameters variation (e.g. resonance frequency) and aging over time.
Such measurements are performed in climate chambers generating hostile conditions to accelerate the life cycle of a product. Under those conditions, a high-quality sensor (microphone and laser) can not be applied for monitoring the state signals of the transducer. Current and voltage monitoring provides the electrical impedance, all electrical and mechanical parameters (e.g. resonance frequency, voice coil offset) and state variables (temperature, displacement, voltage). Those information reveals the exact time of the failure and details on the initial problem and the sequential steps within destruction process (stiffness problem, coil rubbing, short cut of windings, open connection).

The figure above shows the hardware and software parts required for generating the test stimulus and monitoring the state and parameters of a transducer during accelerated life testing.
The figure above shows the hardware and software parts required for generating the test stimulus and monitoring the state and parameters of a transducer during accelerated life testing.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Large Signal Identification (LSI Woofer, LSI Tweeter, LSI Box)

LSI provides a special thermal identification mode which identifies the dominant thermal parameters automatically. The measurement consists of ON/OFF cycles using of different noise stimuli. The input power and the measurement time is automatically adjusted to the particular transducer. All state variables (temperature, displacement, input power, voltage and current) are monitored during the measurement (see example below).   

Power Test (PWT)

PWT is dedicated to long-term testing with test and audio signals using ON/OFF cycling and amplitude stepping. Monitoring of voice coil temperature, displacement, power and other state variables and full identification of linear and nonlinear transducer parameters is provided.

3D Distortion Module (DIS)

DIS provides pre-excitation which is programmable and may be used for long-term testing before the main measurement is finally performed. Maximal values (e.g. SPL level) can safely be detected by performing a series of measurements where the amplitude is increased in small steps until distortion or voice coil temperature exceeds predefined limits.

Suspension Part Measurement (SPM)

SPM provides a long-term operation mode where the variation of the suspension parameters is recorded over time.

Example:

The figure above shows the variation of the stiffness of a spider versus measurement time measured by using the SPM module. After 10 hours of operation in the large signal domain, the stiffness at the rest position is decreased to 40 % of the initial value while the stiffness at high excursion is almost constant.
The figure above shows the variation of the stiffness of a spider versus measurement time measured by using the SPM module. After 10 hours of operation in the large signal domain, the stiffness at the rest position is decreased to 40 % of the initial valu
The figure above shows the variation of the resonance frequency fs and the variation of the voice coil temperature ΔTv versus measurement time t during long-term testing in a climate chamber where the ambient temperature has been changed by 50 degree.
The figure above shows the variation of the resonance frequency fs and the variation of the voice coil temperature Tv versus measurement time t during long-term testing in a climate chamber where the ambient temperature has been changed by 50 degree.

Templates of KLIPPEL products

Name of the Template

Application

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 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

DIS Compression Out(in)

Output amplitude versus input amplitude at four frequencies

DIS Harmonics vs. Voltage

Harmonic distortion measurement versus amplitude

DIS SPL, Harm protected

Harmonic distortion measurement with protection

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 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

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)

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:

  • 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
  • CEA CEA-426-B Loudspeakers, Optimum Amplifier Power
  • EIA 426B Loudspeaker Power Rating Test CD provided by ALMA International



Papers and Preprints:

Y. Shen, “Accelerated Power Test Analysis Based on Loudspeaker Life Distribution,” presented at the 124th Convention of Audio Eng. Soc., May 2008, Preprint 7345.

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.