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Electrical input power

Characteristics:

KLIPPEL R&D System

Real input power Preal

PWT, LSI

Power P­Re dissipated on Re

PWT, LSI

Pn at nominal impedance Zn

PWT, LSI

Short term maximum input power

PWT, DIS, TRF

Long term maximum power

PWT, DIS, TRF

The maximal input power can be defined as the real input power Preal considering the phase between voltage and current, the power PRe dissipated in the dc resistance or as a rated power value Pn which corresponds with the squared value of the maximal input voltage divided by the nominal impedance Zn. Thus, values may differ significantly as shown in the figure below:

 

 

The maximal electrical input power, which can be handled by a transducer, depends on the properties of the stimulus and further measurement conditions (e.g. ambient temperature). The dominant limiting factors are the maximal permissible voice coil temperature and the mechanical load caused by high displacement at low frequencies and high values of strain and stress inside the material due to the acceleration at high frequencies. Approaching the upper limit of the usable working range, the regular nonlinearities generate harmonic and intermodulation distortion, thermal and nonlinear compression of the fundamental component and finally a damage of the transducer. International standards as referenced below define the properties of filtered noise, sinusoidal signal, burst and other stimuli with particular ON/OFF cycle times, amplitude profiles for measuring the short-term and long-term values permissible for the particular transducer.

KLIPPEL R&D SYSTEM (development)

Module

Comment

Large Signal Identification (LSI)

LSI module identifies nonlinear and thermal parameters which reveal the physical causes of the thermal and mechanical limits.

Power Test (PWT)

PWT is the perfect tool for finding the maximal input power while monitoring all state signals and the parameter variation during the test. PWT can monitor up to 2 devices under test (DUTs) by using the DA2 and up to 8 DUTs using the power monitor PM 8. An internal generator provides common test signals (noise, sinusoidal sweep) according various standards, including ON/OFF cycling and an amplitude profile for increasing the voltage. A death report monitors the destruction process at high resolution.

3D Distortion Module (DIS)

DIS module is a perfect tool for measurement of the electrical input power using very short sinusoidal tones and monitoring the fundamental component (displacement or sound pressure), nonlinear distortion and other symptoms (e.g. dc displacement) in the large signal domain. A protection system may skip measurement at high amplitudes when the distortion or voice coil temperature exceeds a limit value.

Transfer Function Module (TRF)

TRF module can be used for generating sinusoidal burst having a shaped envelope of a few cycles to measure the maximal short-term power limits with a very short stimulus (< 1s).

KLIPPEL QC SYSTEM (end-of-line testing)

Module

Comment

 

The measurement of the maximal input power is less important for quality control issues.

 

Example:

 

The figure above shows the increase of the voice coil temperature and input power versus measurement time using pink noise switched on and off according to fixed cycle times and increased by a voltage profile. The increase of voice coil temperature shows significant variation at 200 Kelvin which corresponds with voice coil rubbing at the pole tips. This limits the maximal input power for this stimulus to 13 Watts.
The figure above shows the increase of the voice coil temperature and input power versus measurement time using pink noise switched on and off according to fixed cycle times and increased by a voltage profile. The increase of voice coil temperature shows

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

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.