Sound system equipment - Part 22: Electrical and mechanical measurements on transducers

IEC 60268-22:2020 applies to transducers converting an electrical input signal into a mechanical or acoustical output signal. However, if the electrical input terminals and the surface of the radiator are accessible, this document can also apply to passive and active sound systems such as loudspeakers, headphones, TV-sets, multi-media devices, personal portable audio devices, automotive sound systems and professional equipment. This document describes only electrical and mechanical measurements that help assess the transfer behaviour of the device under test (DUT). This includes operating the DUT in both the small- and large-signal domains. The influence of the target application's acoustical boundary conditions (e.g. car interior) can also be considered in the physical evaluation of the sound system. Perception and cognitive evaluations of the reproduced sound and the impact of perceived sound quality are outside the scope of this document.

Équipements pour systèmes électroacoustiques - Partie 22: Mesurages électriques et mécaniques sur transducteurs

L'IEC 60268-22:2020 s'applique aux transducteurs qui convertissent un signal d'entrée électrique en signal de sortie mécanique ou acoustique. Toutefois, si les bornes d'entrée électriques et la surface du radiateur sont accessibles, le présent document peut également s'appliquer aux systèmes électroacoustiques passifs et actifs tels que les haut parleurs, les casques d'écoute, les téléviseurs, les appareils multimédias, les appareils audio personnels portables, les systèmes électroacoustiques pour automobile et les équipements professionnels. Le présent document ne décrit que les mesurages électriques et mécaniques qui aident à évaluer le comportement de transfert de l'appareil soumis à l'essai (DUT). Cela comprend le fonctionnement du DUT dans les domaines des signaux faibles et des signaux forts. L'influence des conditions de limite acoustique de l'application visée (par exemple, habitacle d'un véhicule) peut également être prise en considération dans l'évaluation physique du système électroacoustique. La perception et les évaluations cognitives du son reproduit et l'impact de la qualité acoustique perçue n'entrent pas dans le domaine d'application du présent document.

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Status
Published
Publication Date
23-Sep-2020
Current Stage
PPUB - Publication issued
Completion Date
24-Sep-2020
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IEC 60268-22
Edition 1.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment –
Part 22: Electrical and mechanical measurements on transducers
Équipements pour systèmes électroacoustiques –
Partie 22: Mesurages électriques et mécaniques sur transducteurs
IEC 60268-22:2020-09(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60268-22
Edition 1.0 2020-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment –
Part 22: Electrical and mechanical measurements on transducers
Équipements pour systèmes électroacoustiques –
Partie 22: Mesurages électriques et mécaniques sur transducteurs
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.01 ISBN 978-2-8322-8815-3

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60268-22:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions and abbreviated terms ........................................................................ 9

3.1 Terms and definitions .............................................................................................. 9

3.2 Abbreviated terms ................................................................................................... 9

4 Type description .............................................................................................................. 9

5 Marking of terminals and controls .................................................................................... 9

6 Physical characteristics ................................................................................................... 9

6.1 Dimensions ............................................................................................................. 9

6.2 Mass ..................................................................................................................... 10

6.3 Connectors and cable assemblies ......................................................................... 10

7 Conditions ..................................................................................................................... 10

7.1 Rated conditions ................................................................................................... 10

7.2 Climatic conditions ................................................................................................ 10

7.3 Standard measuring conditions ............................................................................. 10

8 Test signals ................................................................................................................... 11

8.1 General ................................................................................................................. 11

8.2 Small-signal condition ........................................................................................... 11

9 Acoustical environment .................................................................................................. 11

9.1 General ................................................................................................................. 11

9.2 Free-field conditions ............................................................................................. 11

9.3 Half-space, free-field conditions ............................................................................ 12

9.4 Free-air condition .................................................................................................. 12

9.5 Target application conditions ................................................................................ 12

9.6 Vacuum condition ................................................................................................. 12

9.7 Plane-wave tube condition .................................................................................... 12

9.8 Non-acoustical measurement condition ................................................................. 12

10 Positioning of the radiator .............................................................................................. 13

10.1 Rated geometrical conditions ................................................................................ 13

10.2 Target application condition .................................................................................. 14

11 Measurement equipment and test results ....................................................................... 14

12 Accuracy of the mechanical and electrical measurement ............................................... 14

13 Mounting of the DUT ...................................................................................................... 14

13.1 Mounting and acoustic loading of drive units ......................................................... 14

13.2 Mounting and acoustic loading of an electro-acoustic system ................................ 15

13.3 Requirements for laser vibrometry ........................................................................ 15

14 Preconditioning .............................................................................................................. 15

15 Rated ambient conditions .............................................................................................. 15

15.1 Temperature ranges .............................................................................................. 15

15.2 Humidity ranges .................................................................................................... 15

16 Electrical signals at transducer terminals ....................................................................... 16

16.1 Rated maximum input value .................................................................................. 16

17 Electrical input power .................................................................................................... 17

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IEC 60268-22:2020 © IEC 2020 – 3 –

17.1 Real input power ................................................................................................... 17

17.2 Power dissipated in DC resistance ........................................................................ 17

17.3 Power dissipated in rated impedance .................................................................... 18

17.4 Rated maximum input power ................................................................................. 18

18 Electrical input impedance ............................................................................................. 18

18.1 Complex electrical impedance ............................................................................... 18

18.2 Rated Impedance: characteristic to be specified ................................................... 19

19 Vibration of the radiator surface ..................................................................................... 19

19.1 General ................................................................................................................. 19

19.2 Displacement of a surface point r ......................................................................... 19

19.3 Reference displacement........................................................................................ 20

19.4 Peak and bottom displacement ............................................................................. 21

19.5 DC displacement ................................................................................................... 21

19.6 Displacement transfer function .............................................................................. 22

19.7 Accumulated acceleration level ............................................................................. 22

20 Small-signal lumped parameters .................................................................................... 23

20.1 General ................................................................................................................. 23

20.2 Electrical parameters ............................................................................................ 24

20.3 Relative lumped parameters ................................................................................. 25

20.4 Lumped mechanical parameters............................................................................ 28

20.5 Pure lumped mechanical parameters .................................................................... 31

20.6 Compliance versus frequency ............................................................................... 31

20.7 Distributed mechanical parameters ....................................................................... 32

20.8 Lumped acoustical parameters ............................................................................. 36

21 Electro-acoustical efficiency .......................................................................................... 40

21.1 Reference efficiency ............................................................................................. 40

21.2 Passband efficiency .............................................................................................. 41

22 Sensitivity ...................................................................................................................... 41

22.1 Reference sensitivity ............................................................................................. 41

22.2 Passband sensitivity ............................................................................................. 42

23 Large-signal characteristics ........................................................................................... 42

23.1 Electrical and mechanical nonlinearities ................................................................ 42

23.2 Other loudspeaker nonlinearities ........................................................................... 43

23.3 Asymmetry of the nonlinearity ............................................................................... 43

23.4 Offset from reference rest position, x ................................................................ 45

off

23.5 Maximum reference displacement ......................................................................... 46

24 Thermal characteristics ................................................................................................. 48

24.1 General ................................................................................................................. 48

24.2 Increase in voice coil temperature ......................................................................... 48

24.3 Effective thermal resistance .................................................................................. 49

24.4 Thermal parameters .............................................................................................. 49

24.5 Thermal time constant of the voice coil ................................................................. 50

24.6 Thermal bypass factor........................................................................................... 50

25 Time variance of the loudspeaker characteristics ........................................................... 50

25.1 Fatigue and load induced aging ............................................................................ 50

26 Measurement uncertainty .............................................................................................. 52

Annex A (informative) Practical application guide ................................................................. 54

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– 4 – IEC 60268-22:2020 © IEC 2020

Bibliography .......................................................................................................................... 55

Figure 1 – Rated conditions used to describe the geometry and position of the radiator

in the coordinate system ....................................................................................................... 13

Figure 2 – Equivalent electrical network representing the electrical input impedance

using the LR2 model for the lossy inductance of an electro-dynamical transducer ................. 23

Figure 3 – Analogous lumped parameter network representing the electrical,

mechanical and acoustical elements at low frequencies ........................................................ 27

Figure 4 – Asymmetrical mass distribution function D (y,z ) in the mechanical system

M 0

of a microspeaker that shifts the centre of gravity away from the pivot point ......................... 34

Figure 5 – Equivalent electrical network of a transducer operated in a baffle

represented by pure mechanical elements and additional acoustical elements ...................... 38

Figure 6 – Equivalent electrical network representing the electrical input impedance of

a vented loudspeaker system ................................................................................................ 39

Figure 7 – Nonlinear force factor characteristic of an electro-dynamical transducer .............. 45

Table A.1 – Important characteristics and their application ................................................... 54

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IEC 60268-22:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOUND SYSTEM EQUIPMENT –
Part 22: Electrical and mechanical measurements on transducers
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60628-22 has been prepared by technical area 20: Analogue and

digital audio, of IEC technical committee 100: Audio, video and multimedia systems and

equipment.
The text of this International Standard is based on the following documents:
CDV Report on voting
100/3311/CDV 100/3424/RVC

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60268 series, published under the general title Sound system

equipment, can be found on the IEC website.
---------------------- Page: 7 ----------------------
– 6 – IEC 60268-22:2020 © IEC 2020

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

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of its contents. Users should therefore print this document using a colour printer.

---------------------- Page: 8 ----------------------
IEC 60268-22:2020 © IEC 2020 – 7 –
INTRODUCTION

Measurements of the electrical and mechanical state variables have become increasingly

important for the following reasons:
• Maximum sound pressure output is limited by voice coil heating and transducer

nonlinearities. The large signal behaviour of loudspeakers can be described by nonlinear

and thermal models using lumped parameters. These physical characteristics are important

for transducer design and system integration.

• Mechanical vibration of the diaphragm determines the radiated sound. The modal vibration

of the radiator's surface can be predicted by numerical simulations (FEA) and directly

measured by laser vibrometry. This data represents important transducer characteristics

that can be used to design the desired directivity into the system's acoustical output.

• DSP plays an important role in active systems. Digital pre-processing of the audio stream

requires reliable transducer property information to protect the transducer against thermal

and mechanical overload and to actively compensate for linear and nonlinear distortion

generated in the output signal.
---------------------- Page: 9 ----------------------
– 8 – IEC 60268-22:2020 © IEC 2020
SOUND SYSTEM EQUIPMENT –
Part 22: Electrical and mechanical measurements on transducers
1 Scope

This part of IEC 60268 applies to transducers converting an electrical input signal into a

mechanical or acoustical output signal. However, if the electrical input terminals and the surface

of the radiator are accessible, this document can also apply to passive and active sound

systems such as loudspeakers, headphones, TV-sets, multi-media devices, personal portable

audio devices, automotive sound systems and professional equipment. This document

describes only electrical and mechanical measurements that help assess the transfer behaviour

of the device under test (DUT). This includes operating the DUT in both the small- and large-

signal domains. The influence of the target application's acoustical boundary conditions (e.g.

car interior) can also be considered in the physical evaluation of the sound system. Perception

and cognitive evaluations of the reproduced sound and the impact of perceived sound quality

are outside the scope of this document.

NOTE This document does not apply to microphones and other sensors. Implementation of this document does not

require access to the sound pressures generated in the near or far fields of the radiator. Directivity and other

characteristics describing the electro-acoustical transfer properties are described in IEC 60268-21, which covers

acoustical measurements.The practical application of the measurements for research and development (R&D), end-

of-line testing (QC) and evaluation in the final target application (TA) is discussed in Annex A.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.

IEC 60263:1982, Scales and sizes for plotting frequency characteristics and polar diagrams

IEC 60268-1:1985, Sound system equipment – Part 1: General

IEC 60268-2:1987, Sound system equipment – Part 2: Explanation of general terms and

calculation methods

IEC 60268-11:1987, Sound system equipment – Part 11: Application of connectors for the

interconnection of sound system components

IEC 60268-12:1987, Sound system equipment – Part 12: Application of connectors for

broadcast and similar use
IEC 60268-12:1987/AMD1:1991
IEC 60268-21:2018, Sound system equipment – Part 21: Acoustical (output-based)
measurements

IEC 62458:2010, Sound system equipment – Electroacoustical transducers – Measurement of

large signal parameters

IEC 62459:2010, Sound system equipment – Electroacoustical transducers – Measurement of

suspension parts
---------------------- Page: 10 ----------------------
IEC 60268-22:2020 © IEC 2020 – 9 –
ISO 3:1973, Preferred numbers – Series of preferred numbers
ISO/IEC GUM:1995, Guide to the expression of uncertainty in measurement (GUM)
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
linear behaviour

behaviour of the DUT at small amplitudes where the relationship between input and output

signal can be modelled by a linear system and described by a linear transfer function

3.1.2
reference unit

DUT having measured properties representative of units in the sample lot passing the end-of-

line test
3.2 Abbreviated terms
DUT device under test
SPL sound pressure level
FEA finite element analysis
FT Fourier transform
4 Type description

The type description shall be provided by the manufacturer, including the following information:

• transduction principle (e.g. electro-dynamical, capacitive, electro-magnetic transducer);

• system description including operation principle (e.g. the number of the transducers used in

the loudspeaker system;

• acoustical loading (e.g. horn loading and enclosure types, such as bass reflex, column, line

array, ...);

• power amplification (e.g. maximum output power, class type, minimum load impedance, …);

• DSP processing (e.g. equalizer, active protection), if any.
5 Marking of terminals and controls
The terminals and controls shall be marked in accordance wi
...

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