IEC PAS 62458:2006

PUBLICLY
IEC
AVAILABLE
PAS 62458
SPECIFICATION
First edition
Pre-Standard
2006-01
Sound system equipment –
Electroacoustical transducers –
Measurement of large signal parameters

Reference number
IEC/PAS 62458:2006(E)
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PUBLICLY
IEC
AVAILABLE
PAS 62458
SPECIFICATION
First edition
Pre-Standard
2006-01
Sound system equipment –
Electroacoustical transducers –
Measurement of large signal parameters

 IEC 2006  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
M
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – PAS 62458 © IEC:2006(E)
CONTENTS
FOREWORD.3

INTRODUCTION.4

1 Scope .5

2 Normative references .5

3 Terms and definitions.5

4 Test equipment.8

5 Test method .8

6 Test result .8
Annex A (informative) Additional information .11
Bibliography .13

PAS 62458 © IEC:2006(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
SOUND SYSTEM EQUIPMENT –
Electroacoustical transducers –

Measurement of large signal parameters

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
A PAS is a technical specification not fulfilling the requirements for a standard but made
available to the public.
IEC-PAS 62458 has been processed by IEC technical committee 100: Audio, video and
multimedia systems and equipment.
The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document:
Draft PAS Report on voting
100/991/NP 100/1058/RVN
Following publication of this PAS, which is a pre-standard publication, the technical committee
or subcommittee concerned will transform it into an International Standard.
This PAS shall remain valid for an initial maximum period of three years starting from
2006-02. The validity may be extended for a single three-year period, following which it shall
be revised to become another type of normative document or shall be withdrawn.

– 4 – PAS 62458 © IEC:2006(E)
INTRODUCTION
The behaviour of loudspeakers is traditionally described by parameters according to IEC

60268-5, assuming a linear behaviour. By adding parameters, derived from a non-linear

model, a more precise description can be made for design purposes and quality control in

order to get a more reproducible behaviour for the manufacturing of equipment.

The dominant non-linearities in electro-dynamical transducers are directly related to the

displacement x of the voice coil. The force factor, Bl()x , of the motor, the voice coil

inductance, L (x), and the stiffness, K(x), of the mechanical suspension are not constant but
e
vary significantly with the instantaneous displacement, x. This generates distortion and limits

the maximal output of the transducer. The measurement of harmonic and intermodulation
distortion according to IEC 60268-5 with special test stimulus only gives characteristic
symptoms of the non-linearities. The measurement of the non-linear parameters reveals the
physical cause of the dominant distortion directly. This information is not only important for
loudspeaker diagnostics but also for the synthesis of loudspeaker systems and the
development of electrical control systems dedicated to loudspeakers.

PAS 62458 © IEC:2006(E) – 5 –
SOUND SYSTEM EQUIPMENT –
Electroacoustical transducer –

Measurement of large signal parameters

1 Scope
This PAS applies to transducers such as loudspeakers, headphones, shakers, and other
actuators using either an electro-dynamical or electro-magnetic motor coupled with a

mechanical suspension. The measurement results are needed for engineering design

purposes and for quality control.

The measurement method provides the parameters of a non-linear large signal model (as
shown in Figure A.1) which describes the effect of the dominant non-linearities inherent in
those transducers. The basic terms and measurement conditions are defined for static and
dynamic methods.
2 Normative references
The following referenced documents are indispensable for the application 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 60268-5, Sound system equipment - Part 5: Loudspeakers
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
force factor, Bl(x)
coupling factor between the electrical and the mechanical side of the electro-dynamical
transducer describing the relationship between driving force
FB=×l()x i
(1)
and electrical input current i and back EMF
uB=×l()xv
(2)
EMF
and velocity v of the coil
3.2
electrical coil impedance, Z
e
ratio of the complex amplitudes of electrical voltage and current at the terminals for a small
sinusoidal excitation if the voice coil is mechanically clamped and no back EMF is generated
(u = 0). The electrical impedance also depends on the position x of the voice coil. The
EMF
electrical coil impedance, Z , may be approximated by a lumped parameter model (Figure 1)
e
using the d.c. resistance, R , the inductance, L (x), and additional shunted inductances, (R (x),
e e 2
L (x)), to model the electrical input impedance of the transducer at higher frequencies
– 6 – PAS 62458 © IEC:2006(E)
3.3
stiffness, K(x), of the suspension

stiffness describing the restoring force

(3)
FK= ()xx
R
of the suspension generated by a displacement x

3.4
compliance, C(x), of the suspension

reciprocal quantity, C(x ) = 1/K(x), of the mechanical stiffness, K(x)

3.5
maximal peak displacement, x
MAXd
deplacement which considers the distortion in the loudspeaker’s output signal. x is defined
MAXd
as the voice-coil peak displacement at which the maximum value of either the total harmonic
distortion, d or the second-order modulation distortion, d or the third-order modulation
t, 2,
distortion, d in the radiated sound pressure is equal to a defined threshold, d (used as
3,
subscript in x ).
MAXd
The driver is excited by the linear superposition of a first tone at the resonance frequency,
f = f and a second tone, f = 8,5 f with an amplitude ratio of 4:1. The total harmonic
1 s, 2 s,
distortion, d assesses the harmonics of f and the modulation distortions, d and d are
t, 1 2 3,
measured according to IEC 60268-5. It is recommended that the driver be operated in a baffle
(half-space) to measure the sound pressure in the near field and to use the threshold d = 10%
and to state x
MAX10.
3.5
force factor limited displacement, x
Bl
factor implicitly defined by the minimal force factor ratio
Bl()x
Bl ()x=×min 100%  (4)
min Bl 
− Bl Bl
Bl(0)

which is the ratio of the minimal value of the force factor, Bl(x), in the working range,
±x ,,referred to the Bl value at the rest position x = 0. After defining the threshold, Bl , the
Bl min
peak displacement, x can be found in the non-linear Bl(x)-characteristic
Bl,
3.6
inductance limited displacement, x
L
displacement implicitly defined by maximal variation of the electrical input impedance

Zx(,f )−Z (0,f )
ee22
Zx( )=×100 %
(5)
max
max L
Zf(0, )
− LL
at frequency f = 8,5 f (using the resonance frequency, f ) within the working range –x < x <
2 s s L
x referred to the impedance at the rest position x = 0
L
3.7
compliance limited displacement x
C
displacement implicitly defined by minimal compliance ratio
Cx()
(6)
Cx( )=×min 100%
min C 
− CC
C (0)

PAS 62458 © IEC:2006(E) – 7 –
which is the ratio of the minimal value of the force factor, C(x), in the working range ±x
C
referred to the C value at the rest position x = 0. After defining the threshold C the
min
displacement limit, x
...