IEC 62459:2010

IEC 62459 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment – Electroacoustical transducers – Measurement of
suspension parts
Équipements pour systèmes électroacoustiques – Transducteurs
électroacoustiques – Mesurage des pièces de suspension

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IEC 62459 ®
Edition 1.0 2010-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Sound system equipment – Electroacoustical transducers – Measurement of

suspension parts
Équipements pour systèmes électroacoustiques – Transducteurs

électroacoustiques – Mesurage des pièces de suspension

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.160.50 ISBN 978-2-8322-1083-7

– 2 – IEC 62459:2010  IEC 2010
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Test conditions . 10
5 Clamping of the suspension part . 10
5.1 General . 10
5.2 Destructive measurement . 10
5.3 Non-destructive measurement . 10
5.4 Clamping position . 10
5.5 Guiding the inner clamping part . 11
5.6 Reporting the clamping condition. 11
6 Methods of measurement . 11
6.1 Static measurement. 11
6.2 Quasi-static measurement . 11
6.3 Incremental dynamic measurement . 11
6.4 Full dynamic measurement . 11
7 Static displacement x (F ) . 12
static dc
7.1 Characteristic to be specified . 12
7.2 Method of measurement . 12
7.2.1 General . 12
7.2.2 Test equipment . 12
7.2.3 Procedure . 12
7.2.4 Presentation of results . 13
8 Static stiffness K (x ) . 13
static static
8.1 Characteristic to be specified . 13
8.2 Method of measurement . 13
8.3 Presentation of results . 13
9 Lowest cone resonance frequency, f . 13
9.1 Characteristic to be specified . 13
9.2 Method of measurement . 14
9.2.1 General . 14
9.2.2 Test equipment . 14
9.2.3 Procedure . 14
9.2.4 Presentation of results . 15
10 Dynamic stiffness K(x ) . 15
ac
10.1 Characteristic to be specified . 15
10.2 Method of measurement . 15
10.2.1 General . 15
10.2.2 Test equipment . 15
10.2.3 Procedure . 16
10.2.4 Presentation of results . 17
11 Coefficients of the power series expansion of K(x) . 17
11.1 Characteristics to be specified . 17
11.2 Presentation of results . 17

12 Effective stiffness K (x ) . 17
eff peak
12.1 Characteristic to be specified . 17
12.2 Method of measurement . 17
12.3 Presentation of results . 18
13 Mechanical resistance R . 18
13.1 Characteristic to be specified . 18
13.2 Method of measurement . 18
13.3 Presentation of results . 18
Bibliography . 19

Figure 1 – Measurement of static displacement . 12
Figure 2 – Measurement of lowest cone resonance frequency f . 14
Figure 3 – Pneumatic excitation of the suspension part . 16
Figure 4 – Magnitude response of the normalized transfer function, H(f)/H(0), versus
frequency, f. 17

– 4 – IEC 62459:2010  IEC 2010
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOUND SYSTEM EQUIPMENT –
ELECTROACOUSTICAL TRANSDUCERS –
MEASUREMENT OF SUSPENSION PARTS

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-
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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
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
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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.
International Standard IEC 62459 has been prepared by IEC technical committee 100: Audio,
video and multimedia systems and equipment.
This first edition cancels and replaces the IEC/PAS 62459 published in 2006. It constitutes a
technical revision. The main changes are listed below:
– descriptions of the methods of measurement are adjusted to the state of the technology;
– addition of Clauses 5 to 13;
– integration of Annex A “Code of practice” at the main part of the standard;
– overall textual review.
The text of this standard is based on the following documents:
FDIS Report on voting
100/1625/FDIS 100/1648/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of November 2011 have been included in this copy.

IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – IEC 62459:2010  IEC 2010
INTRODUCTION
The properties of the suspension parts such as spiders and surrounds have a significant
influence on the final sound quality of the loudspeaker. This International Standard defines
measurement methods and parameters required for development and quality-assurance by
suspension-part manufacturers and loudspeaker manufacturers.
Static and dynamic methods have been developed for measuring the suspension parts at
small and high amplitudes. Due to the visco-elastic properties of the suspension material
(fabric, rubber, foam, paper) the measurement results depend on the measurement conditions
and are not comparable between different methods. For example, the properties measured by
static method significantly deviate from the dynamic behaviour of the suspension material
when excited by an audio signal. This standard defines the terminology, the characteristics
which should be specified and the way the results should be reported. The goal is to improve
the reproducibility of the measurement, to simplify the interpretation of the results and to
support the communication between manufacturers of suspension parts and complete drive
units.
SOUND SYSTEM EQUIPMENT –
ELECTROACOUSTICAL TRANSDUCERS –
MEASUREMENT OF SUSPENSION PARTS

1 Scope
This International Standard applies to the suspension parts of electroacoustic transducers (for
example, loudspeakers). It defines the parameters and measurement method to determine the
properties of suspension parts like spiders, surrounds, diaphragms or cones before being
assembled in the transducer. The measurement results are needed for engineering design
purposes and for quality control. Furthermore, this method is intended to improve the
correlation of measurements between suspension-part manufacturers and loudspeaker
manufacturers.
The measurement methods provide parameters based on linear and nonlinear modelling of
the suspension part and uses both static and dynamic techniques.
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 60268-1, Sound system equipment – Part 1: General
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
suspension part
surround of the cone made of rubber, foam, paper and fabric and the spider which is usually
made out of impregnated fabric
3.2
displacement
x
perpendicular direction at the inner rim of the suspension part
3.3
peak displacement
x
peak
peak value of the displacement occurring during a dynamic measurement at resonance
frequency
3.4
driving force
F
total effect of the restoring force, friction and inertia of both the suspension part and the inner
clamping parts at the neck of the suspension

– 8 – IEC 62459:2010  IEC 2010
3.5
transfer function
H(f)
amplitude response given by
(1)
X ()jω
Hf()=
Fj()ω
between the displacement spectrum X(jω) = FT{x(t)} and the force spectrum F(jω) = FT{F(t)}
3.6
dynamic stiffness
K(x )
ac
reciprocal of the dynamic compliance C(x ); it is the ratio of instantaneous force F to
ac ac
instantaneous displacement x for an a.c. excitation signal at point x , given by the
ac, ac
following equation
(2)
1 F
ac
Kx
( )
ac
Cx() x
ac ac
NOTE The dynamic stiffness K(x ) corresponds to the secant between origin and working point defined by x in
ac ac
the force-displacement curve.
3.7
incremental stiffness
K (x )
inc dc
reciprocal of the incremental compliance C (x ); it is the ratio of a small a.c. force F to the
inc dc ac
small a.c. displacement x produced by it at working point x under steady-state condition as
ac dc
given by the following equation
(3)
1 F
ac
Kx
( )
inc dc
Cx() x
inc dc ac
NOTE The incremental stiffness K (x ) corresponds to the gradient at the working point defined by x in the
inc dc dc
force-deflection curve.
3.8
static stiffness
K (x )
static dc
reciprocal of the static compliance C (x ); it is the ratio of a d.c. force F and the d.c.
static dc dc
displacement x produced by it at the working point x under steady-state condition; the
dc dc
static stiffness K (x ) corresponds to the secant between origin and working point in the
static dc
force-displacement curve, given by the following equation
(4)
1 F
dc
Kx
( )
static dc
Cx() x
static dc dc
3.9
moving mass
m
defined by
(5)
m δ mm+
sc
where
m is the mass of the suspension part,
s
m is the additional mass of the inner clamping parts,
c
δ is the clamping factor (with 0 < δ ≤ 1), describing the fraction of the suspension which
contributes to the moving mass.
=
==
==
==
NOTE If factor δ is not known, the moving mass is approximated by using the total weight of the suspension part
(δ = 1) and ensuring that the mass, m , of the inner clamping part dominates the moving mass, m (m >> m ).
c c s
3.10
resonance frequency
f
R
frequency of an a.c. displacement x at which the restoring force, F = K(x )x of the
ac K ac ac
suspension part equals the inertia of the moving mass, m, given by the following equation

(6)
d x
ac
F = K(x )x = m
K ac ac
dt
3.11
lowest cone resonance frequency
f
frequency at which the cone mass and suspension stiffness resonate
NOTE The lowest cone resonance frequency can be approximated by
(7)
1 Κ(x )
off
f ≈
2π δm
s
using the stiffness K(x ) at the offset x due to gravity, the clamping factor δ and the cone mass m .
off off s
3.12
effective stiffness
K
eff
stiffness given by
(8)
Kx( )2= π f m
( )
eff peak R
describing the conservative properties of the suspension part performing a vibration at the
, using the moving mass, m
resonance frequency, f
R
NOTE The effective stiffness, K (x ), or the reciprocal, compliance, C (x ) = 1/K (x ), are integral
eff peak eff peak eff peak
measures of the corresponding non-linear parameters, K(x) and C(x), in the working range used, defined by the
peak value, x . The effective parameters are directly related to the resonance frequency and may be measured
peak
with minimal equipment. However, the effective parameters can only be compared if the measurements are made
at the same peak displacement, x
peak.
3.13
loss factor
Q
factor estimated by the ratio
(9)
Hf()
R
Q=
Hf()
dc
between the magnitude of the transfer function, H(f ), at resonance frequency, f , and the
R R
magnitude of the transfer function, H(f ), at very low frequencies, f (with f << f ).
dc dc dc r
NOTE If the losses are sufficiently high (Q > 2), the transfer function, H(f), has a distinct maximum (peak) at the
resonance frequency, f .
R
3.14
mechanical resistance
R
given by
2π fm
(10)
R
R=
Q
– 10 – IEC 62459:2010  IEC 2010
where
m is the moving mass,
f is the resonance frequency,
R
Q is the Q-factor.
3.15
inner clamp dimension
D
i
diameter at the neck of the suspension part which is clamped by inner clamping parts (for
example, cone and cap)
3.16
outer clamp dimension
D
o
inner diameter of the outer rim of the suspension part which is clamped by the outer clamping
parts (for example, the upper and lower clamping rings)
4 Test conditions
The test should be made at 15 °C to 35 °C ambient temperature, preferably at 20 °C, 25 % to
75 % relative humidity and 86 kPa to 106 kPa air pressure, as specified in IEC 60268-1.
Prior to the measurement the suspension part under test should be stored under these
climatic conditions for 24 h.
5 Clamping of the suspension part
5.1 General
The suspension part should be clamped during the dynamic testing in a similar way as
mounted in the final loudspeaker.
5.2 Destructive measurement
In some cases, it may be convenient to use adhesive and original loudspeaker parts (voice
coil former, frame) for clamping.
5.3 Non-destructive measurement
However, non-destructive testing is preferred for comparing samples, storing reference units
and for simplifying communication between manufacturer and customer. Since tooling of
special clamping parts fitted to the particular geometry of the suspension is costly and time-
consuming, a more universal clamping system comprising a minimal number of basic
elements (for example, rings, caps and cones) may be preferred.
The moving mass, m, depends on the mass of the moving parts of the suspension, the air load
and the mass of the inner clamping parts. If the mass of the inner clamping part is much
higher than the mass of the suspension, the total moving mass, m, can be approximated by
the total weight of the suspension together with inner clamping parts, (δ = 1). In this case, the
mass of the clamped areas at the outer rim of the suspension and the influence of the air load
can be neglected.
5.4 Clamping position
A vertical position of the suspension part during measurement (displacement in horizontal
direction) is mandatory if the weight of the inner clamping parts or the weight of the
suspension part is not negligible. A horizontal position (displacement in vertical direction) may
cause an offset in cone displacement due to gravity, giving a higher stiffness value.

5.5 Guiding the inner clamping part
An additional guide for the inner clamping parts may be used to prevent eccentric deformation
or tilting of the suspension and to suppress other kinds of vibration (rocking modes).
5.6 Reporting the clamping condition
The clamping factor according 3.9 shall also be stated; if not, the default value, δ = 1, is used.
It is strongly recommended that the inner clamping dimension, D , and the outer clamping
i
dimension, D , as well as the geometry of the inner clamping parts be reported. The
o
orientation of the suspension part (which side of the suspension part is used as front and
back side in the measurement jig) should also be reported. The repeatability of the
measurement can be improved by using the same clamping parts and the same orientation of
the suspension.
6 Methods of measurement
6.1 Static measurement
This technique for measuring the static stiffness according to Equation (4) uses a d.c. signal
of certain magnitude (for example, a constant force F ) as stimulus and measures a d.c.
dc
response of the suspension part (for example, the displacement x ) under steady-state
dc
condition. The measurement time required to get a steady-state response depends on the
visco-elastic behaviour of the suspension material (creep) which is usually much longer than
.
the settling time for an a.c. signal corresponding to the resonance frequency f
R
6.2 Quasi-static measurement
This technique is similar to the static measurement as described in 6.1, using a relatively
short measurement time T. The ratio of d.c. force F and d.c. displacement x is the quasi-
T T
static stiffness K (x ) at the working point x . Since the suspension part has not reached
quasi T T
the final equilibrium the quasi-static stiffness is usually higher than the static stiffness
(K (x) > K (x)). Settling/reading time that has a great influence on the results shall be
quasi static
stated with the results.
6.3 Incremental dynamic measurement
This technique for measuring the incremental stiffness K (x ) according to Equation (3)
inc dc
uses a superposition of a d.c. signal of certain magnitude (for example, constant restoring
force F generating a d.c. position x ) and a small a.c. signal (e.g. restoring force F ) as
dc dc ac
stimulus and measures the a.c. response of the suspension part (e.g. the a.c. part of the
displacement x ) under steady-state condition. Neglecting the visco-elastic behaviour of the
ac
suspension material, the incremental stiffness, K (x ) can be transformed into the regular
inc i
stiffness K(x) by
x
(11)
K( x)= K ()x dx
inc
∫
x
6.4 Full dynamic measurement
) uses an a.c. signal of certain
This technique for measuring the dynamic stiffness K(x
ac
magnitude (for example, the a.c. restoring force F ) and measures the a.c. response of the
ac
suspension part (for example, a displacement x ).
ac
– 12 – IEC 62459:2010  IEC 2010
7 Static displacement x (F )
static dc
7.1 Characteristic to be specified
Static displacement x (F ) is the difference of the position of the inner clamping part
static dc
caused by d.c. force F under steady-state condition.
dc
7.2 Method of measurement
7.2.1 General
The static displacement can be measured by generating the d.c. force F by the weight of a
dc
known mass attached to the inner clamping part, as shown in Figure 1. This technique can
also be automated by using step motors with servo control to induce a displacement or force.

Outer clamping
Suspension
Inner clamping
Hanging
mass
IEC  2519/09
Figure 1 – Measurement of static displacement
7.2.2 Test equipment
The test equipment shall consist of:
• a fixture and associated elements to position the suspension part in the horizontal position
while performing a fixed clamping of the outer rim (for example using rings) as shown in
Figure 1;
• a cap or plug which fits to the neck of the suspension part and provides means for
inducing a defined force in the vertical direction. When using the ‘hanging mass method’
(see Figure 1), the cap shall provide a hook for holding an additional mass;
• means for generating a defined force in the vertical direction;
• a sensor for measuring the displacement of the suspension. An optical displacement
sensor (laser) is preferable to a mechanical or electrical sensor.
7.2.3 Procedure
The measurement is performed by the following steps:
a) the outer rim of the suspension part is clamped at the outer dimension, D , by using
o
the top and bottom clamp rings;
b) the cap is set on the neck of the suspension part;
c) the position x of the cap is measured;
init
d) a defined force is applied to the cap. The suspension part is checked for any abnormal
deformation such as creasing, cocking, corrugation inversion, if necessary the force is
reduced;
e) the displacement x is measured after a defined settling time (T = 5 s) to measure
mass
the static or quasi-static behaviour;
f) the difference x = x – x is calculated;
static mass init
g) the suspension part is flipped over and a second measurement with a deflection in the
other direction is performed while using a proper clamping part which considers the
shape of the suspension.
NOTE The Automated Induced Displacement Technique and the Hanging Mass Technique are described in
greater detail in [5] ).
7.2.4 Presentation of results
The results of the ‘hanging mass method’ shall be reported as displacement x for a given
static
attached mass, for example x = 5 mm with m = 50 g.
static
The results of an automated technique which performs a series of measurement where the
is changed, are preferably presented as a curve
magnitude and sign of the induced force F
dc
showing force versus displacement.
NOTE The static displacement x depends greatly on the measurement time T, the initial conditions and other
static
visco-elastic behaviour of the material (creep), causing a hysteresis in the force-displacement curve.
8 Static stiffness K (x )
static static
8.1 Characteristic to be specified
Static stiffness K (F ) is the ratio between static force F and static displacement x
static dc dc dc
under steady-state condition.
8.2 Method of measurement
The static displacement x is measured according to 7.2 and the static stiffness K is
dc static
calculated according to Equation (4).
Using the ‘hanging mass technique’, the static stiffness (see equation below)
(12)
gm
add
Kx =
( )
static dc
x
dc
is calculated by using the standard gravity constant g = 9,81 m/s and the known mass m
add
attached to the inner clamping part (such as m = 50 g).
add
NOTE There are usually significant differences between the static stiffness and the dynamic stiffness which
describes the behaviour of the suspension part with an audio signal.
8.3 Presentation of results
for a
The results of the ‘hanging mass method’ shall be reported as static stiffness K
static
given attached mass, for example K = 5 N/mm with m = 50 g.
static add
The results of the automated technique which performs a series of measurements where the
magnitude and sign of the induced force F is changed is preferably presented as a curve
dc
showing static stiffness K (x ) versus displacement x .
static dc dc
9 Lowest cone resonance frequency, f
9.1 Characteristic to be specified
The lowest cone resonance frequency f is the lowest resonance frequency of a loudspeaker
cone clamped at the outer rim (usually the surround) in the horizontal position, using no inner
—————————
Numbers in square brackets refer to the Bibliography.

– 14 – IEC 62459:2010  IEC 2010
clamping part. The lowest cone resonance frequency is defined as the frequency where the
transfer function H(f) according to Equation (1) has a distinct maximum (peak).
9.2 Method of measurement
9.2.1 General
The cone can be excited acoustically by using an additional loudspeaker mounted below the
cone, as illustrated in Figure 2. The resonance frequency can be measured dynamically by
using an acoustical excitation.
NOTE This technique is less suited to measure the stiffness K of the surround because the clamping factor δ is
not known. The lowest cone resonance f may depend on the amplitude of the excitation signal due to the
nonlinearity of the surround and could be interpreted as an effective parameter. The weight of the cone may also
cause offset x which generates a higher stiffness than found at the rest position x = 0.
off
9.2.2 Test equipment
The essential elements of test equipment needed are as follows:
• a sine wave generator and frequency counter;
• a power amplifier;
• a driving loudspeaker (usually a large woofer) for acoustical excitation of the cone, having
a free air resonance below one third of the resonance frequency of the cone to be tested.
The driving loudspeaker shall be mounted on a square solid plate parallel to the lower
clamp ring surface such that the face of the mounting plate is 0,09 to 0,1 m from the test
cone mounting surface. The area between the driving loudspeaker mounting plate and the
lower clamp ring shall be open on each side to prevent undesirable loading of the driving
loudspeaker. This amounts to testing within the driving loudspeaker’s unbaffled near field;
• an upper and a lower clamp ring to firmly clamp the cone;
• an optical or acoustical sensor for detecting the resonance of the clamped cone. Visual
detection is not recommended.
Displacement
sensor
Outer clamping
Cone
0,1 m
LoudsLoudspeakpeakerer
IEC  2520/09
Figure 2 – Measurement of lowest cone resonance frequency f
9.2.3 Procedure
Proceed as follows:
a) the test cone is placed between properly matched clamp rings;
b) the sinusoidal signal is supplied via the power amplifier to the loudspeaker;
c) the resonance frequency is measured where the maximum excursion of the cone
vibration is observed.
NOTE This technique is described in greater detail in reference [4].
9.2.4 Presentation of results
It is recommended to report the lowest resonance frequency f in Hz together with ambient
o
conditions (such as humidity and temperature).
10 Dynamic stiffness K(x )
ac
10.1 Characteristic to be specified
The dynamic stiffness K(x ) is the ratio of instantaneous force F and instantaneous
ac ac
displacement x for an a.c. excitation signal under steady-state.
ac
NOTE A full dynamic measurement of the linear and nonlinear parameters of the suspension part is required to
explain the behaviour of the suspension in the assembled loudspeaker excited by an audio signal.
10.2 Method of measurement
10.2.1 General
The suspension part is firmly clamped at the outer rim and the a.c. excitation force is induced
at the inner neck of the suspension. The suspension part should be in the vertical position
during measurement (producing a displacement in horizontal direction) to avoid any bias due
to weight. Those requirements can be realized by operating the suspension part at the
resonance frequency f determined by using the moving mass m and the dynamic stiffness K
R
according to Equation (6). It is recommended to excite the resonator by an a.c. sound
pressure signal generated by a loudspeaker mounted in an enclosure, as shown in Figure 3.
This technique can be applied to most kinds of suspensions (spiders and cones).
10.2.2 Test equipment
The acoustical excitation methods as shown in Figure 3 use the following elements:
a) means for generating a signal used as stimulus (for example, sine wave generator);
b) a power amplifier;
c) means for exciting the suspension part by the stimulus (for example, a loudspeaker
mounted in a sufficiently large test box for acoustical excitation, as shown in Figure 3);
d) outer clamping parts (for example, a pair of matched clamping rings to clamp the rim
of the suspension part);
e) inner clamping parts (for example, a cone and a cap) to apply the driving force at the
inner neck of the suspension similar to the final usage in the assembled loudspeaker;
f) means for ensuring a displacement in normal direction of the suspension part (for
example a guiding rod) to avoid any rocking modes of the suspension part at high
amplitudes. The friction of the inner clamping part on the guiding rod should be
sufficiently low by using an appropriate design (e.g. Teflon bearing on the sleeve and
polished surface of the rod) to get a resonator having a Q-factor > 2.
g) means for determining the displacement and force at the suspension part by
performing a direct (mechanical) or indirect (acoustical) measurement. If the
loudspeaker is excited acoustically, the driving force, F(t), may be calculated from the
sound pressure, p(t), measured inside the enclosure.
h) a precision balance.
– 16 – IEC 62459:2010  IEC 2010

Figure 3 – Pneumatic excitation of the suspension part
10.2.3 Procedure
Both the effective stiffness, K and the displacement varying stiffness, K(x), of the
eff,
suspension part are measured dynamically by performing the following steps:
a) the neck of the suspension part is clamped at the inner dimension, D , by using
i
inner clamping parts (for example, a cap and a cone);
b) the total mass of the suspension and inner clamping parts are measured by using
a precision balance;
c) the outer rim of the suspension part is clamped at the outer dimension, D by
o,
using top and bottom clamp rings. The cap is mounted on the upper side while the
cone is on the lower side. It is recommended that the upper side of the suspension
part which points to positive displacement is marked. The measurement of the
nonlinear stiffness K(x) requires a guiding rod for the inner clamping part;
d) the suspension part is excited (for example, pneumatically) by using a sinusoidal
sweep starting at f = 0,8 × f and ending at frequency f = 1,2 × f . During the
s R e R
sweep, the displacement, x(t), and the total driving force, F(t), at the suspension
part are measured versus time;
e) the transfer function, H(f) = X(f)/F(f), is calculated from the FFT displacement
spectrum, X(f) = FT{x(t)}, and force spectrum, F(f) = FT{F(t)};
NOTE The measurement of the driving force, F(t), may be omitted under certain conditions. If the
test enclosure used for acoustical excitation has a large volume and the acoustical compliance, C ,
ab
of the enclosed air is much larger than the equivalent acoustical compliance of the suspension part
under test, the driving force, F(jω), becomes almost constant and the transfer function, H(f) ≈ |X(jω)|,
can be approximated by the amplitude response of the measured displacement. Thus, the sound-
pressure measurement may be omitted for spiders and cones with sufficiently small diameter
operated in a large enclosure (D less than 200 mm for 100 l air volume).
o
f) The loss factor, Q, is determined by using Equation (9). If the loss factor Q > 2, the
resonance frequency, f , equals the frequency at which the transfer function, H(f),
R
has a distinct maximum as shown in Figure 4.
g) The non-linear stiffness, K(x), is calculated from the measured displacement time
signal, x(t), and force, F(t), by using a non-linear system identification technique
[6].
dB
Q
–10
–20
–30
10 20
Hz
f
R
Frequency
IEC  2522/09
Figure 4 – Magnitude response of the normalized
transfer function, H(f)/H(0), versus frequency, f
10.2.4 Presentation of results
The non-linear stiffness, K(x), may be reported preferably as a curve showing stiffness, K(x),
versus displacement, x. Positive displacement, x, corresponds to a deflection of the
suspension toward the side where the cap is clamped.
11 Coefficients of the power series expansion of K(x)
11.1 Characteristics to be specified
The coefficients k with i = 0, 1, …, N of the power series expansion of the dynamical stiffness,
i
defined by
N
(13)
i
.
K()x = kx
∑ i
i=0
11.2 Presentation of results
The dynamic stiffness is measured according to Clause 10. The coefficients k are reported
i
together with the maximal peak displacement x occurring during the dynamical
peak
measurement.
12 Ef
...