1、 IEC 62458 Edition 1.0 2010-01 INTERNATIONAL STANDARD Sound system equipment Electroacoustical transducers Measurement of large signal parameters IEC 62458:2010(E) colour inside THIS PUBLICATION IS COPYRIGHT PROTECTED Copyright 2010 IEC, Geneva, Switzerland All rights reserved. Unless otherwise spec
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9、 Electroacoustical transducers Measurement of large signal parameters INTERNATIONAL ELECTROTECHNICAL COMMISSION T ICS 33.160.50 PRICE CODE ISBN 2-8318-1074-4 Registered trademark of the International Electrotechnical Commission colour inside 2 62458 IEC:2010(E) CONTENTS FOREWORD.4 INTRODUCTION.6 1 S
10、cope.7 2 Normative references .7 3 Terms and definitions .7 4 Test signals9 4.1 General .9 4.2 Large d.c. signal9 4.3 Large d.c. signal and small a.c. signal.9 4.4 Broadband noise signal .9 4.5 Music 9 5 Mounting condition .10 5.1 Drive units.10 5.2 Loudspeaker systems10 6 Climatic conditions .10 7
11、Acoustical environment 10 8 Preconditioning 10 9 Time-varying properties of the loudspeaker 11 10 Methods of measurement .11 10.1 General .11 10.2 Static or quasi-static method .11 10.3 Point-by-point dynamic method .12 10.4 Full dynamic method .14 11 Nonlinear force factor .15 11.1 Force factor cur
12、ve Bl(x) .15 11.2 Force-factor limited displacement, X Bl .16 11.3 Symmetry point, x sym (x ac )17 11.4 Voice coil offset, x offset 18 12 Nonlinear stiffness18 12.1 Nonlinear stiffness curve K ms (x) 18 12.2 Compliance-limited displacement x C 19 12.3 Stiffness asymmetry A K (x peak )19 13 Displacem
13、ent-dependent inductance, L e (x).20 13.1 Inductance curve L e (x) 20 13.2 Inductance-limited displacement, x L 21 14 Current -dependent inductance, L e (i)21 14.1 Characteristic to be specified 21 14.2 Method of measurement21 15 Parameters derived from geometry and performance22 15.1 Maximal peak d
14、isplacement, x MAXd .22 15.2 Method of measurement22 Bibliography23 Figure 1 Electro-dynamical transducer.7 62458 IEC:2010(E) 3 Figure 2 Static and quasi-static measurement setup .12 Figure 3 Setup for measurement of large signal parameters by using the point-by- point dynamic method.13 Figure 4 Set
15、up for dynamic measurement of large signal parameters.14 Figure 5 Reading the maximal peak displacement x Blimited by force factor only .16 Figure 6 Reading the voice coil offset from the symmetry point x sym (x ac ) curve17 Figure 7 Definition of the symmetry point x symin the nonlinear force facto
16、r characteristic Bl(x) 18 Figure 8 Reading the stiffness asymmetry from the K ms (x) curve .20 4 62458 IEC:2010(E) INTERNATIONAL ELECTROTECHNICAL COMMISSION _ SOUND SYSTEM EQUIPMENT ELECTROACOUSTICAL TRANSDUCERS MEASUREMENT OF LARGE SIGNAL PARAMETERS FOREWORD 1) The International Electrotechnical Co
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26、ation 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 Public
27、ation may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62458 has been prepared by IEC technical committee 100: Audio, video and multimedia systems and equipment. This first edition cancels and replaces IE
28、C/PAS 62458 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 4 to 15; integration of Annex A in the main body of the standard; overall textual review.
29、 62458 IEC:2010(E) 5 The text of this standard is based on the following documents: FDIS Report on voting 100/1624/FDIS 100/1647/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 i
30、n 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 pub
31、lication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. A bilingual version of this publication may be issued at a later date. IMPORTANT The “colour inside” logo on the cover page of this publication indicates that it contains colours which are considered to be useful for
32、 the correct understanding of its contents. Users should therefore print this publication using a colour printer. 6 62458 IEC:2010(E) INTRODUCTION Electro-mechanical-acoustical transducers such as loudspeaker drive units, loudspeaker systems, headphones, micro-speakers, shakers, and other actuators
33、behave in a nonlinear manner at higher amplitudes. This limits the acoustical output and generates nonlinear signal distortion. Linear models fail in describing the large signal behaviour of such transducers and extended models have been developed which consider dominant nonlinearities in the motor
34、and suspension. The free parameters of the large signal model have to be measured on the particular transducer by using static or dynamic methods. The large signal parameters show the physical cause of the signal distortion directly and are very important for the objective assessment of sound qualit
35、y and failure diagnostics in development and manufacturing. Furthermore, the model and parameters identified for a particular transducer are the basis for predicting the maximum output and signal distortion for any input signal. The close relationship between causes and symptoms simplifies the inter
36、pretation of the harmonic and intermodulation distortion measured according to IEC 60268-5. Large signal parameters are valuable input data for the synthesis of loudspeaker systems and the development of electrical control systems dedicated to loudspeakers. 62458 IEC:2010(E) 7 SOUND SYSTEM EQUIPMENT
37、 ELECTROACOUSTICAL TRANSDUCERS MEASUREMENT OF LARGE SIGNAL PARAMETERS 1 Scope This International Standard applies to transducers such as loudspeaker drive units, loudspeaker systems, headphones, micro-speakers, shakers and other actuators using either an electro-dynamical or electro-magnetic motor c
38、oupled with a mechanical suspension. The large signal behaviour of the transducer is modelled by a lumped parameter model considering dominant nonlinearities such as force factor, stiffness and inductance as shown in Figure 1. The standard defines the basic terms and parameters of the model, the met
39、hods of measurements and the way the results should be reported. 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 docume
40、nt (including any amendments) applies. IEC 60268-1, Sound system equipment Part 1: General IEC 60268-5:2003, Sound system equipment Part 5: Loudspeakers Amendment 1 (2007) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 electro-mechanical equ
41、ivalent circuit electrical circuit of an electro-dynamical transducer, as shown in Figure 1 R e (T V ) L e (x, i) i i 3L 2 (x, i 3 ) i 2R 2 (x, i 2 ) u Bl(x) v Bl(x) Bl(x) i v F m C ms(x) M msR msZ loadIEC 2511/09 NOTE 1 This Figure shows an example of a lumped parameter model of an electro-dynamica
42、l transducer considering the dominant nonlinearities. NOTE 2 Other equivalent circuits can be applied. Contrary to the results of linear modelling some parameters of the lumped elements are not constant but depend on instantaneous state variables (such as displacement x, velocity v, current i). Figu
43、re 1 Electro-dynamical transducer 8 62458 IEC:2010(E) 3.2 input current and voltage i, u electrical state variables at the terminals of the transducer 3.3 displacement x deflection of the voice coil from the rest position 3.4 velocity v time derivative of displacement x 3.5 d.c. resistance R eelectr
44、ical impedance Z e (s) at very low frequencies where the effect of the back EMF can be neglected NOTE Electrical impedance can be used for measuring the d.c. resistance R eof the voice coil. The d.c. resistance R edepends on the mean voice coil temperature T V.3.6 nonlinear inductance and losses non
45、linear elements to model the effect of the magnetic a.c. field, the losses in the magnetic material, and the losses caused by eddy currents where the equivalent circuit in Figure 1 uses the LR-2 model comprising the inductance L e (x, i), the inductance L 2 (x, i 2 ) and additional resistance R 2 (x
46、 i 3 ) 3.7 nonlinear force factor Bl(x) dependency of instantaneous force factor Bl(x) on voice coil displacement x defined by the integral of magnetic flux density B versus the voice-coil conductor of length l NOTE The product of force factor Bl(x) and velocity v is the back EMF generated on the e
47、lectrical side in an equivalent circuit as shown in Figure 1. The product of force factor Bl(x) and input current i gives the electro- dynamical driving force of the mechanical system. 3.8 reluctance force F madditional electro-magnetic driving force caused by the displacement varying inductances L
48、e (x, i) and L 2 (x, i 2 ) 3.9 stiffness, K ms (x), of the suspension ratio between the instantaneous restoring force F(x) and the displacement x as given by () () x x F x K = ms(1) NOTE The nonlinear compliance C ms (x) = 1/K ms (x) is the reciprocal quantity of the mechanical stiffness. 62458 IEC:
49、2010(E) 9 3.10 mechanical mass M mstotal moving mass including the mass of the moving assembly and the reactive part of the air load on both sides of the diaphragm 3.11 mechanical resistance R msnon-electrical losses of the driver, due to suspension, turbulences and radiation 3.12 mechanical impedance Z loadmechanical impedance which may represent any additional load caused by mechanical elements (cone, panel) or acoustical elements (such as a vented enclo
