BS 5942-7-1987 High fidelity audio equipment and systems minimum performance requirements - Specification for loudspeakers《高保真度音频设备及系统最低性能要求 第7部分 扬声器规范》.pdf

1、BRITISH STANDARD BS5942-7: 1987 IEC581-7: 1986 High fidelity audio equipment and systems; minimum performance requirements Part7: Specification for loudspeakers UDC 621.396+681.84187.4:621.396.623.7BS5942-7:1987 This BritishStandard, having been prepared under the directionof the Electronic Equipmen

2、t Standards Committee,was published underthe authority of the Board ofBSI and comes into effect on 31July1987 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference EEL/32 Draft for comment84/28450DC ISBN 0 580 16066 1 Committees responsible for this Britis

3、hStandard The preparation of this BritishStandard was entrusted by the Electronic Equipment Standards Committee (EEL/-) to Technical Committee EEL/32, upon which the following bodies were represented: Association of British Theatre Technicians Association of Sound and Communications Engineers Limite

4、d Audio Engineering Society British Educational Equipment Association British Kinematograph, Sound and Television Society British Radio and Electronic Equipment Manufacturers Association British Telecommunications plc Cable Television Association of Great Britain Consumer Standards Advisory Committe

5、e of BSI Consumers Association Federation of British Audio Independent Television Companies Association Institution of Electronic and Radio Engineers Radio Electrical and Television Retailers Association Royal Institute of British Architects Royal National Institute for the Deaf Society of Cable Tel

6、evision Engineers Training and Educational Systems Testing Bureau Amendments issued since publication Amd. No. Date of issue CommentsBS5942-7:1987 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii 1 Scope 1 2 Object 1 3 Measuring conditions 1 4 Minimum requir

7、ements 2 5 Basic characteristics on which the specifications depend 2 5.1 Characteristic power 2 5.2 Mean characteristic sound pressure level 2 Section 1. Minimum requirements for characteristics directly related to the reproducing quality 6 Frequency response 3 7 Effective frequency range 4 8 Direc

8、tional response 4 9 Difference of amplitude/frequency response (for stereophonic loudspeaker systems) 5 10 Characteristic total harmonic distortion 5 11 Impedance 5 Section 2. Other characteristics and requirements 12 Short-term maximum input voltage/power 6 13 Long-term maximum input voltage/power

9、6 14 Interconnection 6 15 Characteristics to be specified 6 16 Instructions for loudspeaker kits 7 Figure 1 1 Figure 2 4 Publications referred to Inside back coverBS5942-7:1987 ii BSI 11-1999 National foreword This Part of BS5942 has been prepared under the direction of the Electronic Equipment Stan

10、dards Committee. It is identical with IEC581-7:1986 “High fidelity audio equipment and systems; minimum performance requirements Part7: Loudspeakers”, published by the International Electrotechnical Commission (IEC). BS5942 consists of the following Parts: Part 1:1980 Specification for general requi

11、rements; Part 2:1987 Specification for FM radio tuners; Part 3:1980 Specification for record playing equipment and cartridges; Part 4:1981 Specification for magnetic recording and reproducing equipment; Part 5:1983 Specification for microphones; Part 6:1980 Specification for amplifiers; Part 7:1987

12、Specification for loudspeakers; Part 8:1987 Specification for combination equipment; Part 9: Specification for magnetic sound tape; 1) Part 10: Specification for headphones; 2) Part 11: Specification for high fidelity systems for use in vehicles. 1) Terminology and conventions. The text of the Inter

13、national Standard has been approved as suitable for publication as a BritishStandard without deviation. Some terminology and certain conventions are not identical with those used in BritishStandards. NOTEBS5428 will be superseded by BS6840 “Sound system equipment”. All new parts of IEC268 will be im

14、plemented under BS6840 and all existing parts will be brought under BS6840 when they are revised, amended or otherwise reviewed. 1) In preparation. 2) Awaiting revision of IEC581-10. Cross-references International Standard Corresponding BritishStandard BS5428 Methods for specifying and measuring the

15、 characteristics of sound system equipment IEC268-5:1972 a Part11:1977 Loudspeakers (Identical) IEC268-11:1981 b Section5.1:1981 Dimensional characteristics of single moving-coil (dynamic) loudspeakers (Technically equivalent) IEC268-15:1978 a Part10:1979 Preferred matching values for the interconne

16、ction of sound system components (Identical) BS5942 High fidelity audio equipment and systems; minimum performance requirements IEC581-1:1980 Part1:1980 Specification for general requirements (Identical) IEC581-8:1986 Part8:1987 Specification for combination equipment (Identical) a Under revision. b

17、 IEC268-11:1981 superseded IEC268-14 First Supplement:1973 but as it is identical in technical content no action was taken to amend BS5428-5.1:1981.BS5942-7:1987 BSI 11-1999 iii A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are

18、responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi toiv, pages1to8, an inside back cover and a back cover. This standard has bee

19、n updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS5942-7:1987 BSI 11-1999 1 1 Scope This part applies to loudspeakers and loudspeaker systems which are provided with a baffle or enclosure. It als

20、o applies to systems intended to be assembled by the user (so-called “loud-speaker kits”) provided that the instructions for assembly meet certain requirements (see Clause16). The minimum requirements of this part then apply to the complete device, together with the baffle or enclosure. This part is

21、 not applicable to loudspeakers and loudspeaker systems comprising active components. For the combination of loudspeakers and amplifiers reference is made to IEC Publication581-8: High Fidelity Audio Equipment and Systems; Minimum Performance Requirements, Part8: Combination Equipment. This standard

22、 is not applicable to unmounted loudspeaker units. 2 Object While currently available techniques for objective measurements do not allow complete assessment of the quality of reproduction from loudspeakers, nevertheless, objective measurements can provide essential information about the performance

23、quality. The object of this standard is to give the minimum performance requirements and methods of measurement for loudspeakers and loudspeaker systems having regard to the above constraints. 3 Measuring conditions All measurements shall be made in accordance with the general measuring conditions s

24、tated in IECPublication581-1: High Fidelity Audio Equipment and Systems; Minimum Performance Requirements, Part1: General, and with the conditions of measurement given in IEC Publication268-5: Sound System Equipment, Part5: Loudspeakers. (Under revision.) NOTEIt should be borne in mind that the accu

25、racy of acoustic measurements at low frequencies is severely reduced by the limited size of available anechoic and reverberant rooms, and the numerous sources of error which affect measurements in the open air. According to the clause of IEC Publication268-5 “Accuracy of acoustic measurements”, the

26、frequency range over which the total errors do not exceed 2dB shall be stated. 3.1 Measurements shall be made with% octave band filtered pink noise, unless otherwise stated, and shall be referred to a distance of1m. The longer axis of a loudspeaker system is considered to be the vertical axis, unles

27、s otherwise stated by the manufacturer. 3.2 Owing to the existence of many types of loudspeakers with different acoustical properties and intended for different acoustical environments, it is not possible to specify a single standard acoustical environment in which the tests are to be carried out. T

28、he manufacturer shall therefore specify this environment, selecting from the following: a) Free field, according to the provision of IEC Publication268-5 “Free field conditions” for loudspeakers intended for free-standing. b) Half space, for which methods of measurement are under consideration for l

29、oudspeakers intended for wall or shelf mounting. Pending the completion of the studies, the spatial relationship between the auxiliary baffle and the loudspeaker enclosure shall be in accordance with Figure 1 (flush mounting), while the size of the auxiliary baffle shall be5.5mm 5.5m minimum(“ wavel

30、ength at30Hz). NOTEFor production control purposes, manufacturers may use a measuring environment differing from that specified in Items a) or b) of Sub-clause3.2. It is the manufacturers responsibility to establish a reliable correlation between measurements made in the specified environment and th

31、at actually employed. 3.3 Measurement in reverberant conditions and the relevant performance specifications are under consideration. Figure 1 BS5942-7:1987 2 BSI 11-1999 4 Minimum requirements The minimum requirements given in Clauses6 to16 apply to specifications in half space as well as to specifi

32、cations in free field. 5 Basic characteristics on which the specifications depend 5.1 Characteristic power This is the power that produces a characteristic sound pressure level according to the provision of IEC Publication268-5 “Sound pressure level in a stated frequency band” of94dB at a distance o

33、f1m using a fixed frequency range of100Hz to8000Hz. The rated value is the value stated by the manufacturer. 5.1.1 Method of measurement According to the clause of IEC Publication268-5 “Sound pressure in a stated frequency band” but using a fixed frequency range of100Hz and8000Hz, these being the mi

34、d-band frequencies f m(geometrical means between the upper and lower limiting frequencies) of the corresponding% octave bands. NOTEThe characteristic power should be considered in relation to the rated power of the amplifier, to ensure that sufficient sound pressure level can be achieved. The sound

35、pressure level to be regarded as sufficient cannot be standardized and can only be determined by the user in terms of the required loudness of reproduction. 5.2 Mean characteristic sound pressure level 5.2.1 Method of measurement According to the clause of IEC Publication268-5 “Mean sound pressure i

36、n a stated frequency band”, but using a fixed frequency range of100Hz to8000Hz,100Hz and8000Hz being the centre frequencies of the corresponding% octave bands. The mean characteristic sound pressure level (s.p.l.) can be calculated from the relation: meancharacteristic s.p.l.= If the mean characteri

37、stic sound pressure level is determined at an input power of1W in each% octave band the characteristic power of Sub-clause5.1 can be calculated from the relation: P ch =10 x NOTEThis conversion formula assumes that the sensitivity of the loudspeaker does not change over the input power range from1W

38、to the characteristic power. Since in some cases this assumption may not be justified a check should be made, that, when the characteristic power is applied, the required sound pressure level of94dB is in fact obtained. If this is not obtained an appropriate correction to the calculated value of the

39、 characteristic power is necessary. where: p o = standard reference sound pressure(204Pa) p m = mean characteristic sound pressure where: p i = characteristic sound pressure level in the ith% octave band n = total number of bands here, n = 20due to the limitation of the frequency range to100Hz to800

40、0Hz 201g p m p o - where: x = P ch = characteristic power, watt L(p m ) = mean characteristic sound pressure level determined with an input power of1W in each% octave band 94Lp m () 10 -BS5942-7:1987 BSI 11-1999 3 Section 1. Minimum requirements for characteristics directly related to the reproducin

41、g quality Clause Characteristic Method of measurement Minimum requirement 6 Frequency response According to the clause of IECPublication268-5 “Frequency response”, using narrow-band noise The measurement shall be carried out under free field conditions for both types of loudspeaker referred to in Su

42、b-clause3.2 of this standard. For wall or shelf mounting loudspeakers the measurement shall also be carried out under the half space conditions given in Item b) of Sub-clause3.2 The resulting curve and that from the free field measurement shall then be superimposed so that they coincide at a frequen

43、cy given by where a is the smaller dimension of the frontal area of the enclosure in metres The composite curve, formed by the half-space response at low frequencies and the free field curve at higher frequencies shall then be taken as the frequency response for determining the compliance with the m

44、inimum requirements of this clause NOTE 1This procedure is adopted pending the completion of the studies on this subject NOTE 2If the measurement is carried out with an input power of1W in each% octave band the resulting mean characteristic sound pressure level can be used to calculate the character

45、istic power of Subclause5.1 according to the method given in Sub-clause5.2.1 From50Hz to12500Hz mid-band frequencies (mean frequencies in each% octave band), within the tolerances defined by the diagram of Figure 2, page4, in which the0dB line is the mean characteristic sound pressure level of the m

46、easured frequency response curve between100Hz and8000Hz (seeSub-clause5.2 of this standard) f 360 a -Hz =BS5942-7:1987 4 BSI 11-1999 Clause Characteristic Method of measurement Minimum requirement 7 Effective frequency range According to the clause of IEC Publication268-5 “Effective frequency range”

47、, but related to the mean characteristic sound pressure level calculated between100Hz and8000Hz according to Sub-clause5.2 of this standard Frequency limits (in terms of the mean frequencies of the relevant third-octave bands) are given for the points where the amplitude/frequency curve intersects t

48、he abscissa8dB, both in the bass and treble registers (seeFigure2). If the claimed effective frequency range is wider than the minimum requirements of50Hz and12500Hz the tolerances of8dB and+4dB still apply Figure 2 8 Directional response According to the clause of IEC Publication268-5 “Directional

49、response pattern” (with frequency response curves at various angles from the reference axis) Frequency response curves shall be measured at stated angles from the reference axis of between20 and30 in a horizontal plane and between5 and10 in a vertical plane, on both sides of the reference axis in each case The curves shall fall within a tolerance field of 4dB referred to the curve measured on the reference axis (Clause6 of this standard) from250Hz to8000Hz. The curves shall be aligned so that