This part applies to sound system loudspeakers, treated entirely as passive elements. Loudspeakers with built-in amplifiers are excluded.
Note 1: The term “loudspeaker” used in this part relates to loudspeaker drive units themselves and also to loudspeaker systems, which comprise one or more loudspeaker drive units provided with a baffle, enclosure or horn and such relevant devices as built-in crossover filters, transformers and any other passive element.
The purpose of this part is to give the characteristics to be specified and the relevant methods of measurement for loudspeakers using sinusoidal or specified noise or impulsive signals.
Note 2: The methods of measurement given in this part have been chosen for their appropriateness to the characteristics.
Note 3: If equivalent results can be obtained using other methods of measurement, details of the methods used should be presented with the results.
Note 4: The following items are under consideration:
— loudspeakers with built-in amplifiers;
— measurements under conditions other than free-field, half-space free-field and diffuse field;
— measurements with signals other than sinusoidal or noise or impulsive signals.
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.
GB/T 3767 Acoustics — Determination of Sound Power Levels of Noise Sources Using Sound Pressure — Engineering Method in an Essentially Free Field over a Reflecting Plane (GB/T 3767-1996, eqv ISO 3744:1994)
GB/T 3769 Electroacoustics — Scales and Sizes for Plotting Frequency Characteristic and Polar Diagrams (GB/T 3769-2010, IEC 60263:1982, IDT)
GB/T 6881.1 Acoustics — Determination of Sound Power Levels of Noise Sources Using Sound Pressure — Precision Methods for Reverberation Rooms (GB/T 6881.1-2002, ISO 3741:1999, IDT)
GB/T 6882 Acoustics — Determination of Sound Power Levels of Noise Sources Using Pressure — Precision Methods for Anechoic and Hemi-Anechoic Rooms (GB/T 6882-2008, ISO 3745:2003, IDT)
GB/T 12060.2-2011 Sound System Equipment — Part 2: Explanation of General Terms and Calculation Methods (IEC 60268-2:1987, IDT)
GB/T 12060.3-2011 Sound System Equipment — Part 3: Methods of Measurement on Audio Amplifiers (IEC 60268-3:2000, IDT)
GB/T 15212 Application of Connectors for Broadcast and Similar Sound System (GB/T 15212-1994, eqv IEC 60268-12:1987)
SJ/Z 9140.1 Sound System Equipment — Part 1: General (SJ/Z 9140.1-1987, idt IEC 268-1:1985)
IEC 60050(151) International Electrotechnical Vocabulary — Part 151: Electrical and Magnetic Devices
IEC 60268-14 Sound System Equipment — Part 14: Circular and Elliptical Loudspeakers — Outer Frame Diameters and Mounting Dimensions
IEC 60268-11:1987 Application of Connectors for the Interconnection of Sound System Components
3 Conditions for Measurement
3.1 General Conditions
This standard is to be used in conjunction with SJ/Z 9140.1, GB/T 12060.2-2011 and GB/T 6881.1.
3.2 Measuring Conditions
3.2.1 General
For convenience in specifying how loudspeakers are to be set up for measurement, normal measuring conditions are defined in this part. To obtain the correct conditions for measurement, some values (known as “rated conditions”) shall be taken from the manufacturer's specification. These values themselves are not subject to measurement but they constitute the basis for measuring the other characteristics.
Foreword V 1 Scope 2 Normative References 3 Conditions for Measurement 3.1 General Conditions 3.2 Measuring Conditions 4 Test Signals 4.1 General 4.2 Sinusoidal Signal 4.3 Broadband Noise Signal 4.4 Narrow-band Noise Signal 4.5 Impulsive Signal 5 Acoustical Environment 5.1 General 5.2 Free-field Conditions 5.3 Half-space Free-field Conditions 5.4 Diffuse Sound Field Conditions 5.5 Simulated Free-field Conditions 5.6 Half-space Simulated Free-field Conditions 6 Unwanted Acoustical and Electrical Noise 7 Positioning of Loudspeaker and Measuring Microphone 7.1 Measuring Distance Under Free-field and Half-space Free-field Conditions 7.2 Positioning of Loudspeaker in Diffuse Field Conditions 7.3 Positioning of Loudspeaker and Microphone in Simulated Free-field Conditions 8 Measuring Equipment 9 Accuracy of the Acoustical Measurement 10 Mounting of Loudspeakers 10.1 Mounting and Acoustic Loading of Drive Units 10.2 Mounting and Acoustic Loading of a Loudspeaker System 11 Standard Baffle and Measuring Enclosures 11.1 Standard Baffle 11.2 Standard Measuring Enclosures 12 Preconditioning 13 Type Description 13.1 General 13.2 Loudspeaker Drive Units 13.3 Loudspeaker System 14 Marking of Terminals and Controls 14.1 General 14.2 Positive Terminal 15 Reference Plane, Reference Point and Reference Axis 15.1 Reference Plane — Characteristic to be Specified 15.2 Reference Point — Characteristic to be Specified 15.3 Reference Axis — Characteristic to be Specified 16 Impedance and Derivative Characteristics 16.1 Rated Impedance — Characteristic to be Specified 16.2 Impedance Curve 16.3 Total Q-factor (Qt) 16.4 Equivalent Air Volume of a Loudspeaker Drive Unit Compliance (Vas) 17 Input Voltage 17.1 Rated Noise Voltage 17.2 Short-term Maximum Input Voltage 17.3 Long-term Maximum Input Voltage 17.4 Rated Sinusoidal Voltage 18 Input Electrical Power 18.1 Rated Noise Power — Characteristic to be Specified 18.2 Short-term Maximum Power — Characteristic to be Specified 18.3 Long-term Maximum Power — Characteristic to be Specified 18.4 Rated Sinusoidal Power — Characteristic to be Specified 19 Frequency Characteristics 19.1 Rated Frequency Range — Characteristic to be Specified 19.2 Resonance Frequency 19.3 Tuning Frequency of a Bass Reflex or Passive Radiator Loudspeaker System — Characteristic to be Specified 20 Sound Pressure under Free-field and Half-space Free-field Conditions 20.1 Sound Pressure in a Stated Frequency Band 20.2 Sound Pressure Level in a Stated Frequency Band — Characteristic to be Specified 20.3 Characteristic Sensitivity in a Stated Frequency Band 20.4 Characteristic Sensitivity Level in a Stated Frequency Band — Characteristic to be Specified 20.5 Mean Sound Pressure in a Stated Frequency Band 20.6 Mean Sound Pressure Level in a Stated Frequency Band — Characteristic to be Specified 21 Response under Free-field and Half-space Free-field Conditions 21.1 Frequency Response 21.2 Effective Frequency Range 21.3 Transfer Function 22 Output Power (Acoustic Power) 22.1 Acoustic Power in a Frequency Band 22.2 Mean Acoustic Power in a Frequency Band 22.3 Efficiency in a Frequency Band 22.4 Mean efficiency in a Frequency Band 23 Directional Characteristics 23.1 Directional Response Pattern 23.2 Radiation Angle 23.3 Directivity Index 23.4 Coverage Angle or Angles 24 Amplitude Non-linearity 24.1 Total Harmonic Distortion 24.2 Harmonic Distortion of the nth Order (where n = 2 or n = 3) 24.3 Characteristic Harmonic Distortion 24.4 Modulation Distortion of the nth Order (where n = 2 or n = 3) 24.5 Characteristic Modulation Distortion of the nth Order (where n = 2 or n = 3) 24.6 Difference Frequency Distortion (of the second order only) 25 Rated Ambient Conditions 25.1 Temperature Ranges 25.2 Humidity Ranges 26 Stray Magnetic Fields 26.1 Static Components 26.2 Dynamic Components 27 Physical Characteristics 27.1 Dimensions 27.2 Mass 27.3 Cable Assemblies 28 Design Data 29 Indication of the Characteristics to be Specified Annex A (Informative) Standard Measuring Enclosure Type A Annex B (Informative) Standard Measuring Enclosure Type B Annex C (Informative) Definitions of Terms Used in Clause 13 Annex D (Informative) Listening Tests Bibliography Figure 1 Impedance Curve of Loudspeaker Figure 2 Standard Baffle, Dimensions Figure 3 Standard Baffle with Chamfer Figure 4 Standard Baffle with Sub-baffle Figure 5 Standard Measuring Enclosure Type A Figure 6 Standard Measuring Enclosure Type B Figure 7 Block Diagram of Test Set-up Figure 8 Measuring Apparatus for Stray Magnetic Field Figure A.1 An Example of Standard Measuring Enclosure Type A Figure A.2 The Correction Curve for the Diffraction Effect of the Standard Measuring Enclosure from Free-field to Half-space Free-field (average of results, loudspeakers’ diameter = 30 cm, 38 cm, 46 cm) Figure A.3 The Correction Curve for the Diffraction Effect of the Standard Measuring Enclosure from Free-field to Half-space Free-field (average of results, loudspeakers’ diameter = 6 cm, 10 cm, 20 cm) Figure B.1 An Example of Standard Measuring Enclosure Type B Figure B.2 Construction of Scalable Measuring Enclosure Type B Figure B.3 The Correction Curve for the Diffraction Effect of the Standard Measuring Enclosure from Free-field to Half-space Free-field (average of results, loudspeakers’ diameter = 30 cm, 38 cm, 46 cm) Figure B.4 The Correction Curve for the Diffraction Effect of the Standard Measuring Enclosure from Free-field to Half-space Free-field (average of results, loudspeaker diameter = 6 cm, 10 cm, 20 cm) Table 1 Indication of the Characteristics to be Specified Table B.1 Dimensions and Ratios of Scalable Enclosure Type B
