1 Scope
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 3241 Electroacoustics — Octave-band and Fractional-octave-band Filters (GB/T 3241-2010, IEC 61260-1995, MOD)
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 3785.1 Electroacoustics — Sound Level Meters — Part 1: Specifications (GB/T 3785.1-2010, IEC 61672-1:2002, 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
