ANSI CTA-2031-2008 Testing and Measurement Methods for Mobile Loudspeaker Systems (Formerly ANSI CEA-2031).pdf

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1、 ANSI/CTA Standard Testing and Measurement Methods for Mobile Loudspeaker Systems ANSI/CTA-2031 R-2014 (Formerly ANSI/CEA-2031 R-2014) September 2008 NOTICE Consumer Technology Association (CTA) Standards, Bulletins and other technical publications are designed to serve the public interest through e

2、liminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting the purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards, Bulletins and other techn

3、ical publications shall not in any respect preclude any member or nonmember of the Consumer Technology Association from manufacturing or selling products not conforming to such Standards, Bulletins or other technical publications, nor shall the existence of such Standards, Bulletins and other techni

4、cal publications preclude their voluntary use by those other than Consumer Technology Association members, whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by the Consumer Technology Association in accordance

5、 with the American National Standards Institute (ANSI) patent policy. By such action, the Consumer Technology Association does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. This docu

6、ment does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this document to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its u

7、se. This document is copyrighted by the Consumer Technology Association and may not be reproduced, in whole or part, without written permission. Federal copyright law prohibits unauthorized reproduction of this document by any means. Organizations may obtain permission to reproduce a limited number

8、of copies by entering into a license agreement. Requests to reproduce text, data, charts, figures or other material should be made to the Consumer Technology Association. (Formulated under the cognizance of the CTA R6 Portable, Handheld and In-Vehicle Electronics Committee.) Published by CONSUMER TE

9、CHNOLOGY ASSOCIATION 2015 Technology Phone 800-854-7179; Fax 303-397-2740; Internet http:/; Email 2.2 Informative References The following documents contain information that is useful in understanding this standard. 2.2.1 Informative Reference List AES2-1984 (r2003), Specification of Loudspeaker Co

10、mponents Used in Professional Audio and Sound Reinforcement 12.2.2 Informative Reference Acquisition AES Standards: Audio Engineering Society, Inc., 60 East 42nd Street, Room 2520, New York, New York 10165-2520, USA; Tel: +1 212 661 8528; Fax: +1 212 682 0477; Internet: http:/www.aes.org 2.3 Acronym

11、s and Symbols Acoustic Wavelength DUT Device Under Test Fs DUT as resonance MLSSA Maximum-Length Sequence System Analyzer RCF Room Correction Factor RMS Root-Mean-Square RSDC Resistance RSRRated Impedance SPL Sound Pressure Level THD Total Harmonic Distortion Xmax Maximum Excursion 3 General Test Co

12、nditions CAUTION WEAR EAR PROTECTION! High sound levels can cause hearing damage with prolonged exposure. The operator is advised to wear appropriate protection such as ear plugs, preferably balanced attenuation devices which will still permit the operator to listen critically for distortion or othe

13、r signs of distress in the device under test. During testing the device under test (DUT) shall be operated as per manufacturers instructions. Complete systems shall be tested intact. For purposes of CEA-2031, the DUT shall include all elements of the loudspeaker system, such as any pre-loaded driver

14、s and/or passive systems, which are typically offered to the consumer as a single unit for acquisition. Testing shall be conducted at an ambient temperature of 25 C 5 C and relative humidity of 30% to 80%. If a crossover or filter network is specified by the manufacturer, it shall be installed accor

15、ding to the manufacturers instructions. All test equipment shall be properly calibrated, and its calibration shall be documented. 4 RMS Power Handling Testing Applicable tolerances shall be stated with all physical dimensions. 4.1 Measurements Measurements with random noise shall use equal energy pe

16、r percentage bandwidth (pink) noise. 4.2 High-Frequency Drivers 4.2.1 Power-Handling 4.2.1.1 Test Conditions and Equipment The DUT shall be tested in free air in accordance with the test procedures for power compression, distortion and accelerated life described in ANSI/CEA-426-B. 24.2.1.2 Displacem

17、ent Limit The manufacturer shall specify the maximum excursion (one-way or peak-to-peak) of the device that, when exceeded, results in permanent mechanical damage to the device. 4.2.1.3 Statistical Study The manufacturer shall assure sufficient statistical study of a given class of product to establ

18、ish a rated power. 4.3 Low-Frequency Drivers 4.3.1 Power-Handling 4.3.1.1 Test Conditions and Equipment The DUT shall be tested in free air in accordance with the test procedures for power compression, distortion and accelerated life described in ANSI/CEA-426-B. If it is desired to report a secondar

19、y rating that is based upon testing in a sealed enclosure then the above test may be repeated with the low frequency driver mounted in a manufacturer-recommended enclosure. 4.3.1.2 Displacement Limit The manufacturer shall specify the maximum excursion (one-way or peak-to-peak) of the device that, w

20、hen exceeded, results in permanent mechanical damage to the device. 4.3.1.3 Statistical Study The manufacturer shall assure sufficient statistical study of a given class of product to establish a rated power. 4.3.2 Enclosure Specifications The manufacturer shall specify for a given driver the recomm

21、ended enclosures or enclosure type. The manufacturer shall also note any differences in the rated power of a low frequency device if its performance in a given enclosure is significantly different from that observed with the unit mounted on the standard baffle to radiate into 2 steradians. 4.3.2.1 A

22、dditional Power-Handling Information If the rated power for a given low frequency driver/enclosure combination is different from that observed when the driver is mounted on the standard baffle to radiate into 2 steradians, the manufacturer shall so state. 5 Associated Amplifier Power Loudspeaker rat

23、ings obtained using this standard shall be specified for a specific amplifier power measured in accordance with CEA-2006-A. 6 Sensitivity For subwoofers, a calibrated microphone shall be used to perform a near field measurement of the sound pressure level (SPL) of the DUT when the DUT is operating w

24、ith one Watt of input power at the center of its published operational bandwidth, or 50 Hz. (See 9.2 for an explanation of near field measurements.) For all speakers other than subwoofers, a calibrated microphone shall be used to measure the SPL of the DUT at one meter when the DUT is operating with

25、 one Watt of input power referenced to an appropriate voltage level at the nominal impedance (see section 7) at the center of its published operational bandwidth. 37 Nominal Impedance, Zmin, Range The rated impedance, RSR, of the DUT shall be 1.15 times the DC resistance, RS, of the voice coil, meas

26、ured at the terminals, at 25C. If the loudspeaker requires a different multiplier, the loudspeaker manufacturer shall state both RSRand RS for the specific DUT. The voltage to be applied to the speaker shall be calculated using RSR. Test voltage shall be equal to the square root of the product of th

27、e optimum amplifier power and RSR, of the DUT. 8 Speaker Size Speaker size shall be defined by the following dimensions: Tweeter protrusion from surface (cm/in.) Surround clearance at maximum excursion (cm/in.) Cutout diameter (cm/in.) Mounting flange width (cm/in.) Cone diameter, i.e., side-to-side

28、 dimension at half way point of the surround (cm/in.) Cone area, calculated from cone diameter (cm2/in.2) Magnet diameter (cm/in.) Mounting depth (cm/in.) Screw pitch (cm/in.) Speakers with rectangular/square mounting flanges shall be identified as “square” or “rectangular.” When only one value is r

29、eported for a diameter or width dimension that value shall indicate the width of a square, or the diameter of a circle, as appropriate. For oblong shapes two dimensions shall be reported with the shortest dimension reported first, followed by the longest dimension. Figure 1 illustrates the various s

30、peaker dimensions. Figure 1: Speaker dimensions profile drawing cone diameter magnet diameter cutout diameter mounting flange width tweeter protrusion surround clearance at maximum excursion mounting depth 4screw pitch Figure 2: Speaker dimensions top view If a speaker has optional accessories inclu

31、ded that will make it suitable for alternative cutout sizes, mounting depths, screw pitches, etc., this shall be disclosed to the consumer in the form of a secondary speaker size. 9 Frequency Response 9.1 Free-Field Measurements All free field frequency response measurements shall be made such that

32、the measurement distance from the acoustic center of the device is large with respect to: a) the largest dimension of the radiator, and b) the square of the largest dimension of the radiator divided by the wavelength of the highest measurement frequency. NOTE-It is suggested that the measuring dista

33、nce be at least four times the largest dimension of the effective radiating surface, or two times the square of the largest dimension of the radiator divided by the shortest wavelength to be measured, whichever is larger. In any event, the manufacturer shall specify the actual distance at which the

34、measurements were made. 9.2 Near-Field Measurements The DUT shall be placed on the floor or, when outside, on a comparable flat surface with at least 2 m between it and any wall, ceiling or other obstruction. See Figure 3. All unmounted speakers shall be tested on a square test baffle whose area is

35、at least 10 times the area of the speaker. For example, a 50 cm (20 inch) diameter speaker has an area of 2027 cm2(2.2 sq. ft.), and must be tested on a baffle at least (2.0 m2) (22 sq. ft.) in area. A 1.5 m x 1.5 m (5 ft. x 5 ft.) baffle meets this requirement. The microphone shall be centered on t

36、he axis of the diaphragm of the DUT and separated from the diaphragm by no farther than the distance specified in Table 1. The distance specified in Table 1 is 0.1r, rounded down to the nearest 0.5 cm, where r is the radius of the diaphragm. Once the measurement is taken at this distance the result

37、shall be mathematically converted to an equivalent value for a one-meter free field measurement distance. NOTEWhen measuring the radius of the diaphragm the width of the gasket on the outer edge is not included. This radius only includes the actual radiating area of the driver. Typically this includ

38、es approximately the inner 1/2 of the surround. 5DUT 2 m min. 2 m 2 m Side View DUT 2 m min. 2 m 2 m Front View min. min. min. min. Figure 3 Minimum Spacing for Indoor Near Field Testing Table 1 Maximum Microphone-Diaphragm Separation Distance Radius of Diaphragm Distance to Microphone(cm) (cm) 5. 9

39、 0.5 00-9.910.00-14.99 1.0 15.00-19.99 1.5 20.00-24.99 2.0 25.00-29.99 2.5 30.00-34.99 3.0 35.00-39.99 3.5 40.00-44.99 4.0 45.00-49.99 4.5 50 r .00 or greate 5.0 hen performing a near field measurement, each radiating element (driver, port, passive radiator, etc.) but ch dBn= 10log(Sdn/Sd0) Wmust be

40、 measured. The measured output of each element shall be scaled appropriately, based on its radiating surface area, and summed together. This may be accomplished by performing multiple measurements of each element at different times. It may also be accomplished by using multiple, identical, microphon

41、es (one for each radiating element) and a mixer to sum the outputs. The gain of eamixer channel shall be used to scale the output of each radiating element based on its radiating surface area. The following equation should be used to calculate the relative gain of each channel. 6Sd0is the surface ar

42、ea of the largest radiating element, Sdnis the surface area of the nthradiating element .3 Ground Plane Measurements so that its major radiating element faces towards the microphone, he following considerations should be taken into account when planning and executing measurement ) It may be noted th

43、at a 2 m measurement distance is convenient. At that distance, SPLs match those ) DUT and microphone should be placed as far as possible from walls and any other large acoustic unded by UT ) Size of acoustic space, particularly the distance between the DUT and measurement microphone nt. the ents, nd

44、 Low frequency limit (Hz) 0.75 min. distance to boundary (m) and dBnthe relative gain to be applied to the nthradiating element. 9Place the DUT on the floor oriented which also rests on the floor. See Figure 4. Measurement distance shall be at least 1 m. Figure 4 Basic Ground Plane Measurement Set-U

45、p for Subwoofer System with Driver preferably one-twelfth octave or greater. The bandwidth of this measurement shall be sufficiently broad as to extend at least one octave (preferable two or three octaves) beyond the bandwidth of the DUT. If smoothing is used for the measurement or the display of th

46、e data it shall not exceed one-sixth octave. Using a small level input signal such that the DUT is operating in a linear manner, measure the frequency response of the DUT. From this frequency response measurement, determine the frequency at which the maximum SPL occurs. Record this frequency and SPL

47、. Determine the upper and lower frequency limits of the DUT for which the SPL is -10 dB relative the maximum SPL recorded in the previous step. Record these frequencies as they represent the operable bandwidth of the DUT. The sensitivity of the DUT shall be calculated as the average (mean) SPL over

48、the operable bandwidth of the DUT. The data used for this calculation shall be logarithmically spaced so as to yield a result more in keeping with the perceived loudness of the DUT. This test may be conducted indoors or outdoors. The use of an anechoic chamber is not required. 9.5 Specification of F

49、requency Response Limits Once the sensitivity of the DUT is determined, it is a very straight forward matter to specify the frequency response limits. The upper and lower frequency limits shall be determined by the frequency at which the response curve is greater than or equal to the level of the sensitivity less 3 dB. 10 Maximum Linear One-Way Excursion For the purposes of determining the maximum linear excursion, it is established that as a result of free air single tone sine wave excitation of the DUT at resonance (Fs),