1、 ANSI/CEA Standard Testing and Measurement Methods for Mobile Loudspeaker Systems ANSI/CEA-CEA-2031 R-2014 September 2008 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstanding
2、s 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 technical publications shall not
3、 in any respect preclude any member or nonmember of CEA 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 technical publications preclude their voluntary use by those othe
4、r than CEA members, whether the standard is to be used either domestically or internationally. Standards, Bulletins and other technical publications are adopted by CEA in accordance with the American National Standards Institute (ANSI) patent policy. By such action, CEA does not assume any liability
5、 to any patent owner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. Note: The users attention is called to the possibility that compliance with this standard may require use of an invention covered by patent rights. By publicati
6、on of this standard, no position is taken with respect to the validity of this claim or of any patent rights in connection therewith. The patent holder has, however, filed a statement of willingness to grant a license under these rights on reasonable and nondiscriminatory terms and conditions to app
7、licants desiring to obtain such a license. Details may be obtained from the publisher. This document 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 safet
8、y and health practices and to determine the applicability of regulatory limitations before its use. This document is copyrighted by the Consumer Electronics Association (CEA) and may not be reproduced, in whole or part, without written permission. Federal copyright law prohibits unauthorized reprodu
9、ction of this document by any means. Organizations may obtain permission to reproduce a limited number of copies by entering into a license agreement. Requests to reproduce text, data, charts, figures or other material should be made to CEA. (Formulated under the cognizance of the CEA R6 Portable, H
10、andheld and In-Vehicle Electronics Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2014 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 Infor
11、mative Reference List AES2-1984 (r2003), Specification of Loudspeaker Components 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
12、 661 8528; Fax: +1 212 682 0477; Internet: http:/www.aes.org 2.3 Acronyms 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 Leve
13、l THD Total Harmonic Distortion Xmax Maximum Excursion 3 General Test Conditions 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 wi
14、ll still permit the operator to listen critically for distortion or other 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 inclu
15、de all elements of the loudspeaker system, such as any pre-loaded drivers 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 filt
16、er network is specified by the manufacturer, it shall be installed according 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
17、.1 Measurements Measurements with random noise shall use equal energy per 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, distort
18、ion and accelerated life described in ANSI/CEA-426-B. 24.2.1.2 Displacement 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 a
19、ssure sufficient statistical study of a given class of product to establish 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
20、 life described in ANSI/CEA-426-B. If it is desired to report a secondary 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 speci
21、fy the maximum excursion (one-way or peak-to-peak) of the device that, when 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 Spe
22、cifications The manufacturer shall specify for a given driver the recommended 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 uni
23、t mounted on the standard baffle to radiate into 2 steradians. 4.3.2.1 Additional 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 m
24、anufacturer shall so state. 5 Associated Amplifier Power Loudspeaker ratings 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
25、of the sound pressure level (SPL) of the DUT when the DUT is operating with 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 t
26、o measure the SPL of the DUT at one meter when the DUT is operating with 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 th
27、e DUT shall be 1.15 times the DC resistance, RS, of the voice coil, measured 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
28、RSR. Test voltage shall be equal to the square root of the product of the 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 (
29、cm/in.) Mounting flange width (cm/in.) Cone diameter, i.e., side-to-side 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 sh
30、all be identified as “square” or “rectangular.” When only one value is reported 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 firs
31、t, followed by the longest dimension. Figure 1 illustrates the various speaker 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:
32、 Speaker dimensions top view If a speaker has optional accessories included 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
33、 All free field frequency response measurements shall be made such that 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 high
34、est measurement frequency. NOTE-It is suggested that the measuring distance 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
35、 event, the manufacturer shall specify the actual distance at which the 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 u
36、nmounted speakers shall be tested on a square test baffle whose area is 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 f
37、t.) baffle meets this requirement. The microphone shall be centered on the 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 t
38、he diaphragm. Once the measurement is taken at this distance the result 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
39、 includes the actual radiating area of the driver. Typically this includes 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 Sepa
40、ration Distance Radius of Diaphragm Distance to Microphone(cm) (cm) 5. 9 0.5 00-9.910.00-14.99 1.0 15.00-19.99 1.5 20.00-24.99 2.025.00-29.99 2.530.00-34.99 3.0 35.00-39.99 3.540.00-44.99 4.045.00-49.99 4.5 50 r .00 or greate 5.0 hen performing a near field measurement, each radiating element (drive
41、r, port, passive radiator, etc.) but ch dBn= 10log(Sdn/Sd0) Wmust be 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.
42、 It may also be accomplished by using multiple, identical, microphones (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 t
43、o calculate the relative gain of each channel. 6Sd0is the surface area 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
44、account when planning and executing measurement ) It may be noted that 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
45、distance between the DUT and measurement microphone nt. the ents, nd 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
46、shall be at least 1 m. Figure 4 Basic Ground Plane Measurement Set-Up 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 th
47、e DUT. If smoothing is used for the measurement or the display of the 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 freq
48、uency at which the maximum SPL occurs. Record this frequency and SPL. 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 sensit
49、ivity of the DUT shall be calculated as the average (mean) SPL over 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 Frequency Response Limits Once the sensitivity of the DUT is determined, it is a very straight forward matter to specify the frequency response limits. The upp
