1、 ANSI/CTA Standard Standard Method of Measurement for In-Home Loudspeakers ANSI/CTA-2034-A (Formerly ANSI/CEA-2034-A) February 2015 NOTICE Consumer Technology Association (CTA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunde
2、rstandings 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
3、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 technical publications p
4、reclude 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 with the American
5、 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 document does not purp
6、ort 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 use. This document
7、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 of copies by enter
8、ing 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 R3 Audio Systems Committee.) Published by CONSUMER TECHNOLOGY ASSOCIATION 2015 Technology Phone +41 22
9、919 02 11; Fax +41 22 919 03 00; Internet http:/www.iec.ch 3.2 Informative References The following standards contain provisions that, through reference in this text, constitute informative provisions of this standard. At the time of publication, the editions indicated were valid. All standards are
10、subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards listed here. 5 ANSI/CEA-2034-A 3.2.1 Informative Reference List AES Convention Paper 5638, Characterizing the Amplitude Response o
11、f Loudspeaker Systems, presented at 113thAudio Engineering Society Convention October 2002, Allan Devantier CEA-490-A R-2008, Test Methods of Measurement for Audio Amplifiers IEC 60263 ed3.0 (1982-01), Scales and Sizes for Plotting Frequency Characteristics and Polar Diagrams IEC 60268-1 ed2.0 (1985
12、-01), Sound system equipment. Part 1: General IEC 60268-1-am1 ed2.0 (1988-01), Amendment 1 - Sound system equipment. Part 1: General IEC 60268-1-am2 ed2.0 (1988-01), Amendment 2 - Sound system equipment. Part 1: General IEC 60268-2 ed2.0 (1987-06), Sound system equipment. Part 2: Explanation of gene
13、ral terms and calculation methods IEC 60268-2-am1 ed2.0 (1991-05), Amendment 1 - Sound system equipment. Part 2: Explanation of general terms and calculation methods IEC 60268-5 ed3.1 Consol. with am1 (2007-09), Sound system equipment - Part 5: Loudspeakers NIST Special Publications 811 2008 Edition
14、, Guide for the use of the International System of Units universally abbreviated SI (from the French Le Systeme Intgernational dUnites) 3.2.2 Informative Reference Acquisition Audio Engineering Society (AES): http:/www.aes.org/e-lib/browse.cfm?elib=11234 CEA Standards: Techstreet, 3916 Ranchero Driv
15、e, Ann Arbor, MI, USA 48108; Phone 800-699-9277; Fax 734-780-2046; Internet http:/; Email IEC Standards: International Electrotechnical Commission, IEC Central Office, 3, rue de Varemb P.O. Box 131, CH - 1211 Geneva 20 Switzerland; Phone +41 22 919 02 11; Fax +41 22 919 03 00; Internet http:/www.ie
16、c.ch NIST Standards: National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8930; Phone 301 975-6478; Internet http:/www.nist.gov/publication-portal.cfm Email inquiriesnist.gov 3.3 Definitions Continuous The root mean squared value of a signal over a one second inte
17、rval Normalized Transfer Function A transfer function measurement that has been referenced to (divided by) another transfer function measurement Peak The instantaneous maximum value, either positive or negative, of a signal Point of Rotation (POR) The point on the front baffle of the loudspeaker tha
18、t intersects the reference axis 6 ANSI/CEA-2034-A 3.4 Symbols and Abbreviations CF Crest Factor dB decibel DUT Device Under Test ERDI Early Reflections Directivity Index FFT Fast Fourier Transform HD+N Harmonic Distortion + Noise Hz hertz kHz kilohertz LFCS Low Frequency Calibration Source m meter M
19、IV Maximum Input Voltage Pa pascal PIR Predicted In-Room Amplitude Response POR Point of Rotation RCF Room Correction Factor rms Root Mean Square SPDI Sound Power Directivity Index SPL Sound Pressure Level Note: Throughout this document all references to “dB SPL” refer to sound pressure level refere
20、nced to 20 Pa. SPLMUCOSound Pressure Level Maximum Usable Continuous Output THD+N Total Harmonic Distortion + Noise V volt 3.5 Compliance Notation As used in this standard “shall” and “must” denote mandatory provisions of the standard. “Should” denotes a provision that is recommended but not mandato
21、ry. “May” denotes a feature whose presence does not preclude compliance, and implementation of which is optional. “Optional” denotes items that may or may not be present in a compliant device. 4 Test Setup and Conditions CAUTION WEAR EAR PROTECTION! High sound levels can cause hearing damage with pr
22、olonged 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 other signs of distress in the device under test. 4.1 General Test Setup and Conditions All
23、testing shall be conducted in an anechoic chamber or equivalent environment. During testing the DUT shall be operated as per manufacturers instructions. Complete systems shall be tested intact. Testing shall be conducted at an ambient temperature of 22 C 5 C (71.6 F 9 F) and relative humidity of 30
24、% to 80 %. If the conditions are different, they shall be noted at the time of the test. Both of these items shall be recorded at the time of the tests. The ambient atmospheric pressure (in Pascals) shall also be recorded. 7 ANSI/CEA-2034-A For powered loudspeakers the mains voltage used to power th
25、e DUT shall be within 1 % of the rated value specified for use by the DUT (i.e. for a DUT that requires 120 V, the mains voltage used shall be between 118.8 V and 121.2 V). All test equipment used during the tests shall operate within its linear operating range. For example, amplifiers shall be suff
26、iciently powerful that they never clip or distort during any of the tests. All test equipment used during the tests shall operate within its linear operating range. For example, amplifiers shall be sufficiently powerful that they rarely clip or distort during any of the tests. If a crossover or filt
27、er network is specified by the manufacturer, it shall be installed according to the manufacturers instructions during all tests, including frequency response and maximum SPL tests. If a small loudspeaker (satellite, bookshelf, etc.) without a manufacturer-specified filter network is being tested the
28、n a two pole Butterworth 80 Hz high pass filter network shall be used. All test equipment shall be properly calibrated, and its calibration shall be documented. The frequency response measurements shall be a transfer function type measurement employing a dual channel FFT or similar measurement appar
29、atus. The measurement system shall have an amplitude resolution of at least 0.1 dB. See Appendix E for a list of all equipment needed for perform the tests in this document. 4.2 Verification of Frequency Response at DUT Input Terminals Measure the voltage at the DUT input terminals over the range 20
30、 Hz to 20 kHz and confirm that it is within 0.5 dB from the specified voltage. If it deviates more than 0.5 dB the appropriate corrective action shall be taken, such as the addition of equalization prior to the input terminals of the DUT. 4.3 Measurement Resolution and Calibration The measurement re
31、solution shall be no wider than 1/20 octave. The specific bandwidth, resolution and test stimulus used should be documented. Calibration of the microphone and data acquisition system, and of the post processing of the resulting data, shall be such that the system yields a measured sound level identi
32、cal to that of a stable pure tone stepped or swept with an rms input voltage of 2.83 V. 8 ANSI/CEA-2034-A 5 Directivity Response Standalone Loudspeakers The following procedure applies to conventional floor standing loudspeakers, or to small loudspeakers intended to be used on stands, both of which
33、would normally be placed away from the walls. Loudspeakers intended to be installed in walls or ceilings or mounted on walls or ceilings are not covered by this section. The procedure is described in two parts, one dealing with the acquisition of the raw data and one dealing with the post-processing
34、 of this data and its presentation. The description assumes that an anechoic measurement space (chamber or outdoors) is available. This is a requirement for data that are not significantly compromised in terms of frequency resolution or signal-to-noise ratio. It is recognized that such facilities ar
35、e not available to all users of this document. Appendix A references some methods for acquiring data that may be useful approximations to anechoic data. The objective of these measurements is to be able to anticipate how a loudspeaker might sound in a normally reflective room. No single curve can su
36、fficiently describe how a loudspeaker might sound in a normally reflective room. To better predict its sound, many measurements shall be made at multiple positions surrounding the loudspeaker. These data shall then be processed to estimate the direct, early-reflected and late-reflected sound in a ty
37、pical small listening room. 5.1 Data Acquisition The specific bandwidth, resolution and test stimulus used shall be documented. Measurement Environment Measurements should be made in a reflection-free environment a qualified anechoic chamber or outdoors. Acknowledging that not everyone has access to
38、 such facilities, Appendix A references methods for acquiring data that approximates data acquired in a true anechoic space. Measurement Apparatus Amplitude response measurements shall be made at 10 intervals on one horizontal and one vertical orbit around the DUT. The orbits intersect at the refere
39、nce axis, described below, which defines the zero degree azimuth and elevation angles (i.e., the “on axis” measurement). Make 72 measurements (36 horizontal and 36 vertical). Measurements at 0 and 180 are duplicated, so the data set consists of 70 distinctive amplitude response measurements as illus
40、trated in Figure 1. The measurements shall be made using a single, stationary microphone. The loudspeaker shall be placed on a rotating table, the front edge of which does not project beyond the front of the loudspeaker baffle. The base of the loudspeaker should be horizontal, as it would be in norm
41、al use. However, if this results in the reference axis of the DUT being tilted up or down, the turntable shall be mounted at an angle so that the reference axis of the DUT is horizontal for the purposes of making the measurements. For convenience and measurement consistency, it is useful if the rota
42、ting platform can be vertically adjusted to compensate for loudspeakers of different heights. A possible setup is illustrated in Figure 2. 9 ANSI/CEA-2034-A Figure 1: The 70 microphone locations used to acquire the amplitude response data (from Toole, Sound Reproduction, Focal Press, 2008) Figure 2:
43、 One of several possible physical arrangements within an anechoic chamber that allows rotation and vertical adjustment of the loudspeaker under test. The objective is to minimize acoustical clutter around the loudspeaker and the microphone The reference axis shall be aimed at the microphone and the
44、DUT rotated in 10 increments to complete measurements on the horizontal orbit. The DUT shall then be placed on its side, and the height of the DUT adjusted so that the reference axis is again aimed at the microphone, and the process shall be repeated. When the DUT is placed on its side to conduct th
45、e vertical directivity measurements it shall be rotated about the DUT reference axis. Care must be taken to Vertical Axis Horizontal Axis Reference Axis 10 ANSI/CEA-2034-A ensure that the height of the reference axis never deviates more than 5 cm (2 inches) between the horizontal and vertical measur
46、ements. This is illustrated in Figure 3. With large floor-standing loudspeakers placed on their sides it may be necessary to provide special outriggers to support the off-center mass. By definition the POR is the point of intersection of the rotational axis of the turntable and the DUT reference axi
47、s. The POR should be located on the front baffle of the DUT, and shall not be any farther than 5 cm (2 inches) from the front baffle. Figure 3: DUT orientation for horizontal & vertical directivity measurements showing the DUT Reference Axis and the Measurement Point of Rotation The Reference Axis T
48、he reference axis should be specified by the manufacturer. It approximates the direct-sound listening axis for a seated listener in the prime listening location, at a normal listening distance. Defining the reference axis requires that assumptions be made, and perhaps for this reason manufacturers r
49、arely specify it. Because the reference axis is needed to perform the tests described in this standard the following method shall be used to define it whenever the manufacturer has not specified it. The starting point of the reference axis shall be either the center of the high-frequency driver (normally a tweeter) or a point midway between the high-frequency and midrange drivers. The specific point that is used shall be specified in the final report. The orientation of the reference axis depends on t
