【 Weak current College 】 EIA-426-B standards introduction

Part I introduction to CD drive power test
ANSI/EIA-426-B-1998 (Loudspeakers, OptimumAmplifierPower) is about power amplifier fed to speakers of standard best power from the United States national standardization organizations, ANSI (AmericanNationalStandardsInstitute) and EIA electronics industry association (ElectronicIndustriesAssociation) joint publications. The standard audio system by EIAR-3 Committee working group, as the amendments to the standard EIA-426-A. EIA-426-A mainly provides for wide-band systems accelerated life test method. In revision before the speaker manufacturer survey respondents broadly considered necessary for the test signal in EIA-426-A standard spectrum, test duration and power calculation methods and other issues. Revised criteria for extended 426-A 426-B, recommended and speakers connected an audio amplifier of maximum rated output power, contains the best amplifier output power of power compression, distortion, and other performance assessment method, described in power compression, distortion and accelerated life test areas of acceptable performance limit.
Speakers can bear the ultimate power is actually a very complex issue. It depends on the speakers in the relevant parts of the heat damage and mechanical damage limits, both with the input signal power, and with the input signal such as peak factor, rise time, spectrum distribution and other factors. Also, do not consider the quality of the ultimate power and not much practical significance. In fact, it should be concerned not exceeding the number of Watts of amplifier power output, for most programs, you can get from the speaker's sound quality is acceptable. I think that this should also be the reason why EIA-426-B standards named best of the speakers, amplifier power (Loudspeakers, OptimumAmplifierPower).
United States speaker Manufacturers Association ALMA (AmericanLoudspeakerManufacturersAssociation) in 2001, launched and coordinated EIA-426-B standard test signal discs. Used as a substitute for expensive signal generation equipment, improving the reliability test, with a view to promoting the broader EIA-426-B standards. This disc also contains a number of criteria other than the signal EIA-426-B, such as the higher frequencies of pure tone, and explosive sounds, and so on. All signals in the dish by signal processing and data analysis program synthesis by mathematical methods and on PC using IgorPro4.0 program generate wav file. At present this dish in the United States market retail price of 100 USD. In many of the audio-related Association, to the Member's price is usually US $ 50.
This section simply describe the dish containing the test signal, not the application relates to its depth. On the test signal of the specific application, in this article described in part II.
A detailed description of the test signal
Track 1: level set the reference tone
Track 1 is 1000 Hz reference signal that is used to calibrate other tracks on this CD test signals in the signal level. Recording time of peak is negative 6 DB, duration is 60 seconds. In addition to the explosive sounds, this CD discs on all test signals are used and reference tracks the same peak recording. At the start and end time, each with a width of four cycles of the slopes of signal for improved transient response. Track 35 to 68 in the explosion sounds is just the peak recording 6dB.
Track 2: for life test of random noise
Track 2 is an in-band 40Hz to 10kHz between Gaussian random noise, suitable for a pair of speakers to do accelerated life test. In equal percentage bandwidth Spectrum Analyzer on the test, the signal spectrum in the following order with 6 40Hz Butterworth high pass filter (Butterworth) filter from 40Hz to 1kHz is flat, in between the 10kHz 1kHz per octaves negative rate of 3 DB down in the above 10kHz 4-order Butterworth (Butterworth) low-pass filter filter. Its peak factor for 6dB by software simulation of symmetric clipping diode, the result is the amplitude of clipping of Gaussian random noise. This signal duration is 30 minutes.
Track 3: for power compression test of variable sweep frequency sine wave signal
Track 3 is a variable sweep frequency sine wave test signals for power compression test signal, its spectrum is basically the track 2 is the same as noise. The composition is a signal from 40 Hz to 10k Hertz uplink frequency scanning, duration 0.25 seconds, and then by 10k Hz to 40 MHz for the downlink frequency scanning, duration is 0.25 seconds. This length 0.5 seconds synthesized signal continuously repeated, a total of 10 minutes. Because the Head-Office of frequency are equal, so the transition is seamless and smooth.
Track 4-34: for distortion test-tone signal
Track 35 to 68: for peak power and dynamic margin assessment of explosive sound signal
The second part of the test method
First, test the required facilities
With a sound track repeat playback of CD Player; output power greater than the required test power audio amplifier; and EIA-426-B standard matching test signal discs, you can also use comply with the criteria in Appendix A EIA-426-B other test signal generator; RMS voltmeter, input impedance at least speakers rated impedance of ten times more bandwidth to at least communicate to 10kHz 40Hz; bandwidth covering 40Hz to 10kHz sine wave signal generator; a third octaves real-time audio Analyzer, use 2 or 3 types of filters, to display the overall sound pressure level; Test the microphone, the whole direction in 40Hz to 10kHz frequency response between the non-uniform degree is smaller than 0.5 DB sound pressure level dynamic range upper limit to the minimum standard consistent with EIA-426-B 140dB; specified in Appendix b in switched 20 DB attenuator.
2. test conditions and considerations
Each test should be done with a no other test of a new speaker to do. Speakers should be provided by manufacturers for testing, in the absence of provisions should be in the area of the appropriate barrier Board tests. Continuous power under accelerated life test can be done in the free space. Tests should be maintained in the ambient temperature is below 20-30 ° c, relative humidity up to 30-80% of the room or Cabinet, speaker resonance frequency changes shall not exceed 5 per cent.
If the manufacturer provides a divider or crossover network, you should follow the manufacturer instructions for installation; if no such provision, the amplifier and the voltmeter should be connected directly to the speakers terminals. First confirmed the speakers with a rated impedance of, and then use EIA-299-A this rated impedance calculation should be imposed, to test voltage on the speakers, the test voltage must be equal to the power amplifier and speakers the best rated impedance of the square root of the product.
To test the speaker in a long time in one equivalent to half the best amplifier power of test signals and its performance parameters or product integrity will not be unrecoverable or unacceptable variations in capacity, thereby simulating the speaker working life. In this test, the speakers should be can't quickly fail because its the same product in the previous test has experienced the entire frequency range in power test. This test is that speakers such as free air resonance frequency and other parameters will not create permanent change. So, the speaker had a permanent damage, we found that it did not pass this test. If you need to reduce this damage to the measured product risk, you can experiment with a Spectrum Analyzer or ear the speakers have been closely monitored, in the event of unusual, immediately disconnect the test signal. At this point, the speaker may have had a permanent damage, and no permanent damage. If you do not have permanent damage, cannot think it passed the test, nor can it fail test. But if the speakers are adopted this test, you think its rated power has been verified.
Before burning machine, select the test signal of the disc with a sine wave signal correction, adjustment of the power amplifier output level, so that the ratio of the second section is the test voltage (power amplifier rated the best power and speaker impedance of the square root of the product)-3 DB, which is the test voltage multiplied by 0.707. In the CD player set the repeat playback, so that it repeats the test signal discs in weighted random noise test signals (track 2), the signal applied to the speakers, continuously repeat one hour, in the end make magnetic circuit cooled to below 35 degrees Celsius, test and document the speaker resonance frequency.
Then an official test, in test signals disc select calibration sine wave signal, adjust the power amplifier output level to make it equal to the second section of the work of the test voltage (power amplifier rated the best power and speaker impedance of the square root of the product). In the CD player set the repeat playback, so that it repeats Gaussian random noise signal, the signal applied to the speakers, continuously repeat eight hours.
After the end of the test, at least one hour of recovery and confirm the magnetic structure of surface temperature has cooled to below 35 degrees Celsius, then feed the speakers a equivalent to half of the test voltage of sine wave signal in the factory to the rated bandwidth, no scanning frequency rated bandwidth, 40Hz to 10kHz. If no tests caused by noise or structural damage will result in the speaker is not suitable for booking application, and the resonant frequency of decline than pot is the records refer to the resonant frequency of 10 per cent, the speaker has adopted accelerated life test.
Test sequence: first do power compression tests, and then do the distortion test, final do accelerated life test.
III. power compression test
Used to test the power of the power amplifier, speaker, the best acoustic output is compressed.
IV. harmonic distortion
5. continuous power under accelerated life test
Closing remarks
And speaker that matches the power amplifier is one of the best output power, using a power too great a power amplifier increases the chance of damage to the speakers. EIA-426-B standards is trying to find the best power.
However, even if the user is completely in accordance with the standards selected EIA-426-B power amplifiers, or there is no way to fully guarantee the security of the speakers. Because even if amplifier output power is not high, if the gain control, bass boost, Equalizer control, volume control, etc., causes the output of the amplifier is a flat clipping signal, so the speakers still exists the risk of burn-out. Clipping is the enemy of the speakers, because clipping, the topping-out phase to signal that the fed to speakers of DC, speaker vibration parts no movement, input power 100 percent are converted into thermal energy, and no back-EMF, therefore particularly vulnerable to damage.
In addition, it should be pointed out that, under this standard, also referred in particular to the protection of the operator listening and related protective measures.