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楼主 |
发表于 2010-6-28 00:30
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PMPO(瞬间峰值功率)----美国联邦贸易委员会于1974年定标的标准功率
Peak Music Power Output (PMPO), sometimes misused in advertising as Peak momentary performance output, is a much more dubious figure of merit, of interest more to advertising copy-writers than to consumers. The term PMPO has never been defined in any standard, but it is often taken to be the sum of some sort of peak power for each amplifier in a system. Different manufacturers use different definitions, so that the ratio of PMPO to continuous power output varies widely; it is not possible to convert from one to the other. Peak power is twice the sine wave power, so, for example, a 5 channel system using amplifiers which can output 10 watts for a few milliseconds with an unspecified percentage for distortion would be specified as '100 watts PMPO'. Sometimes, an extra factor is applied to get an even higher figure. The term PMPO is considered misleading and meaningless by audio professionals. Most amplifiers can sustain their PMPO for only a very short time; loudspeakers are not designed to withstand their stated PMPO for anything but a momentary peak without serious damage. Sometimes the PMPO which can be delivered into an unrealistic resistive load, rather than a real loudspeaker, is quoted. There have been genuine attempts to measure "peak music power" as described below, but in general the term is not at all useful.[citation needed]
The true power output of an amplifier can be estimated by examining the input current. Linear amplifiers tend to be about 60% efficient at best. A switch-mode amplifier, known as Class D, can achieve much higher efficiency, sometimes as high as 95%. A linear car amplifier labeled "500 W PMPO" but fitted with a 5-ampere fuse can, at most, deliver an average power of 5 A × 14.4 V × 60%, or about 43 watts. (100% efficiency is always used for PMPO.)
Peak momentary power output and peak music power output are two different measurements with different specifications and should not be used interchangeably. Manufacturers who use different words such as pulse or performance may be reflecting their own non-standard system of measurement, with an unknown meaning. The Federal Trade Commission is putting an end to this with Federal Trade Commission (FTC) Rule 46 CFR 432 (1974), affecting Power Output Claims for Amplifiers Utilized in Home Entertainment Products.
Remembering that neither specification is universally standardized and different companies use different definitions, the typically understood differences between Peak Momentary and Peak Music Power Output are as follows. Peak Momentary Power Output is measured by the components ability to pass a single peak or a short train of peaks, usually fewer than ten contiguous wave cycles, without distortion or loss in power output. Peak Music Power Output, in contrast, is measured by the components' ability to pass at least ten contiguous wave cycles without distortion or loss in power output. For example, RADAR amplifiers only care about peak momentary impulse power, and CW Linear amplifiers only care about RMS, because a continuous sine wave is all they produce. |
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发表于 2010-6-27 22:25
全世界都错了，就你对了！
专牛角尖的菜鸟，没有必要纠缠了，此贴永不回帖！