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How, just how??? | by ayteebee | 2008-07-10 14:09:00 |
| Lies, Political Platforms, and MarketSpeak |
by OddParity |
2008-07-11 06:09:56 |
Obviously, those USB speakers (Exhibit A) cannot produce 120 W of acoustic power, ever. They can't even consume 120 W of electrical power continuously. But maybe, just maybe, they could contain enough energy storage in the form of super-capacitors to consume an instantaneous 120 W of electrical power for a nanosecond or two, provided that the test signal is zero for 10 minutes while the capacitors charge, and then has an instantaneous spike to maximum.
Exhibit B probably has the same problem: insufficient power supply capacity, but enough energy storage in the filter capacitors for the amplifier circuit to output 280 W instantaneously until the stored energy is depleted.
The test conditions used for most consumer audio specifications are so far beyond realistic simply because the marketers know that Joe Public doesn't have enough technical knowledge to spot the trick, and they can get away with publishing big, impressive, yet functionally meaningless numbers.
I've done sound reinforcement work, and I can tell you that the specs on professional equipment are a lot more sane, because the sellers know that the buyers tend to have significantly more technical knowledge than the general public. But even those specs are somewhat misleading, because the test conditions are carefully chosen to highlight the strong points and dodge the weak points of a particular model's design. Savvy buyers will apply various rules of thumb in an attempt to renormalize the specs to find potential purchases, but will refuse to buy until they take the equipment for a test drive with real inputs and outputs. |
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[ Reply ] |
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If I were writing regulatory standards... | by OddParity | 2008-07-11 09:14:49 |
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