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As just one example, this spec of a JBL 15 G2 says:

300 watts low-frequency and 100 watts high-frequency (bi-amplified) - actual power delivered to the drivers.

and also says:

110 - 230 VAC, 50 - 60 Hz., 175 watts

I can only imagine that these ratings are being measured differently. But I can't figure how.

(just to make sure it wasn't simply a typo, I found another example : 500W RMS speaker power, 130W power supply)

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    \$\begingroup\$ Speakers have long been rated "optimistically". Alternative facts.... \$\endgroup\$ – John D Mar 11 '17 at 0:20
  • \$\begingroup\$ Yeah - but this seems beyond optimistic. The JBL one goes as far as saying "actual power delivered to the drivers". Is there really no other explanation other than "absolute nonsense"? \$\endgroup\$ – GreenAsJade Mar 11 '17 at 0:24
  • \$\begingroup\$ Big output capacitor for one single 300W bounce. \$\endgroup\$ – Janka Mar 11 '17 at 0:29
  • \$\begingroup\$ Well, if you have some energy stored in capacitors you could deliver much more than the input power on a transient basis. But you can't violate Pout = Pin*efficiency so absolute nonsense has a part to play. \$\endgroup\$ – John D Mar 11 '17 at 0:30
  • \$\begingroup\$ Peak power - say from the moment the drumstick hits the snare drum - is much higher than average power (RMS measurement) allowing exaggerated peak power claims. The power supply rating is more honest, and an RMS power measurement would be at best 70% of that. \$\endgroup\$ – user_1818839 Mar 11 '17 at 0:30
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It's down to crest factor for real analogue signals like speech: -

enter image description here

The avaerage power is very much lower than the peak power. Compare music/speech with a sine wave: -

enter image description here

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This looks like the old ridiculous "PMPO" rating which was about 20 times the RMS rating. So you had a 5W ghetto blaster being rated at 100W PMPO, and so on. Marketing and science exist in universes where truth has different meanings.

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I can only imagine that these ratings are being measured differently.

yes, they are. one could be peak / instantaneous power and another is rms - there could be perfectly good rationale for that. one is honest and another is not as honest.

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When it comes to speakers power is a different measure from electrical power.

It's literally about how much "BANG" you can get out of the speaker.

It kind of comes back the Watts vs kW.hr thing. Sure it can whack the woofer with a 300W pulses and make a really load noise.. which as a consumer, is what you care about. However, sound doesn't work that way and is never continuous.

The fact that it really only uses 0.175kw.hrs... nobody cares.

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