Quote:
Originally Posted by glennQNYC
I guess I'm taking issue with the statement that power ratings "are all considered to be marketing B.S.."
This is a misconception and just simply isn't true.
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First off, if a speaker is more efficient, it can be louder with fewer watts assuming it is being powered by the same amplifier. If a particular driver (basic component of a speaker) has an efficiency rating of 85dB, it will be louder than a driver with an efficiency rating of 82dB with the same exact amount of power (Watts) being fed to it.
And power ratings? They are B.S. because there is no consistent measurement of how these power ratings are measured. An amplifier that's rated at 25 Wpc can easily sound better at higher volumes than an amplifier that's rated at 200 Wpc. Some really cheap amplifiers rate their power ratings based on peak power which is 100% useless - these are those no-name amplifiers that say they are 1000 WATTS but are the size of a 50W amplifier.
That's usually not a big concern though because most reputable amplifiers are rated at RMS power. However, even at RMS (root mean squared - basically average) power, there are different ways to measure. To measure amplifier power, you have to have a cutoff of what you think is acceptable level of distortion. An amplifier with a 25Wpc rating can easily output a 50Wpc RMS signal with higher levels of distortion. The problem, of course, is that higher levels of distortion make the music sound terrible. That's why more detailed spec sheets will indicate Watts ratings with a distortion rating (50W @ 0.1% distortion).
To throw ANOTHER wrinkle into this is that different amplifier topologies can have different levels of acceptable distortion. 5% of distortion for one type of amplifier can sound good while 1% on a different type can sound terrible.
So to sum it up, power ratings almost mean nothing. If you want to get down brass tacks, you have to listen to the setup.
As far as your example about PA systems in stadiums... Well they just have to take the speaker efficiency rating and match it to amplifiers that are rated by reputable manufacturers. They have to use experience to know what to buy. Those systems are usually vastly overpowered as well so they don't run at near maximum volume. So there's plenty of wiggle room and they don't have to spec out a system exactly to a certain volume level.