Watts Peak Sine

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In general, an amplifier is rated at Watts RMS into an 8 (16,4,2,1) ohm resistive load.
There is no confusion with phase angle because there isn't one.
An argument that an amplifier power rating is meaningless because the load is not resistive is really rather pedantic and tedious. I guess one option is to give no rating at all because the load is unknown and varies with frequency....which causes the output to vary with frequency. Then the output voltage varies with load and sags at lower impedances and also the output impedance varies with frequency. Imagine the number of characterization curves we would need to untangle that mess.
Thanks for the pedantism and tediousness.
Those who are involved in conceiving, making, studiying or measuring amplifier circuits are interested by maximal voltages and currents they can deliver. Maximal dissipated powers in loads are numbers of very little interest because they are not the values directly measurable on which they work.
That's how things happen in practice and why I found amp power specifications, despite their universal usage, inappropriate, at least in this kind of discussionabout the"type" of Watts. Using voltage instead of power begins to make things immediately clearer.
 
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Yes, I prefer voltage ratings - but I don't hold out any hope of getting them much outside of some pro amps. We're stuck with power ratings and have to make the best of it.
With specs such as on the sub in question we can only guess what the test conditions were. Was the signal high passed? Is the rating continuous? The manufacturer may have more info available, but at least the plate gives some idea.
 
We seem to be forgetting our antecedents: transformer coupled tube amps. For these, "power" is a meaningful parameter since they are "power amps" and speaker impedance was addressed (mostly) by the transformer secondary winding.

Until negative output impedance amps become the norm and new notions arise, as forr suggests we really should look at today's amps as voltage machines with a low-impedance derating parameter.

B.
 
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