How much amplifier power do you really need?

[RebelMan]

@RebelMan: To be frank, a lot of what you wrote above doesn't make much sense to me.  For example:

* What is the distinction you're drawing between "clean" and/or "linear" power and any other kind?  Power is a well-defined, single, measurable quantity so in itself it can't be clean, dirty, linear or non-linear.  Maybe you are talking about distortion instead.

* Why does it matter "at what load" the power was measured?  Power is power.

Your argument based on the loudness of an 85 dB/W (at 1m?)  speaker driven by a continous 350 W (RMS) would be valid.  But that is not the point: the video is talking about instantaneous power needed to drive the speakers with a faithful signal at music peaks.  @Confused helpfully made that clear by quoting the description of the power meters from CH Precision's documentation.

What this discussion revolves around is the crest factor of the music being reproduced.  For some uncompressed music this can be over 20 dB, meaning that to reproduce the full dynamic range of the music the amplifier needs to have more than 100 times as much power available (for peaks) than the average (RMS) value for a given volume.  This is a good article that goes through the maths.

I'll start with the second question first.  Power is not power.  Power is the measure to do WORK or the potential to do WORK.  In the strictest sense (as it applies to electronics) power is the amount of work that is needed to move electrons through a given medium.  When fewer obstacles are present electrons are more free to move and thus more work is needed to keep them moving.  The converse is also true, when more obstacles are present electrons are less free to move and therefore less work is needed to keep them moving.  So unless the system requires large amounts of power less will do.  How can anyone tell how much power they need unless they measured it?

GOOD, power that is sufficient in supply at any given time for any given load.

CLEAN, power that is free from artifacts inherent of the architecture's design and components.

LINEAR, as the demands for power increase (instantly or continuously) the supplies of power also increase in lock step.

The problem with the video is that it does not indicate what the conditions are at that "instant".  What is the load when the amplifier displays 350W?  My example amplifies the problem when snapshots of power are taken out of context.  I made the assumption that the load was 6 ohms the instant 350W was needed to prove a point.

How can you conclude that an amplifier needs 100 times more power available for peaks when we don't even know what those peaks are?  That's purely conjecture.  You cannot solve what you do not know.  Again how do you know?  You need to measure.