How important is the efficiency of a speaker to you?

A high efficiency speaker takes less watts to drive to the same volume level as a lower efficiency speaker.

ALL OTHER THINGS BEING EQUAL... If a speaker is 10 dB louder than the other, it takes 1/10th the power to drive to the same volume level.

The amplifier takes time to make this power (i.e., slew rate). So the amp "slews" 3.16 times faster to reach the same volume level resulting in increased dynamics for the high efficiency speaker.

"an amp operating withing it’s specifications that is producing 100 W RMS at a given frequency will reach peak power in the same amount of time as a 1 W RMS amp will."

You missed the point. I said ALL OTHER THINGS BEING EQUAL. So the same amp, be it 1 watt or 100 watts, is used with both speakers.

Obviously a 100 watt amp will produce 1 watt (0.278 times the voltage) quicker than it will produce the full 100 watts.

Even a perfect square wave has a "rise time" and obviously it passes through 1 watt on the way to 100 watts.

"I’m sorry, but your understanding of slew rate and how it applies to how an amp operates is simply incorrect. Slew rate describes how fast an amplifier is capable of changing, not how fast it is changing. It describes the maximum rate of change, not how how fast it is changing for a given input."

I understand this.

So then, you are saying that slew rate has NO IMPACT on how a speaker sounds??? So then why do the "better amps" try to achieve higher slew rates, resulting in "squarer" square waves?  In fact, by your terms, why bother to even measure it?

The whole article flawed because it is based solely on the use of sine waves.  I don't know about you, but I listen to more than sine waves (and possibly flutes).

But square waves, sawtooth waves, and complex waves have "verticle" (i.e., instantaneous) rise times and this is where slew rate would come into play.

But to "composite" a square wave from sine waves would take sine waves way up into the ultrasonics and where would that put the slew factor???

A Hammond uses exactly the technique to which you allude. But it never achieves anywhere near a true square wave.

Actually, one could make the argument that a sine wave is just a bunch of square waves with short duty factors and their amplitudes arranged in a "wave" pattern. But again, how many would it take to achieve the true sine pattern?

No musical signals with an instantaneous rise time?

If you play a square wave and the amplifier produces 17v/ms and the speaker needs 17 volts to reach the desired volume, it can occur in no less than 1 ms.

If the other speaker is 10 dB more efficient it only needs 5.4 volts to play the same volume so it can occur in no less than 0.32ms.  That's the math.  Whether the speakers can actually keep up is another matter/discussion.

Regarding being right... it seems that you read one thing and think it applies to all cases..., and obviously it, and therefore you, must be right. Show us something where slew factor is discussed in relation to other wave forms as they actually exist. You are only presenting one side of the argument.

You can also make a more efficient speaker by "tightening up the tolerances" (i.e., tighter fitting voice coil/gap) and increasing the number of windings within the same area (e.g., using flat-wound wire), without causing other problems.

BTW, a lighter cone will also allow the driver to play to a higher frequency without break-up.

My "Merman" speakers are extremely efficient, and sensitive, without horns, and can easily do "live concert levels" and I wouldn’t have it any other way.

Remember that the volume control is nothing more than a "focus knob" and sometimes you really need that volume to bring the cut into focus.

Also, I feel that an "immersive experience" takes realistic volumes to achieve.  You can't immerse yourself in a tub of water if it only covers your toes. 

If you want the peaks to be at realistic levels, yeah, 150 watts is probably about right to get you to about 107 dB or maybe only a bit over 100 dB when you consider thermal compression.