Is the most efficient speaker the best speaker?

All things will never be equal. If the sensitivity is above 91dB, things are pretty good. 95dB and above, they can be driven even more easily. However, I love the sound of Maggies, 86dB sensitive, and Legacy Whispers at about 95dB sensitive, and some horns at 100dB plus, and have heard many efficient things which made my ears bleed. Thus, the bottom line is how well matched your amp is to your speakers, regardless of sensitivity. Jallen

NO. Still too many variables. Otherwise one technology would have won out long ago and that has not even come close to happening with any piece of equipment. Think it through.

I think with all other things equal, then I say yes it is best to have high efficiency speakers so the amp can cruise along in an effortless mode and for the right solid state designs class A all the time.

why not?

Many varied factors come in to play. A well designed high efficiency speaker has the inherent advantage of increasing the pool of usable amplifiers. This opens the door for the inclusion of low power(high quality) amps such as SET,DHT-push pull, first watt etc. These types of amps with an appropriate speaker can sound fantastic. A good high efficiency speaker in general tends to be very dynamic and immediate even at moderate/lower listening levels. Just as with the less efficient speakers, some are better implemented than others.

Maybe yes, maybe no. But SETs are the best amps, and the first watt sounds best. So you're going to need efficient speakers, if you want the best sound IMHO.