Speaker sensitivity vs SQ

@ clearthinker
An excellent first post. As you can see by Duke’s response above you are correct, there are other factors that are impacted by and to be considered when evaluating a speaker’s efficiency.

MC’s response to your thread is somewhat puzzling, you do seem to "get it".

Encouraging to see at least some get it. Not surprised at all to see the O P does not.

There is an inevitable tradeoff relationship between box size, bass extension, and efficiency. And it’s a fairly brutal relationship.

This observation nail the question with the beginning of an answer...

With active speakers and DSP box size and bass extension are being challenged in interesting ways. Look at the Develiat Phantoms down in subwoofer range with appossing drivers and a lot of watts. 

I am amazed at how many small manufacturers there are out there. Do they all support themselves as a business or is it hobbyists making themselves look bigger than they are?

I have owned all manner of speakers--conventional sealed box, bass reflex box speakers, electrostatics, planar magnetics, etc., and all types of speakers, with varying efficiencies, can deliver decent sound.  But, over time I have gravitated toward high efficiency speakers because they can be utilized with my favorite amplifiers (most of which are low-powered tube amps) and because they tend to deliver superior dynamics.  I know there are theoretical reasons for this--low power being delivered to the driver for any given volume level means less heating of the voice coil (heating causes an increase in resistance that then reduces the ability to deliver more power, in other words the driver output does not increase linearly with increase power (i.e., dynamic compression)--but, whether or not this is true, I tend to find higher efficiency speakers more dynamic sounding).

I currently own a system with twin 12" woofers in an Onken cabinet, midrange supplied by a compression driver/horn combination, and highs delivered by a bullet tweeter.  Horn systems like this tend to be large in size, which is why the industry went away from these systems, particularly when stereo required installing two speakers (and HT requiring even more speakers).  I don't think it was sound quality that killed horn-based system.