Speaker sensitivity vs SQ

OP,

It is about the cost of building/selling/ever decreasing market for large speakers as many have said.

I wouldn’t want to pay for the speakers I luckily inherited, and the typically large house with large listening space they would sound best in.

likewise, I wouldn’t want the challenge of finding small speakers that sound so good I have to have them, nor then have to pay for the additional power they would need.

audiokinesis

8 CF!

You made me drag out my drawings for the enclosures I designed, for the drivers I inherited, with the help of Electro-Voice Engineers and my AV Consultant for my current speakers.

Deducting elements within the enclosure, I ended up with net internal volume 6.01 CF

And, responding to my youthful excess, we designed a rear tuned port to squeak out a bit more from the 37 lb 15" woofers. I left the ports open in prior location, ’hear/feel those canons! I closed them when I moved here. Bass is tighter, bass imaging very good, I frequently advise front facing subs located near the mains to achieve imaging of bass. I advise against ports, if any front firing.

They shouldn’t fit here. They are big, this house is a small split level. I got very lucky here, they fit, look, sound great. Whenever we go to other people’s houses, or look inside a house when they are for sale, I always look for where they would go. I see very few houses with a good space for them, even the big Victorian Monsters in the six historic districts of my town.

They are in the background of my ’cleaning LP’s photo’ in my listing on eBay

https://www.ebay.com/itm/133612076659

They are extremely efficient, I could shake the walls with 5 watts probably, I sometimes think about trying my friends 8 wpc amps, but they were driven by 30 wpc mono blocks originally, the amps still work, I have stayed in the 30-35, now 45 wpc size, not too big, not too heavy, not too much heat range. That is the max size tube amp I would want to pay for, or less.

Thanks for inspiring me to look at those old drawings, jogs some great memories.

millercarbon is recommending to exclude all Magnepan speakers as options. In doing so, he is recommending to exclude the best imaging, soundstage, midrange, and treble producing speakers on the market in their price ranges. It's fine that he makes such a recommendation, it doesn't mean anyone should listen to his recommendation or to me, for that matter.

Speakers alone make no sound. Complete systems do. Need to examine the complete system before any meaningful comparison can be made.

My understanding is MC prefers high efficiency speakers because they tend to be easier to drive and will work well with most any amp. There is truth to that. However high efficiency speakers also tend to be large and often expensive. Also bulky and more than many would prefer to have to deal with. That’s why the trend is towards smaller speakers that are necessarily lower efficiency if also extended in the bass. Amp choices for best possible performance are still plentiful but more limited. Many tube amps need not apply.

MC is also a Tekton fan. Tekton does tend to offer larger speakers that are more efficient than most but not as efficient as true "high efficiency" speakers like Klipsch, Avantgarde, Volti, Classic Audio Design, and others. Notice most of those are also large and apply horn/waveguide technology to deliver true high efficiency in something some might want in their homes. Tekton offers good value compared to many for large more efficient than most speakers.

So high efficiency alone can be a good thing but like always no one approach has all the advantages that all will care about most.

Also I gather MCs mindset is real men like large manly speakers that may not be very pretty whereas you are perhaps a bit of a w-ss if you care about aesthetics and how they look in your house. That’s for the wife to care about and the real men to ignore.

At least that is my understanding of how MC thinks, FWIW.

This isn’t an example of my preference but an efficient full range speaker. I guess it would also tick the manly man speaker box as well. I also mentioned the Phantom earlier again not as a preference but what can be done with small enclosures, active crossovers and DSP. I guess these are the opposite. 

https://www.jtrspeakers.com/jtr-noesis-215rt

A low sensitivity speaker can be very bit as dynamic as a high sensitivity speaker. It is just a matter of power.
Has anybody ever wondered by no two loudspeakers sound alike? Assuming there is only one accurate sound, that would mean that everyone except for maybe one company has it wrong. More probably nobody has it right.  There are so many varied considerations in speaker design that it is difficult to be versed in all of them. So, we are left to art and our own devises, hearing. We all have our theories and preferences which is what makes this fun. 
I personally don't care at all about efficiency. I separate sub bass from everything else because the considerations are so vastly different. I care about directivity, uniform radiation and radiation type (line vs point source). Because of the directivity mandate I prefer ESL line sources and horns (point source), one moderately inefficient 89-90dB/watt/meter and one very efficient 100+dB/watt/meter. Both are a much better impedance match to air thus the transfer of sound from the driver to air has inherently less distortion. Dynamic drivers sound rounded off to me as if the tips of the transients are missing (no idea if this is correct or not). Many like that "smoothness" and certainly prefer the size. For many it has been the only type they have been exposed to. 
ESL line source speakers are a bit tricky as they do not conform to the usual rules. Even though they are less efficient, because they project power into the room better than a point source an ESL playing at 90dB at 1 meter will be substantially louder and more dynamic back in the room. Than a dynamic speaker playing at 90dB at 1 meter.
Because small ESLs can be rather timid I am of the opinion that if you are going to do ESLs get them 8 or 9 feet tall (depends on your ceiling). It is a major difference in performance, so much so that a pair of subwoofers will never be able to keep up with them, takes at least 4.
As for subwoofers, we have been blessed with modern drivers, amps and crossovers. With enough power you can make a subwoofer do almost anything you want within it's volume constraints. The real problem is the room. If you have to you use multiple units and keep the crossover below 80 Hz. With some speakers like planar magnetics and ESLs there are advantages to crossing higher which means placing the subs in a symmetrical array otherwise you can put them anywhere as long as they are up against a wall. If you put a sub in a corner it is going to be louder than the others.
Can you make an efficient subwoofer? Sure, I made one, or rather we made two. We put 30" Hartley woofers in 25 cubic foot enclosures and drove each one with 20 class A watts. Ridiculous would be an understatement but it worked. You can not use most modern subwoofer drivers in large enclosures. What happens is the voice coil bottoms out making a very disturbing sound. You could use multiple drivers so that each one sees a smaller volume but you still have a very big speaker. There is this thing now with dipole subwoofers. If you have been mislead to think these work just measure their performance. The data will make you cry. There is no circumstance under which a dipole subwoofer will perform reasonably flat from 18 to 100 Hz. I've never measured the efficiency of one but given the degree of cancelation going on I can't imagine that it will be very good. 
IMHO  full range drivers by themselves do not cut it. You can get a very nice midrange and if you lock your head dead on with the driver some treble and in a transmission line enclosure even a little bass. You can do better with Parts Express, Madisound and a little smarts. Horns are great as they are directional and do not bounce sound all over the place. I love the visual statement some of the systems make. There is nothing cooler than those multicolored and wooden horns. Reminds me of "His Masters Voice" and boy do they go loud. If your thing is pee-watt amplifiers these are definitely your speakers. Good horns will not honk at you like PA speakers and like ESLs the micro-detail and transients are excellent as both are much more efficient at transferring sound to open air. Listen to a drum solo and those snare drum snaps.