Loudspeaker sensitivity and dynamics: are the two inexorably linked?

Magnepan's sensitive and dynamic?! I like Maggies as much as the next guy, but those are not two adjectives I would ascribe to them. In fact, Maggie detractors have long found them lacking in exactly those two areas. They are in the range of 82-84dB, and require huge amounts of current to "come to life".  

@cleeds 

1+ There is no connection at all. Good examples are Horns and ESLs two vastly different types of loudspeakers. Horns are very efficient while ESLs are not. Both are very dynamic in the portions of the frequency range they can handle correctly primarily because their transient response is so fast and they are not spraying sound all over the place both being very directive in specific patterns. An excellent example of an instrument that both get right while other types of speakers struggle is the snare drum. Both ESLs and Horns have limitations in terms of frequency response requiring crossovers and low frequency support. While you can make a bass/subwoofer horn, the size requirement is extremely prohibitive so most horn systems revert to regular dynamic drivers. ESLs do well down to 100 Hz then suffer greatly actually limiting their dynamic potential. Supported by subwoofers people can't believe how loud an dynamic ESLs can get. Just ask skos.

In my experience there is no direct correlation at all. I own a pair of Thiel CS6 speakers which are some of the least sensitive speakers out there (86 dB) and I drive them with a Krell KSA 300S. I've been to 3 audio shows (AXPONA, Tampa, and PAF) and I've heard quite a variety of horn speakers. There was a large variation in the sound quality from the horns I heard but none of them were more microdynamic than my Thiels. You can blame the room or many other factors but my point is that in my direct experience I can't make a blanket judgement that horns are better at any aspect of SQ. I also can't make a blanket judgement that dynamic cones or any other design is uniformly better. I have heard fantastic speakers that had horns, dynamic drivers, and film diaphrams. And one of the worst sounds I heard at a show were from speakers with horns.

All drivers have a bit of a built in "dynamic compression" due to the suspension. So a high efficiency of the same sd, may in fact be more dynamic as it is in a lower excursion so not suspension "compressed". This may not be noticeable at all (should not be) at medium levels if you chose the correct speaker, but as you crank it up, it may become more noticeable. This is still within the gap. A cheap or poorly designed driver will also get increasing compression if the coil moves out of the gap. To be complicated, gap strength is not linear. 

Amplifiers also have a non-linear gain with respect to power, and it can differ with different loads. 

So to each their own and enjoy.   Build a Kleinhorn and power it with a Schiit REKKR.  Use an active crossover on your mains to take the deep bass out of them so they are not trying to produce midrange while approaching XMax. Pick an amp with sufficient overkill as to be on the more linear portion of the transductance curve and sufficient dynamic current.   

Do be careful lumping technologies together. All ESL are not the same, all direct radiator, all horn, all panel...   

As others have more or less said, given enough high quality power, even good lower sensitivity speakers could sound very dynamic although the system may “struggle” to do so. 

in my experience, high sensitivity speakers ( maybe 95+ db) can have the ability to sound more live than others & I’m not knowledgeable enough to understand the details of the physics involved. It’s simply what I hear.