Loudspeaker sensitivity and dynamics: are the two inexorably linked?

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. 

I drive my 91dB B&W 804S speakers (plus REL T5/x) with 12 glorious tube watts from an AudioNote Oto Phono SE. I’m very happy with the combo. Should I upgrade my speakers to something different? Probably. But for the moment I’m good. Dynamic range is excellent.

@bobbydd wrote:

I’m not referring to maximum loudness or volume, rather that the music sounds less reproduced and more that the instrumentation and vocals are more real sounding through higher sensitivity speakers.

Is this a real phenomenon? Or is it more the particular gear I’ve experienced?

Oddly it’s rare to read such fine expressions uttered here, what sounds "less reproduced." It says a lot without stepping into the realm of pretending what’s heard is a facsimile of a real, live acoustic event, and yet it’s at the heart at what can be more readily offered with the attainment of certain physical attributes of a speaker, of which dynamic capabilities are a core aspect and intricately linked to both high sensitivity and prodigious air radiation area.

It’s also about how one assesses and is habitually exposed to ’dynamics;’ I’ve heard quite a few low eff. speakers that, on the face of it, sounded rather dynamic, but when compared to larger and more dynamically capable speakers (because such, factually, there are) it becomes obvious that the latter is somewhat more relaxed yet visceral, effortless and "liquid" sounding in its dynamic portrayal, which to me can be condensed into a more singular impression as a "less reproduced" presentation.

I’ll concede to poster @mijostyn’s findings on at least very large, high-passed (and properly subs augmented) ESL’s that can be dynamically astute, but they also have plenty of displacement to yield while being transiently excellent (with narrow dispersion) - a powerful combo on top of being a crossover-less speaker plane. I do believe the Soundlab’s aren’t that inefficient but rather in the 90dB range? So hardly a typical representative of a low eff., direct radiating speaker - of limited size, no less.

As others have already said, low efficiency does not translate to lack of dynamic range.

Dynamic range in lower efficiency speaker, given high power, high current amps, can, and does equal the dynamic range of high efficiency speakers. 

And for me, that 'liveness' that people talk about with high efficiency speakers (although I don't concede that this is an attribute of high efficiency), comes at the expense of too many other attributes, for me to make the trade off.

I've heard plenty of high efficiency speakers: Klipsch Forte, Heresy IV, La Scalla, etc., JBL L82, Zu, and others, and all the ones I've heard,  trade off their efficiency for (IMO) less than optimum timbral accuracy, lack of a focused and layered soundstage, greater frequency response aberrations. And most of them, to me, seem to create a veneer of sounding like a PA system, that overlays everything. 

Unless one gets into the higher echelon of high efficiency speaker; Cessaro, Acapella, AvantGarde Acoustics, etc, at which point, there seems to be no real tradeoffs between high efficiency, and most of those other attribute missing from most of the other high efficiency speakers, at lower price ranges.