Perplexed on how single driver speakers can cover such a large Hz range

I've heard a few systems with a single driver where I thought the sound was quite good, overall, and particularly good in certain aspects.  The single driver systems I liked were the Charney Audio Companion (particularly with the AER driver) and the Voxativ Ampeggio and Songer Audio S1.  Most of the others I heard had too rough and peaky upper midrange colorations; I did not mind as much the lack of really deep bass.  I agree with those above who say that using the full-range driver as a wide range driver in a multi-way system is a better application of such drivers. With the right wide-range driver, the crossover points can be set low enough and high enough to be out of the range where the ear is most sensitive to crossover anomalies.  Also, wide range drivers allow for the use of simpler crossovers with shallower slopes.

I've heard a number of successful custom builds using such drivers in multi-way system.  Many are custom-built systems using some fairly exotic Western Electric and Jensen drivers (like the field coil M 10 and M 18 drivers).  Among successful modern multi-ways are the two-way are the Cube Audio Nenuphar Basis (to me, MUCH better than their single driver systems), and the Songer Audio S2.  I've heard really nice horn-based systems where gigantic horns were used to allow a very low crossover such that the compression midrange was crossed over to the bass driver at 150 hz and the crossover to the tweeter was around 8,000 hz.  Even the best of these systems have compromises, of course, mostly in that they don't go extremely deep.  But, the speed, purity, liveliness and vivid quality of wide-range drivers used correctly makes such compromises worthwhile.

And there is that little thing called MASS and the other one ACCELERATION (btw, they don't like each other much). So yeah, and can CLEARLY feel the OP. Imagine the force needed to shake that massive cone 10,000 times per second back and forth. Obviously, something has to give. 

I’m a longstanding fan of single driver speakers. My main speakers are an upgraded pair of Voxativ speakers, i.e., their driver was upgraded to a more power magnet and a custom horn created that was tuned for upper mids. I’ve come to experience that the cabinet design greatly influences the depth for the lower frequencies. Single driver speakers are thin on deep bass, but I love their speed. The preferred dynamic range was achieved only with the inclusion of a pair of subs inserted into the 2 channel system. BTW, Voxativ now has single driver models with with built in subs. 

Also have to mention  the Walsh driver solution to  keeping the sound coherent across the hz specturm.    Their composite cone is inverted in the cabinet and the sounds rolls off the back of the cone in a 360 degree fashion (they attenuate the back of the speaker sound via sound absorber for better imaging)  .  As the signal from the voice coil travels down the speaker all of the individual hz responses are reproduced and come off the cone in parallel so that the result is a completely coherent line source for the sound (CLS) .    Another advantage of this solution is  a very large sweet spot in the room .  

@ronboco See video linked below starting at 6:30 where Jon Ver Halen, Cube Audio’s US distributor, explains the unique engineering solutions incorporated into their Nenuphar loudspeakers to overcome the frequency extreme limitations of traditional single driver designs of the past as well as several other improved aspects of their design:

https://www.youtube.com/watch?v=Ma7dvPyr5T0&t=1s