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

The old constraints described above for crossoverless single-driver speakers have  been nearly, if not totally, eliminated:

https://www.cubeaudio.eu/reviews

+1 about electrostatics. But even though my Sound Labs get down to 30Hz, they can’t play those lower frequencies at a decent volume, so I added a subwoofer. 
 

To OPs question, think of the surface of a pond that can have different sized waves crossing at the same time from different directions. Your speaker cone is like the pond, vibrating lower frequency waves and high frequency waves all at the same time. The speaker can do that. That’s what music is. As others have pointed out, the quality/accuracy of the sound reproduced by a single cone driver is debatable. 

Speakers don't exactly create different frequencies and then put them together. The single signal is a complex combination created by a signal composed of all the frequencies a microphone picks up. The signal is a complex of hills and valleys one after the other all combined into one ever changing signal.

Where you really want one driver to be reproducing all frequencies is in the heart of the music---the midrange. The Eminent Technology LFT magnetic-planar driver reproduces 180Hz to 10kHz, with no crossover in that range! In the LFT-8b an 8" dynamic driver in a sealed enclosure does 180Hz down, a ribbon tweeter 10kHz up.

My 2 cents:

- Most speakers under $2k have junk crossovers, resonant cabinets and mismatched drivers. You're losing a lot of detail in the midrange and you don't even know it. It's only clear after you listen to a decent pair of single driver speakers. 

- Most speakers with the exception of true "full-range" towers don't extend past 50Hz. So the whole "fullrange drivers can't do bass" argument is so ignorant to the fact that most speakers use midrange drivers for bass. Most speakers benefit from a sub. Nobody is going to convince me that Harbeth P3SR or KEF LS50 have deep bass. 

- If you live in a reasonably sized flat you're not going to push the volume to night club levels. My guests often complained that the music was too loud on my small single driver speakers. But the same could be said about a large Bluetooth speaker. How much volume do you need? 

These factors have convinced me to buy the Closer Acoustics OGY blind and I have no regrets. Just find me a better (new) speaker under $2k. The midrange, treble and imaging is step up from the KEF LS50 Meta. The bass is fast and punchy thanks to the transmission line. But don't expect deep full-bodied bass. You can get that from a subwoofer. 

I'm also surprised by the enthusiasm surrounding coaxial drivers which exhibit a lot of the same problems as single driver speakers: doppler effect, weaker bass due to smaller speaker excursion (the woofer cone acts as a horn, a moving horn is problematic). And on top of that, coaxial drivers have crossovers and the multiple drivers aren't moving at the same speed causing a time delay.