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

I think you can get full-range drivers to play some good bass, in-room.  But the cost would be cabinet size.  You can take a larger 10"-15" full-range driver, but with their reduced xmax, they need a big enclosure to reach into the lower frequencies.  Something like 8, 12 or more cubic feet in size to get the appropriate bass output, which most people can't or don't want to sacrifice.

marshinski15

You have some great help here from the replies.  I will will give you my take.

First up, in the normal run of things you would like to have a full range of frequency response.  But (1) the midrange is where most of the music is; (2) The avoidance of crossovers is a benefit - but this is (a) mitigated by quality (whatever that is) designs of the crossover and (2) systems (eg  ATC) where all three drivers in a three way system have similar cone designs.  (3) And this is my main point: it depends on your music.  Say your real interest is in string quartets: then the benefits of a single driver come to the fore.  Disclosure: I have not heard a single driver system. 

They play into break-up modes, that’s how. 

If you get a chance, give a listen to the Manger speakers. The Manger MST covers a large part of the frequency range, assisted by one or two 8” woofers.  Different technology altogether and extremely well executed.  Active or passive models in modest but elegant enclosures.  Nothing else like them on the market in many respects.  

@andrei_nz I hope you could listen to single driver speakers someday. Yes, string instruments (especially guitars) sound way better on single driver speakers. Vocals sound more clear and natural too. This sealed the deal for me as I listen to a a lot of folk/country music.