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

Let's pretend the cone has to play 2 tones, for example, 100 Hz and 3000Hz, simultaneously.  Imagine looking at the speaker cone in slow-motion.  As it is progressing through its' 100Hz cycles, the cone is also moving, (vibrating), just ever so slightly, at 3000Hz, at the same time.  

That's super-basic explanation, but hopefully it helps.

Here's a little video that may help, as well:

https://www.youtube.com/watch?v=077zpf8gI9E  (FFwd to 4:30 mark)

I just received the Music Direct mailer, where they showcase such a speaker. I don’t remember the details because I had to swat a fly and the mailer went in the trash. In ancient times I put together a five driver per side speakers with some exotic British “full range” long throw metal drivers that were about 21/2” in diameter. I used a high order active crossover to subs. Very efficient and driven by 10 watt per channel SE 300b amps. Everything was analog in those days and the musicality and imaging was really nice on a budget. Think of bobbing up and down on the ocean while rapidly splashing. The short wavelength simply ride on, or modulate the longer wavelengths.  Like all designs there are obvious pitfalls to this approach.  I’ll have to take a look at that MD speaker online.

EVERY speaker design has to compromise somewhere, and this is certainly no exception. In forgoing multiple drivers and crossovers the single driver will have limitations/distortions — it’s just physics.  But, any skillful designer can effectively minimize the compromises while maximizing the benefits of the design.  Such is the art of speaker design.