What are the smallest speakers that are clean and flat down to 20hz?

I asked for the smallest that could do it. Nothing impossible about that since some clearly can and do just a matter of how small that can be.

shadornes Barefoot recommendation was a good shot.   On paper clearly  a lot of bang in a smaller package if not quite able to hit the 20hz mark.  

Goldenear Triton Two+.  Plays flat to 16 Hz.  Smallest speaker I've seen that goes that low.  Two powered oval drivers and 4 passive radiators I believe.

BTW Triton three plays to 21 - but you said 20...so the Two+ is my answer.

Of course there is always the *quality* of the bass to be considered. It's not simply a question of frequency response.