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

Hey Chris (ct0517) sorry, I just saw your post asking me about Phil Collins. I missed it somehow. Anyway, I’m not that familiar with Phil's playing, though I do know he is, as am I, a lefty. I never got into Genesis (I’m not a fan of Progressive Rock in general) or his solo career, but there is no question he’s a fine player, and singer as well. He has employed drummer Chester Thompson on at least some of his solo LPs, who is himself quite an accomplished player. Their styles are not up my alley, which is that of Roger Hawkins (Muscle Shoals session player), Levon Helm (The Band), Jim Gordon (L.A. session player, Derek & The Dominoes, Traffic), and Buddy Harman (Nashville session player).

OP,  Demo the Kii 3s for yourself.  All of the blather will fall away and the music will fill the room.

Does not quite meet the parameters you posted, but very impressive low frequency extension for speaker type and cabinet size. Smaller footprint then the majority of stand mounts. 

http://www.decware.com/newsite/HORN.html
Scroll down the page for specifications.

No affiliation with Decware

Open baffle, down to 18Hz

http://www.spatialaudio.us/x1-main

So bass is one of these subjects that never is settled, as most people will hear and FEEL the sound waves. Perceived bass is
all up to the individual listener to make it what it is. I'm very familiar with the Ohm speakers an "Mapman" knows and every time someone tell me they can hear below 20hz with their (insert model)
I laugh because that's kind of saying you can hear a mouse fart...sure you can, but mouse farts are very, very quiet.

As far as bass I'm using a four 18" driver infinite baffle system
that  will shake my house to the point it's scary and it can put out 120db with no effort at 20hz. My large Ohm speakers 4/5000
will comfortably crank out 25 real hertz all day long but anything below that level is negligible in a true sense and still nowhere close to what the sub can do....

peter