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

@mapman  

There is no need to boost everything to flat of equal loudness as music is produced for human hearing in the first place / so it is balanced accordingly and a speaker should be flat overall.

One issue with flat to 20 Hz is that rooms give a natural 6db per octave boost as you drop below about 40 Hz. So ideally a speaker should have some roll off if it is to perform flat in a room. A speaker flat to 16 Hz like the ohm f-5015 is likely to sound awful in most rooms without EQ.

Hartley 18" and/or 24" subs might be flat to 20 Hz. Everything else is a pig in a poke.

Mapman
Compensating with equalization is then analogous to using performance enhancing drugs. that is assuming the amp and speakers can handle it.

imo - The smart speaker manufacturer realizes most rooms do not support 20 hz, and builds this EQ into the speakers design for the full range models. The speakers can handle it if they were designed to. In some cases this changes the load the speaker is looking for and actually makes them easier for the amp. I can give an example if you like.

Shadorne I think we are saying the same thing. 

No small loudspeaker can output 20hz flat. And if you designed one that did its output would be so low to be of no use.