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

Good stuff folks, keep it coming.

noble I just want to know the small speakers capable of it in a typical room.

I’m familiar with the swarm approach. That’s probably the most effective approach in the end if done right I’d say..

30hz isn’t bad as long as the size is small accordingly. I could probably live with that. But 20hz or even lower maybe is best.

I really mean  the speaker does not roll off much or at at all at 20hz in a typical room.  How flat it is or not will largely depend on room acoustics from there right?  If it can only be done in a smaller room fine, just say so.  I'd expect one capable of it in a smaller room to be physically smaller than one for a larger room.

^That's why speakers should be anechoic spec'd. It gives us a standard neutral base line. Now you just need to provide us with your specific criterion, so the equation can be completed.   +/- 3 dB seems to be fairly standard, though better is well, better. :-)

3 dB at 20 Hz which is half as loud at 20 Hz

To be audibly half as loud is usually considered 6-10db on account of the ear being on a logarithmic scale.

I really mean  the speaker does not roll off much or at at all at 20hz in a typical room.  How flat it is or not will largely depend on room acoustics from there right?  If it can only be done in a smaller room fine, just say so.  

The room will have some influence certainly, but if you really want 20Hz response **with any sort of dynamic range**, its not going to be a small speaker.  Note emphasis.

Headphones are small and can go down to 20hz.  They're pretty small speakers.