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

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

His question stated "smallest" that plays to 20 Hz.

I’ll grant you that 48" is a tall speaker...it also has some depth but it is a narrow speaker.

Lets have some fun here: Name me a pair of speakers (no subs allowed) that play to 20 Hz that are smaller than Triton Two+. Bonus if they go to 16.

We'll use area (LxWxH) as the "smallest" deciding factor.

I think "Plays flat to 16 Hz. " might be a bit generous:
http://www.stereophile.com/content/goldenear-technology-triton-two-loudspeaker-measurements#XYlmKGoz...

I still maintain that this is a silly exercise for several reasons:

• LF extension without distortion figures is kind-of meaningless
• Most sounds below ~32Hz are from environmental noise rather than music
• Room size and in-room response is a huge factor. It’s one thing to achieve flat response to 20Hz in a closet or Honda Civic vs. a 5,000 cu. ft. listening room
• We have not very clearly defined "speaker". For example, the DuNu DN2000J is a lot smaller than the Triton II+ and are fairly flat down to 5Hz with low distortion. It can do this because the "room size" is only a few cubic mm.