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

from the manual

http://www.kii.audio/phocadownload/Kii_THREE_manual_online_EN.pdf

Technical Specifications:
Compact DSP controlled monitor speaker
4x 6.5” woofer, 1x5” midrange, 1” waveguided tweeter, all individually driven
Amplification: 6x250W full-custom Ncore
Active Wave Focusing crossover filter
Frequency response: 20Hz to 25kHz +/- 0.5dB
Phase response: minimum (best possible time coherence).
Long term SPL(*): 105dB
Short term SPL(*): 110dB
Peak SPL: 115dB
Controlled Directivity: 4.8dB (80Hz - 1kHz, slowly rising thereafter)
Size: 20x40x40cm, 8”x16”x16” (WxHxD)
Weight: 15kg (33lbs)
Inputs: Analogue, AES/EBU
Selectable correction for free-standing, near wall or in corner

I think we have a winner!
Incredible!

Impressive on paper.   Next we need a stereophile write up with measurements.  Has anyone heard Kii 3?

^With those dispersion characteristics, and everything else; is the ideal surround sound speaker?

bdp, a 5-string electric bass will go a fourth (possibly a fifth) lower than 42 (E)--down to B or A (27.5), about the same as a standard piano.

From having recently tuned a piano I can tell you that it's really hard to discern precise frequencies down in that range.