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

Kii audio model 3s. 

The Excellent Deavialet Phantom is that type of speaker yhat can place with grace 
Or knock or thump you in the chest 20hz test tones confirmed . my brother bought a pair of yhe easy release models from last year thin 2- 6inch pistons in a automobile  like a Ducati twin engine horizontally apposed and and unit is only as big as a soccer ball but can knock out the sound pressures !!

Yg Acoustics Kipod II Signature. Bass is covered by only an 8" driver in active sealed inclosure.  Deep, deep bass. 

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

Also what bass driver or drivers do they use?

Thanks.
mapman

Without being EQ'ed the lowest bass I have heard from a large sized bookshelf, has been a pair of Sonus Faber Extremas, that have an ABR using a Kef B139 with voice coil for switched resistive damping to tune to the room, with a pair of Krell 250 monoblocks up them.

Cheers George 

http://www.stereophile.com/content/thiel-cs35-loudspeaker-specifications#4SSuUmxSowLoD8Ce.97
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