a tweeter can play as low as a parthenon.
the question is, can you HEAR it - the SPL is so low, that it will barely output any sound.
the reason why the misconception exists, is because people compare ONE 15 to ONE 10, when in all actuality, a PAIR of 10's will equal the cone area of the 15 (roughly - more like a 13~14 lol)... the whole idea is, the response is THERE - you just dont move enough air to hear it.
all the speaker has to do is move 10 times (in-out) per second to play a 10hz tone.
i feel comfertable saying, all speakers can do this. but not a the SPL (PRESSURE LEVEL) of a 15, or 18.
on the flip side, the 18 CAN play a 1000hz tone, but it wont be as loud, because the cone does not move far enough to push enough air because its struggling to push the cone. it CAN play those tones - just not enough SPL to hear //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
to proove this point with a woofer, set all EQ to 0 and all filters to flat\off. play a high note, and lightly touch the cone. does it move? WOAH! its playing that note!!
im sure it would work with a tweet the same way.