Well, Sir. It all depends on size... oo-er missus
For music, we can hear down to about 20Hz, and below that we feel to sound wave energy and hear the overtones and harmonics that are at 20Hz and above. For example, the bigger pipe organs can get down well below 20Hz, so if you were in the audience listening to a piece being played that made use of those lower notes then it was your body vibrating plus hearing the harmonics.
The LFE track for movies ranges from 120Hz all the way down to a theoretical minimum of 3Hz, but you'd have to have a hell of a sub to get down to that cleanly.
In music systems it's pretty difficult (but not impossible) to get floorstanding speakers that will go down to 20Hz cleanly and with the same audio energy as they produce at say 50Hz. They're just big and very expensive. It's one of those Law-of-Diminishing-Returns-things. The thing is for music, we don't need speakers to get much below about 40Hz to feel like we are hearing really good bass.
Movies is something different. There's something about the sound of a T-Rex stomping, or an 88 shell, or the Cyberdyne offices exploding that calls out for huge bass. We can get a taste of it from floorstanders that get down to say 45Hz @ -3dB, but it's not the same as a 12" sub hitting 15Hz in-room, or something even bigger digger deeper.
