What sort of Answer u want......
let me try to explain.... Woofer is a Big speaker, which is used to produce just Bass.... usually u must have seen it placed between two speakers in the cars..... and the think which we call takhta, in which speakers and woofer get fitted, u can call that takhta as bass tube.... but bass tube is enhanced look of that takhta as it encloses the bottom of speakers and woofer so as to produce quality sound... got it?