Originally Posted by Legault
What exactly is a sub bass ?
We're not clear what you're referring to by sub bass. If you clarify where you heard or read sub bass, it would help us to answer your question.
Sub could mean a few things...
There's a MusicMan S.U.B., sort of a budget model Stingray.
There's a Kala SUB, which is their import line of their Solidbody U-Basses.
Sub Contra are notes much lower than traditional bass guitar tuning. Look up Jauqo III-X's work and instruments.