Old School Dub :

Dub is characterized as a "version" of an existing song, typically emphasizing the drums and bass for a sound popular in local Jamaïcain Sound Systems. The instrumental tracks are typically drenched in sound processing effects, with most of the lead instruments and vocals dropping in and out of the mix.

New School Dub : 

The dub sound--rhythms, bass lines, mixing sensibilities, and vibe is experiencing a massive resurgence that is stretching across contemporary music. In the 1990s and beyond dub has been influenced by and in turn influenced techno, dance music, ambient music, and hip hop, with many dub tracks produced by non traditional musicians.