This tab illustrates how to play 12th's on the bass.
12th's are simply 5th up an octave.

Example)

 |Root    5th     |Root    12th    |
 |D       A       |D       A       |
G|————————————————|————————14——————|
D|————————————————|————————————————|
A|————————12——————|————————————————|
E|10——————————————|10——————————————|
 |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |  

notice that the 5th and the 12th are the same note.

There are three kinds of 5th's:

—Perfect Fifth (5) — 7 half steps (frets) away from the root.
—Diminished Fifth (b5) — 6 half steps (frets) away from the root. 
—Augmented Fifth (#5) — 8 half steps (frets) away from the root.

In this respect, there are also 3 kinds of 12th's
—Perfect 12th (12) Diminshed 12th (b12) Augmented 12th (#12)

(if this doesn't make any sense, check out my intervals tab.)

Here's how you play each 12th:
(the root note is E, the interval is above the tab)

 |12th            |b12th           |#12th           |
G|16——————————————|15——————————————|17——————————————|
D|————————————————|————————————————|————————————————|
A|————————————————|————————————————|————————————————|
E|12——————————————|12——————————————|12——————————————|
 |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |

Perfect 12th are the only out of the three that do not create any tension.
They have a very strong and stable sound.
Because of this, I find them to be the most useful.
Since they do not esstablish if the chord is major or minor,
you can use them over both.

The diminshed and augmented 12ths are very unstable.
because of this, they need resolution.
here's the best way to resolve these 12th's

 |E (b12)         |F major         |E (#12)         |A major         |
G|15——————————————|14——————————————|17——————————————|18——————————————|
D|————————————————|————————————————|————————————————|————————————————|
A|————————————————|————————————————|————————————————|————————————————|
E|12——————————————|13——————————————|12——————————————|17——————————————|
 |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |1 + 2 + 3 + 4 + |

notice how the b12 wants to resolve down a fret,
and the #12 wants to resolve up a fret.

I hope that this tab has been helpful.
send me a message if you have any questions.

thanks,
—Connor Larkin