Set it on the deck it's easier and more accurate to set, also, if the deck have selectable slope be sure to set those as well.
Last edited by Sonic; 05-03-2013 at 02:26 PM.
The slope on the amp will only be in effect if you are using the filter on the amp.
If you use the deck filters then it should have either fixed or adjustable slopes, check the user manual.
Typically, slope are set as follows.
For the sub: lpf - slope 24 or 18 db/octave (24 is more commonly used).
For the doors: hpf - slope 12 db/octave (most commonly used).