crossover set to full pass if u are using passive crossover

bass - 0
treble - 0

Even if you are running passives, you still need to set to HPF, unless you want your comps to play down as low as 20hz by setting to FULL.
And I have never come across any comps that can play so low.
For the sub, set to LPF.

What comps are you using??
Check the FR and if possible, reduce the HPF to 63hz at 18db/oct.
This would give you more ooommmmp in the front stage..

FR=frequency response.
Normally for comps, the manufacturer will state the FR, for example,  50hz-20,000hz.

You can run full pass if you have an enclosure for your mid/woofer.

The supplied passive crossover with your component set basically handles the crossover points for your tweeter, but only a lowpass (to prevent it from playing gradually all the way up above, i.e 5,000-6,000Hz) for the mid/woofer.

Therefore, like what some of the forumers here have pointed out, you still need a high pass (to prevent it from playing gradually below a certain level that you set) for the mid/woofer, or else it could play all the way down and damage the drivers if you play really insanely loud (there is difference tolerance level from different speaker drivers). If you do not play very loud, then it it fine but many people high pass to clean up the bass so that the midrange (or the part where vocals/voices are prominent) improves.

However, if you find that you have mount or install the mid/woofer properly, it can be set lower, so that it can play more lows without being muddled or cover up the midrange frequencies too much. You will also notice that if you use better cabling or better amplification, your mids behave differently as well.

So, there are quite a few factors involved when you decide on the high pass point for your mid/woofer. Perhaps, if you are in the stage of learning, you can just set it at 80Hz and bring it up gradually to 100Hz or down to 60Hz... yes, I repeat, gradually... to see which one sounds best to you. Normally, based on years and years of experimenting, you will NEVER find a sweet spot where everything sounds excellent (i.e just enough midbass, just enough clarity on the mids and mid-highs). Usually, something has to be given up for another.

Before you go into tuning, things will be much easier when:
1) Your install is excellent ichiban!! (30-50 bucks installs just would not be sufficient, honestly)
2) Your cabling is no sub-standard
3) Your amp gives enough juice to your speaker and your amp is not starved of power (suppy)

lol... mnkh27 did a very good explanation already. Perhaps u need to understand more about FR aka frequency response of all the drivers. Rough example will be

Sub: freq played should be 80hz and below with steep slope like 18db or 24db so that ur bass is clean

Midrange: any freq from 80hz or 63hz all the way up to ur tweeter freq eg 4000hz

tweeter: from 4000 onwards

For passive setup, the frequency cut off point has been set via ur passive cross-over. So, for your case, just need to set the HPF for the midbass to play. What mnkh27 is trying to tell is that freq cut off point can be adjusted according to drivers ability. However also very much depends on the installation.

essay pulak... you want essay ah, gimme your email!!    or read my blog.

I thought i replied u already

LPF on sub from 80hz all the way down (63 or 50)

HPF: from 80hz all the way up (100 etc)