main thing is getting the phase right,you should one of the settings will be louder,that will be the right one,then set the volume level for the room on the sub,the blend in the crossover so can just here the integration of sub and exterior speakers,i always start a little to high then back off a bit till you hit the sweet spot,if you can hear the bass all the time its to high as Martin said it enhances bass and vocals,just goes lower than main speakers,secret is you don't want to notice the sub,if the loudness is right and still not right then back off the crossover a bit.remember the phase is not right it will never be right,you really can hear the louder the sound on the phase then its right.if you set it up for 2 speakers if you go to 5.1 the balance of the front spk will be the same as using it in stereo.rel have phase knob 1 or 2,and remember to change the setting for slam for movies and music for music,if you want to do the sub crawl for positioning the sub,the easiest way is to put the sub in your sitting position and you move your self around the room when you hear the sweet spot put the sub in that position,much easier than moving the sub around the room.when i set the crossover i lie on the floor next to the sub with the wife in the listening chair and adjust it,a little to high it will be booming back off a little till she says it correct,if you cannot get it just right back off the subs volume.using the av amps will usually set it to about -4 db (pioneer) oppo has a better set up in the settings,but it still will not be as good as manually

av amp test tones are never right

THIS MAY HELP SOMEONE

Bit of a bass head here...
Currently I have only an improvised sub (BK electronics sub plate-amp stuck into an old 18 inch bass speaker cab). The above set-up instructions resonate with my own experiences playing about with that. So yes! Useful.
Especially:
1. The helpfulness of having a second person to tweak controls so that one can remain in the listening position, and;
2. The way that tweaking one setting inevitably effects the fine tuning of the others.
The sub never fails to raise a smile. And once set up adequately (ie reasonably integrated into stereo image, added dynamic heft without too much smeer) I prefer to have the sub with my smaller woofered speakers (<12 inch) than without it. Setup seems less fiddly and critical with larger woofered main speakers but the benefit : cost ratio starts to narrow. I don’t use it with my 18 inch mains.