Combining a sub-woofer with Bookshelf Speakers

Yea, turn the OX point all the way down, 30-60. Set the gain to 12
Listen... Continue to raise the XO until you get the boom, then, lower it. until it goes away.

It’s a little to high, just like jjss49 said. Now to get a tad more punch, you could increase the gain, and you won’t get the boom...

Placement, to far from the mains with one Sub can be a little tricky. I would try center, forward (10-20") on the sub first. I push it back (away from the seated position) until the timing if off (muddy) then pull it towards your set until it blends MB to BASS. About an inch at a time. The low mids should be very clear. Phase shouldn’t be an issue with one bass unit, if you don’t get to far from the mains... A big room and a bookshelf can have issues to.. They can disappear to good sometimes..Best used in smaller rooms, and closer to the seated position..

Have fun..

Regards

I know, add 4.. LOL he's working with ONE!

If the OP wants to hear and feel the bass, at the seated position.

Bass forward...in the center. Ya won't ruin the whole reason for the small footprint, to begin with..

Bass everywhere is OK at best...Good yes, best NO...

A  nice nugget is to beard the stand on the bookshelf. 

Increase the bass in the lower regions.. can be tricky...But can look neat
with a little thought..on the baffle visual...

Regards