minus 10db @ 100hz

room mode?

+1 got the same issue at about 90hz which is just about one of the worst places to have one, no way to crossover properly.

Must be a room null. Common frequency to have problems.

Is the mini eqing the subs only? Also, eq is tough to correct nulls. Likely to be related to your mains.

Edit, wow, some quick posters Oops.

yep integration with your mains could also be the culprit, try switching around your xover point and see if that changes anything. Have you double checked that all you speakers are in phase?

haha, I try my best

not necessarily overlap, just move the crossover point on both, either up or down, might help to alleviate the problem, but as tuxedo said, that area is pretty common for room modes as well. where are you crossed atm?

If changing the polarity didn't fix it then it could be the room mode. I would move the sub around to a number of spots, even if you can't place it there permanently to see if it changes.

I recently threw together 4 sealed MFWs and put them in front (2 left and 2 right) and was underwhelmed by them only to find that there was a terrible null at my left front corner. Moving the subs around fixed the issue.

I agree with beast, move the XO up and down and measure each time. See what that yields.

Post some details about your room and system. If it isn't a polarity issue then it is a modal issue only solved with altering subwoofer placement. You can also try moving the mic around if you can put your software in RTA mode and see if this issue is present in other places in the room.

My money is on it being a room mode issue best solved by multiple subwoofers.

also try delay ion MiniDSP or changing subwoofer distance setting