Xover
I tried the Xover at 100HZ and there were even greater dips.
Here are results of it crossed at 80 HZ reversed phase.
The question I have is that the crossover is set at 80 HZ, I thought at around a frequency of 80 and above the response would start to roll off but I see no evidence of this. I measured from 20 hz to 110 Hz. Does this FR look like there is no Xover enabled. I did this test with the Sub only and no mains.