It seems weird that people are referring to the extreme peak in response as a good thing because sensitivity goes up. some may think this, I do not. I dont want that massive peak in the response.
In short the posts are saying that having the Low freq filter on channel 2 causes a massive peak in output at ~30hz because the 2nd channel is inverted and thus the cut becomes a boost in the signal. This does increase sensitivity as its outputting more per input then before, but it also creates a huge spike in output around a specific freq.