The bass decay time below 50Hz doesn't really matter too much. The wavelengths of those frequencies have an inherently long duration. That curve is very choppy though, it is almost as if there is some kind of comb-filtering, like there is a phase conflict. You need to make sure everything is playing together in phase.
That is good, but the Y-axis is still a bit wide. Limit the top of the Y-axis to 95dB.