UnitedPlugins has discounted their low end treating plugin SubBass Doctor 808 to €29 until March 10th, 2021 (Reg. €59).
SubBass Doctor 808 is a safety net for all who mix while travelling or produce in a home studio. If your monitors do not deliver the lowest frequencies right or your room is perhaps not 100% acoustically treated you need SubBass Doctor's advanced protection. It filters the harmful frequencies and guards the lowest basses not to exceed the healthy limit. But it compensates the loss in healthy sub frequencies ensuring you don't lose even a little bit of the sub-bass power.
A 15-days fully working trial version is available.