I was making some test and noticed that every time I insert a HP filter at around 20-90 Hz some low level activity appears in the spectrum.
It happens with PRE filters, as well as with StudioEQ (I use Elements 9.5).
Is that DC offset? and does it mean those filters are not transparent and maybe are causing some harm to the audio? It doesn’t happen with other parametric EQs I have, like Toneboosters EQ or Izotope Neutron Elements.