If I build an inline 6dB/octave filter that is -3dB at 120Hz, where would it be -6dB at? I know it would be -9dB at 60Hz but since the slope is not linear, -6dB won't be at 90Hz but I don't know where it would be.
Also, if -3 at 160Hz (-9 at 80Hz), where would -6 be?
This filter will be for use with the MTM Oticas.
