Paul - I think the contradiction is due to the differences in whether the reactive component (capacitance or inductance) is in series or parallel. Without any formulas just to keep things simple, let's take a simple first order crossover design used in a two way speaker. When you place a capacitor in series with the tweeter it acts as a high pass filter, allowing the highs to pass with attenuated frequencies below the crossover frequency at a 6dB per octave rolloff rate. Similarly an inductor in series with the woofer provides a low pass filter, allowing low bass frequencies to pass with higher frequencies above the crossover frequency being attenuated by 6dB per octave. However capacitance in a power cable is a distributed value based upon the cable's length (i.e. 20uF per meter), and that capacitance is in parallel with the load instead of being in series. In such an application the parallel capacitance has the effect of filtering higher frequencies where noise exists well above the desired line frequency of 50 or 60 Hz. **So in this case the parallel capacitance acts as a low pass filter, the opposite of series capacitance's effect.** I hope that these real world examples help to provide a clearer understanding of the filtering effects of reactive components, and whether they are implemented in series or parallel which will have opposite results. The supporting mathematics can be a bit confusing, since the reactive components of an AC impedance are represented with imaginary numbers. That's something that I'm afraid is beyond the scope of this forum.