Coils (inductances) Decrease Impedance as Frequency gets lower. The formula is Inductive Reactance = 2 times Pi times the Frequency times the Inductace value. As frequencies go lower, so does the inductive reactance. The Impedance is the vector sum of the Inductive reactance and any pure resistance in the circuit, which is not frequency-dependent like the reactance; therefore the Impedence of a coil decreases with decreasing frequency (and increases with higher frequencies). Capacative reactance is the opposite- Lower frequencies have higher reactance and vice versa.
I actually just had dealt with this issue when I was building a small circuit to make an oscilloscope display like the ones found in Marantz tuners. When using a Capacitor and Resistor (for phase shift) the lissajous pattern was kinda blurry. When I changed the capacitor with a coil, the blurriness went away. This is because the capacitor blocked the low freqencies and passed the high ones (more fuzzy display). With the coil the lows were passed and the highs were blocked, so the pattern was less fuzzy.
I actually just had dealt with this issue when I was building a small circuit to make an oscilloscope display like the ones found in Marantz tuners. When using a Capacitor and Resistor (for phase shift) the lissajous pattern was kinda blurry. When I changed the capacitor with a coil, the blurriness went away. This is because the capacitor blocked the low freqencies and passed the high ones (more fuzzy display). With the coil the lows were passed and the highs were blocked, so the pattern was less fuzzy.