In a LCR circuit the frequency response is a factor of all three variables.
For a first order low pass filter you will simply have an inductor and a speaker element. Which is what I assume you're trying to make? I dont know how or what you're testing, but frequency response of the speaker would probably be the best thing to test.
What exactly are we trying to accomplish here as the ultimate goal?
I thought that might be the case. I was thinking that if I had the abbility to build a crossover testing board w/ a variable inductor, multiple L-pads, and zobels that I MIGHT be able to limited my parts changing while trying to come up w/ good crossover values for any given drivers. I did locate industrial variable inductors and thought that maybe I could apply the same principles of construction but use 10 or 12 awg wire to make one large inductor.............say something around 2.0 or 3.0mH and adjucst it as I tested. Hopefully.................i am really new to this and if it could be done with any good results then it has probably been done already.