How do inductors help impedence matching?

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.

An inductor of 1.5mH would correspond to an 850Hz crossover for 8 ohm driver (and 1700 Hz for a 4 ohm driver). It must be in series.

If the speaker is 8 ohms, the 8 ohm tap will maximize power. Try the others if you want...it will not hurt anything. If your ears are happy without the inductor by all means leave it that way. What you have done is to use the 15" driver to a higher frequency, and attenuated the horn tweeter by leaving the woofer in parallel with it. Attenuating a horn tweeter is not a bad idea (IMHO).

Thanks for many informative responses.

Gs5556 - the inductor is in series, used as a low-pass filter and "impedence matching" component.

Ed_sawyer - have read many of your posts here and at AA, and found some of them imformative. In this instance, your reply is a statement of the obvious:

"removing the coil is going to basically remove the low-pass on the woofer" (thank you...)

"go model the crossover using existing values, in an online crossover program and see what the points and slopes are" (As Bruce says, the model has little bearing on resulting sound. Besides, I did model the xover about 4 weeks ago)

"you are better off leaving it at 8 ohm tap most likely" (why? have you tried the other taps? I'm interested)

"Bruce Edgar himself" (yes, we talk)

"Basically, leave the Xover alone, you stand to do (more) damage to the sound and the gear by fooling with it and not knowing what you are doing" (as Bruce says, the crossover values he uses are the result of an iterative process, and the Titan and Edgarhorn values are the results of his years of listening. My MF driver is different than his)

I am still forming an impression about the Fane, but in general agree with you. Am very interested in listening to the Fostex and T350. Ed, I would be very grateful if you share your experience with these in your Edgarhorns.

I asked alot of basic questions in different ways because it helps me to learn and gain a deeper understanding, which I try to apply in my system.

Joeylawn36111 - thanks for your explanation

Eldartford - you're priceless. Thank you.

Scott