As suggested, the only part worth playing with IMO is that steel core inductor. You have already indicated there is a certain amount of distortion associated with ferromagnetic core inductors. Core hysteresis will cause a certain amount of distortion, though the laminated steel core inductors used in this design will have low hysteresis at the frequencies in the low-pass section of this crossover. While distortion due to saturation is also possible, this would only occur at very high power levels (several hundred watts for most common inductor core sizes). I don't know if the distortion due to hysteresis will be audible in your application, but if you want to try any one thing, there is certainly the most possibility for improvement in this inductor. You may or may not want to add a series resistor to the inductor. Here are the reasons why.

Decreasing the resistance of the inductor will have two primary effects.

1. Altering the bass response of the woofers by changing the qts of the system. Typically this effect can be summed up as: lower series resistance, leaner (some would say tighter) bass; higher series resistance, more pronounced (some would say boomier) bass. Depending on your preference for bass alignments, you may like the more damped bass provided by a decrease in series resistance.

2. Altering the acoustic output across the range of the woofer by changing the resistive attenuation. This may manifest itself as a more prominent midrange due to the increased level of the woofer with respect to the tweeter. With such a small change in resistance as you are proposing, you will likely not notice the difference.

Changing the resistance of the inductor will not have an effect on the crossover frequency, as the filter effect is not a function of resistance (fixed regardless of frequency) but of impedance (changes with frequency).

The increasing impedance of an inductor with frequency is as you probably already know, the reason an inductor functions as a low pass filter. The impedance is the sum of the resistive and reactive components of the inductor at a given frequency.

At the 2200Hz crossover frequency, the impedance of the inductor will be:

Z=R+iX (ignore the i because we are only working with one complex impedance in this equation)

R = 0.30 Ohms

X = 2*pi*Frequency*Inductance

X = 2*pi*2200*0.75E-3

X = 10.37 Ohms

Z = 10.67 Ohms at 2200Hz

If you notice, the reactance of the inductor depends solely on the inductance value and frequency, thus the crossover filter frequency will rely solely on those values as well.

Note that in RLC circuits, the resistance value of the circuit determines the sharpness of the notch. In these circuits the sum of the inductor resistance and resistor value should be kept the same.

Added: The inductance of wirewound resistors is very small (see thread

here for details) and should only be of any minor concern for large resistance values in series tweeter circuits.

Have fun with your project!

David