Dear friend, for ur further understanding of the
intricacies of xover design (I just learned this word and i was dying to use it
), i will reveal to u the secret formulae for a 2nd order filter: the inductance is
L=Z/(2*pi*f*Q), the capacitance is C=Q/(2*pi*Z*f), where Z is the drivers impedance, f the xover cut frequency, Q is related to damping and is 0.707 for Butterworth (wich gives -3db at f) and aprox 0.5 for LR (which gives -6db at f). As u can see from this lowering Z by half will also lower f by half increasing Z also increases f.
The reason i dont encourage u to cut the coils is that u cant tell for sure where is the half of the wire's lenght. u could cut in steps and measure the response after each cut.
Lets see what we've learned until now. We have a xover that cuts at 3k (aprox) 2nd order at 8 ohms. With ur woofers impedance at that freq being bigger than 8 ohms its fair to say it will cut higher. However the tw impedance is quite linear so the tw is cut about 1.5k-2k which is 2 low. From the pics u posted it seems much easier to modify the tw coil so do it. cut the tw coil in half and double the capacitor. BUT I remember there was a 4 ohm resistor between the filter and the tw if this is so leave it right there for it will make the total Z around 8 ohms so the above modifications wont be necesary. Also that resistor provides a 3db loss in Spl also required for the tw is more sensitive than the woofer. So the tw part is done. Now for the woofer u should put a Zobel network so that the woofers impedance will result in 8 ohms. Yes 8 ohms so that the filter cut point will be at 3-4k same as the tw.
So the modifications u should do the simplest way i can think of:
for the tw if the 4 ohm resistor is still there leave it if not put one
for the woofer put a 8.2 ohm resistor mb even a 10 ohm resistor in series with a 33u capacitor, all this connected in parallel with the woofer so thats between the xover and the woofer.
Give it a try.