I ordered two 4-pi crossovers and changed the resistors to the 20 and 30 ohm and used with the 3-pi speakers around 1-2 years ago . I ended up changing the 20 uf to a 12 uf cap and shorting out the .5 millihenery choke in the low end circuit. I also changed the resistors to a lower value. Now the 3-pi crossover has been changed to two 10 uf caps. in the woofer circuit. Ok the newer one sounds right to me and now works right with the 20 plus 30 ohm resistors which equal out to 25 ohms resistance. I thought the 4-pi and 3-pi were using the same crossover besides the resistor values being different. Well anyway It works great now. I am using the delta12lfa and the Psd2002.