I'm studying the possibility of building my own tower speakers using a pair of 4 ohm 8 inch woofers connected in series for 8 ohm load and also a pair of 4 ohm full range speakers for 8 ohm load that should work as mid-range and tweeters. Those drivers are per tower of course. The problem I'm having is that I don't know what crossover I should use. I was thinking about a second order 2 way Butterworth that can be found on some online calculators adjusted to about 1,000 Hz because the woofer is listed to about 2,200 Hz in the higher end and I want to make sure I don't reach the break up point. The full range speakers can go deeper than that so I won't have gaps in the frequency response. Do you think that crossover will be enough to work with 2 drivers per side (I mean 2 woofers in the woofer side and 2 full range drivers in the tweeter side)? I was also thinking about using a low pass filter and a high pass filter hooked in parallel to the terminal cups and hook the 2 woofers in series to the low pass filter and the full range speakers in series to the high pass filter. Will that give me a 8 ohm load? Can somebody tell me about more crossover alternatives?