Need to fire up my simulator to check the actual graphs, but since I think this is just for fun, I don’t sweat a lot 😉 I think they build a bandpass filter and both woofer works in different region. The two mid woofer is not working on same region. They use 1st order for high pass section, F3 at around 8 kHz I think (if I calculate them correctly). Also you can find small inductor with ferrite. The internal crossover uses “bad” non-polar eletrolytic. I think it’s good enough for most people, but not for me 🙂 Need to be improved a little bit in the low bass region. I think the subwoofer is for movie (THX Certified) than music. This system has a little bit bright sound, metallic, a little bit harsh, not too detail for music, and average mid. Anyway, since this is just for fun, so let’s do it. It’s quite challenging for me, since you know that I don’t (never) expect much from a multimedia based computer (some of them are good, but not good enough for my taste). The target of this mod should fulfill 3 main criterias: I think so far MX5021 is one of good candidate to be modded (though I prefer Altec CS21 or 621/641 series, but they have been discontinued).