agree, that’s why many of us like full range speakers. However, what do you do with two, three, or got forbids, four way speakers?
From what I understand you're using a 3 way speaker and sub and calling it 4 way well With Genelec you can build a 5 way but it needs to be calibrated with GLM, these are fully DSP speaker systems and are very easy to integrate in a variety of rooms. You're making this way to hard. I know some are discussing DIY but that's not the same as what's being with SOTA from companies like Kii, Dutch and Dutch, Genelec, Dynaudio etc...