you really have a lot of homework left.... you can't figure phasing without understanding the drivers being used and how slopes and parts will affect phasing.... it has not been mentioned, but remember there is acoustic phasing as you have been discussing, but there is also electrical phase. The rare time that I see that mentioned here on Agon is when discussing using tubed amplifiers, but individual drivers can vary phase when you change crossover points or slopes or even part grades when it comes to coils. Most of you have probably seen on occasion a tweeter or midrange is wired out of phase or reversed positive and negative. This is done on purpose when phasing gets too far out of whack to bring it back in line. On paper only, at 6db per octave, a driver goes 90 degrees out of phase, 12 db goes 180 degrees (which is when you reverse terminals), 18 db goes 270 degrees and 24 db come full around 360 degrees. In real practice most of the time, these numbers are not near accurate. So 6/6 slopes can get you close in phasing, but why did Joe Di'Apolitto use 18 db slopes in his mtm designs.... harder slopes often sound better, they roll off any bumps in a drivers frequency response and they give the same type (in reverse) phasing as 1st order slopes.
I have seen a ton of discussion in this forum about why 1st order slopes, but it is a rare few that understand why and how the drivers combined with crossovers affect phase and even time alignment.
I have seen a ton of discussion in this forum about why 1st order slopes, but it is a rare few that understand why and how the drivers combined with crossovers affect phase and even time alignment.