Dennis,
With all due respect - there are many factors involved... you mentioned the drivers - obviously the surrounds have a certain amount of mechanical "break in" - this was most noticeable on the bass initially...
As for what physical laws? I can't say - what I can say is what is heard. Here are a few variables that come to mind:
Sonicap Platinum - upgraded caps - I am positive I have read in many places it takes a few hundred hours before optimal performance is reached - maybe a factor...
Internal wiring - also new, and the dialectric will stabilize over time. If this is 5 minutes or 2 weeks - I don't know.
What I can say for certain, what they sound like today is MUCH different from two plus weeks ago... this is not due to "ears becoming acclimated"...
Notable sonic changes - sound was "compressed" when speakers are new, soundstage compressed as well... dynamics, both macro and micro weren't there... bass was "weak" and not as fast as it is now.
The sound was "there" however, sounded more like details, rather than music.
The sound now is much more "relaxed", "effortless", the attack is there, the decay is there, harmonics are there... the sound is similar to if an acoustic guitar was plucked in the room... you hear the strings, you hear the note, the resonance, the decay, etc. Initially it sounded like a recording of a guitar (maybe even tape recording, as the bass wasn't fleshed out yet), now the sound is very lifelike.
What I can not explain is if the W18 & G2 measure the same on day 1 and day 60 perhaps they don't sound the same... perhaps the crossover you are using is fully broken in, and not new, perhaps the wiring from the crossover to the drivers is also broken in, etc.
The other variable that has become much more noticeable is much of the changes with break in are much more apparent as the associated gear is more refined. I used to be in the boat that "break in is nonsense"... as the system has evolved, also has the clarity, the finesse, the detail, etc. Subtle changes, such as a power cord, or tubes are just as noticeable as a speaker that has a woofer that isn't as fast as the mids and highs, as well as the soundstage collapsed and such...
Just a few wandering ideas...