ATC are known for their dome mid driver. This is what they are most famous for and supposedly this dome has magical properties.
The idea of splitting the signal into parts has the advantage of being able to deisgn drivers which are optimized to reproduce the frequencies they cover.
However as with all speakers that use multiple drivers, splitting the signal into parts requires the parts to be summed up again using a crossover. The result will never be as good as if the signal had remained undivided to begin with. It takes GOLDEN EARS to really hear these deficiencies. I’ve not heard or read anybody speak about this so it can only be assumed that 99% of audiophiles aren’t good enough to really identify these flaws. I have been to speaker demonstrations where the speeakers were wired up out of phase to each other. Apparently I noticed it immediately whereas the guys doing the demo couldnt hear it. It was both laughable and shocking at the same time and goes to show how even flagrant mistakes can go unnoticed.
I did once hear the ATC SCM25. I heard no magic going on in the mids. In fact I was not impressed with what I heard overall.
heres a post from a ATC SCM25 user
https://gearspace.com/board/high-end/976060-atc-scm25a-revealing-just-wrong.html
I can barely listen to some older songs I used to like purely because they sound so bad on these monitors...