What else would a crossover have to do besides those three things?This generally demands a custom made crossover since simply manipulation of slope/level/frequency is, more often than not, only part of the functions required.
This is a fairly common refrain when this topic comes up, but I often wonder just how much of it is verifiable - and indeed, actually verified - and how much is merely repeating what someone who was supposedly knowledgeable on the subject had to say? Someone who probably was a passive crossover designer to begin with? And probably did not even peruse active options for whatever speaker he was designing?That is certainly one valid point. However, my point was that this requires knowledge and skill since there is no off-the-shelf crossover that will do these things out of the box. Either one must design it or program it. This, alone, makes active biamping, though desirable and advantageous, out of the reach of the vast majority of audiophiles.