Active Subwoofer Crossover

"one feature in particular that i found has made a significant difference is the ability to time delay the mains. once the crossover and delays are dialed in, the integration between the sub and mains is absolutely seamless".

"I’ve changed the crossover to 45 hertz and like the overall sound better".

+1 to both.

Also, a 45 Hz crossover means that bass can be separately adjusted if needed, say, for a particular recording, without unduly affecting the chestiness of male vocals or other lower-midrange sounds.

I've found more flexibility, with subwoofer crossovers in particular, to be key. Pretty difficult to overrate in an ideal setup, let alone in anything like a problem room or with unusual gear. 
Cheers.

Ricred1, sorry I overlooked your last post until now, my bad. Assuming you’re still looking for an answer, 80 Hz is really only a ’standard’ from the pov from a consensus of manufacturers...originally introduced to help consumers mix and match different brands of speakers, subs and receivers together back when surround sound was being introduced. It began as a midfi kind of thing. As you go up the food chain, the bigger working budgets allow the majority of manufacturers to solve the same possible integration problems in various ways...subs that cover higher frequencies, or satellites that go lower, etc. In that territory there is no standard, per se, since audio companies are perhaps more free to solve things for their own customers the way they see fit...but, some solutions may seem a bit more "universal" (or flexible) than others.

As for phase, there has never been a way to reliably identify the correct phase of a recording other than by ear. Whichever way sounds better, presumably, is the more correct choice for a preamp phase switch (if you have one), but it is to be applied to each recording. Some phase controls, like the ones for subs that offer a continuous range from 0-180 degrees, can be used to compensate for the difference in phase response at the lp between the sub(s) and the speakers, especially when the subs have to be placed and positioned in the room with tonal response as a top priority. This is dialed in by ear with respect to the lp, too. It can work pretty well, really...or at least if your subs are forward firing. Downward firing subs, or omni-directional as well as at least some of the more non-traditional sub designs (like transmission line, possibly) may or may not respond to a 0-180-phase control as well as a traditional forward-firing design. An ideal overall solution might be something like the DEQX, which can make linear the phase response of the entire speaker chain from top to bottom...very high performance, but also very expensive...and, of course, absolute phase of the recording would still be unaffected by that and independently still require a +or- phase switch. I don’t have such a switch for absolute phase, but haven’t really lost lots of sleep over it, I guess.

Hope this helps.