I’m not familiar with the Anthem’s handling of bass management, but my understanding of the Outlaw 950 leads me to believe that choosing different crossover points for main, center and surround does not produce a ‘gap.’ In digital mode, if L/R are set at 60Hz, the center at 80Hz and the surrounds at 100Hz, the sub receives all that is below each setting, channel by channel. When using analog bypass mode with bass management ‘on,’ all speakers get the same 80Hz crossover split.

As to timing and phase, I suppose an ideal adjustment could be achieved with enough course and fine control over time delay for each channel, but only for one point in space. Since some of us will be listening with two ears and those ears may move from place to place within the listening area, maintaining any exactingly obtained phase relationship for the listener would seem impossible. ‘Ballpark’ would be about the best one could hope for. Then there are the myriad effects of reflected sound and/or standing waves. There is almost no end to the things that need to be taken care of in the pursuit of an unattainable ‘perfect sound.’ I think we end up with the pursuit of an ‘acceptable’ sound.

Four imperfect solutions:

One, put the subwoofer/s under the chair or over the head of the listener. If that means the sub is four feet from the listener’s ears, then all the other speakers should be four feet away also, and all delays at zero.

Two, similar to one, however most speakers’ placement is normal and the delays are set normally. The sub, under or over the listener, would need to be delayed even more than the other speakers because it is closer to the listener.

But sub placement near the middle of the room is rarely good for low frequency response.

Three, each loudspeaker has it’s own subwoofer adjusted in phase with that one loudspeaker. But such subwoofer placement is also rarely the best.

Four, the subwoofer phase of one or more subs, some people liking stereo subs, some people liking a separate LFE sub, are set to agree with an aggregate of either the main L and R, or L, C, R, or all speakers in operation at once. As a listener shifts position, the listener receives the best compromise available within realistic means wherever they are.

My own real world example is the running of stereo subs via an Outlaw ICBM between pre/pro and amp, each sub not too far from, but not co-located with, the my main L and R speakers. Each sub is in general phase ‘agreement’ with the appropriate L and R speaker, which certainly helps with stereo listening. For surround listening, phase ends up approximately correct for the center speaker also, whose low frequencies are sent to both subs equally, so center and sub sounds reach the middle of the room at nearly the same time. The rear speakers are about the same distance from the center of the room as the fronts, so there is general timing agreement for those speakers as well, if one listens near the middle of the room. Listening from near either end of the room means ‘all bets are off’ if one is concerned with maintaining some type of exacting timing/delay relationship, but this hasn’t detracted from my enjoyment.

With no perfect adjustment for everywhere in the room, and with a fully enjoyable result obtainable with correct coarse adjustments, it doesn’t surprise me that most equipment treats this issue in a minimalist fashion.