Thanks for the excellent review. If crosstalk reduction were more common, more recordings might be made in a more "hands off" way. As I stated earlier, I’ve not heard BACCH myself, but I’ve used a physical divider, and as you experienced I too heard that less processed recordings tend to do the best, except in the case of purely processed electronic recordings, which can also produce glorious spacious presentations. I think it's interesting that you mentioned "Homeless" in your review. That's been an important track for me as I set up different systems because it should sound amazing with it's rich and dramatic vocal dynamics and harmonizing. I think that track does a good job of revealing problems with listening rooms and speaker placement because it requires clear solid energy in most room's transition zone, where rooms have a way of ruining things.
I think you bring up a good point about most high end stereo equipment manufacturers ignoring the crosstalk issue. Why aren’t more people talking about it? I think a big part of it is that for the longest time there wasn’t any really practical way to address it in many listening scenarios. Recordings were made in two channel format, expected to be played back with a stereo pair of speakers, and the shortcomings were self evident and accepted because, as we all know, it can be very pleasant to listen to, and better than mono.
A similar accepted limitation with most video/film presentation is that we don’t expect it to be in 3D. 3D can add a lot to the visual experience, but it’s a lot of extra effort, and unlike with audio, the crosstalk is visually unbearable so some kind of glasses usually have to be worn if a large audience is to enjoy the effect from various viewing angles. With audio the crosstalk also profoundly reduces the quality, but our mind is more forgiving with audio crosstalk than with visual. Early 3D glasses were of the red/blue lens type, and this obviously had a seriously negative effect on the visual experience despite making it 3D. Similar weirdness can happen when attempting to correct audio crosstalk with crude methods. Now with polarized glasses and other methods it’s possible to get a clear, high quality 3D image with accurate color and very minimal visual artifacts. Similarly DSP can be used with audio now to practically remove the crosstalk artifacts we’re already living with while adding hardly any new audible issues. It’s a huge win.
But you are right - it’s more complicated to set up. More players coming on-board with this type of technology could, in time, make it much easier to implement.
About the quality of your components impacting crosstalk - they don’t. It’s a physical setup problem inherent to using two speakers. It takes some specific processing or a special speaker arrangement such as Polk uses to address it successfully. That said, there are different kinds of crosstalk. What BACCH is addressing is inter-aural crosstalk across your head coming directly from the speakers. This is by far the most severe crosstalk that reduces the overall sound quality, degrading the stereophonic effect, and also introducing severe comb filtering for center panned sounds at each ear, and at frequencies we’re very sensitive to. There’s also room reflection crosstalk, where the sound from the right speaker bounces across the room to the far wall and then enters your left ear. I think BACCH may be able to address these early reflections as well to some degree. There is also crosstalk between channels that can occur in electronic devices. This is generally not much of an audible problem in modern electronics.