Need a very neutral interconnect-

I define "Blacks" as a slightly darker and thicker air around individual acoustic images in open (natural and pleasant) sound stage. This helps to see/identify acoustic images clearer. It's not like a halo/haze (bad! you don’t want that!) which is the outline of acoustic images but more like background. Blacks make background quieter that the sound stage is not confused with many objects in sight. Blacks can be small just around images or huge to cover whole back ground. Some cables or gears have very dark background such as early Mark Levinson gears which famous for quiet and silky black background.

I have XLO type 5 and type 5.1 speaker cables. They are identical in the sound stage, resolution, and imaging. However, Type 5 sounds slightly darker around acoustic images, and Type 5.1 sounds natural and transparent that you see through the sound stage like nothings there which makes easy to see the picture on the back wall. Theoretically, Type 5.1 is the better cable. I choose XLO type 5.1 speaker cables for my home 2ch sound system because my room is acoustically pretty dead and the back wall is dark. This makes the pleasant sound more stand out from the dark back ground. I choose type 5 cable for my studio set up because my studio is acoustically live/bright and the back wall is with 2 big glass windows. This darker background helps to see/hear acoustic images without interference from bright surroundings.

I have an extra Type 5.1 cable that you can compare both cables at my Los Angeles studio. Also, I have few isolation devices you can hear the difference.

A background lacking hifi reproduction gear generated noise is all this should mean. I want to hear the glass clinking Madmen era laughing drunk ass NY crowd at the Bill Evans show...or the cool man low hum of anticipation at a symphony...the room Yo Yo used for his solo Bach. Otherwise you can keep your dead background, and add "black" to the lexicon of useless audio terms invented by reviewers...like "speed" and "PRAT". I'm stickin' with "alive" and "ambient" and "warm" in my listening room...dead will be here soon enough.

Correction for above post!

my room is acoustically pretty dead and the "Back wall" is dark.

Back wall =>> wall behind speakers = Front wall.
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My experience is similar to Mihorn's. The way I put it is some components/cables that have more of a "quiet" or "black" background is like hearing a band playing directly in front of a thick, black curtain. Everything on the stage is a little more solidly present and clearly defined in its own space, but things like air, space, reverb trails, see-through transparency -- while still there -- are a bit squelched relatively speaking.

By contrast, other components present more like a stage that is set in the middle of a room where you can see right through the band and sounds fly off freely in all directions making it easier to get an idea of the recording space/venue. Things like reverb trails seem to trail off further into space, and it's a little easier to place players in more of a 3D space although the images are more airy and less solid sounding. It's kind of like the difference between a "they are here" vs. "I am there" listening experience. I have no idea which presentation is more accurate and I enjoy each of them depending on the type of recording and music I'm listening to. I also find the "black" background makes me feel like I'm sitting closer to the band whereas the more airy presentation pulls me several rows back where sounds are more distant but I have a better perspective of placement within the venue. The cynic might say it's a little like turning the treble control a little up or down, but I think that's a little too simplistic. Anyway, that's my experience with it and the best analogy I can come up with to convey it. Hope it helps someone somehow.

Well by Milhorn and Soix's definition of black, which I understand through their descriptions and have heard in some systems over the years including my first real hi-fi system from the mid 80's with a CJ pre-amp that was really good at this, a darker presentation. It seems to me that such systems are obscuring musical and ambient information with greater focus of the instrument's fundamental tone which would also obscure harmonics, decay and ambient cues of the venue. To me this is clearly less resolving therefore less accurate. Not that it's a bad thing, just a matter of choice, certainly not mine. I have never heard this effect in live music only on hi-fi systems.

So it seems, at least to me, there are different meanings of "the blacks" to different listeners'.