It would seem that the latest version of the ZiTrons, while they have "bass" definition, have distinctly less bass weight than other generations of Shunyata cable. For example the original Python power cord has considerably more bass weight than the ZiTron Cobra power cord, although the Cobra excels in definition. However, weight = solidity of image, a reason that the original WATTS had such image density (earlier WATTS had more mid bass than treble, especially generations 1 and 2, and 3, all of which I had back in 1987 thru 1993). And Dave used Transparent to fill in the early WATTs' lack of bass, just as he used the Rowland Coherence 1, which had more lower midrange-to-low-bass power than the other legendary preamp of the time, the Audio Research SP-11. The Coherence filled out the WATTs' lower midrange paucity (and so did the Transparent cable of the time.)
Transparent cable has a much "richer" mid bass thru lower midrange than Shunyata. I notice that brass instruments on the Cobra do not have the same "body" that they did in previous generations. The "goldenness" of brass (the way it sounds live, thanks, not on recordings, although some recordings have beautiful a brass sound) is less apparent. Midbass is where the "authority" comes from in sound, and I immediately noticed the Cobra lacked in the body previous generations of Shunyata had in spades. I believe this is also mentioned in the Audio Beat review by Mickelson, where he specifically mentions the Cobra's bass as more "sinewy" than muscular (my bolding, not his). Transparent has always been a bit closed in at the top, especially the original Ultra line, back circa 1994, which was one very dark cable. I remember Tom Miiller of TAS telling me that it was going to sound that way, and when I got it, it did.
When a cable is weighted at the bottom, but does not have equal extension at the top, the cable will sound "dark." If the treble is extended - and airy - it will NOT sound dark, but it must have both those virtues in equal measure. The Shunyata is extended in the treble, and airy enough, but has a lightweight sound in the mid bass. Still quite good, but tonally more ice milk than ice cream.