It took a while to familiarize myself with the Tubulus Concentus due to some server issues & replacement hardware, but I think I've got a handle on it now. The .75m Concentus replaced a 1.2m Furutech HF-X NCF, which imo should get more recognition for i2s at its low price point. The chain I'm using is DIY server/Jcat USB XE > NA Muon USB > SU-6+Hypsos > Concentus > modded Spring 3.
As far as the Concentus goes, the first thing that hit me was the sweet, realistic treble. A lot of people use sweet as a synonym for "rolled-off", but that's not the case here imo. It just sounds so right and easy to listen to, without any loss of detail or spatial information. I don't really consider myself a treble-head at all, but the more attention I pay to the digital side of my chain, the more sensitive I get to changes in treble reproduction. The bass is the second thing to impress -- right off the bat, there was a ton. Since my cable was secondhand, Idk whether or not it was fully burned in, but after a couple weeks in my system the whole frequency spectrum is beautifully balanced, and the bass still goes low and hits hard when the music calls for it.
The last thing to come into place, and what had me worried initially was the midrange. For the first couple days the Concentus beat the Furutech in everything but midrange saturation/density -- the Furutech has a really fun sort of "engagement factor" that I think stems from how it portrays the midrange. Initially the Concentus' thin midrange was a letdown, but it really filled in nicely over time and landed exactly where it needed to.
Other general qualities: image placement and soundstage is just a no-brainer. It's a silver cable in an air dielectric, no need to worry there. It goes wiiide and deep, but never sounds unnatural or disconnected to my ears. Dynamics are also surprisingly good -- I didn't expect much improvement here, since Furutech's house sound is already pretty dynamic, but the Concentus has surprised me a few times.
