Got mine earlier today and have given them a few good hours of head time. They're really, really good. Probably my second favorite EDM headphone so far (see signature for what cans I use, note that I haven't had a chance to use my SR-404LEs yet).
That said, they aren't dethroning the TH-X00 PHs for me. They almost sound like a junior version of them, with more similarities than differences.
As much as I like them, here are some nitpicks:
Blue's highs aren't quiet as bright as the TH-X00 PH's and probably wouldn't need any adjustment on the Loki. LSD by Ghastly is one of the most treble-harsh songs I know and the Blues handle it well, presenting most of the energy without harshness, but there is some veil. TH-X00 PHs have noticeably more energy but border into harsh without some Loki tuning.
Bass on the Blues is emphasized, extended, impactful, and fast. That said, I don't love it. I'm not sure I can describe this well, but I think there's two main issues with it: 1) the Blues sound like a sub near your ear rather than just consuming you with bass, and 2) it sounds a bit mechanical at times...the oscillations in some basslines are almost too clean and fast, like I can count the Hz instead of just experiencing the sound. The basslines in Stay For It by RL Grime (ft. Miguel) and Loco Ono (Jayceeoh Remix) by Bassnectar are good examples of both of these behaviors.
Lastly, I'm particularly sensitive to "ess" sounds in vocals, especially higher-pitched vocals. Most headphones hold/ring the sound too long and sound harsh to me. The Blues are not an exception. I expect most headphones to struggle with Yael's vocals in Body and Soul by Borgore (ft. Yael), but the Blues also struggle with Charlie XCX's vocals in Love gang by Whethan (ft. Charlie XCX) and I even catch a tiny bit of it in Miguel's vocals in Stay For It by RL Grime (ft. Miguel). It's not a matter excessive vocals either, the Miguel lets it rip in Stay For It with the TH-X00 PH's but he's a bit more subdued on the Blues in addition to the hiss ringing.
The soundstage is a little better than on the TH-X00 PH, but not a ton. It's mostly moot for what I listen to, but Yosi Horikawa songs struggle almost equally on both. There's almost no layers of depth like there are on my HD700 or HE-400i. Imaging doesn't seem that bad though.
The Blues also respond really well to the Loki, which is a nice plus. My Beyerdynamic DT990 Pro and Monoprice M1060C can't cope with much of a bass boost so having so much flexibility is nice with the Blues.
Nitpicks aside, if I weren't already enamored with my TH-X00 PH's, these Dekoni Blues would probably be my daily driver.
EDIT: They also flare up the hotspot on the top center of my head. But basically every headphone I have except the HD700 and HE-400i do that at least a little after a couple hours.
Not like I know from experience or anything......
