So..I just got mine Sennheiser HD560s, a quick impression:
- build quality and feel can't be compared to Beyerdynamic DT990/Custom One or Fostex T50RP MK3. I realized that I strongly prefer metal headband and sliders. Sliders on HD560s have hardly any friction and they move very freely. The only slight advantage is their lower weight due to complete plastic build. I've read a lot about Sennheiser plastic being very sturdy, but the doubt is still there and I kind of expect them to break at some point.
- sound out of the box is.."shouty", bass is "ok", treble could be a little lower/smoother(? it's hard for me to describe it). In direct comparison to Fostex I like Fostex more.
- Oratory PEQ fixes most of the issues, but bass and overall "smoothness" is still not on the level of Fostex (maybe I'm just too used to their sound)
- "out of the head" effect is very, very nice on HD560s, the typical left-righ channel separation is missing. I could listen to them without virtualization/crossfeed effect, in fact they sound better without it. Tilted drivers might be my favorite feature from now on.
- comfort out of the box - not terrible, but not great either. It's probably too soon to evaluate it as I expect earpads to loosen up a bit. Round profile of earpads is more comfy than the "old" version of HD600/650, but not on par with Beyerdynamic ear pads. If I keep them, I'll buy 3D printed adapter rings and try Dekoni/Brainwavz/Beyerdynamic ear pads (already own them, so no additional expense except the rings). I expect the sound profile to change, but maybe I'll find a "good enough" compromise between increased comfort and not so degraded sound quality.
I will certainly give them more time and more thorough comparison with Beyerdynamic Custom One + Fostex T50RP. I am especially curious how will tilted drivers play along with virtual surround in games/movies.
All in all, not "love at first sight", but they might grow on me.
Edit: kept the headphones on my head for a few hours, comfort didn't change much. :\ I will try to attach DIY leather comfort suspension strap, it will look funny, but could help.
Also I played with EQ, after some tests I prefer more simple change than Oratory's one - more bass + fix of ~3-8kHz region only (I kept these filters from Oratory preset). Other frequencies IMHO don't need any change. With GEQ I can get "close enough", even though PEQ sounds better. For anyone interested I'm using these settings at the moment:
Filter 1: ON LSC Fc 105 Hz Gain 5.5 dB Q 0.7
Filter 2: ON LSC Fc 100 Hz Gain 1.8 dB Q 0.9
Filter 3: ON PK Fc 3230 Hz Gain -1.2 dB Q 4
Filter 4: ON PK Fc 4450 Hz Gain -3.2 dB Q 5
Filter 5: ON PK Fc 5490 Hz Gain -3.5 dB Q 3.5
Edit2: I did a comparison with Beyerdynamic Custom One headphones while connected to my TV/PS4 console. HD560s shines here, especially due to the fact that they are open and tilted drivers probably add some "magic" too. Sound profile with both headphones equalized is similar, but HD560s are a touch more clear. Bass is stronger on Custom One headphones, but it's muddy in comparison with HD560s (I will probably need to modify my EQ settings). Music and games sound better on HD560s. Movies are a tie and both headphones can be quite sibilant/harsh, but I am starting to suspect that my Samsung smart TV (or Netflix app) does some shenanigans to the sound profile as almost all my headphones are sibilant when watching Netflix shows, even if I tune down all frequencies above 2kHz by -9dB. It doesn't happen (or I just don't notice it enough to be bothering) with games or Youtube videos/music, or when I test the headphones on my PC.
Long story short - Fostex T50RP MK3 with PEQ stay as my main music headphones, Sennheiser HD560s with GEQ will be my primary choice for TV/gaming and Beyerdynamic Custom One Pro stay as a backup and for times when I need a good isolation (from outside noise or to not to disturb others).