Let me put it straight. before buying these I have never heard any decent headphones. What I wanted was neutral sound (because you never know how much they will color your music) and some changeable parts (because you never know how long they will last). I also appreciated bass adjustment since many people are usually complaining about lack of bass on analytically-sounded phones. Oh, and yes, I didn't want to sell my computer to buy them, you know. So I found Beyerdynamic Custom Studio.
Sound
I listen mainly to black, experimental metal and some asian folk music. Don't laugh. And as I said already I had nothing really to compare with, speaking about adequate headphones, but here's the thing: I immediately heard every single details on Blu-ray PCM-stereo track, it was 16 or 24/48 I guess. My entire lossless 16/44.1 library sounds fantastically.
Here you have quite detailed highs, amazing vocals and decent bass. Overall I would call headphones dynamic and brightly sounding. They can't provide even as much bass as your average musical headphones, though, but here you go. They're studio things... Again, it's always better to compare stuff with something before buying, but I'm sure you will be satisfied for 100% if you nee entry level neutral headphones and you don't know how much bass you would need. Because sonically I found totally nothing to complain about. I'm pretty sure people working in home studios will like these as well.
I tried these with Fiio E10k, Creative SoundBlaster E1, iPhone 6 and iPad Air. Guess what? Fiio is the best obviously. The scene is bigger and thing are quite a bit more separated but still I can't say listening to my 16/44.2 ALACs through iPhone 6 is horrible. It's rather good. They gently handled every single source I've put them through. Now that's something you're not expecting from studio headphones usually.
Anyway I think they are capable of much more. Just like any good phones. Will definitely check them out with some Schiit!
Bass adjustment has four positions. First has almost no bass at all, last one somewhat goes out of the control. Maybe first position can be somehow suitable for monitoring, but not for music, I guess. But still you have these second and third positions which sound brilliant. You just need to choose one. Or adjust bass for you mode! Who knows.
Design
They're instantly super comfy, at least for a few month. After that period of intense use I ended up with drivers touching my ears. It happened again when I changed pads. It's just ear cups being not to deep. So when pads become shallower drivers are coming closer to your ears and rest depends of their size. Otherwise they are quite roomy and quite comfy. You can't fold them, still headband made of rugged spring steel so it's amazingly flexible. No problems disassembling thing, replacing pads, cleaning stuff.
You can customize headphones by changing side plated that you buy on Beyer's site or from resellers. There's quite wide range of them. They're made of aluminum in Germany as well but quite expansive. Still, you can make your own probably. You can change headband cushion as well. There're few color variants made of synthetic leather.
Interesting stuff goes on with ear pads. When you decide to change them know this: they have the same pads as DT 770s do (EDT 770VB - black or EDT 770V - light). Not DT 990 (EDT 990VB). They're just black out of the box. When I first decided to buy new pair not a single reseller had them so they argued with me to buy EDT 990VB claiming that they're the same. It turned out they're not. Custom Studios have generally closed design so they have same pads as closed design 770s do. Now you can imagine 990s have breathing and "open" pads. So I returned them and bought EDT 770V (light). Now they look as DT 770 Pro. You can call it customization as well.
Every single part except drivers themselves I guess is interchangeable with Custom One Pro.
I have few things I don't quite like here though. First is that plastic parts serving as connectors of cup holders and headband are wearing off over time and don't hold position properly. But headphones are quite cheap, so you can deal with that one. Another thing is that cable connector is proprietary. Yeah, you can change it, but only for cable from Custom On Pro or for the same one. You can get straight one or coiled.
Verdict
If you have collection of more or less neutral headphones intended for music and (or) home studio use that are priced in midrange, you should definitely have these in there, just next to your ATH-M50x. If you just need first one, go buy them.
