I've logged around 60 hours of burn-in now, and I am already much happier and have a lot to say. For $200, I'd better have something to talk about, right?
The first and most drastic change I noticed came rather early, at the ~15 hour mark, after a long session without listening. The biggest flaw was much improved. The mids had opened up and were sounding pretty good, especially compared to the muddled and suppressed sound they had in their factory fresh state.
Since them I've been burning them in with heavy regular listening and a few solo hours here and there. Logistically, that part has been surprisingly difficult. I don't have a dedicated music source, so freeing up a device for that purpose isn't always an option. I can't leave them lying around at home with 2 unsupervised cats. Can't do it at work; too distracting, and I don't want to have to explain the unlistened-to headphones to everyone that comes in my office.
I have to start with the mids... through 60 hours, the mids are in a different universe than out of the box. Becoming lush and vivid, they are almost as good as the bass. Incredible turnaround, particularly the lower mids. Now works with the bass to do some amazing things, especially for bass guitar. The best single sound I have ever heard come from these, or any headphones for that matter, is intervals being played on bass. Spectacular. Center mids are very well balanced and strong but are slightly muddy at times. Center through upper mids are rather clear and never tinny but could be sharper. These problems only exist for percussion, piano and electronic sound. String instruments are great and vocals are excellent. Probably the strong suit after bass.
There are some clarity and separation problems with the uppermost mids and much of the treble. If that range gets really crowded, it can sound a lot like the emptying of trash cans. Passages heavy with cymbals turn into a flood of disagreeable noise. Rather annoying, but could be a lot worse and I can't imagine it stays this way. Things take a sharp turn for the better as you go up. The slight harshness is all but gone, and there are hints of a nice little extension profile developing way up. Not something I expected.
Bass was great before and is better now. Frequency profile seems unchanged. Overall presence is being fine tuned. Harmonic response is very noticeable, almost live sounding. Has become really fluid. Close to perfect in terms of versatility and accuracy. This may have to do with the lower mids shaping up. I could be wrong, but I think the CKS1000's intent is to accentuate bass with the focus on fidelity, not effect. You hear the sound as it was recorded, with a high degree of percision. You won't exactly get distorted, rumbling or ground shaking type of bass, because that's typically not a true, recorded sound. But these are more than capable of deep, heavy bass. I haven't come across a bass note or passage these can't handle.
Overall, separation continues to develop throughout and the soundstage is just beginning to form and expand. I can't say enough about the lower half. Still plenty of room for improvement, mostly in the neighborhood of 5khz, which can sound dreadful once in a while. Crowded mixes strain the separation and soundstage. The most layered of songs come through with an effect similar to loudness distortion, even to the point of dampening the bass a bit. The biggest weakness is percussion, which goes both ways. Usually has a great sound but suffers with busy drumming, unless it's all kicks and toms. (Edit: was only guessing, but just tested this with "Hot for Teacher" and it absolutely passed.)
I should note that I am still using the stock tips and am just now looking into getting some others. This all could change with that in addition to burn in. I get good isolation-enough to tune most common sounds out but not being so walled off as to get hit by a train. I probably have the intended sound, or close to it, but these are fairly uncomfortable. After a lot of listening my ears are actually sore. I think this is a combination of the size/shape of the earpieces and the large stock tips being a little too big for me. The earpiece size doesn't seem like a problem with the right tips.
Less importantly, the build kinda sucks, I guess. Microphonics can be horrible when walking, but mostly goes away if you fix the cable to something. I guess a shirt cilp would work, I usually just rig it with shirt buttons or find another way. I also hate the dual cable. The control/mic connector causes some kind of cracking/cackling sound at random so I use the regular connector. So there's no function, but I have a stiff, weighted object in the middle of what would otherwise be one continuous cable. Very annoying. That, along with the shape and size of the earpieces cause these to constantly be tangled, even if I'm just putting them down for a moment.
Yeah, I could probably write about these things all day, but to the point... As of now, I'd say they sound pretty damn good and are worth what I paid. And apparently they still have a long way to go, which is awesome. My advice is, while it may take several hundred hours for CKS1000 to fully mature, you'll still get good returns much earlier in the process. Just stick with it and enjoy.
Edited by acompli - 9/28/13 at 3:31pm