Pros: Incredible detail, good tonal balance, good build quality, swiveling cables
Cons: Very strong treble presence with a huge peak, can be fatiguing, needs deeper insertion to avoid sibilance, swiveling cables
The following is taken out of its context from my review here http://www.head-fi.org/t/687962/asg-2-ck100pro-and-ue900-reviews-the-dysfunctional-family I just thought that the CK100Pro deserved a review here. I don't own it but have auditioned it extensively over about 8 days. Though I just might buy it later...
CK100Pro: The Sheldon Cooper of iems
Contrary to the warm and caring curling mom, the CK100Pro is quite similar to Dr. Sheldon Cooper of The Big Bang Theory. If you're not familiar with that show, you should google it. Incredibly intelligent and sort of a wonderchild, Sheldon Cooper has a thing for always pointing out every single mistake that anybody makes. A small flaw becomes a glaring error in the eyes of the CK100Pro. Sheldon also has a tendency to explain everything, so does the CK100Pro. Given the right circumstances, the CK100Pro is potentially the most detailed, highest resolution iem in its price bracket (just guessing now but it fits with what I've read and what I've heard). If asked to play too loud or play flawed material, it can potentially be the worst listening experience of your life.
The CK100Pro's strengths are details, details, details, details and details. A slightly elevated mid bass that doesn't bleed into the mids make for a little harder impact that's still very fast and well textured. Mids that have good presence and great detail across the spectrum. Treble that's extremely detailed and if given the right song and the right fit and the right volume, is very smooth and extended. A good soundstage with good separation and layering and an airiness that makes for an uncongested listening experience.
The weaknesses are the inability to play music that's not well produced, inability to play on louder volumes and the possibility of a bad fit that induces sibilance.
The CK100Pro works particularly well on lower volumes. The most detailed iem I've heard on lower volumes. Easily beating out the ASG-2 and UE900. The isolation is good if a good seal can be achieved. So good that it blocks out most of the commuting noise making it a good choice for noisy environments. However the sound is very different from the ASG-2 which is also a good commuting iem. While the ASG-2 manages to sound full despite the noise, the CK100Pro manages to sound pretty flat despite the noise.
The sound: The sound of the CK100Pro is mostly neutral but with a boosted treble. The bass is fast and can hit hard, the mids are pretty much neutral in tonality but lean more towards cold than warm. The treble is very detailed and extended. It feels a bit like using a fine sand paper. I guess that would make it a dry treble. Extremely detailed, part of it due to the high level of treble and upper mids present.
The bass is very fast. Not much decay compared to ASG-2. Still has good texture. There is a very small mid bass emphasis. Impact is greater than rumble. Doesn't really affect the tone and doesn't bleed into the mids. Not much to say here. The bass hits and runs.
The mids are tonally pretty neutral. If anything I would say leaning towards cold. No real flavour, just very transparent. The upper mids can be harsh on occasions. That has more to do with recordings and volume than the iems. It's actually very hard to describe the mids as I can't really think of anything to describe them with. They almost don't do anything wrong. They also don't excel at anything since they're so good at everything. But very detailed. The mids are rarely the problem.
The treble is bright. There is a lot of it. The emphasis is more towards 9kHz than 8kHz. That makes sibilance seem a bit brighter than usual. Given that the fit is good. If the fit is poor and too shallow, the treble will be ear piercing and you will wonder why you ever put them in your ears. Best case scenario the treble has good fundamentals (more upper mids than treble really) very good detail and great extension with a good sense of air. High pitched instruments sound very lively.
Imaging and soundstage is superb. A large soundstage that's wide and decent in depth and height. The fact that it's airy and never congested is a bigger plus than the absolute height or depth to me. The imaging is great and separation is top notch. Sometimes I feel that with the great details, the tonality and the imaging, it's so realistic it's unrealistic. That I'm hearing what I expect the instruments to sound like, placed where the sound engineer placed them. Instead of hearing the music. I'm hearing instruments and vocals instead of music. Details instead of emotions.
Is the CK100Pro a good buy? If you like details, can handle lots of treble, can shove things into your ears that weren't really built for it and can live with the swiveling cables, yes. The build quality feels premium except for the cables. The swiveling cables is a great annoyance but also great for getting a good fit and a good over ear placement of the cable. It also sees to it that the housings can be rotated to fit the angle at which your ear canals start.