Performance

In order to test these earphones fairly I had them burning in for almost 100 hours. Before that you should not expect them to be able to perform their best. The sound became so much more balanced and the grain completely disappeared. To begin with, the treble was really harsh and fatiguing to listen too, but that was cured with some burn-in. The midrange also became a bit more natural in its presentation which is a nice thing.

To test these demanding earphones I used both my Cowon along with an amp and without to test the effects. Besides using the DAP plus amp combo I also tested it with my Octavart "The One" DAC & Amp which I have hooked up to my computer. The Yuin OK1s proved to be just as hard as the PK1s to drive properly. I started off testing them just in combination with my Cowon iAudio i7 which is quite powerful for a DAP, but it was nowhere near powerful enough to control the OK1s. The sound was lifeless and it was pretty clear that the sound quality suffered from the lack of power. The highs were severely rolled off and the bass response was quite poor, both from a quantity and quality point of view.

After pairing the Cowon DAP with my old and trusty Go-Vibe V6 the sound quality got a major boost in the positive direction. The bass became much more present. Besides gaining amplification it also became way more textured and detailed. The transformation was quite mind boggling and I had to A / B the two a couple of times to believe my own ears. The midrange is really rich and highly detailed, compared to my LiveWires. The Yuin OK1s have a much more in your face kind of sound whereas the LiveWires gives you the impression that the artist is quite away from you. The midrange quality is better than that of the LiveWires due to its amazing speed, it is just so much more revealing. The LiveWires are fun and have lots of bass. The Yuins are different, for starters they are way more analytical in their presentation and have a more neutral sound signature. The highs have a decent amount of sparkle, but it is nowhere near fatiguing at least not in any of my rigs.

The sound stage is quite good for a pair of earbuds. When amped you get a real sense of space between the instruments both depth and width. The sound stage is more 3D than the PK1s where the positioning tends to be limited to left or right or anything in between. Vocals sound more natural on the OK1s. The midrange of the old PK1s suffer a bit from a bloated midbass and bass, the OK1s are more analytical and less colored. Where the Yuin PK1s can be considered warm I would call the OK1s lukewarm.

The mids and highs of the Yuin OK1s are really quite amazing, much better than that of the old Yuin PK1s. They are much more refined and convey small details a lot better. Sonically they seem to be way better balanced for a natural presentation. If you are looking for a pair of natural sound earbuds the OK1s are definitely a major step up from the old PK1s. You do loose a bit bass and midbass which is the reason why the PK1s sound fun, however, I will gladly sacrifice that in return for the balance and more lifelike presentation of the OK1s.

The Yuin OK1s are true performers when amped properly. When you run them off most normal DAPs they will sound plain and dull to listen to, however, once you give them some juice to work on they spring to life and deliver an outstanding sound quality.

As earbuds the OK1s are highly recommendable. When fitted with the canalphone adapters the OK1s are not all that good. First of all the seal is not all that good. I was able to get a good seal about 1/10 of the times I inserted them, and I lost the seal shortly after insertion. The problem is that the canal adapters extend from the main body of the earphones in a 90 degree angle and therefore do not align well with your ear canals. A normal canal points downwards and backwards coming from your inner ear. And since there is no offset compared to the body of the earphones they misalign. In order to compensate for that you have to angle the whole earphone which in turns forces you to press them against either your earlobe with the big adapter or your ear's concha with the short adapter on. No matter what you do, your ear’s anatomy ruins the fit. This is in my opinion a major design flaw because it is not anatomically correct.

The comfort while using them as earbuds is really good. The shape of the earphone's body is nice and wraps around inner edge of your ear nicely. The fit was quite good just like with the older PK1s, they stay in place and do not irritate the ear.

Durability

The Yuin OK1s seem to be fairly well built just like the older earphones made by Yuin. The joints between the different plastic pieces are not seamless, but despite the rather rugged finish they are quite durable. The metal piece around the earbuds grill is much stronger than the plastic canal adapters. The cable is actually one of the things that has undergone a radical change. The original Yuin PK1s came with a plastic cable of dubious quality resembling the stuff you would find on a much cheaper earbuds. The cable on the all new OK1s is a much more durable kind that is quite a lot better.