Performance

The Yuin OK2s are not the most demanding earphones when it comes to power, however, they do need a quite powerful and clean headphone-out to sound their best. This is definitely an advantage over the Yuin OK1s and PK1s because you do not have to carry around a portable headphone amplifier when you are on the move. To test these earphones I used both my Octavart "The One" DAC & Amp and my Cowon iAudio i7 sometimes along with the Go-Vibe V6. Just like its bigger brother I had the OK2s burning in for almost 100 hours before I did some serious listening.

The OK2s do sound very good just running straight off a good DAP. I was quite surprised to find that the sound quality being run straight out of my Cowon was incredibly clear and had plenty of definition both in the highs and lows. The OK2s are not that far behind the OK1s in terms of sound quality as one might think. The real difference between the two as I see it is detailing and speed, where the OK1s had a remarkably fast presentation the OK2s are a bit less refined. This is noticeable with percussion and on some tracks with lots of instruments. The sound stage and separation was not quite on par with that of the OK1s, but it was not too shabby either. It still has a bit of layering, but the sound is not as clear and transparent as that of the OK1s coupled with a good amplifier.

What surprised me a lot is that the OK2 seem to have far better control of the bass compared to my old PK1, even when the PK1 are amped they still have a hard time matching the speed and control that the OK2s offer. The PK1s do have a lot more bass and mid bass, which is far from as refined as that of the OK2s. The only thing that the OK2s lack in comparison to the old PK1s is the punch, the PK1s have a much more powerful presence when it comes to percussion and other intense sounds. The highs are brilliant on the OK2s, in that respect they sound a lot like the OK1s. The highs are not quite as detailed as that of the OK1s , which you can clearly hear when you are either listening to classical or even just listening intensely to the hi-hats' sound, it is a bit more brittle and less coherent on the OK2s than it is on the OK1s, but again it is a subtle difference.

The funny thing about the OK2s and OK1s is that they share the same sound signature, they both have a very neutral sound that does not overemphasize any part of the spectrum which I find great. The OK2s have a wee bit less bass than the OK1s and it does not go quite as deep. The bass is not boomy on either the OK2s or 1s and there is not a lot of it either so these earphones are definitely for people seeking better tonal balance and refinement rather than amount of bass. In comparison to its bigger brother the OK2 lack a little bass and precision in the same area. That being said the bass quality of the OK2s is still miles ahead of my other earbuds which include JVC Gumy 'phones, Sennheiser MX500. Where the OK1 really excel at detail the OK2 are a bit less precise and lack some refinement that being said they are still really good for a pair of earbuds.

When comparing the OK2s to the OK1s and PK1s unamped I definitely prefer the OK2s, because they do not sound as dull without an amp. So if you are looking for a pair of great earbuds and do not plan on buying an amp you should definitely try the OK2s. In comparison to the OK2s the OK1s have even better detailing and speed, the mids of the OK2s just lacks a little bit of definition and texture to be on par with the OK1s.

As earbuds the OK-series are highly recommendable. When fitted with the canalphone adapters the OKs are not all that good. I was only able to get a good seal about 1/10th 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.

Comfort wise the OK-series is just as good as the older PK1s. The body of the OKs comes a bit nearer to your ear canal, but it does not hurt comfort at all.

The OK2s benefit a bit from amping, but nowhere near as much as the OK1s and PK1s. The differences are minute and I do not think that they are worth spending time and pocket space on amping. Of course this depends on your DAP, but generally you gain very little from amping the OK2s.

Durability

The newer OK-series earphones are constructed fairly well. The build quality is quite tough and the plastic pieces seem to be bonded together nicely. The finish is not that good and you can clearly see where the parts have been joined together. They do seem really sturdy and can take a lot of abuse before giving way.