The OK1's bass is good when amped. Unamped, it will lack and completely change the tonality. The OK1 is one I consider amp required to use. Tonality is even and the low end is well extended doing so. I haven't found the Ok1 terribly sensitive to low frequency EQing. Design seems to be a porter enclosure design with the ports exiting right behind the wire exits. You can cover these up and hear the bottom end loss. Frequency response extends to 50Hz before rolling off quickly. You get good bass down to that point, but some techno songs or anything with synthesized 20Hz, 30Hz tones will be missed. With a ported design, it is very tough to get this low end response, and you may not want to try. I personally don't see a need to EQ these buds.
Kostalex, I would have an easy time ranking the OK1 up right next to the ER4S in the H2 category. I've swapped between both on a large array of songs on numerous days, and I've come to the conclusion that the OK1 is on the same level of the ER4S, the only earphone I've used where I could say this. They vary a little bit here and there. The OK1 has a little more bottom end output (ER4S could gain via EQing). Both run to around 50Hz and drop off. The OK1 has a little more top end sparkle/clarity. The ER4S seems to roll off at the very top just missing that top end bite. The OK1 is slightly more extended on the top. The ER4S has a little more upper midrange output then the OK1. Back to back, the OK1 comes across slightly more balanced. The ER4S still has a little better sound stage, location of instruments, etc. but the OK1 isn't far behind and has great separation. The differences are light, noticeable but not significant. Both sound very similar to me. Overall, they are very on par with each other in my book. Every other headphone I've used, I could always quite easily say the ER4S was better, no question. The OK1, I really can't say. That's pretty remarkable.
