OK! So before I start, I want to preface this by saying this will be an honest review. To be fair to these headphones I'm not really going to try comparing them to anything, because nothing I have listened to had the goal of these, which is mind numbing (or ear vibrating) bass. If I had a pair of Sony XB500s or Thunderpants or something then I'd have something to compare to, but alas, I do not.
Also, my impressions are slightly biased to positive due to thoughts being that these were going to be the Skullcandy Skullcrushers redux. Which in many ways they are, but these are basically the Skullcrushers done right.
Impressions were done with Cowon J3 PMP at AC Gears in NYC for about 45 minutes total. All music was OGG -q8 or MP3 V0 or better.
Bass without the "Sensation55 Drivers" (aka the ear vibration function) - This actually surprised me, as I thought they were going to be bass machines, and they really aren't. There were some songs where I expected to hear the kick of a bass drum or the bass guitar and it was barely there (OK slight exaggeration, because it does kick, but still I was actually expecting more). For bass heavy music it was certainly there, so they aren't lacking bass, but if anything for what they describe, it feels like the bass is lacking. The positive part about this is that it doesn't impede on the other sound ranges. So overall the bass is good, as expected, perhaps a bit weak if you were expecting extremely hard hitting bass from these headphones without hitting the switch.
Bass with the "Sensation55 Drivers" - "Bass you can feel" is how they describe this. If there was ever an advertising line that was accurate this is it. These things vibrate your ears. I mean that literally. If you turn up the switch to 100% it feels like just your ears are up against a club monitor speaker. So if that is what you are looking for, these are your headphones. Unfortunately it does affect the other frequencies, but that is to be expected. And it isn't as bad as I would have thought. I personally think that full blast for the switch is far too much, but I can see people enjoying it. For me 50% was plenty, it gave some vibration but wasn't over powering and didn't harm the midrange or the highs as much, or sometimes not at all depending on the song to my ears. The amount of bass is still impressive though. Even next to the Sony XB series, these have a lot of bass. However there is a caveat, that switch under 50% almost does next to nothing, at least not that I could hear.
Midrange - The midrange is recessed and rather unimpressive. The vocals seem distant for some songs. I'll say this, it isn't BAD, but they are certainly recessed and didn't wow me by any means, but they weren't bad and were again largely unaffected by the bass for the most part. The biggest thing is that the midrange felt dull, and that is a word you'll be hearing again. Everything sounded rather flat and dull.
Highs - The highs were unsurprisingly attenuated (big shocker). The highs also felt flat and dull. Nothing really sounded good for the highs. From guitars to trumpets, nothing sounded right. It either sounded dull or like frequencies missing. I should mention, while the highs are definitely the worst part of these headphones, I still can't say they are completely awful, because they aren't.
Further impressions of the Sensation55 drivers - Let's face it, if you are looking at these headphones this is why. And I'll be honest, for what they are and what they do, they are actually good. You shouldn't be expecting the bass to be incredibly detailed or fast, but it is powerful and you will feel like you are in a club or movie theater. They react surprisingly well to bass amount and volume as well. Bass light songs even with the dial turned up to max, barely vibrated, which is a huge plus compared to the Skullcrushers, which just gave you an awkward head massage.
Overall - These are fair headphones. They aren't really good for any genre of music outside of what you would hear in a club, but they aren't awful for those other genres either. The only genre I completely didn't test because I knew it wouldn't be worth it was classical, and I didn't want to have something be completely negative. These are not for classical music and you don't really need to listen to classical to get that impression, and jazz is highly questionable, except maybe jazz fusion. What these really excel at is club music, and honestly I could see these being fantastic for movies as well and perhaps games.
These are as far away from audiophile headphones as I have listened to in a long while, but I could honestly see myself recommending these instead of Beats if that is the sound people are looking for. For the right music or right uses, these are surprisingly decent set of headphones. I feel like Skullcandy is really making the effort to up their game in the headphone market.