Here are my initial impressions between the two. Copy and pasted from this thread since I am being lazy
I hope you like them. They are definitely more "fun" cans then my HD595's. If you want a primer on what they will sound like, read @Baycode's review. After having them for awhile, I agree almost completely with his conclusions(except for the bass and I don't have an issue with the weight). Unfortunately, I can't answer your questions on the 558's or 598's. I can give a little feedback in regard to the 595's. I still like my HD595's. They are more neutral then the X2's and the mids are a little more forward. The bass, IMO, is superior on the X2's. It's not that the HD595's don't have bass if properly amped, it just not as detailed nor does it have the "punch" of the X2s. Personally, I can't tell that much difference between the sound stage of the two and the treble sounds great on both. Then again, I've only had the X2's for a week so this could change as I do some more A to B comparisons. Anyway, looking forward to your impressions once you receive them.
edit: On a side note in regards to gaming, if you haven't, check out this thread. I don't do FPS's so I can't speak to the "competitiveness" of these HP's, but they have a virtual sound stage as good if not better then the HD595's. Also, if you use a TrackIR, you can place the reflector on the top of the HP and not use a hat.
So I actually pulled the trigger on X2 and now it's here!
I am relieved, I actually made a good purchase. This is my impressions of the headphone, new out of the box.
So I have an iTouch 4g, an xperia ZL, and fiio e10k.
Have HD 558, and tried X1 and L2 in a short audition
Using headphone to listen to all kinds of music from pop to classical and gaming.
I was afraid to buy X2 when i heard X1 through my phone, the bass was so thick it's like in your face, sure it's better than a bright headphone since i like warm character, but that much of a bass is too much for me.
The X2 compared to X1 has a leaner, tighter bass and what's interesting is X2 still delivers an impactful bass when the recording calls for it.
I couldn't say much about the midrange and high since the bass on X1 was so overwhelming that i forgot to pay attention on the mid and highs.
Compared to L2, i can tell how people said the L2 is the brighter phone, it's true, L2 simmers more on the high and the bass is not impactful though it is morr detailed and textured.
Now compared to HD558, played from fiio e10k:
1. Packaging My god that box is huge! No special accessories, the content is almost exactly the same as HD 558. Cable (with clip), phone, adapter, that's it... The clip is useful though not the best solution for cable management There is microphonic on the cable, but this is an open headphone, it's not as bothersome as IEM is
2. Comfort X2 is heavy, especially after i am so used to HD558 weight. The 558 is way more comfortable, the 558 also plays better with glasses compared to X2[size=13.3333330154419px] [/size][size=13.3333330154419px]but in time i am sure i will get used to X2 too with that reduced clamping force and what not.[/size]
[size=13.3333330154419px]And the X2 headband will mess your hair...[/size]
The X2 has all the characteristics of an open headphone, airy sound, spacious sound stage, and it leaks sound like there is no tomorrow. Though as open headphone, the quantity of bass pumped from this thing is pretty unusual, thus giving it a tilt toward warm character. Compared to the 558, the X2 is less forgiving toward bad recording, revealing artifacts and noises that is not meant to be in the recording. But in turns, X2 has better overall clarity while the 558, when compared, revealed this infamous Sennheisser Veil which also gave the 558 that laid-back presentation it has. The X2 with the more forward presentation, also gives the better sound stage (width, depth, height), airier sound, and better separation. Both are pretty spot on in imaging, though the X2 gives better distance between instruments.
Highs: The X2 highs are amazing when compared to Senn HD558. it is more detailed and better extended which gives guitars and cymbals a satisfying sound. Though in some cases, the treble range could sound a little bit too aggressive when my ears are already used to the 558 smooth sound.
Mids: The vocals in X2 has this quality body that makes my 558 sound thin, thanks to the added bass i guess. The mids has better clarity, sound more natural and more articulate compared to the 558.
Lows: The X2 lows are better extended than the 558 which gives more impact when the bass come. Overall the lows are textured and has a good timber but it lacks tightness. This is the only point in which 558 trumps the X2, bass tightness. But the quantity pumped from 558 is not at X2 levels.
Btw, the fiio e10k bass boost will bring the X2 bass level closer to the X1 though not as thick.
the sound is not fatiguing. My longest listening session is about 8 hours or so and it has been pretty enjoyable.
I like how the sound is very linear in this phone where each range stays in its own course.
Overall this is a very enjoyable headphone that i find myself trying to grab X2 whenever i had the chance.
Well, the X2 cost around twice-ish the price of 558 in my country. Does it perform twice as better? Well, it depends really. I can see why people are saying that the higher you go up the price ladder, the lesser price-performance you'll get.
Sure the X2 sounds better than Sennheisser HD 558, but how much value you put on those performance increase will be the deciding factor of whether it is a good or bad purchase.
For me X2 is the direct upgrade from 558, same character with overall better (much better on some) performance on all range. Well, except for comfort.
Now let's see what happened after burn-in...
So i leave the X2 for burn-in when i am not using it.
around 40 hours burn-in, the sound settled nicely in X2. The mids opened up and the bass gained a bit of tightness though not as tight as i hoped. It feels like the harsh edges is being refined. It doesn't change the overall sound signature, but it sounds nicer.