If they're more detailed, have almost the same midrange, have stronger bass impact, have the same soundstage, and cost $174, they will be the new best headphones in the world
If they're more detailed, have almost the same midrange, have stronger bass impact, have the same soundstage, and cost $174, they will be the new best headphones in the world
I haven't heard the HD598 so I have no idea how they compare other than I can guarantee the orthos don't have as good sound stage. I was just wondering if you had heard any of them.
I also like a very good soundstage too. The LCD2's soundstage and treble was my biggest problem with them. If I didn't hear the Stax O2 MK1, I would have probably opted for an LCD2 system though.
If someone was looking for midrange, soundstage, non-fatiguing sound, effortless sound, easy on the wallet, easy to drive, the HD598 is a no-brainer, at least to try. If you already have $500+ headphones, you may still find things to like about this headphone.
I updated the review and thread title. Upon further listening, I found the midrange to be congested (not treble grain), a common issue with this type of sound signature. Heavy bass exacerbates the situation.
The problem is generally in pop music.
Since this is the case, we probably won't be getting a refined HD598 any time soon. I haven't heard a signature like this without being congested unless it's electrostatic. Maybe Sennheiser will surprise us, but I doubt it.
EDIT: Screw it, they're the best headphones in the world.
Feel free to try out the K601 too 
I was planning on doing a review or comparison of them, but I got tired of it and just got too engrossed in the music. I always thought the HD-598 had the smoother sound signature, but it may be the other way around. I guess it depends on the music. HD-598 definitely has the more forward sounding mids and vocals feel more upfront, but the K601 is not far behind. Very slightly behind. The K601 still has very engaging mids. K601 most definitely has the clearer sound. They used to be much more expensive, but they're now found for much cheaper. I imagine they're not a fast seller and it's a shame. They both have the same amount of detail I think.
I tested both in gaming and I think I prefer the K601 for gaming. I'd rather give up a little bit of soundstage for a clearer sound. Imaging on the K601 seems just as good as that of the HD-598. The soundstage of the K601 doesn't really come close though to the 598.
For anyone that cares, the K702 had a ton more detail for gaming and was even more clear than the K601. The most interesting thing is that compared to the K702, it feels like the treble is a tad chopped off, but it still has more than enough treble. I prefer the K601 by far for brightly recorded music, but it doesn't tame it to me. The more I listen to the K601, the more it reminds me of the HD-600 is some ways. I think the K601 might be a bit more clear and has far, far more engaging mids. Now I know why I sold my HD-600 two years ago and kept the K601.
Overall for music, K601 might have a slight edge, but maybe just a tad less engaging mids. Many people wrongly assume the K601 will sound like the K702 and it really doesn't. Trebleheads (or bassheads) will probably hate the K601. It's definitely a non-fatiguing headphone that could be listened to all day if needed.
K601 seems to be picky about amps though and needs a very good one. My Asgard can't drive it well at all. My Micro Amp and E9 loves it. E9 and K601 has perfect synergy.
Basically K601 and 598 are so similar I think. Both are around the same price too. I imagine people who love the 598 will like the K601. HD-598 might be a little more comfortable, but the K601 is built better and should last longer. I got my K601 for $188 new and it's a steal for that price.
Here's some charts I cut and pasted into one file. I love that K601 graph. It doesn't totally look like what my ears are hearing, but close.
I also found an old K501 graph. Was that ever hard to find! Looks nearly the same as the K601.
I'll get back to you tdock in a bit. I just have to quote an exceptionally smart Head-fier right now, "Try the HD598. Be a believer. Hear the future."
How would these headphones do with trance music? Its primarily mid-range with some vocals, but not in any way acoustic music. I think i might be getting a pair of these, my current headphones (Phiaton MS 400) are just a bit to bassy for that kinda music.
EDIT: How much amping do they need? You say the anedio D1 DAC is enough to drive it, but that thing costs like what? 1200$? I dont have that kinda money :P. Is a simple 200$ DAC/amp enough to drive it?
Excellent review! I really enjoyed the first section with all the quotes; very original and a refreshing twist on standard reviews. And I think it's official now: I'm pretty sure you like these more than I do! And why did I have a feeling your review would come out before mine? I've been planning a review on mine every since I got it nearly a month and a half ago. I remember, as soon as I listened to it, I was like, "Now this is a headphone that needs a review". It's quite special, indeed. And you have a VERY interesting way of saying just how special it is. And I'm glad I'm not alone in this one. Regardless, great job; and I hope to get my review out soon as well, just to show how amazing awesome these headphones really are.
On to the question about the removing of the foam on the HD558 to make it sound like the HD598 -- it doesn't work, I tried it. I had the HD558 and the HD598 side by side for a few weeks before the HD558 left, and believe me, removing the foam doesn't do much to the sound. This isn't the HD555 and HD595 where the two headphones were EXACTLY the same besides the foam in the HD555 and none in the HD595, this is completely different. The drivers are different in both of these headphones, so removing the foam isn't going to improve the sound in a technical form; only the driver and housing could do that. That said, between the HD558 and the HD598, I greatly preferred the HD598. Obviously, the sound is the biggest change, with the HD598 being an all around more refined sounding headphone. But it also has more energy to the sound too, as it's sound signature is brighter than the HD558. By no means is it a bright headphone, but in comparison to the HD558, the HD558 sounds incredibly dark. And the second thing for preferring the HD598 is it's comfort. The HD558 has got the famous Sennheiser clamp, and reminds me of the clamp on the HD650; but only this time you cannot stretch it, because it's plastic and not metal. The HD598 has a much lighter clamp, resulting in much added comfort. And I swear the leather-like stuff is more comfortable than the velour on the HD558.

Feel free to try out the K601 too 
I was planning on doing a review or comparison of them
Basically K601 and 598 are so similar I think. Both are around the same price too. I imagine people who love the 598 will like the K601. HD-598 might be a little more comfortable, but the K601 is built better and should last longer. I got my K601 for $188 new and it's a steal for that price.
Here's some charts I cut and pasted into one file. I love that K601 graph. It doesn't totally look like what my ears are hearing, but close.
I also found an old K501 graph. Was that ever hard to find! Looks nearly the same as the K601.
I may one day try the K601 or K501. I'm a bit worried the K501 will lack the low end of the HD598 and the K601 lacking the soundstage of the HD598. I do agree that my ears don't match the charts 100%, but close enough. Please get your review done between the K601 and HD598! I will definitely read it if you do.

How would these headphones do with trance music? Its primarily mid-range with some vocals, but not in any way acoustic music. I think i might be getting a pair of these, my current headphones (Phiaton MS 400) are just a bit to bassy for that kinda music.
EDIT: How much amping do they need? You say the anedio D1 DAC is enough to drive it, but that thing costs like what? 1200$? I dont have that kinda money :P. Is a simple 200$ DAC/amp enough to drive it?
For trance, I would probably use a different headphone. I think Trance will deserve a bit more bass impact than the HD598, but I would buy the HD598 as an excellent contrast to your Phiatons. I think they would be a fantastic couple of headphones to complement each other.

Excellent review! I really enjoyed the first section with all the quotes; very original and a refreshing twist on standard reviews. And I think it's official now: I'm pretty sure you like these more than I do! And why did I have a feeling your review would come out before mine? I've been planning a review on mine every since I got it nearly a month and a half ago. I remember, as soon as I listened to it, I was like, "Now this is a headphone that needs a review". It's quite special, indeed. And you have a VERY interesting way of saying just how special it is. And I'm glad I'm not alone in this one. Regardless, great job; and I hope to get my review out soon as well, just to show how amazing awesome these headphones really are.
On to the question about the removing of the foam on the HD558 to make it sound like the HD598 -- it doesn't work, I tried it. I had the HD558 and the HD598 side by side for a few weeks before the HD558 left, and believe me, removing the foam doesn't do much to the sound. This isn't the HD555 and HD595 where the two headphones were EXACTLY the same besides the foam in the HD555 and none in the HD595, this is completely different. The drivers are different in both of these headphones, so removing the foam isn't going to improve the sound in a technical form; only the driver and housing could do that. That said, between the HD558 and the HD598, I greatly preferred the HD598. Obviously, the sound is the biggest change, with the HD598 being an all around more refined sounding headphone. But it also has more energy to the sound too, as it's sound signature is brighter than the HD558. By no means is it a bright headphone, but in comparison to the HD558, the HD558 sounds incredibly dark. And the second thing for preferring the HD598 is it's comfort. The HD558 has got the famous Sennheiser clamp, and reminds me of the clamp on the HD650; but only this time you cannot stretch it, because it's plastic and not metal. The HD598 has a much lighter clamp, resulting in much added comfort. And I swear the leather-like stuff is more comfortable than the velour on the HD558.
Yes these headphones sound right. Unfortunately, it seems dynamic drivers can't reproduce such a balanced mid range without congestion. It seems orthodynamics can, but they lack the soundstage. It's really unfortunate. Hopefully Sennheiser will produce something with this sound without congestion, so I will continue my complements towards the voicing of this headphone, the best headphone.
I also have hope that Audio Technica may make a headphone with such a sound signature without the congestion. They've been making great midrange voiced headphones with their W-series, but the congestion was as much part of their signature as their midrange. They had it down with the W11R which is much less congested than the HD598. If they can make an open variant, they've got a winner.
Me too!

I may one day try the K601 or K501. I'm a bit worried the K501 will lack the low end of the HD598 and the K601 lacking the soundstage of the HD598. I do agree that my ears don't match the charts 100%, but close enough. Please get your review done between the K601 and HD598! I will definitely read it if you do.
So because you think a particular headphone is "the best in the world", that makes it so?
Something to ponder - if the cheap HD598s are the "best headphones in the world", don't you think the guys who have the money to buy something like an Orpheus, or the guys who use the T1, HD800, LCD-2, HE-6, etc, would all prefer using a $200 headphone that doesn't really scale that well with source, than their $1000, $2000, $20,000 headphones and setups that cost more than some peoples' houses?
Also:
b-jek-tiv]–adjective
Okay. This is overkill. You do realize he's not serious, right? I'm sure he is quite aware of the "technically better" headphones out there. Besides, it's all preference. My FX67's are the best IEM I've ever tried.

So because you think a particular headphone is "the best in the world", that makes it so?
Something to ponder - if the cheap HD598s are the "best headphones in the world", don't you think the guys who have the money to buy something like an Orpheus, or the guys who use the T1, HD800, LCD-2, HE-6, etc, would all prefer using a $200 headphone that doesn't really scale that well with source, than their $1000, $2000, $20,000 headphones and setups that cost more than some peoples' houses?
Also:
b-jek-tiv]–adjective
I know. It's Sunday morning and I'm waiting for breakfast. 
I appreciate OP for his passion and excitement however during 40 years of playing with mid-end, hi-end gear, I have learned one thing that's there is no such thing as the " BEST". "BEST" is not an universal adjective to attache to ANY audio gear.
I have l audtioned some 30K pair of speakers with the associated equipments that cost more than a 15K, they are awesome in term of re-producing music but I would not call them the BEST in the world pair of speakers. There is no perfection in the Hi-end audio world that why Audio Nirvana is a matter of personal preference as Katun stated.
The acronym " IMO" adding to the title of the thread would be more appropriate, IMO.