Pros: Soundstage, excellent mids, tasteful bass, active but smooth treble, great on vocals, classic rock, less aggressive electronic music
Cons: Not the fastest or most crisp sound, bass could be a smidge tighter; Sennheiser house sound isn't for everyone
My chain: FLAC/320kbps MP3 -> Foobar 2k WASAPI Output-> HiFiMeDIY Sabre DAC -> E11 -> HD598
My first taste of the Sennheiser house sound came in the form of the HD439, which I purchased while looking for a balanced all-rounder for casual listening on the go and in coffee shops while writing. I enjoyed the signature, so when it came time to look for an open headphone, the first place I looked was Sennheiser.
I usually favor phones that have slightly elevated bass and are a bit darker, and after reading reviews saying that the HD5x8 series shared the same drivers, I decided that the HD558 was likely the best way to go, assuming it wouldn't sacrifice anything to the HD598 in terms of technical ability. While I enjoyed the HD558 (my review can be found here: http://www.head-fi.org/products/sennheiser-hd-558/reviews/8544), they didn't quite feel like a keeper; the bass felt a bit loose and tended to bleed into the mids, and I felt that the highs were lacking. I returned the 558s and found a good deal on the 598s, and here we are.
For those deciding between the two models, my best advice would be to try them; failing that, it would mostly come down to preferred sound signature and choice of genres. While the 558s and 598s share the same drivers, they are obviously tuned with different listening styles in mind. Both maintain the Sennheiser house sound, and everything that goes with it: a well-layered but cohesive presentation, fantastic mids with a tasteful but not overdone lushness, slightly elevated bass, and smooth treble. They share a very similar midrange presentation and level of detail, but the HD598 has a slightly more open and euphoric sound given the added treble emphasis, whereas the HD558 is more seductive and enveloping. Personally I find the bass on both to lack some control, but noticeably moreso in the case of the HD558; the 598 isn't what I'd call tight either, but has less tonal emphasis while maintaining similar impact and extension. The HD558 is definitely what I would call a dark sounding can; the HD598 is brighter but not bright, still warm, and feels more balanced and natural to my ears. It essentially takes everything the HD558 does right, and refines it.
But let's forget about the HD558. Right now I'm listening to The Rain Song and the intro sounds smooth and subdued, just like it should, with just enough crunch in the acoustic guitar to separate it from the rest of the music nicely. Vocals are top-notch; if I was a female I would be swooning, I feel like Robert Plant is wooing me right here in my living room...but seriously, acoustic guitars sound great here, I can't see how I might prefer them any other way These probably wouldn't satisfy a metal head who needs real crunch and punchy bass for electrics and kick drums, but for me they do just fine. Over the Hills and Far Away is another track that these really do well, the touch of warmth again makes acoustic guitars sound positively seductive, while keeping them appropriately separated. There could be a bit more pluck to them, but only some of the time; that would be my only complaint, if anything.
Speaking of metal, moving on to Aerials by System of a Down. The intro is given sufficient drama; when the guitars drop, you really feel the sound come from all around you. Very impressive. Not as dynamic as it sounds on my D2k, but the vocals have even more emotion, less harshness, and are much more intimate. Guitars, as expected, don't sound as immediate and textured, likely due to the "Sennheiser veil" consisting of a dip in the upper midrange/lower treble. Moving on to Sugar, it becomes more obvious that drums aren't quite what they should be; they are there, but not with the realistic weight/pound of the D2k, or the punch the DT770 LE give them. They're there, just there. Not bad, but not great.
Now for Infected Mushroom. The soundstage on the HD598s does wonders for these guys: they are world-class producers and all of the dynamic and spacial elements they've tweaked in there are very clearly audible. Listening to Sa'eed, and again the bass could use a little more punch to be realistic. It's not underwhelming, but not noteworthy either. The dynamics needed for this song are here, but the thickness in the lower midrange makes it feel not quite as lively as it does with some other phones, like the DT770 LEs, which are faster and have slightly tighter bass. Moving to Change the Formality, the bass feels better suited here. Also the synthesized textures and tiny nuances are really there and alive, the superior treble and resulting increase in the precision of imaging is noticeable here vs. what I remember with the HD558; still a bit thick at times, but noticeably more energetic. Vocals are great, of course. On to I Wish, again those little synthesized textures are really audible here. The vocals are a little closer than I would like with a euphoric and minimalistic track like this, I'd ideally like a slightly more open feel with slightly less chesty vocals and tighter bass. Still this is all nitpicking; overall the sound signature works well here, with the bass being appropriately tactile, the midrange doing full justice to vocals and synths, and the treble coming out just enough to give the appropriate euphony and compliment the warmth. This track doesn't need warmth, but it doesn't hurt either. Bust a Move sound great too, the acoustic at the beginning sounds just right to me ears, not too much crunch, not too warm, just right. Bass is tactile enough to be felt, just barely. The warmth of the HD598 does impede the dark energy of this track ever so slightly, but still, everything is there, it sounds good, just not amazing.
As for Medeski Martin & Wood, well, this is where these cans shine brightest so far out of anything I've listened to. The slight warmth works with the jazz feel, and polite nature of the 598's bass keeps it out of the way on Anonymous Skulls, which has lower bass tones that can be a bit overbearing with my DT770s and, to a lesser extent, the D2000s. This is one of my favorite songs of all time, probably in the top 20, and the 598s do both instruments and synthesized tones full justice to my ear. On End of the World Party, I would like a little more subbass coming through on...whatever the hell that instrument is! It still sounds great, but just doesn't quite have that full throatiness my D2000s and DT770 can give them. I love MMW, they do stuff nobody else is doing, at least that I've heard; if you like them, these cans do them justice: they still sound jazzy and light, but don't miss out on the fullness that the electronic elements add.
Ott is another band that the 598s are really doing full justice to. Queen of All Everything has this great laid back but euphoric sound, all of the natural textures come through with full realism and even a certain crispness. The bass feels just right here; if it was any tighter, it would actually distract from the soft nature of the track. This is a real pleasure to listen to. Rogue Bagel is coming through nicely too, everything is well-layered, bass isn't getting in the way of vocals or strings but still has a nice heft to it that is appropriate for the reggae-psydub sound. Everything sounds much more alive and 3-dimensional than either of my closed cans.
Overall I have to say I really do recommend the HD598. I had a harder time saying as much about the 558s, just because they were too dark to be all-rounders and had sloppy upper bass that held it back from excelling with my more vocal-centric music. The HD598 is a definite step up, not necessarily in detail, but definitely in presentation and overall refinement, balance, and realism. If you are looking for a solid open can with a smooth sound sig, tasteful warmth, and a great soundstage, look no further.
Music used for this review:
Change the Formality
Bust a Move
The Rain Song
Over the Hills and Far Away
System of a Down:
Medeski Martin & Wood:
End of the World Party
The Queen of All Everything