[NimbleTurtle]

I don't know if it's just me but after about 80 hours logged into my HD 598, the sound has improved A LOT. The bass is no longer a weak and somewhat loose thump. It's far stronger than before and sometimes, it's to the point where percussions feel a little TOO strong.  Soundstage is wider than before and the sound is definitely less grainy. 
 
This could all be a result of psychological bias but I doubt it. In any case, I compared this with my friend's HD 595 today. That headphone can't even compare to the HD 598 rofl. The soundstage on the HD 598 is far better as well as the bass. Also, the midrange on the 598 is amazing for male vocals. 

 

[deathmonkey6]

Thanks for posting this! Expecting my 598s tomorrow and wondering what to expect.
 
How are you powering them? Amp, ipod, computer, home stereo?

 

[NimbleTurtle]

I'm listening to them out of a laptop. I'm a little bit effy about getting an amp at the moment. Still doing a lot of research but apparently, an amp can downgrade the sound quality in many ways (distortion, coloring, static, etc.). And from what I learned, getting a high end amp actually makes low impedence phones make these worse. But iono. 
 
Even if you don't like the headphones at first, you should like the sound better after many hours for two reasons. One, your mind will no doubt adjust to the sound signature of the hd 598. It's kinda like how people who listen to the AD 700 and then upgrade to the hd 598 thinks that the hd 598 is bass heavy (it's closer to bass neutral-lean). Second, the actual mechanics of burn-in will kick in... it's a subtle difference but noticeable enough. 

 

[fabio-fi]

Very similar to what i felt with my cans. And no, if you get a amp for them they scale nicely, i use the Centrance Dacport when using the notebook and you can notice the difference, nice instrument separation and treble extension. The bass improves as well. 

 

[KG Jag]

It took about 2 to 3 days of burn in out of an AV receiver for mine to settle in.