About the foam in the 558, when I opened the cans and removed it, the sounds become clearer and wider but a little bit bloated. Which means drums and bass no longer retains the force that it used to have. Songs like "You'll See" by Madonna or "It's All Coming back to Me Now" just sounds horrible. I don't recommend it. The foam-less 558 still sound very different to the 598. I think 598 are one of the best in its price range, can't say no to that stunning good looks and perfect comfort.
I completely agree. What actually sparked my interest in the HD598 in the first place was when a co-worker and I swapped my UE Super.fi 5 Pro for his mod'd HD558s for a weekend. He claimed the mod made them sound like the HD598s. I was like," Uhm, ok? " not knowing a single thing about either. I auditioned them virtually all weekend while researching both models, which interestingly enough were often paired with each other (and sometimes the HD518s). At the same time I was watching an add on Kijiji for a pair of HD558s slightly used (classic headphone sell story of not knowing a store's return policy on headphones) for $120. After a good 20 hours of listening enjoyment that Sunday I finally decided to buy the pair from Kijiji. However, when I checked the listings they were gone, BUT a pair of NIB HD598 (complete with plastic ring seal intact) for $200 posted just minutes earlier. I did not hesitate. $180 out of my pocket and an hour later they were mine! Anyway, the point to my mini-story here is that the instant I put on the HD598s and pushed play I knew right away, without hesitation, or any burn-in, that the HD558s are NOT a poor man's HD598. I didn't even bother A-Bing the two as the difference out-of-box was very apparent (to my ears), and the fact that I just literally pulled a marathon session with the HD558s. Anyway, my 2 cents.