[eervig]

When I read reviews of some of the lower-end Sennheisers and such, I hear them referred to as "optimized for mp3s" - as in Sennheiser saves us money by catering only to the tones and frequencies not eliminated by lossy codecs. This seems slightly absurd to me, like it might just be marketing nonsense, but I suppose it's not outside the realm of possibility. Anybody understand this a bit better?

 

[zmd]

That's just a load of marketing BS with no meaning. We're talking about cans that have inherent flaws/deficiencies and aren't really transparent enough to let you appreciate "CD quality" 128 kbps encoding.
 
Headroom has the Sennheiser HD558 pinned as being forgiving to poorer quality audio sources or somesuch, so you can see them admitting it outright.