It just smells awful; I can't compare it to anything. Did you smell your foam?
I'm not the first person who bought the 650s who thought they were a tad bright. And let's put this in perspective here, they are comparing them to other Sennheisers like the 600, not any 'bright' headphones. So it's subtle.
In fact, many have said they prefer the HD 600 sound over the 650.
Having never listened to the 600, I would have to guess that it's more balanced in this area, since I've heard others state it already.
I really don't care about others opinions who say these are bass-heavy phones. I don't hear that. Bass is pretty well-controlled.