Honestly, to keep the HE400 sound without the sibilance, I wouldn't have raised the dips in the upper mids, and just reduced the problem areas.
Raising the upper mids would alter the sound signature.
I guess that's why I don't EQ, I hate messing with the inherent signature, unless a headphone is absolute garbage.
The most I'd do overall for a good headphone is raise sub bass more than anything.
I've already done that. I didn't like the result because the sound loses much clarity(the hp sounds "muffled"). By raising the upper mids, clarity is kept while harshness and sibilance are reduced.
Edited by Okamoto - 4/26/13 at 9:38pm