The HE-400 can be very good with Jazz depending on the type of jazz and such. Gives it a nice energy, though without certain instruments being too fatigueing (saxophone in Miles Davis 'Kind of Blue' comes to mind)
Why won't you touch an EQ? You don't listen through the computer or something? It isn't a very drastic EQ we are talking about here, and I doubt it will degrade the audio in any way.
Why is it that HE-400 sounds much better with DSP like Dolby Headphones and ProLogic?
I'm using this features on Xonar ST and it is a big difference, the music opens up more, soundstage is glorious, the mids change for the better, without these effects mids seem muffled.
Before these orthos, those effects did nothing good to dynamic headphones, so I didn't use them, but now I cant do without Dolby DSP.
I'm using vintage amp and/or Xonar ST with LME49990 and I have no problem with sibilance.
Dolby headphones DSP muffles everything for me, make it seem very muted. That is with foobar and stereo recordings. To me, that sounds very bad. On the other hand you can do stuff to improve on that. I have a custom channel mixer DSP, that converts stereo to multi-channel, and then I apply dolby. That sounds quite decent, actually, but still lacks some clarity.
What is ProLogic?