Some comparison of HE-6 to Beyer T1 and Stax SR-407:
Treble and midrange:
T1: right tone (to me); most 3D-like and best sound texture; only sounds enclosed when in comparison to HE-6; high resolution and could cause strain with poor recording
407: right tone; least "immediately" impression but it grows on you quick; most effortless and super smooth; high resolution and well extended but not sparky; absolutely no strain even with poor recording
HE-6: when just switch to it, some part of freq band is not quite right; most open in soundstage but focusing is not as good as T1; may sound dull and plain at midrange (even a little veiled or misty) while the high may sound thin; least clear among three; the stain level with poor recording is at middle.
Bass:
T1: tightest and impactful but least amount
407: sheer amount is amazing and is deep, but not as tight and impactful as T1
HE-6: more amount than T1 and more impactful than 407.
As you can see, I need some help on the HE-6 system.
Still, there is certain magic on HE-6 that keep motivate me to discover it.
My HE-6 is currently driven by Phoenix + NAD216 (125W/ch). I can only use 3~6/99 on the volume level with balanced Ref-7 input.