My first impressions.
It has a slight treble roll off. This makes it lack the sparkle that other Grados have, but it also makes it sound considerably warmer and more pleasing. Its a mixed bag if I like it or not. I guess I have to say that it is just different. Not better or worse.
Midrange is fantastic. Smooth and warm with some slight Grado trademark edge here and there. BUUUUT 110-310Hz region is bit boosted giving it rather thick sound. Reminds me of RS1 somewhat, but not as "woody" colored.
Bass. Quantity is good and its extension is incredibly good for open headphone! Even low notes have some authority! It is still bit boosted though and personally I would still prefer slightly tighter presentation overallbut it is good as it is. Perhaps burn in will settle it down, perhaps not. Still, it isnt a mudfest like SR225 with flats and bass details are still very audible.
I think most of the problems might come from opamp in my DAC. I use OPA627BP in my Keces to give it bit more meat cuz LME49710 upgrade was bit too thin and plasticky sounding for SR225 and SA5000. But now I think maybe OPA627 takes HF2 eenyweeny over the edge in lower midrange and bass thickness. I have to switch opamps and check.
*edit* Back to LME opamps. It certainly helped with treble roll off. The sparkle is back and bass is tightened too though punch is also lessened. There is still bit of thickness in the 110-310Hz region but thanks to brightened sound it doesnt bother anymore and is actually good for guitars! Now the problem is that SA5000 and SR225 do not have that good synergy with my KECES anymore. Too bright and thin.
This is a problem because I like all three headphones yet synergy matching is critical with all of them. What sounds good with HF2 does not work with SA5000 and vice versa. Damn...
Its amazing how mere opamp change can make turn the synergy matching upside down. Do I really have to have two sources for both headphones sound signatures? Changing opamps everytime I switch headphones is not really fun.
*edit2* Oh yeah, forgot to mention, my Head-Fone HF2 number is 335.