I have to disagree that my Sonarworks custom calibrated HD800 is bass heavy. Neither the HD800 average profile sounds bass heavy to me.
They're perfectly neutral to my ears - I can compare with my reference KH120 studio monitors + dual KH810 subs in my professionally treated room and even with my trusty Sony MDR-7520. My studio friends are amazed too.
All three sound very similar - neutral. However, calibrated HD800's detail resolution is out of this world. My best studio monitor ever till HD800 calibration was 7520 (I even prefered them over my regular speakers). But after HD800 calibration, I have never heard something like that (and I have tried many many headphones before, even more expensive ones), and I keep using my calibrated HD800 more and more these days.
I dare to say that sending my HD800 to Sonarworks HQ for individual calibration seems like a best investment I have made to my studio in past 7 years.
These guys know for sure what they're doing. Anybody willing to give his/her HD800 a new fresh breath, I can't recommend Sonarworks enough!