http://www.sonicsense.com/blog
I tried some different comparisons on this site.
The AKG K702 vs Sennheiser HD650 was definitely revealing.
They use a you-tube like linkand they play excerpts of the reference track and the headphone reproduction as recorded from their dummy head alternately.
The 3 I listened to were
The AKG K702 vs Sennheiser HD650,
The Ultrasone ED8 vs Fostex TH900, and
The AKG K812 vs Beyerdynamic T1 vs Ultrasone ED10 vs Sennheiser HD800.
As I was using one of my HD600's that was connected to my computer, I found that in the first one the HD650 part sounded quite noticeably laid back compared to the reference portion of the comparison.
In the second, the Fostex TH900 sounded richer than the reference portion,
In the third, my HD600 were not filtering enough plankton to discern any real difference between the K812, T1 and HD800.
What was very noticeable though was that both the Ultrasones sounded abyssmal, especially the ED10 in their respective tests.
Happy comparing, dudes.
btw, Tyll may find their method of setting up the headphones for the comparisons interesting..