It looks kinda similar to me...
it actually looks like the HE-500 has a higher peak than the HE-400, unless im reading it wrong.
Don't post graphs if you can't interpret them properly ("It looks kinda similar to me..."), also comparing graphs across two different sources (even if they are measured by the same person, the compensation curving, smoothing, and scaling are different) makes the comparison null.
Here are two pairs of measurements (each pair with exact same plotting parametres*** this is important!).
Measurement pair 1:
Measurement pair 2:
Note the critical difference being the 12kHz peak of HE400 that even has some temporal ringing trailing after it, THAT is the problematic peak. HE500's cleanly-decayed smooth hump centered around 10kHz is actually very smooth-sounding and adds to the treble detail and spark with no grain or tizz. Also, the upper midrange valley in HE400 accentuates its already biting treble, while HE500's midrange is in-line in levels with its treble hump meaning the treble sounds coherent, not standing out of laying back.
Lastly, measurements are just measurements - they are but a window to the truth. Impressions/reviews-wise you can't find enough praise for HE500's treble smoothness. You don't have a real perspective to argue with, if you haven't auditioned it yet!
Edited by jerg - 5/8/13 at 4:48am