AKG Q701 pads.
Hifiman fitting rings.
Double sided tape.
~30 minutes of your time.
Step 1: Attach double sided tape\foam to the plastic portion underneath the AKG pads.
Step 2: Attach Hifiman fitting rings onto the double sided tape, squeeze to allow proper adhesion.
Other pads for comparison:
Hifiman Velours, Hifiman Pleathers, Homemade Angled Jergpads, Homemade AKG-Hifiman hybrid.
The final result. Make sure to attach the pads with the thickest portion facing the back of your head.
Impressions with HE-400:
Comfort is amazing, the sound is not.
Despite supreme comfort, after pumping some bass heavy tracks and playing a bit of COD4 & TF2 I went back to Jergpads. The sound was bass-light, spacious, and airy. These pretty much start sounding closer to AKG Q701 but with shy bass and recessed mids. HE-400 are just one of those headphones where any changes in distance between the ear and the driver lead to drastic changes (usually for the worst). The only reason why one might want to do this mod to their HE-400s aside from comfort is for the sake of gaming, otherwise these are just too bass-light for music.
HE-400 is the only Hifiman I've tried this on and wouldn't be surprised if folks with other Hifiman models end up yielding positive results. I'd expect this mod to work out much better on the HE-500 as there are users who have reported great results with the AKG pads.
I'm still in search of the ideal comfort pads for HE-400s that don't sound like ass.
Edited by Bogatyr - 3/14/14 at 1:37pm