I have now tried focuspads for one week, velour one week and pleather for one week, because I guess your ears take some time to adjust. Trying them for a week makes the differences much more audible than A/B them quickly. Took me a week to realize, the focuspads are godsent for the he-400.The problem is they cost 40 bucks haha. They seem to attain the treble detail without destroying your ear like the velour. I still like velour most for best recorded source files because of the increase in treble.
Pleather
Darkest sound, romantic sound, but not so defined
Most forgiving
Least aggressive treble but very high treble peak and least sibilant of the 3
Vocals sounds ODD, sounds like singing in a cave or something
Least bass impact, but most subbass
Smallest soundstage
For some reason they sound quite addictive, but the vocals are quite odd, they have some sort of bloom to them.
This might be placebo, but I feel pleather has the most decay.
Focuspads
TL;DR: It sounds straight up like hifiman combined the velour and pleather
WIll get you closest to HE-500 with velour.
Finally some decent female vocals!
Forgiving of bad source files, its between the pleather and velour
Vocals most forward, I think this is as good as vocals gets on the he-400
You thought stock pleather bass was good? This improves on it a lot.
Least treble spike
Sibilant, but not as much a velour
Best imaging, size of the soundstage is between the pleather and velour
Combines the awesome punchy bass of the pleather and the improved mid/highs of the velour
Best mids of all 3
IMO sounds most linear of all 3
Velour
Most treble, sounds best of all 3 with good quality recordings
Least forgiving of bad source material
HOLY **** its so sibilant ***!
Bass decay so damn quick
Most visceral of all 3
Biggest soundstage
Most bass impact, you feel it on your jaw bone
Least sub bass and low bass
Really fun for movie watching
Sounds most like a speaker
The velour makes the he-400 sound like the younger brother of the LCD-X and HE-6.
Best for electronic music