Very similar experience to what
@arielext had...
I received the Dekoni Elite Fenestrated Sheepskin (for Beyerdynamic DT990) and, to my ears, they really open up these headphones from an FR perspective. With the stock velour pads the mids are quite warm, I suspect due to bass bleedIng into the mids. The Dekoni pads cut back on that - the bass is still right there where you would expect but no longer intruding on the mids. The treble doesn’t seem to me to be much affected either way, still clear and non-fatiguing.
also the Dekoni are thicker than the stock pads, so my ears are no longer touching the felt covering the drivers, so comfort has gone way up.
all in all a nice upgrade... but, since the pads are almost half the price of the Tygr 300 r, is it a worthwhile investment? That would be a personal decision for each. To me, yes.