So I think I like these 1840 pads on the 7520 with certain types of music. I mean, they're terrible for isolation, but I like the comfort of the velours, my ears don't really get hot wearing them.
And in terms of sound, it definitely opens up the soundstage and mellows out the bass significantly (a bit on the bass-light side perhaps), which I'm starting to like on some types of music. The bass would sometimes sound a bit boomy when using the 840 pads (not the 1840), but with the 1840 pads that's completely gone. And the sound is a bit drier, as apposed to being wet (on the 840 pads the sound is definitely on the wet side). So on acoustic music, it sounds quite nice actually. On electronic music it sounds a bit better with the 840 pads, as those emphasize the bass a bit more. But I like the dryness of the sound, meaning that most soundwaves get absorbed by the velours and don't end up bouncing around the pads a bit before entering your ears. This seems to improve instrument separation a bit.
Next up, I think I'm going to try the 940 pads, since those are velours as well, but designed for a closed headphone. So maybe they'll isolate a bit better, and might end up putting the bass response between the 1840 and 840 pads (hopefully, as I suspect that'll be my sweetspot for bass response).