The pads for the 5xx have a larger diameter than the 4xx, both inside and outside. These Dekoni pads are tuned for the 5xx specifically, as shown by the frequency graphs linked in the details section.
They're mighty comfortable too.
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Edit: I should also mention that the pads for the 4XX/350/35X/X4 use a different mounting plate than the pads for the 5XX. Also, while the pads or the 5XX sure look like they'd fit on the R7DX, they do not.
I don't own either the R10D or R10P, but judging by the photos posted by reviewers of both, I'd say they do not fit. Both R10D and R10P appear to use hook and loop (~Velcro) to hold the pads on, whereas the HE-5XX (and Deva) use a more conventional set of plastic posts/clips on the earpad mounting ring slotting/clipping into plastic holes on the headphone assembly.
You might be able to DIY the eadpard hook and loop after cutting off the mounting posts/clips, but I'm not sure about the sizes lining up correctly.
Are the rings glued on as with the original pads? I'm interested in pad-rolling but the outlier ring makes it very impractical, of course. Thank you in advance!
danieljohnsonrnIf you just want the mounting ring without pads and glue, you could always try contacting Dekoni and asking if they'd sell you a pair. I'm not saying they will do it or not, but hey, you never know until you try.
https://dekoniaudio.com/contact/