I don't doubt you, has anyone tried to get confirmation? I had the impression that any new HD6 series would have the same pads (HD6XX, 650, 600, 660s) and the HD58x has those pads too.
I have both the 6XX and the 58X, and compared the pads. They seem to be the exact same thickness, even though I don't have a measuring device.
Can u give us some more details on how the pads affect the sound? Thanks
Both the Elite Hybrid and Fenestrated Sheepskin pads increase driver distance from the ear, so soundstage is increased ever so slightly at the cost of intimacy. I found that putting the Fenestrated Sheepskin on the 6XX brought both the bass and treble up a bit too much for my liking and sort of balanced the sound in a way that I didn't want. Not to say that it sounded bad but as 6XX naturally has an accentuation around 5-6k, my personal philosophy was that I wanted to keep that peak as it makes female vocals/electric guitars stick out a bit more for me, making 6XX unique compared to the rest of my collection. I found that the Elite Hybrid pads, gave the sub and mid-bass just enough of a boost (I found it to be a weak-point with the stock pads) and didn't affect the highs too much (took a little energy off the top if anything), creating to my ears, better synergy. It does make 6XX sound slightly darker in presentation, but it's something I don't particularly mind.
That left me with the 58X using the Fenestrated Sheepskin. I have to say that 58X sounded great with stock pads, but I just love experimenting and had good prior experience with Dekoni in general, so I just bought the Fenestrated pads on a whim. Sennheiser ended up tuning the final production model a bit differently from 6XX/650, bringing down that 5-6k peak relative to the elevated bass, and smoothing out some of the treble dips and peaks I tested it out with the Elite Hybrids, but didn't like the synergy between them. For me personally, it brought up the bass and treble too much so that it scooped out the already-tuned-lower mids. Yet, if you are looking for more of a V-shaped sound, it is a combo you could try. The Fenestrated Sheepskin pads ended up being a better pairing, giving the bass and lower mids a gentle lift, while bringing the low-treble down just enough so that you get a bit more airiness in the high-treble.