This is probably obvious to many here, but man, I didn't realize what a big difference changing the earpads on my hd6xx's would make to the sound. I only changed them because they were so worn out, but I guess I had grown accustomed to a muddy sound with bad low end definition and reduced highs. $50 for the genuine Sennheiser earpads, though... sheesh

I own the ndh30 and I tried the mm100 and mm500 but preferred the lcdx over the mm100 and since I use realphones anyways the lcdx was quite a lot cheaper than the mm500 and once I calibrated both I preferred the lcdx still. With calibration the lcdx still gave me slightly more bass clues that I was seeking. The mm500 is provably the best if you're not going to calibrate at all.

That's cool just checking lots of guys dismissed them after testing on the wrong way. We all have different heads and ears that take to certain tunings more than others. Which is why it's so much better to try and not rely on others. Even when they have ringing endorsements.

I used to alternate between the NDH 30, MM-500, and HD600 for a while. In the end, I now only use the MM-500, but which of these three is the best really depends on factors like EQ and more importantly, how you’re using the headphones.

For example, the choice would be different between a situation where the monitoring environment is so bad that you can only rely on headphones and one where headphones are being used as a complement to an already excellent set of monitor speakers. The genre of music you make, your musical preferences, your playback levels, and whether you use them for long sessions will, of course, also affect the evaluation. Personally, I think all three are excellent headphones.

This is not obvius, indeed. Sennheiser silently changed their OEM stock pads for the 6XX series some years ago (2021 I think). With the new pads (stiffer and taller), there is much less of a bump at 200Hz and more clear and extended highs.
I have bought the HD650 again after selling it years ago: They sound much better now with these new pads.
Last silent revision we know of the 650/6xx itself, other than the pads, is 2017.

I agree. Once you get into this echelon it's more about learning them. And one or two cheaper pairs to check specific other things from a more consumer perspective.

That’s really interesting. I didn’t realize they were different pads, I figured that mine had just softened from so much use. That makes sense, though. I honestly don’t remember them ever being this clear.

Imagining that the MM500 is the best choice if money isn't an object and you're working entirely on cans (and not recording anyone).