Haven't seen a lot of reviews for this pair, so I figured I'd throw my 2 cents out there. I had been eyeing these for a while, so when I saw them on Thomann as an open box model with full warranty and 300 euros off, I knew I had to get them. They're hooked up to a Fiio K9, playing lossless redbook quality songs through Apple Music. No spatial audio shenanigans.
The build quality is solid, with the MM-500's having a nice weight to them. Every part feels well constructed and well designed.
The comfort for me is great. The clamp force is solid without being overbearing, and the weight doesn't bother me at all. The inner diameter of the pads could've been a bit bigger though, because my ears barely fit in there, and I don't think I have particularly large ears.
As for their sound, they're definitely mid-forward. There's not a lot of bass there, but whatever is there is nice and snappy. Bass extension is very good. The highs are laid-back, but don't feel damped. All the detail is still there, it's just pushed to the background. Vocals, and female vocals in particular, get all the room to shine here. They're pushed all the way forward, and just seem to float above everything else in the mix. I really like these for anything from Fleetwood Mac, SZA, Yerin Baek, Jack White and even Carpenter Brut.
However, the mixing DNA of the MM-500 is unmistakable. While seperation and placement of instruments are excellent, the soundstage is very intimate. And if there's something wrong with the music you're listening to, you're gonna hear it. So if you like to focus on the vocals and you listen to well-mixed music, these might be for you. Otherwise, I'm sure there's better options out there, especially given their hefty price tag.
As an HD600 simp, this is the best stock tuning i've ever heard on a headphone. I had to bend the headband a little to reduce the clamp because it was definitely too tight for me.
I'm glad you are enjoying them as well. Great headphone.