Comfort/build quality/cable: The MM is extremely comfortable for my medium sized ear canal, the fit is very secure, especially with the included AZLA tips. The passive noise isolation is also great. I find myself using iems as an earplugs in loud environments quite often and these work nicely for that.
The build quality is outstanding, the shells feel very premium and look absolutely stunning in person, probably my favorite looking iem to date.
The cable doesn't seem to be microphonic to me. It isn't light but not heavy either, the weight is just right. Very comfortable for hours and it does feel extremely premium, just like every other top of the line PW AUDIO cable.
The sound: Just like the Mason FS, the vocals and string instruments presentation on there are on another level, way above everybody else.
I've never heard an acoustic guitar and violin sound so authentic in any IEM. It actually sounds like you are playing the thing without the vibrations of it against your body. The vocals sound like the person is singing detectly to your ears and you can feel it in a way. I've never had so much fun with any headphones in my life, let alone an iem.
The tonality on MM is unmatched. I often do prefer there over my Genelec studio monitors for pure musical joy that UM bone conduction gives me and that is saying something. Even amazing sounding speakers can sound somewhat lifeless after these.
Overall the MM are extremely nuteral, dynamic, crisp, enjoyable, fun and everything in between.
The low end is extremely well controlled, very balanced and as punchy as you want it to be even for metal/djent/thall type of genre.
The soundstage is stupid wide. Wider than Mason FS, Mext and my trusty U12t's. Imaging is spectacular, I would say The best on any iem that I've heard in recent years.
The course: depending on the source, you could or couldn't feel/hear the UM bone conduction properly. With some daps/amps these become just a great sounding IEMs, with some it completely transforms and makes you feel and hear the music like never before. I do find them to pair best with the Cayin products (N8 II, C9 amp, HA-300 MK2, RU6 etc) and LP6. The better the source, the better they will sound. I personally run them through my Cayin C9 amp with an external dac and I'm very pleased with the sound.
Negatives: There is one negative for me personally.
I do find them unusable for tracking, It just doesn't feel right. I often do prefer to wear an iems when I'm tracking and practicing guitar so that was a little bit of bummer, but I already knew what I'm singing for after purchasing my very first UM product.
Conclusion: If you can afford these, please do yourself a favor and buy a set, I'm extremely happy with mine after 9 months of having it and can't recommend them enough.
Otherwise please do consider getting the MEXT, both are fantastic, the MM just gives you way more and has a better control over all of the frequency spectrum.
