Received the UM Mason FS today and wanted to share first impressions.
Out of the box it did not wow me. But I think that's not what these IEMs are about. Later more on that.
Generally it sounds quite neutral, definitely not warm. Many reviews mention them as the king of vocals. And I can definitely sign that. Vocals are superbly clear and very emotional. It's definitely the stand-out feature of these IEMs.
The bass is there when demanded. And can hit quit well. It is nicely textured and clean, but it comes with the typical BA timbre. It does not interfere with the mids at all.
8/10
The mids are highly detailed and well textured. But there are IEMs that have even more texture, e.g. Trailli, Odin or Phönix. As said, vocals are so good, you can hear every nuance, breath etc. It involves you quite emotionally, even it is a neutral oriented set.
9/10
The treble is more on the relaxed side, altought there seem to be some smaller peaks. But it is definitely not sibiliant. It does not have a sugar like or silky treble. It's more analytical but still enjoyable.
7/10
Regarding the technicalities: The soundstage is crazy wide. I believe it is the widest soundstage I have heared in any IEM. I don't have the Traillii here at the moment for comparion, but I think it is wider than the Traillii. It is very detailed, especially vocals and the bass has great texture too. But the treble is a bit lacking (maybe recessed is the better word). Instrument separation is very good. I don't find the general timbre very accurate. It's definitely lacking compared to the Traillii.
The more I hear it, the more I like it. I need to give it definitely more time. I am mainly searching for a complement for my Traillii, and I like the neutral sound of the Mason paired with it's great technicalities. But it is somehow not the best all-rounder, some songs on my playlists sound great and I seem to find things in tracks I haven't experienced before, but also many songs are just ok.
Songs like PANG! - Don't Speak sound incredible on the Mason FS.