Unit #4 showed up today. Mostly going to be comparing them to my existing closed cans, since that's my frame of reference.
First impression? Wow this is comfortable. The earcups are slightly smaller than my NAD HP50s, But dont' feel that way, and the cans spread their weight well on the head. I do get a bit of the pleather/leather "are your ears sweaty, or do they just feel that way?" after a while, but that's it. I could wear these for hours.
They are quite stylish, and very well made. Better made than any pair I own, including my Senn 650s.
My iphone 6 will power it just fine. It's loud enough at 2/3 volume... but it's just not as good as my PSB M4U1 out of the same iphone. it's significantly worse than the PSBs out of my work laptop. Sure these will work out of an unamped source, but the're not my first choice by a longshot... not for sound quality anyway. Style/comfort I might go for it, but wearing $400 headphones around in public just feels weird to me.
Putting them on a real DAC and amp though, what a change. Took it home and hooked it up to my Modi 2 and Vali 2.
The Bass doesn't hit as hard as either of the Barton twins (M4U1 and HP50), but it's textured significantly better, which is impressive because the Barton twins were already very good at that. In general the PM-3s seem to be finding instrument texture better than anything else I've got significant experience with.
Midrange is a mixxed bag, comparatively speaking. it's very very good, but I must admit I'm used to the "roomfeel" of the HP50 and M4U1's midranges, however they can feel over-emphasized on certain tracks and even muddy if enough midrange is thrown their way. The PM-3s on the other hand are much more polite, and I'm pretty sure the sound is more "authentic" if that makes sense. I'm honestly not sure which I prefer.
The Treble is actually very similar to the Barton-tuned phones. Rolled-off and inoffensive. I like it that way most of the time. I've got Alessandro MS-1s or beyer DT-880s if I just have to have crazy air guitar metal riffs.
Soundstage is a bit less than the M4U1. About on par with the NAD HP50s, maybe a smidge edge to the HP50s. Way less than the HD-650s of course, but they're open so that's to be expected.
Certain songs sound quite different, in a good way mostly. I don't think it's the PM-3s are colored so much as they're mostly neutral and my reference point headphones are colored. Although since I've been listening to those roomfeel phones for years now, my brain is tuned to listen for that signature. I'm curious to see how I feel about the PM-3's signature after a week of listening to them.