By the way I read most of your impressions... I just try it for 1 hour and its a beast and for its price a banger, but I find the sound a little bit congested or like it has a veil... if this gets corrected with burn in... then its an endgame...
testing all filters the default one sounds more natural to me, I dont think the sharp roll off has more soundstage than any other but maybe its because the lack of burn in
We found out that sharp roll off has the most dynamic and bassy sound and also im medium gain you get an edge up in that same direction for more fun and punchier sound.
After my burn in I find the sound is more open and fluid, not restrained or contested like you calling it. I also found the best sounding filter would be slow roll off and low gain, that is the setup I found to make m5u to sound as closest possible to my wm1zm2.
In short slow roll off there is a layer of warmth which may hide some details a little bit, the sound overall is very pleasant and warmer with very interesting bass decay.
If you favour more clean sound you can try short fast roll off filter its very close to the default one yet not as warm.
Fast roll is very dynamic and strong, I find it a little sharp on the treble in occasions.
My favourite atm is slow roll off and I play with gain level between low and medium. Also set fast roll off medium gain if I listen to edm, for audiophile music I am in between slow roll off and short delay slow roll off, I set default filter if I really want that warmer warm and cozy feeling as its a very gentle tuning and never ever sharp on the treble.
Slow slow roll off is overly smothered out in my opinion haven’t really used that one so far.
After my burn in period of 265 hours I find m5u way better then it was before, everything improves. The only part that I really miss in comparison to my wm1zm2 is the airiness and the huge soundstage of the mighty 1zm2. Some music seems to have a slightly more natural feel for vocals in sony, sony is a tad more audiophile oriented so it is a bit normal it has an edge in that regard.
But m5u is faster, more tight, more blacker background and also more sharper in details, in sony things sound like hazy not as precise. Overall m5u if had a little bit more airiness and soundstage by 10% it be a darn flagship and would kick ass to sony territories.
I am still in process of deciding which I prefer more, for now I am 40 sony and 60 m5u. The fun factor and musicality of m5u is undeniably good.
Hope that helps!
Tiger