Ok, so here's my "one week later"-review:
Wow. What a headphone. It's like I've injected musical gold right into my head.
After getting past and over the initial comfort issues, I now am thoroughly enjoying these gems of IEM:s.
They really can (like their full sized brother M4U 2) root out the bad recordings from the good. They are very revealing, but always musical. Extremely dynamic.
Lows:
Just as I wanted, tight, accurate and not over-blown bass. It has just enough sub extension for my taste, to provide enough for the bass to be the glue that holds the music together. Great detail; I can make out what kind of effects the bass player has used on the recording with ease. As a bass player, I take great joy in hearing bass as it's supposed to sound. Fat, punchy, supporting the music and (hopefully) not taking over too much. There is (AFAICT) no bass bleed at all, probably due to the fact that there are separate drivers in this IEM for bass and mids/highs.
Treble:
Again, very musical treble. Enough top end to make crash/splash cymbals shimmer and sound crisp, yet never strident or harsh. That's one of the issues I have with the M4U 2; it can at times have slightly harsh or strident/tiring treble, especially in active mode. While not a huge problem, I can definitely recognize it's there sometimes.
The M4U 4:s have so far shown no harshness whatsoever, even at higher volumes, which is a huge plus, seeing how IEM:s can have a tendency to tire you out due to the whole in ear thing. I.e., having harsh treble is worse for me in an in ear-model, since the treble is quite literally right inside my ear.
The resolution is (to my ears) great as well. It really reveals bad production/mixing/recording of cymbals, and really shines with good production. I'm listening to "Coma Ecliptic" right now, by Between the Buried and Me, mixed by Jens Bogren. A fantastic album with an incredibly dynamic and musical production, and it's a pure joy to listen to through these IEM:s.
Mids:
Well, I saved the best part for last.
Wow. The mids are even sweeter than on the M4U 2:s. So natural, so smooth, so musical. I know I'm repeating myself here, but man, oh man, the mids are to die for. Male voices sound absolutely stunning, guitars - whether acoustic or electric - cut like knifes, saxophones and harmonicas vibrate like they are being heard live. Female voices have a gravitas and a heft to them, that I've lacked in other headphones. Joni Mitchell's voice on "Shadows and Light" has never hit so hard for me until now.
Again, musical mids.
Summary:
Wow. I never thought I'd find a headphone I liked better than the M4U 2:s, but the M4U 4:s have done just that. The overall dynamics, musicality and balance of these IEM:s have blown me away. The old cliché of "hearing things in music you've never heard before" is applicable here, to a great extent.
Another musical homerun from Paul Barton, one which I'll be enjoying for years to come. I might even go so far as to get rid of my 2:s - they are THAT good. Now I am getting ready to have a friend ship some Sony hybrid tips from Japan (thanks for the tips
@dweaver), in sizes S and SS, to see if they are as good as rumoured. BTW, can you confirm if they fit the M4U 4:s?
I really can't find anything to fault these IEM:s on. For the price I payed for them, they are nothing short of perfect.
All the listening has been straight out of the headphone jack of my Macbook Pro and iPhone 5, no amplification or DAC used - but honestly, I might sell my full size headphones to finance a DAC/amplifier, because these IEM:s might be the only headphones I'll ever need listening to music.
My hat's off to Paul Barton and the crew at PSB - you hit it out of the proverbial ball park with the M4U 4:s!
