Hmm, good question.
I should preface that we all hear differently, and what sonics mean to someone is based on their individuality, but I am more than confidant that you are aware of this.
I will write more info in my EnjoytheMusic.com report, but I'll explain a bit here.
First up, I have dreamed about owning a K10 ever since its release, especially due to its near universal acclaim. I am aware that there are those who like the new Empire Ears Zeus and Campfire Audio Andromeda over K10, but almost everything you said about the description of the K10 is what I have been lusting over.
This next bit is a super succinct description of my audio gear to give you a taste of how I define and liken my gear, to give you a small insight of my tastes (won't include DAC's or amps because that'll be too long):
In my search for a personal nirvana of headphone gear and equipment, I absolutely love gear that sounds and is voiced like a single-source, but also a cohesion of frequencies.
This is something that is evident in (and possibly reinforced from) my choice of favourite speakers, the John Blue AudioArt JB3, with its 3" driver and super smaller tweeter whizzer cone embedded in main driver, and huge double magnet. My speakers are not truly technical but purely musical, with blooming but not too bloated bass and excellent near-field imaging, fantastic for almost any genre of music but predominately vocal work, acoustic instruments, jazz, classical, some electronica like Daft Punk and Disclosure (rather than Deadmau5 and Noisia). Mid's are probably it's best quality, but more with guitars; just enough bite and sweetness. However, I do not use my speakers for critical listening but for multitasking, gaming, films and TV, etc. Music is very infrequent. Also, this speaker is not as good at cohesion but excellent as a single-point source/voice.
Now, my Audeze EL-8 Titanium headphones (2016 drivers, and internally driver-wise the exact same as 2016 EL-8 CB) was the very first headphone that gave me that feeling of 'cohesion of frequencies' and 'single-voice' like quality, whilst having complete authority and thwack of sonics (lower mids, bass, and breathless treble). There is an almost monitor like quality to the EL-8 Ti, but packs in a tremendous amount of detail and resolution, something my older AKG K 712 (and even older AKG K 701) headphones do, but the EL-8 Ti is much clearer and grain less in its sonic prowess.
Sometimes this gets too much, and I switch over to my Meze Headphones 99 Classics Walnut Silver headphones; that headphone has comfy bass that smothers you over accuracy, and a midrange of sweetness with grip (with DHC Elite Molecule 22 pure silver balanced cable). It is a great way to cleanse and change up my sonic palate between my EL-8 Ti and JB3 speakers.
So, when I heard the K10, I was floored. Absolutely stunned.
It was like I was getting my JB3 speakers, EL-8 Ti, and the 'sweet, grippy mids' of 99 Classics, all in one IEM.
INSANE I TELL YOU!
I also had a visceral impact of music too, something I love from my EL-8 Ti.
Yet, the Katana, was not far off from my above description, but had a different change up. It was like having my JB3 speakers, EL-8 Ti (but less impact and thwack), and comfy bass like my 99 Classics (but with far greater detail and accuracy), yet less sweet mids of 99 Classics, together.
For me, effortless sonic tapestry = no standout frequency, but
not flat.
How? Well, flat frequency is a mathematical, measurable, theoretical line.
But, a piece of gear that does not have a standout frequency does
not have to be flat, no, such gear has the confidence to display music
without sounding flat; music that you can just walk through in your mind, float away with, giving you everything at once but not letting any singular part of the music pull or sway you.
I really find this hard to describe, because when I critically listen to music for enjoyment, I start writing
worlds in my head, so the brilliance, vibrancy, etherealism, and realism of those worlds is relies on what gear I am using.
Thus, Katana is better at transporting me to my musical nirvana without distracting me over one sonic quality over another, just presents music in one cohesive, single voice.
I do not consider the Katana flat, as that would be closer to the Etymotic ER series, or Ultimate Ears UERM, or even Noble Savant.
I find it engaging that it somehow, simultaneously, does not emphasise any sonic trait yet still presents a massive musical presence beyond your mind. Effortless is the closest descriptor I can think of at this moment.
Had the Katana not existed, the K10 would have been the ultimate IEM for me, and it is still amongst the best IEM’s/CIEM’s on the planet.
The Katana, to my ears, is superior in only that ability to be more amorphous.
For some users, the K10 with its better visceral impact (mainly, but not excluded to, on mid-bass) is a better quality to have than to lose, but the Katana swaps that for a more
natural sound (to me), and I liked it.
To be honest, I wish I could have had a switch to go between the two on a single IEM ha ha ha!!!
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Oh no, I wrote too much, oops.... :/