Yes, and the more your ears get used to the IEM the more details you'll notice.
I like the tuning of the ZVX but to me they were a bit bass heavy, the D-Fi are too but to a lesser degree, physically (both) are a bit heavy and depending of the tips it can bother a bit after a time.
Now I mostly use the Kefine Delci (some cymbals can sound a bit bright and unnatural in some tracks) also they are the most comfortable IEMs I ever have.
I used EQ but after a while I just wanted something that can use with various sources without changing EQ settings every time hence the search for a natural IEM (but I might end EQing the Delci in the treble region though).
Insertion depth is the most significant factor I found on the ZVX for addressing the bass, and I did add a small low end shelf to cut out some bass, so I'm happy with the bass. In a way, I wish it had more, but that's because I have been so used to the CCA CRA. In my audition so far, I have not yet listened to bass heavy songs such as hip hop, but will soon.
Whether it is my ears or burn in, or the songs I am listening to, or the effect on hearing after a bit of sleep, the top end does not seem as harsh on the ZVX, this morning. I get the impression that I am beginning to reach the limit, of what a headphone can produce, and to hear any better, I now have to address my audio source.
Over several months, if I look at the entire audio chain, I have made incremental improvements. I've skipped some of the intermediate steps, in each of the following enhancement areas, of the audio path.
0. It does appear that our ability to hear clearly, may vary throughout the day. I may be wrong. Time I also took my health and exercise more seriously, and sleep, to maintain my ear health. Diet(what I eat - that I'm already doing very well with)
1. Learnt to use better tips, that fit better, and produce a better seal - very important to hear the bass better.
2. Learnt to fit them at a depth that improves the frequency response, and use this insertion depth to adjust the frequency response to my preference. Very small changes have a significant impact. Less so on the ZVX, cos with the stock tips I'm using, they are not the most isolating IEMs. But this helps with comfort. Less pressure on the ear canal.
3. Listening device (moved from some cheapie Sony ear buds, to the KZ ZVX)
4. Cable - now using the stock cables that come with the KZ ZVX.
5. DAC - went from the in-built DAC on my laptop to a TempoTec Sonata BHD
6. Learnt how to better adjust the volume level digitally on my computer (my main listening device)
7. Learnt how to EQ the audio to dial out the most offensive aspects of the headphone and maintain a few presets for each headphone.
8. Went from 48K and this is now upsampled to 96K, which adds a dash of extra clarity.
9. The source. I am now at the point where I think I've done the 80/20 on all other components of the audio chain, and there is probably little value in doing anything further on items 1 to 8 above. So what's left, is to improve the source.
Hitherto I've been listening to free Spotify. I recall comparing this to a trial I had on Tidal, and Tidal was audible better, even though I was not listening to the full lossless Tidal service.
So for any further realistic listening, of any critical kind, I think I can only make a proper impression, when listening to the lossless CD Quality or higher resolution versions of the source audio.
I think audio professionals and enthusiasts should think of this craft/hobby from an end to end perspective. So rather than just the headphone, the device at the end, one has to optimise the entire chain. It does make me wonder, what kind of limitations exist with the opinions of many users and reviewers, which are responsible for sometimes a diverse conflicting set of opinions on IEMs and headphones. It does not help that the manufacturers make changes to products along the way, which are not disclosed publicly, so one can only judge the product one has in one's own hand.
Best headphone in the world (i,e step 3), without attending to the other components in the chain, is counter productive. The British phrase, you cannot polish a turd (a polite word for brown matter). Question is - how much effort, time, diligence does one devote to each of these components. All of them have a contribution. The one thing that stands out is clearly the source. For me that is where the rabbit hole needs to dig deeper into. Cos that has now become my limiting factor - Moving away from free Spotify for any critical listening. And then and only then will I bother to consider improving anything else. What's the point in "upgrading" from a single DD IEM to anything else - Planar Magnetic, Hybrid, etc, which will only show me exactly how $hitty my source is?
That's how I feel about the KV ZVX. It's beginning to show me the limits of my source. I really cannot have any further valid impressions, when I'm feeding it a compromised lossy source. So for this reason, no more IEM purchases for me, until this compromise is solved.
It's been a bit of a rabbit hole. So casual listening on Spotify - checked. But critical listening, cannot be achieved if my source is compromised. I remember comparing Spotify and the original CD's of a Black Eyed Peas album, and one from Jesse J, about a decade ago. like chalk and cheese. As they say in one 7up advert, the difference was clear.
