Thanks a lot! You saved my evening
If you have time, please listen to Alien Flame - Shometyle
https://tidal.com/track/297807511
For me it is reference track for determining the quality/quantity of bass
Using YouTube Topic or official videos where possible insofar as I only have an Idagio subscription and if ever may opt for Qobuz.
The Blaze "PRELUDE". Full and deep bass. Crackle effect on the left driver. I suppose textured pulsing motif and synths. I could call it a "spherical microcosm" lest that be too flowery.
Infected Mushroom "Becoming Insane". Damned sharp and incisive guitar transients coming from each driver. Maybe some slightly beyond-driver vocal effects. It is simply quite engaging. Switching to one of my headphones set up for neutral DSP speaker simulation, the imaging experience is of course different between having a coherent stereo line in front of you as opposed to having that line wrapped into an arc between the drivers and maybe sometimes a bit to the backs of the ears as in my large headphones. Textured. Aggressive. "Very technical". Not much differences through my EQed Meze Elite with premium silver cable. I can't think there to be anything missing. A lot of things overlaid, its being feasible to hone in on the parts, be it certain vocal or guitar parts in the background. Not at all "congested".
Liaze, Equal "2003". Reasonably tactile and deep bass thumps. Main vocal an inch or so in front of my face, its sounding fine with treble content (like from the tongue) rendered. Ambient components show through. Accordion or similar is textured. Articulate. Sounds as wide as I would expect from the Arya Stealth.
shometyle "ALIEN FLAME". Clear. Blaring (in the sense that those "blare" sounds are as blaring as they should be). Textured. The bass thumps feel leaner compared to the other tracks. The deeper bass swells are reasonable. Articulate metallic effects. The bass thumps can be accompanied with texture details. "Tings" imaging ahead and up; unless this was mixed for binaural playback, for me, any literal "holography" or height differences in imaging are HRTF-related "errors" to me from a speaker reference. Those tings are also reasonably focused, though one can hone into the attack envelope; I suppose it was in the last few tings that they sharpened the attack, unless the attack earlier in the track was being masked by the other sounds; I wouldn't know.
Cardi B "Bodak Yellow". Maybe I'm hearing YouTube compression/mastering in the vocals. That was in the music video; maybe it does sound a mite better/clearer in the Topic video. Not much to say other than that the Topic video's recording sounds clear.
FluxPavilion "I Can't Stop". Sharp bass transients, nothing crazy, or craziness is likely not in the mix. Textured and articulate. The track comes off as maybe having more "space" between the sound sources as opposed to be filled with ambient fullness, which is to say, perhaps an intentional clarity or "economy of sound". The left-right echoing of vocals is around the front left and right for me if not from the headphone drivers. "As separated as ever within the confines of headphones." "All the content is there."
Pendulum "The Island, Pt. II (Dusk)". Wide. Quite articulate. Every part of the "brrrps" or whatever are defined. It's an exercise of listening for details in the synth decay or whatever. Organ is imaged ahead, maybe favouring the front right. The drums after then are maybe inside my head, at least the higher-frequency transients. It again sounds very "separated". Bass impact is reasonable. I can hear the details of the drum membranes in the flanking drums that close the track, those transients feeling reasonably vivid and tactile (insofar as other recordings through the same chain could sound yet more vivid).
Avicii "Seek Bromance (Avicii Vocal...)". I checked out both the "Edit" and "Extended" versions. Large and clear. Detailed. Spacious ambience in the lulls. Reasonably sharp imaging and tactility of the percussion taps. Coherent. Quiet background vocals and effects around the left driver (in the extended version) can be discerned.
I've personally only ever heard "congestion" as a result of tonal issues with the upper bass and lower midrange being too forward, or treble content being overemphasized and masking everything or making everything sound noisy, this being resolved with EQ if not "mental burn-in" per my getting used to a tonality. I doubt that the L&P W2 and FiiO K9 Pro ESS differ tonally; one test you could do is to compare the sound of pink noise through both, making sure to get the volume as close as possible.