Good you brought up this thread. His descriptions are so on point. I even saw i already left a comment in this thread lol.
I'm looking for exactly the same "headphone which has a natural tonality of the Sennheiser HD600 or STAX SR L300 combined with planar like bass".
I really wonder which LCD-X he listened to though. I agree that it isn't a good headphone but very dark? I remember the LCD-X to be brighter than LCD 2 and LCD 3.
One headphone that maybe could fit the bill is the Grado PS1000e. Only listened to the PS2000e but it was a pretty solid allrounder with hefty bass while maintaining an overall neutral FR. Tonality was equally great. Female vocals were on par with HD600, male vocals and instruments, especially pianos, were superior. Soundstage was maybe the best i've heard together with the Utopia.
So PS1000e could be a good choice here.
(Didn't keep 2000e because comfort sucks so hard, Grado qc, very heavy and attached crap cable on a flagship headphone)
Currently having a HE1000 V2 on the way. Maybe that will be an improvement over the HD600.
Maybe unexpected, but here I am.
Thanks for your recommendations.
Actually, thanks to all of the contributors.
Did not expect to see new posts appearing that long after my initial post.
Specifically to your question regarding the LCDX-Revision:
Not sure when the LCD-X was manufactured, but it was a brand new delivery to Thomann (where I bought it from).
I had to wait for a couple of weeks before I got them. They were on backorder for a long time.
Based on the reviews/measurements, which appeared throughout 2020, I am sure it was the "2020 revision".
Please have a look at the measurement in this Video (timestap is within the link).
How to EQ Headphones - Featuring Audeze LCD-X 2020 (not 2021)
For this revision, the frequency response from 1khz to almost 5khz is very recessed.
This measurement does match my listening impression.
To me the most fitting description is "muffled".
I am not insisting on that they sound "dark". Maybe it is even the wrong terminology as they have quite a lot of air.
However, 1 to 5khz is a key area for many instruments. 1 to 5khz covers the complete 6th and 7th octave and the beginning of 8th octave.
7th and beginning of 8th octave is quite high notes already. Maybe that is why I thought they were dark.
The 2021 version is supposedly (much) better for 1 to 5khz, but did not listen to them in person.
To be more precise, I did not listen to any new headphones since the audition in January 2020.
When the stores closed due to the pandemic, I had a lot of time to spent with my current setup and to reflect on my experiences and requirements.
In the end I decided to stick with my current setup.
The search is not over (is it ever?), but it is postponed to another day in the future.