This is how it looks like.

It is glued on, and people using wax or other stuff in their hair style, might accelerate the cushions degradation.

I hope you mean "better tuned"

I own a Sennheiser Game One since 2016 which has also a HD5xx chassis, changed the earpads once and have zero issues with the headband cushion. And if I need to change it, I can do that with little effort. I do not sesne a problem here. On the bass my understanding is that the HD620s has more...

There is no dip, all frequencies are exactly how the Sennheiser Wizzards planned them to be.

Even though I never had a listen on the ie600, I would go for the IE900 if you can afford it. To me it is perfect from bass to treble. I got mine at release and I am always eager to put them on ever since the first day.

I like the earhooks, have zero complaints about them. But the sound is even more to my liking.

First you wrote sounds like garbage.. I am ok with sounds good.

I run them like all my headphones from the Sony NW-WM1A. I cannot call the DAP underpowered. High gain 78% volume. But depending on the condition your ears are in ymmv.

4XX is which headphone?

You might want to check out Forzaaudio Noir Hybrid HPC, it is a bit more expensive, but very well made. I have it since the HD660S came out. I love the cable.

I can agree with you on the build quality of the DT1990 pro. But they have two gripes for me, the round earcups are to small for my ears and they sound to uneven compared to the HD6XX series.

I run it from my Sony WM-1A. pPerfect match. Balanced 4.4mm out.

Hi Rob, interesting to read for me. I still hold on to my HD660S2. That headphone in contrast did completely meet my preference without any further open demands. I only could use a closed Sennheiser in that ballpark. But maybe it will be a HD820S some day for me. Need to sell the Sony Z1R or...

The temperament is in the music, not in the listening chain. If you like it hot, what about a Beyerdynamic T1 first gen? Ringing ears for free....