The only written review says the headband is “well padded and hard” so I guess it is pretty stiff. It should be less of an issue on sennheiser headphones since they’re pretty light.
Personally, I prefer the 650 headband over the 600 nuggets. I just got the 600 band for free when I bought my 6XX so I had one lying around.
The sound quality is top tier for its price. This is probably the best sounding headphones for around 100 usd, but it needs an amp.
Aside from the comfort issue, theres the usual hifiman QC roulette lol. You might get one with a broken driver. Although it’s rare, it’s best to purchase from a seller with a good return policy just to be sure.
6XX (used) and zero red. I’m still looking at the new Fiio JT1, might buy it before the year ends.