[out_of_protocol]

Not really? Hard to find new though, 598 is older model, 599 is almost the same and more available

https://www.amazon.com/_/dp/B01L1IICR2/ - HD599 new, $149

https://www.amazon.es/_/dp/B01L1IICR2/ - HD599 new, €115

https://www.amazon.es/dp/B07Q7S7247 - HD599 new, €101

https://www.ebay.com/itm/296053418289 - HD598 used, $88

[jacknews]

OK, if the 599 is the same. I simply googled, and found this for hd598: https://www.amazon.com/Sennheiser-HD-598-Over-Ear-Headphones...