SRH840 is my favorite closed model for enjoyment, but not for critical listening.
The KNS8400 cable bears even the slightest noises straight into the left earcup. It's impossible to use unless one is absolutely still. I contacted KRK about it, and they contended that I had a defective cable. But I don't believe that it was defective: I believe it's badly designed because several other members have complained about it.
I guess I made the right choice then as I want the headphone to do double duty.
Assist me with tracking and mixing.
And listen to music for pleasure.