@mapman ,
"I am wondering how long it will take for this new sound absorption technology to show up in headphones? That could be interesting also."
I'm sure it will be as open backed phones are barely practical outdoors anywhere near a main road.
I've switched to using closed backs as I found myself needing too much volume to overcome the sound of constant heavy traffic near where I live.
I know headphone manufacturers already use different methods to deal with the dreaded headphone backwave for their closed back models but maybe this KEF Metamaterial technology is simply far more effective than using foam etc.
If so, then we can surely expect the likes of Sennheiser, Sony, Audio Technica, and Beyerdynamic etc to all respond shortly with their own responses.
In fact I can imagine a few departmental heads soon asking awkward questions of their R&D departments as to why KEF got there first.