Killer speakers like that, that carry such a strong full detailed rendering of what's coming out of the guitar, really show their potential when loaded into a very well made closed back cab. You put speakers like that in a really good closed cabinet and the harmonic complexity makes the box resonate in just the right ways to constructively add to total output of tone. IMO open back cabinets do a disservice to speakers like that due to the tonal bleed out going on out the back of the amp. Sure the open back has a nice brightness to it, but I estimate only about 10% of that extra bright tone actually finds its way to the ears of the audience members. Mostly its just something experienced in the near vicinity of the amp. And what ever small increase in top end that does find a way out towards the crowd is cancelled out and then some by the forfeiture of tightness and definition inherent in a speaker box that can't vibrate/resonate a in very uniform way compared to a good closed back.
I used an open back cab for years, and never could get it to sorta do what i wanted my amp to do so last year when I bought my Komet Songwriter 30 head I wanted a matching 2x12 cab. And Komet cabs are very very well built. After playing on an old marshal 4x12 basket-weave loaded with original heritage G12H30 Greenbacks, I realized that that was the feel and sound I wanted my cab to emulate so I got the cabinet with the pricey speaker upgrade to two Celestion Heritage G12H 30 Green Back (made in England). I also requested that even though they only technically offer and advertise an open back design cab, i wanted it closed back which they did for me. My speakers kind of act similar to the EV's in the way they both are designed to be flat frequency response thats tight and harmonically balanced. No crazy stand-out frequencies. (of course my speakers don't have near the head room yours do!)
Speakers like that do such a good job of physically interacting with a good cab which results in a pretty sweet final product of a harmonically complex, pure tone, that leaves the cab in a powerful purposeful mission to be heard, felt, and tasted by a waiting audience
Well thats my "brief" opinion of closed back vs open back speaker cabs especially for speakers like EV12L.
Im just rambling cuz I saw your post right after getting home from a gig at which I was really happy overall and even a bit surprised a few times to hear my rig, namely my cab, push such clear, tight, fat, thick, tones out considering it was a really lame low key wedding reception meaning we weren't nearly as loud and energetic as usual
I'm sure he uses closed cabs though.