[JLM]

Same price as the 2012 released original LS50 ($1500/pair USD).  Same size, very similar appearance.  Reportedly the driver assembly has been updated, but the big news is the use of meta absorption which reportedly absorbs 90% of the back wave from 600 Hz on up to ? for a cleaner sound.  Back wave effects have been a long time issue to me.  Dipoles of course don't trap them, but release them (unnaturally IMO) into the room out of phase.  But in box speakers the back wave has to go somewhere and the easiest route out is back through the cone material, again smeared and out of phase.  So effective absorption seems to be the answer.  In a few speakers the back wave is redirected away from the cone via a slanted internal baffle (transmission lines and pipes are naturals for this). 

https://www.youtube.com/watch?v=HLA4TbVkRkQ

https://darko.audio/2020/09/kef-tease-metamaterial-absorption-technology/#:~:text=From%20KEF's%20press%20release%3A%20“Harnessing,the%20prevention%20of%20audio%20distraction.”

[Norman Tracy]

KEF's META is very interesting.

This video helped clarify for me they are talking about the tweeter's backwave, https://youtu.be/O_US3Kml0Cg. Steve Guttenberg Audiophiliac rave review repeatedly saying the LS50 Meta sounds like an open baffle speaker https://youtu.be/oKTYvP7YQ0Q left me with the impression the Meta structure was acting on both woofer and tweeter. This interior view shows the new cross brace that stiffens the box which in my experience helps woofer+box systems sound less 'boxie'.



KEF's talking points repeat that the meta absorber on the tweeter is one of several improvements that give the reported improvement in sound as this graphic details. BTW in this exploded view the META absorber is the three parts on the far right. These are assembled on the back of the driver with the tweeter's backwave delivered thru the center hole.



Searching "sub-wavelength resonators" starts a deep dive into the topic like this article https://www.nature.com/articles/srep19519

[JLM]

Didn't link Guttenberg because he drives me nuts due to being so scatter brained. 

Wonder why they stopped at 620 Hz and didn't go much lower. 

[MarvinTheMartian]

No reason to go lower than 600Hz for a tweeter only absorber.

https://us.kef.com/pub/media/wysiwyg/ls50/20-KEF-LS50-Collection-WhitePapers.pdf

Shawn

[Rich123]

I have a pair of these and discovered the cabinet is stuffed full of foam.  And the port is seems to be large and close to the woofer which might be a semi-open baffle configuration.  The speaker is supplied with foam plugs for the ports.  I think I'll put them in now.