Concrete Audio Speakers...Speaker Enclosures made out of Concrete ?..

Has anyone heard these?  I would find opinions intriguing.  I moved my system from our main room which has polished concrete floors into another area where I put down an engineered product over the concrete with immediate improvement in sound quality.  Just trying to think about how to abstract one into another.  Not sure.  I suspect the book shelf on stands vs the floor standers vs the wall mounts would all sound completely different given the contact points but uncertain.  Very interesting concept. 

"...the alkaline that constantly seep out of the concrete would cause any finish applied to them to peel off."

Having "any finish" on them is blasphemy. We, the purists, would want them in "natural concrete".

here's the videos on how to make your own concrete speakers 
 
https://www.youtube.com/watch?v=xCPMxgY_ZN4
 
 https://www.youtube.com/watch?v=LsegJY347dE&t=126s
  
https://www.youtube.com/watch?v=8XLqTvL51t4
 
 https://www.youtube.com/watch?v=CIGmRkhFjIQ&t=78s

Very very small concrete speakers SOUND TEST...put some GOOD headphones on and listen to this.. 
 

  
https://www.youtube.com/watch?v=BuQK82Fwb1U&t

They do sound quite bad to me.