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.