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

If you wanted to make big concrete speakers, the way to do it would be to make them modular.  Stack 6" high sections on top of each other separated by thick gaskets. They need to be something that is assembled in place.  You don't want to try to move 500lbs of concrete in one piece.  I don't know if concrete by itself is great idea but it could certainly be a big part of a great box.  It's incredibly dense and won't resonate at low frequencies.  Maybe some high frequency damping is in order but that's certainly doable.

@jpwarren58 ha! 
@roxy54 ha! 

Kenjit Not having heard them your blather is one of ignorance.... naturally.

I have  a system of CNC’d aluminium billets incorporating 6 x 2” full range speakers in each module, 6 modules per channel. Custom amplifiers drive them and I dare anyone to say they ring. The sound is top quality! I compare these to my other system (250k) and yes there is a difference naturally but the solid aluminium speakers are in the high quality sound range.

I’ve spent time listening to Acora’s granite enclosed speakers at the 2019 CAF and they sounded great, even in the minimally treated hotel room. 

StoneBjelk Concrete speakers... Sounds LIVE
  

  

 
https://www.youtube.com/watch?v=TB6V9yxW4P8