Very interesting & you are definitely onto something.
Back in the 80s, I built a pair of tubular-shaped, line-source speakers out of concrete. If I can find a pic, I will post it later, but each speaker contained a series of 6 small (4" dia) full-range drivers mounted vertically. They imaged almost as well as a 'stat, but had alot more dynamic range. Unfortunately, they were lacking in deep bass or the top octave of treble. But within their range, they were pretty amazing. B&W, among others, have used concrete in some of their monitor speakers with good results.