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

I had some Essence speakers in the 80's.  Each driver, 5 per side, were mounted to concrete, then finished on the outside with medite, then walnut, except the bottom, woofer.  Each speaker housing was separate for time alignment and made a nice pyramid.  10k in '82 was a lot of money, but they sounded fantastic. Before and after speakers were Snell Type A and Quad ESLs.