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

I don't know how concrete enclosures sound. I do know that cinder blocks make decent speaker stands. I used some, back in college, for my large Advents. Cheap, minimal resonance and meets a certain post-industrial chic.

I've heard a round (actually grout) underground vault. It had 4 18" pipe intersections. It was bell shaped. Two were blocked, top was a manhole cover. No bottom, just sat in the sand. This was not concrete, no rock, just fiberglass strands about 4-6" long and an epoxy/grout mix.

2 pro 15" drivers. It had an interior of 20 CF and 1500 pounds or so. It rang so bad, I had to spray the interior with expanding foam.  It bassed  up the whole 2 acre yard. 

A column of Corian at 5/8 thick 18" x 20 x 72" with little bracing will hit a 1/2 ton.. pretty quick. Just a front baffle of @Corian and sides of MDF 550-600 lbs

I'm dealing with 410 lb each, NOW.. With HDF/MDF 

Concrete is the heaviest because of the BIG rock, a lot of weight. Also tough to pump. Light grout mixes that are made with accelerators, can fluff to about HALF concretes weight. Fiberglass, Stainless all kinds of stuff go in the mixes.

Regards

Huh???

For some inexplicable reason, Jern has not ventured yet into making 3-way floor-standing speakers.
http://jernspeakers.com/

The easy way to do this is use a router and cut out very large slots into the wood at a depth of 32 millimetres and fill them with concrete..