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

hdcls
Regarding horns: the room matters. I have had Altec 604Cs for ... 43 years now. They DID sound a little horny (tsk tsk) at first (and I have stayed with these speakers because at my price point, to my ears there is nothing that comes close to their performance), but as the other components improved the condition improved.

I am now in a semi-anechoic room, and the condition has largely disappeared.

In addition to concrete transmission line speakers, Rauna of Sweden also made a small pair of bookshelf monitors with a front bass reflex port - Rauna Tyr II’s. Picture Vandersteens but only 13” tall weighing 30 Lbs each and going down to 40-45 Hz. 

I first heard them in the mid 80’s and was blown away! I found 2 pairs of them in the last couple of years and refinished the rosewood tops & mdf bottoms and they are Excellent & very fun speakers. If you find a pair, most likely the wrap around foam grills have have disintegrated but that can be purchased and make sure you get the Tyr II, not the original Tyrs. The Tyr II’s had binding posts on the back, original Tyrs underneath.

Millercarbon concrete and extruded polystyrene are sometimes mixed together, so you could end up somewhere in the middle sound wise.

Hello highend666.  Granite/Quartz countertops are frequently broken during transportation and installation. Broken bits can be had for very low prices and the shops that have them will cut them for you. I have made seven cabinets out of broken counter tops. You can make the fronts out of any kind of wood product you like, the backs too. Glue the countertop pieces together with construction adhesive or silicone rubber. Heavy, but acoustically inert.

British audio engineer, Gilbert Briggs, who founded Wharfdale in the late 30's wrote a number of interesting books on "loudspeaker" design. He installed speakers into bricked-in corners in a room - must have had a very supportive partner. My takeaway from one of his books was the use of bonded dissimilar materials so that their natural resonances would tend to cancel each other out. Taking his advice, I glued 12" square sheets of mosaic tiles, then grouted them, on the inside surfaces of my cabinets - enjoyed listening to those speakers for 50 years. Probably for the same reason Wharfdale sold loudspeakers with sand-filled voids in their walls in the 50s.