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

If it was so good most companies would do it. Those companies that have done it haven’t been successful.

A concrete wall could be used but not a box.

Kenjit

Read what they say about these Betonart Arrivato Concrete speakers
https://translate.google.com/translate?hl=en&sl=de&u=https://www.lowbeats.de/test-betonart-arrivato-standbox-mit-perfektem-gehaeuse/

Match these speakers with the $20K Audio Note 300B Meishu Tonmeister amp and your be in Audio Heaven.......

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.