Concrete is interesting but you need to create a mold for a hollow concrete box where you are going to have metal lathe running through it. Concrete won't hold together without it.
Not to mention that mounting hardware would be difficult. I doubt that a hammer drill will work near the edges of a round hole like that without fracturing off. Maybe it would. I am not sure.
This seems like it would be harder than you would think. That being said, a company did launch a speaker that has a stone cabinet and evidently it sounds great. Acora Acoustics makes their's out of black granite.
They are about midway down this article. You can see mine a bit further down under Verdant Audio.
http://www.theabsolutesound.com/articles/axpona-2019-andrew-quint-on-loudspeakers-under-20000/
Not to mention that mounting hardware would be difficult. I doubt that a hammer drill will work near the edges of a round hole like that without fracturing off. Maybe it would. I am not sure.
This seems like it would be harder than you would think. That being said, a company did launch a speaker that has a stone cabinet and evidently it sounds great. Acora Acoustics makes their's out of black granite.
They are about midway down this article. You can see mine a bit further down under Verdant Audio.
http://www.theabsolutesound.com/articles/axpona-2019-andrew-quint-on-loudspeakers-under-20000/