here's the videos on how to make your own concrete speakers
https://www.youtube.com/watch?v=xCPMxgY_ZN4
https://www.youtube.com/watch?v=LsegJY347dE&t=126s
https://www.youtube.com/watch?v=8XLqTvL51t4
https://www.youtube.com/watch?v=CIGmRkhFjIQ&t=78s
https://www.youtube.com/watch?v=xCPMxgY_ZN4
https://www.youtube.com/watch?v=LsegJY347dE&t=126s
https://www.youtube.com/watch?v=8XLqTvL51t4
https://www.youtube.com/watch?v=CIGmRkhFjIQ&t=78s