My first PC at the time was a benchtable. Since I run the z9 mini at home in my living room, I had to think of course because of the volume. In addition, I realized that there is a fourth slot for another hashboard.
So I ordered one more and started building the new case.
I wanted to work in a very natural way and therefore chose spruce wood.
Cooling is crucial for operating an open benchtable. I love Noctua and I take Noctua. 5 fans are planned in my concept.
https://noctua.at/de/nf-a20-pwm
I started with the construction of the fan frames for floor and ceiling as well as the basic framework.
A frame had to be equipped with gates and styrofoam. There are for the hashboards later.
I also made a frame for the control board.
Assemble everything.
The 4 hashboards and the 3 noctua.
Of course, new cables had to be ordered.
My setup is running. Currently at standard 500 mhz.
Next step is successful overclocking. But I have to adjust the frimware or have it adjusted.
Setup was sooo awesome and SILENT !!! ;-)
I'll call you again and hope you like my setup?
Write me your opinion.
Greets to All and special thanks 
Happy Mining !!!