For maximum stiffness, I printed these without infill, all perimeters. The filament is Greentec Pro CF.
I got the general specifications from the book “Mastering the sound of the acoustic guitar” by Giuliano Nicoletti.
These are mainly for playing a test tone and generating chladny patterns at different stages of guitar making, but they also sound surprisingly good as desktop speakers!
When it comes to acoustics, strength is not the only variable. I’ve seen printed speakers where the infill is set as minimally as possible, then the print is either filled with sand or resin to change the natural frequency of the model.