I have some Audio Engine A2+ speakers and they're excellent but about a year ago the capacitors or something on the internal DAC started going bad and the right passive speaker was getting quieter and quieter. I was having to asymmetrically drive the speakers in the Windows audio mixer to keep it balanced. This was getting worse and worse so I took the active speaker apart and inspected the circuit board. There was no easy fix evident so I decided to convert it to a passive speaker and get an external amplifier instead. I decided to go with this amplifier by Fosi Audio. This worked but for the past 6 months my desk has been kinda a mess with the cables. I decided this could be remedied with an under desk mount.
I have this desk. My desk uses hollow tubes for the main structure and I needed threaded mounts so I used some 10-32 rivet nuts to add some mounts the tube region. For the back support I just predrilled and used some short number #10 flat head wood screws that wouldn't poke through the desk. Note that my print wasn't perfect: I did it out of PC-Blend and it had a small layer shift, and I forgot to add cutouts for the feet and a tiny countersink for the heads of the rivet nuts. Rather than reprint I just used a countersink bit and drilled holes for the feet. I made those changes to the model I have uploaded here. Your desk is probably different so the stl most likely isn't of much use and you need to modify it if the tube region is different. The tube on mine sticks down 1.580" from the desk underside.
The author marked this model as their own original creation.