Made for the JBL Boombox 3 model with aux input, not the wifi model, but who knows, it may fit.

Why I intend to use the boombox outside for a few hours with 120V AC power cable attached along with an 3.5 aux cable. Documentation states that you get more power to the speakers when it is powered vs on battery. I wanted a modicum of rain resistance, so thus the world's first-it-just-may-work rear port cover was created.

Tips

• You can modify the fusion 360 file. There are some user parameters to adjust the height and width and aux port diameter. You can fine tune the cutouts more on the Cutouts Sketch.
• Dimensions are a bit large to ensure the TPU has a nice friction fit.
• If you want the full cover with no cutouts, adjust the file or use your slicer to add a block or two to fill in the cutouts, no Fusion 360 needed.

Warnings

• Not tested with real rain rejection ability (yet). That said, I'll gamble with mine. Wish me luck.
• If you cook your JBL Boombox 3 due to rain intrusion, use it as a doorstop. It'll look cool.
• If you burn your house down or get electrocuted, call emergency services and then post so we can all laugh.