This is a small enclosure to hold one of the common small TPA3116 power amplifier modules available on ebay. THese come in various formats. I use one with small footprint. See picture to match against eBay types.
It has a sliding lid to give access to screwing in power and loudspeaker connections through access holes.
The OpenSCAD file has options for the audio input openings. Either a front access for the on board jack plug or rear panel for linking through to on board jumpers; or both. The rear one can be positioned in the centre or off to the side. The side position avoids it getting in the way of the screw holes.
Picture shows rear central audio.