This project has been a long time coming. I started collecting the components for this in June 2019.
Basically it’s an Australian 50 cal ammo box with speakers from some old panasonic surround sound speakers I have had in the shed for 5 years. It’s powered by a bluetooth amp module which is really loud. There is a 12v SLA battery providing the power. It gets surprisingly loud and sounds very clean.
I lined the inside of the box with 6mm ply to reduce rattles from the tin box. There is a basic filter capacitor to drive the tweeters. It was a challenge working in such a confined space and trying to squeeze everything in. Most of the wiring was done on the bench and then everything installed – speakers, then amp, then battery. The battery is charged via a 2.1mm socket underneath the power switch.
Update – the 12v SLA battery was completely discharged too many times and no longer could be charged. I replaced it with a Lithium battery that is the same size and capacity, but a lot lighter and able to be discharged a lot lower than an SLA battery.