I brought a 2x50 watt Bluetooth amp board of eBay for $20.00. I found a set off Kenwood speakers in a hard rubbish collection.
I needed a power supply and I looked a a few options and then remembered that I had a bit of a collection of Ryobi One 18v batteries.
I fashioned a connector for the battery out of a piece of wood with a couple of holes and a couple of spade electrical connectors hot glued in the holes.
I wired the battery to amp board and connected the speakers on the bench, it fired up and connected to my phone without a problem, it sounded pretty good so I headed out to the shed to find something to make a box.
In the shed I found some leftover bamboo flooring. I ripped up the parts for a box on my table saw.
I decided to keep the speakers in the original boxes. I cut the speaker boxes down the thickness of the bamboo, then cut holes in through the board the same size as speaker boxes then used the original screws to clamp the back of the speaker boxes to the faces through the holes in the bamboo.
on the back of the bamboo box I traced the battery stem then cut a hole out, making sure that the battery fit snug through the hole. I then positioned the battery connector to line up with the terminals.
I mounted the amp board so it was positioned just below the the top plate of the bamboo box. then I worked out where the buttons were on the amp board, drilled holes above them. I used bullet head nails cut down to extend the buttons through the box.
I screwed the box together and pushed the battery into the hole. powered it up and sat back, relaxed and lissened to some tunes.
I went back and added a power button as I found the battery slowly drained if left on all the time.