Bluetooth speakers aren't exactly rare creatures, but if you have a particular DIY bent -- and some spare PVC pipe -- you can make your own.
In some ways this feels like doing something just because you can, given that the thick walls of PVC pipe aren't going to have the finest acoustic qualities known to mankind. There's very little doubt that your finished product would sound like no other Bluetooth speaker on commercial store shelves.
Still, it's a plan that uses parts sourced cheaply from eBay, so if you're on a real budget crunch and just need something loud without necessarily being that refined, it might be worth doing as a fun hack.
Portable Bluetooth Speaker 2x3W Finished ! [Instructables]