Anker - Rave Neo 2

Get a soundcore rave neo 2. It's portable, IPx7 rated, around 7.5 pounds, has a heavy duty strap and it's 80 watts! It's VERY loud! It's about the size of a mini backpack for like a 10 year old. It also has as an EQ in the soundcore app and you can control the lights too from the app! Battery last a good long while too, around 14 hours! it's around $130

Anker Neo Rave. Good volume and bass. Bluetooth and aux in. Blinky lights. 3 or 4 hours of battery life fully cranked.

Search for " Bluetooth Speaker" or Subwoofer on amz or wherever. Or jst buy a regular BT boombox and leave it plugged in. I have two of the Anker Boom2 + and two Anker Rave 2 Neo. 4.7 Stars to the first pair and 3.8 to the second. Both sound great, waterproof, float, have impressive battery life, and have app controls for lights, EQ, bass +, etc. They will play in sync with each other, however, pairing can be tricky for the Party Cast mode. In that mode, according to Anker, you can link up to 100 speakers. I've done it with four and it works just fine although, again, pairing takes a minute. It's difficult enough that there are YouTube videos to help if you have trouble. The Boom2+ will pair in partycast mode with the Rave2, or they will also pair *in stereo* with each other. Extra star for that and the boom part. To be clear, all of he anker speakers you can buy are stereo, but the ones with the TWS feature will pair and act as left and right channels. This makes them more useful in enclosed spaces, IMO. The PartyCast mode speakers will play in sync, but will not be separate channels. More useful for outdoor spaces where people may be moving around more and where L and R channels are important, IMO.