I use a fairly cheap receiver with decent speakers. Sound tracks are on an MP3 player. My speakers are not waterproof but there are speakers that are made to be out in the weather if you need them.
Bluetooth is seeming more and more convenient.We have a Bluetooth speaker that sits on the porch behind a few decorations. I can't remember what we paid for it, but they still sell it at Sprint. We take it camping, to Fourth of July picnics, sand volleyball, and tennis. It's pretty sturdy and has decent sound quality and range. It's not weatherproof, but our front porch is covered and we haven't had an issue so far. We've also used an old laptop with external speakers
iPod shuffle (original) with a portable speaker for it from a Playlist in iTunes ^v^ Louder than you'd think. I can also use a prtable CD player with computer speakers or hooked directly into a lightning FX unit.
I dig it.Last year I used a Sony 5.2 receiver, long enough speaker wire to run it through from the receiver in the living room to the front porch. Bought some cheap Sony speakers from Goodwill. Then I used an iPod Classic 160GB, hook it up through the USB and made a playlist of Halloween sounds to run a good 4 hours on repeat and shuffle. It seem to do good, scared a lot of small kids cause of the type of sounds I was using. Best device is definitely an old iPod.
Mounted speakers are very convenient. Any time I can find a permament solution we do it. May take a little work or $$ in the beginning but wil be worth it in the long run. Our outdoor theater is also permanent.