Added relatively cheap audio to my 500 today. Picked up a Ecostone from Costco for $70. It is waterproof, shockproof, Milspec, etc. Here is a link from amazon for info:
http://www.amazon.com/ECOXGEAR-Portable-Outdoor-Bluetooth-Speaker/dp/B00I9HD8PK/?tag=sxsweb24-20
It sounds really good. Even up to top speed you can still hear the music. Its not going to drown out the motor or put out thumping bass but it works pretty good all things considered. I placed it just behind the seatback, it almost fits perfectly and wedged in there pretty tight..didnt come loose in a quick test ride. I may add something to secure it better, it has a 1/4 20 threads for a solid mount. Anyway here is a pic:
http://www.amazon.com/ECOXGEAR-Portable-Outdoor-Bluetooth-Speaker/dp/B00I9HD8PK/?tag=sxsweb24-20
It sounds really good. Even up to top speed you can still hear the music. Its not going to drown out the motor or put out thumping bass but it works pretty good all things considered. I placed it just behind the seatback, it almost fits perfectly and wedged in there pretty tight..didnt come loose in a quick test ride. I may add something to secure it better, it has a 1/4 20 threads for a solid mount. Anyway here is a pic: