Soundsystem for bicycle Before starting to build a soundsystem for my bicycle I would like to ask where I can be redirected or provided info for a) a ready-made solution, b) a set of clear instructions on how to make one.

My requirements are:


It has to fit somewhere on the frame or the rack (maybe pannier style) - a trolley is not an option as I do not have space to store it.
The battery has to last a minimum of 5 to 6 hrs
It has to be loud enough for a city Critical Mass ride (many cyclists circulating together)


Thanks in advance!
I have seen numerous people riding down the path with a sound system on their bicycle. Without exception they use the simplest and most portable solution: a bluetooth speaker. This meets all of the requirements of outdoor usage:


Self Contained
Waterproof
Long Battery Life
No wires to run 
Lightweight and portable
Inexpensive




Tie it to your bike rack and pair it with your phone. I've done it myself once, but be warned, you will need a louder one outside (especially at a critical mass ride). So you may have to invest in one of the larger models.