I am in the UK and I have ordered a budget sound kit from exoray and now looking for a good speaker to use with it, the only problem is that I don’t have much space at the back of the pack as it holds the batteries for the pack and gun. Exoray recommended using 6"x9" car speakers but these are just too big.
I’m using two 6 1/2 inch Bose speakers. One inside the cyclotron facing out towards the lights and the other up underneath the crank generator facing my back). Had to do some modifications so they would fit but they have a great sound.
I used a generic 130mm 40w speaker with a Canuk amp (as recommended by Rob). It works pretty good. I mounted it inside the cyclotron and drilled speaker holes in the centre. The holes are hidden by the bumper. I had plans for a second small speaker mounted in the crank generator but I didn’t need it.