The speaker is located on the luggage rack up there with my HID lights, and is worked out very well. In the photo below, it is located above the drivers side on the rack with the red dot in the middle of it.
Still would like to get some real air horns like the big trucks or even better some train horns in the future.
If you are looking for a place to buy a electronic air horn (horn mode of a siren) & speaker, give Gall's Inc. a call, or check out their web site. They have a good selection and good prices. Other options, electric horns like ones on RV's and ambulances, see PPL Mobilehomes, Or for the real thing, check with Hadley, they also make some that are just like the train horns (tri horn) Hadley Products.
I am using a PA-300 Siren now that was a surplus item that cost me about $50 at the time. The PA-300 has the electronic horn on it, anis great. The PA-200 is okay, but no electronic horn option, but worked great for the car alarm siren.
Federal Siren PA200- connections