Siren that sounds close to a car horn?
12V car horns are a bit heavy and use 18-30A (eg. the Screaming Banshee) to run so aren't a good solution on a bicycle.
OTOH, a single-tone, 12V motorcycle horn uses much less current (1.5A) but sounds feeble and not anything like a car horn.
Also, to complicate matters, li-po batteries for use on remote-controlled toys aren't available in 6V or 12, but rather 7.4V or 11.1V formats. But then, 12V lead batteries are big and heavy.
So I was wondering if someone knew of a good compromise in terms of weight and current for use on a bicycle.
Re: Siren that sounds close to a car horn?
Have you tried an Airzound? It sounds like the airhorn from an 18-wheeler.
I once had a pickup truck back out of a driveway, right in front of me, while I was clipping along at about 25mph. I blasted my Airzound, and he pulled off the road in a hurry, half on his grass and half on his driveway. It scared the crap out of him so much that he just wanted to get the h*ll out of the way of whatever he didn't see.