Making the horn louder

This Lambretta is going to be used regularly, and almost exclusively around the city. For this reason I wasn't happy with the dull 'quack' of the AC horn which would frankly be useless on anything but the quietest of roads.

I did a bit of googling about how to resolve this, and everything I found referred to fitting a battery; the only way you can get a good horn sound at all revs is by having a DC horn.

I have no intention of fitting a battery, so a bit more googling and some high-school physics led me to try out a bridge rectifier with a DC horn. A rectifier turns AC into DC.

I bought a KBPC35-04, made up some wires with spade connectors, and fitted it with a generic motorcycle 12V DC horn. Here's what it looks like:



And guess what? IT WORKS! Now I have a half-decent horn sound, whatever my engine speed. Clever huh? :)

I think I'm going to try a 6v DC horn with it too - apparently running a 6v horn on a 12v system gives you some extra welly.

Update: The MOT inspector didn't seem to like my horn - he thought it was too quiet at higher revs. I can hardly tell the difference.