Fellow Vulcaneers --
I installed a compact Stebel Nautilus Air Horn advertised as "the loudest motorcycle horn in the world." It's definitely loud enough to be annoying and startling. I will use it only when absolutely necessary, so as not to irritate any cagers. In all the years I've been riding, a loud horn has saved my butt on a couple of ocassions, once when a cager started backing into me.
The installation required a relay but it comes with a good diagram and fairly simple instructions that even this electrically challenged rookie could do it. The ony down side is the price: around $50 with shipping. However, it does come with wiring, connectors, relay, inline fuse and attachment bolt. It's quite small/compact for a horn producing so much volume!
Link to horn:
This is how I installed it: (see pics atch)
* mounted relay to frame with tie-wrap under left side front cover
* 4 relay connections: 2 stock horn wires--1 red to battery--1 red to new
* 1 new horn connection: 1 blk to ground (I used the top air cover bolt)
* mounted horn to left side air cover bottom bolt using left-over small flat
metal bracket from previous horn installation.
* ran red wire under gas tank to battery with fuse
Although not connected, I covered the stock horns with plastic chrome covers for appearance.
Check it out and lemme know what you think!