I've never been a fan of air horns for a couple of reasons. The ones I've heard sound good but I like the simplicity of straight up car horns. If you are going to go to the trouble to wire in a relay for the compressors amperage draw why not just go with louder higher amp drawing electric horns instead & skip the middleman compressor?? Not to mention the delay that some air horns have.
I'm also afraid that having a super loud compressor driven horn would scare the crap out of the blue-haired land yacht pilots that are thick as flies down here. That kinda defeats the purpose of a horn.

Might scare 'em into runnin' you over instead of just lettin' 'em know where you're at!

A pair of car horns is a familiar sound that is light years better than a stock motorcycle horn!
Ten bucks worth of electrical components & a pair of junkyard car horns with a bit of ingenuity is IMHO the way to go.
