I had a pair of air horns on Retreat when I bought her. not bad, but nothing like friends with REAL air horns.
Then I bought a 38ft Motorhome. On our first freeway trip, I was cut off by a dimwit who needed a blast from some REAL airhorns so I hit them, FIAMM trumpets, a matched pair, sounded real nice! However, Real Nice wasn't what I needed, so I replaced those with a pair of Western Star Truck horns. Well, the first one said Western Star on it, the second one said HADLEY. Better! Now, what to do with the Fiamms? Retreat now wears those. Only trouble is the compressor that happily drove the original air horns wont drive them. So, I tried a Harbour Freight pair, the little red plastic horns like the set I put in the console of my dinghy, took the compressor off, fed it to one of the Fiamms, no joy, so I now have a functional pair of high pitched, very loud, little red air horns under the flybridge, and another HF compressor, this one from a triple horn set, feeding one of the Fiamms. Not satisfactory. The next iteration will be a tank and a bigger 12v compressor just haven't sorted it all out yet.
For now I have lots of noise, just not quite the noise I want.
And, so far, not too $pendy.