I never did hear the OEM horns for my Box, they were dead by the time the engine was rebuilt. Dead horns are increasingly popular in the Boxster world. Replaced with the biggest horns from Autozone that fit the space (size - small), the new horns were capable of only a feeble "meep". Under the car, and buried behind plastic, it was a muffled feeble meep at that. Though mainly ignored by most drivers, they did bring a smirk to some soccer moms faces as they glanced over their shoulder forcing me off the road with their mini vans. I really think that the two times I was forced off the road while wildly meeping away like a mad man the other cars didn't see me due to my cars small size, and didn't hear me due to inadequate horns. Or it could be that the meepers generally invoke the humor response when the startle response is called for. Either way, the only time I use the horn is if someone is threatening to run into me. It's generally considered impolite to honk at folks, and I like to be polite, particularly since this is Texas and 1 in 4 cars has a gun in it (Drive Friendly!).
Enter the air horns. Finding a place to hide them was a challenge. They are too big for the wheel wells, too big to simply mount under the car, too big to mount behind the aluminum bumper, way too big to mount where the current meepers are.
The first requirement is they don't change the appearance of the car. I was considering mounting them on top of the hood, or fender, but declined that option for a couple of reasons. First I'd have to upgrade from red plastic to chrome horns, and second I'm saving that for my bright yellow 1972 convertible Coupe Deville with the rack of a Texas Long Horn mounted as a hood ornament.
There is one spot where they can hide with access to get the sound out.
The compressor fits nicely behind the trunk liner. The relay mounted to the compressor completely separates the OEM and air horn power feeds as the compressor draws much more power than the OEM horns.
The air hose also fits behind the trunk liner and exits through a hole just in front of the emergency trunk release
The wiring runs through a hole poked into an unused rubber plug to the main battery positive terminal (with an in line fuse - the red wire and small black square near battery positive cable) and to an access cover just above the relay box in the cabin. Buy the good fuse holder from Autozone, it's worth the extra buck and a half.
I soldered a short piece of wire to the horn relay terminal that runs to the horn button and put a connector on it so the steering wheel horn button runs the new horns.
After installation this is what can be seen. No one will ever notice these horns as they'll be looking at all of the chips on my front bumper.
These air horns are loud - painfully so. I can't describe just how loud, but think of a continuous explosion and you get the idea. They are also strident with discordant tones emphatically stating if you don't move you risk being crushed like a bug. I think that checks the startle response box.
I left the meepers hooked up with their bigger brothers but you'd never know it. They cannot be heard at all over the racket of the air horns going off.