[OliverB]

I added a hi/lo American pair of EL GRANDE FIAMM horns to my ‘13 451. Just removed the original horn, fabricated a wiring harness to go between the original left side spot to the right side spot where I bolted on the second horn. Nut was already welded to chassis. Tight clearances though! kept original factory wiring to left side horn, using that to also supply the second right side horn with the new harness. Sound was great and no problems. No pics, unfortunately.

 

[Shalmaneser64]

Evilution (of course!) has a good DIY thread: Evilution - Smart Car Encyclopaedia

Ooops! That was in the post right before yours.

Thank you Sir! Going blind in my old age...

 

[Shalmaneser64]

So finally got around to installing my Hella horns properly. Opted not to mount them down in the frame. Found a good location to mount them, right up front. Modified a horn harness from Amazon.