How to wire stebel and stock horn together

[paddyo]

Disconnect the connectors from the stock horn. Using 2 spade connectors on one end and two flat female connectors connect one of the horn connectors to the 85 pole on the relay and the other horn connector to the 86 pole on the relay. I ran 2 wires under the tank to the area under the seat. I used 14 gauge wire. Using 12 gauge wire, connect the 30 pole to the positive of the battery through a fuse holder with a 25 amp fuse in the holder. The stock horn draws 3 amps and the stebel draws 18 amps for a total of 21 amps. Again, using 12 gauge wire, connect the 87 pole of the relay to the positive of the stebel and to one of the connectors on the stock horn. I soldered and shrink wrapped the wires to form a "Y" so the horns would be hooked in parallel rather than in series. Again using 12 gauge wire, run the negative of the stebel and the remaining connector of the stock horn to a ground. Again I soldered and shrink wrapped the two wires together to form a "Y" to connect them in parallel rather than in series. I ran the ground wire under the tank to the frame ground under the seat. I put the relay below the seat and in front of and below the fuse blocks.

The reason I want to use the stock horn as well as the stebel is that sound is additive and since the stock horn is already there, I wanted to use it. Here is formula for calculating how much additional sound additional horns will produce.

Horn1dBA + log(10^horn2dBA/10 + 10^horn3dBA/10 + ... + 10^hornNdBA/10)

For this to be correct, horn1 has to be the loudest horn. The stebel is 139 dBA and the stock horn is 105 dBA. So, in this case:
139 + log(10^105/10) = 139 + 10.5 = 149.5 dBA