[OuchDamn]

It's not the best idea to run higher power horns from the stock wiring. You will need to use the stock horn wiring for the trigger on the new horn relay and power the horns directly from the battery. This will both reduce strain on your horn circuit and enable the horns to buzz at full volume. I have read about many issues developing after using the stock wiring to fully power aftermarket horns. It generally doesn't seem like a good idea. An additional relay to the battery is the way to go. Different relays have different pin placements, so the exact wiring will depend on your specific relay you get. Here is a generic diagram that will give you a basic idea of what you will be wiring.

As for removing the front grille, it is most likely necessary although it's not as difficult as it seems. I don't believe it would be very pleasant to install the new horns with the front grille in place.

I believe subispeed sells brackets to install new horns on. I think they even put together some all inclusive kits with brackets, wiring and relays. Most people want them directly behind the grille vents for max forward volume, plus they look neat.

As for installing them on the factory brackets, I don't know that one but I'm sure someone with more knowledge of the subject will hopefully help out.

Good luck.

 

[OuchDamn]

Thank you for this informative reply. But additional questions/comments:

The word and function of "relay" is a mystery to me. (Yeah, I know, dude with a PhD. . . .) I don't believe I've ever seen one, or know how to determine appropriate compatibility. "Different pin placements." Huh? And, I assume use of a relay will allow me to keep the stock wiring, yes?

Grill removal is, I think, a non-starter. As noted, I don't have a garage and presently live in a complex, at which there are rules about outdoor auto-repair. Besides, I tried something like this many years ago when I tried to replace the damaged fender on a `74 Plymouth Duster (ohhhh, that slant 6); disaster ensued. So, there's got to be another way.

Finally, how to identify the terminals described in the graphic? Does Subaru have a schematic that would show me?

Apologies for total ignorance in advance 😬. . . .

TRB

Think of a relay as a high current remote activated switch. For instance think of your headlight switch on the stalk of your steering wheel. That is a very light duty switch that cannot handle the high current draw of the headlights. That little headlight switch doesn't have the proper beefy contacts to run all of those amps to your headlights so It will send a 12-volt signal to a relay and the relay will switch and handle the high current draw from the circuit.

Different relay brands and styles have different pin configurations. All of them are easily found on Google with a search of the model number of the relay. They all do the same thing more or less. They are readily available at your local automotive store.

If you're not wanting to take the grille off I agree with @Pugetpower and hire a local stereo installer shop or even a local non dealer Subaru shop / mechanic to do it for you. They would be able to knock the project out reasonably quickly with good results. Hope this helps..