[DaveL]

For the wiring part, if you are going to use Hella horns (or any other that draw more current than the stock horns) the most foolproof method is to buy the wiring harness from Subispeed. I don't think you can mount new horns in front of the radiator/condenser, which is where they should be, without at least removing some front trim panels, and if you tried to get by with removing only the upper trim panel and just reach down I think that would be very difficult. So if you really can't move the bumper where you live, installing new horns yourself may not be feasible.

With regard to mounting the horns, Subispeed claimed to me in an email that their mounting bracket for the Hella horns, which could also be used for the PIAA horns does not fit the SK Forester. I'm not sure they are correct, but that was their response to me when I raised this question.

I have the PIAA Superior Bass horns on order, but plan to remove the whole bumper/grill assembly to mount them. I plan to use the stock wiring (the current draw for the PIAA horns is similar to the stock horns, so no need for relays). I believe that the mounting point for the horn over on the passenger side can be used as is, but for the center horn I anticipate needing to fabricate a short mounting bar out of flat aluminum stock in order for the horn opening to point down. I will make my own ground wires and run them to a suitable grounding point. I don't know if the stock horn wire terminals will fit onto the PIAA horn tabs without modification, but I have a good collection of small low voltage terminals I can use to modify that situation as needed.

 

[DaveL]

Installed the PIAA Superior Bass horns tonight. Can not imagine doing it without removing the bumper. Bumper removal was not difficult, though I ran out of daylight and putting it back on after dark was a bit tricky. Would have been much easier in daylight. I like the sound. Not overly loud, but a much deeper tone than the OEM horns.

The horns were harder to install than I expected. For the front horn, I created a little bracket, so the horn opening could point downwards. The only difficulty here was that the stock I had selected was too wide where it mounts to the body, so I had to cut it down. For the passenger side horn, it worked to just attach it where the OEM horn was attached, but would have been easier if the mounting arm on the PIAA horn were just a little bit longer. It was a tight squeeze for the wires. I considered making an extender, but decided it was not worth the effort, given that it worked and I was losing daylight. If I need to remove the bumper for some other reason later, maybe I will create a short extension.

I used the horn mounting bolts for the grounding location for both horns, as do the oem horns. The OEM trigger wires fit onto the PIAA tabs easily. The PIAA-supplied ground tabs needed to be forced/bent a bit to fit around the OEM attachment bolts, but it worked OK.

Pictures attached. It was dark by the time I was taking the pictures, so they are not great photos, but hopefully will be helpful anyway.

 

[DaveL]

Here is one recent thread
('19+) - 2021 - Another Horn Question - like to...

 

[DaveL]

I like the sound of the superior bass horns. Do you think the bracket you made is necessary? Cant you just attach the bracket to the one where you removed the OEM horn?

You need the bracket if you want the horn opening to face downward. If you are OK with the horn opening facing sideways then I think you can get away without a bracket. I don't know how important this is, I just know that PIAA says the opening should face downward.

As I mentioned in my post about my install, I think it would be very difficult to install the horns without removing the bumper cover. Removing the bumper cover is not very difficult.

If I were doing this again, I would be tempted by the JDM horns, to avoid needing to fabricate a bracket, though I do like the sound of the PIAA Superior Bass horns, so am pleased with the result.