Installed my Hella Supertones today and decided to do a write up for anyone who was as lost as I was when I first set out to put them in. This is the simplest method to get the traditional 'two in the grill' look, and I have not installed the relay or grounded the horns. Supposedly you lose 2 dB by not doing this, but that's not to say these aren't ear-splittingly loud without doing these things.

Not a difficult install by any means (try getting rear bumper spats on without taking the bumper off and without jacking the car up...), but not having the right tools will potentially halt you up. Took about an hour and 45 mins including pic taking.
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You'll need:

A socket set
Set of small spanners
Split washers (9mm and 6mm)
9mm nut (to suit factory horn bolt)
6mm bolt, nut & washer
Heat gun
Electricial shrink wrap
A length of twin-core automotive wire [1.5mm] (enough to get from your battery area to the other side of your grill)
2 sets of male/female spade connectors
Wire strippers
Wire crimper
Screwdriver/thin metal rod (to get the grill off)
15mm wide bracket (~100mm x ~50mm)
Zip Ties
Voltmeter (optional)
Welder/welding skills (optional)
Zinc it/other protective coating (optional)

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Before we get started: I didn't disconnect my battery for any of this, but it's recommended you do just to make sure nothing goes wrong. Also, this mod is to be done at your own risk! Like any DIY, things can go wrong and I won't be held responsible.

1. Remove the front grill (take care not to snap any clips!) and unbolt the standard horns. There should be one in the grill with a 12 mm bolt, and one located near the battery with a 12 mm bolt. Don't lose these bolts, as you will need them later! I'd suggest finding out which lead is positive and which lead is negative at this step: makes life a whole lot easier later on (although I've heard it doesn't matter how you wire them up, it's best to play it safe!)





2. I used the factory mounting point in the grill for one of the horns. Simply hook up the horn to the factory leads (the copper terminal on the horn is +ve) and bolt it in. Reconnect your battery and give it a toot; if your ears aren't ringing, you've done something wrong!

IMPORTANT! Make sure your front grill clears the horns. If you mount it up to the factory spot, then it should, but just check so you're not left with two horns mounted in a spot that'll need adjusting.



3. Grab some of your twin-core wire and cut a length that will extend from the battery-well horn wires to the other side of your grill, ensuring you leave some excess (the wires will need to reach the bottom of the horn on the other side). Once you've cut your length, attach some male spade connectors to one end. Slide some shrink wrap over the existing wiring (note which one is positive!), clip it all up, and get the heat gun on the shrink wrap. Run your wire along the radiator beam, zip-tieing it to the empty holes along the RHS (for the LHS tie it along the bonnet release wire, but leave the last 15-20cm untied until the end).







4. Next step is to sort out how you're going to mount the horn on the other side. I found a 15mm wide bracket in the shed and cut it to sit on the underside of the top radiator support. Make sure you've got ample room to bolt the horn onto, and make sure it's symmetrical with the other horn. Mark out where your bracket will bolt to on top of the beam, as well as mark out where your horn will bolt to the bracket.





5. Drill a hole for a 9mm bolt in the bracket where your horn will attach to, and a hole for a 6 mm bolt where your bracket will attach to the beam. I'd suggest doing a test fit at this stage too. Don't go OTT with tightening; we're not done with the bracket just yet...




6. If your set-up is anything like mine, you'll have noticed the horn springs whenever you tap it. To solve this, I took it off and welded an offcut on to brace it, then hit it with some Zinc It. Make sure you leave space to be able to do up bolts etc, or else things are going to get stupidly difficult.



7. Position your horn in place, and grab the other end of your wire and trim it closer to the right length. Strip the wires and attach female spade connectors to the ends, and plug 'em in to the horn. Attach your bracket, bolt the horn on, and position it accordingly.



8. Test the horns, should hear a different noise to the first time around (as the horns are dual-frequency) but should still be ear-splittingly loud. Re-assemble the front end of your car, put the mountain of tools/whatever away, and you're done!

helpful info mate cheers hopefully i succeed by following these instructions lol

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White GC8 [MY00WRX]

can you now do 1 for a datsun?

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[I]Personal chef[/I]

If you supply me with said datsun free of charge...
Shouldn't be that much different if the standard horns are the same style, just have to make sure the bumper/grill clears them really.

moved to DIY

Great write up!

How do you find the noise of the horn now?

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[COLOR="Gray"]550Nm off a 2L... Just wish it was in the dak dak...[/COLOR]