According to this video, the Bad Boy uses a relay and requires gas tank removal:



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If they don't need a relay then they aren't loud enough.

Mind you, his removing the fuel tank was a choice made by where he wanted to run the wires.

You can use the original horn wires - all you need is a direct feed from the battery (via fuse is you want) to the relay then the original horn "go" wire tells the relay to feed to feed that new power wire to the new horn. He spoke about not having the relay anywhere it was hot, makes sense.

 

On my '18 Heritage I found I can run wires along the frame tucked up under the tank of the right side with out the need to take off the tank. I currentlly have three wires in a flexible plastic conduit for the power and control of my Camera system, a camera cable from the rear camera and now the two wires, again in a flex conduit, that connects to the wires for the horn all tucked up and out of sight.

I did not eleiminate my stock horn, so I just tapped the two wires that run to the relay into the existing horn wires, so both horns TOOT together. There is not a lot of room under the seat of the new softails with the monoshock and access to the battery is next to impossible. I used double stick tape to install the Relay under the seat under the right side frame. Wrapped the exposed terminals with tape to insure no acccidental shorts. Liked the Idea of the relay socket but did not think about it until I watched the video. Since I mounted the Wolo on the right side just in front of the saddle bag, the wire runs from the horn to the relay and ground were short. Picked up direct battery power from just behind the main power fuse that is located under the left side panel on the my Heritage. No fuse, but I might add one in the near future,

 

That has been my experience. I researched horns thoroughly last year and yeah, all of the ones as loud as I would want need a relay to protect the horn switch.

Right after I got the bike, I did replace the OEM horn with a "bolt-on" from an auto parts store. It's louder, but still not nearly as loud as I want.

 

Yup, that was my point (although I didn't say it).

For example, the Denali SoundBomb take 22 amps - far too much for the horn button but OK for a horn button to control a 30-35 amp relay.
Don't hold the button down or you'll flatten the battery! Ha!

 

I'm not asking for much. Maybe something like this:

 

One thing I've read online in some of the reviews of the Stebel Nautilis and Wolo horns is durability when mounted to a shaking Harley engine. I've read a few reports of the horns coming apart after long term use. Of course when you do a google search you will get very old results sometimes so I don't know if that has changed. I don't know if the mini beast is more durable or not, but it's a hell of a lot more expensive. It might be worth the extra cost IF it was more durable, but IDK if it is or not.

 

The '17 and up horns are not by any means quiet, but they sound just like car horns. I've never liked that!!

I want an air horn that sounds like and is as loud as a fire truck horn. *THAT* will get the other driver's
attention and make the text-while-driving crowd jump right out of their shorts.

 

The Wolo Big-Bad Max Air horn is a good "loud" choice for the $$$$. Only bad thing about this horn is that, unfortunately because it is an air horn and needs a compressor, it is to big to fit as a direct replacement for the stock horn that is mounted under the frame above the oil cooler on the newer M8 bikes. If you can find a place to mount it that you can live with, I can recommend it.

 

That's what I've been pursuing somewhat. But.....it occurs to me that there could be a downside to a horn that's "too" loud. If it startles the cagers too much it could cause an accident instead of preventing one.