So I used to have a pair of Hella Supertone horns in my old Subaru. But I sold the car and kept the horns. What to do with them? Hmmm... Replace the weak CRFL horn! Yes! Because I had a pair of horns, I hooked the 300hz to my CRFL and the 500hz to my girlfriend's CBR. These things are LOUD! Very loud. They are even louder if I hook up a relay to wire them "properly". I just plugged them up to the factory harness for now. Ease of installation: Easy, after I figured out how to get it to fit. On the CBR, the horn fits (barely!) the stock location. On the CRFL, I mounted to the stock location, but the horn sits outside the plastic. I'll grab a pic in a few minutes. Oh, I didn't tell my GF that I upgraded her horn. She nearly had a heart attack the other day when she used it the first time.
the factory harness uses a relay to send power to the horn. no need to add additional relay. especially because these horns only draw aprox 1.1amp so no issue for the stock harness.
I'm a firm believer in LOUD horns - I've upgraded on pretty much every vehicle I've ever had. Haven't done the CRF yet though...