@Zamman
Mate,ive used the exact same horn for around 8 months on my FZ.
though i have only used one of them rather than both since i thought that was more than enough.
anyway only on my I-day ride the horn went Kaput!but it never affected my FZ in anyway!
i personally think the Type R horn is cheap and good...when used as single it isn't unnecessarily loud either!

By seeing the components u mentioned, I can say the first mistake you did is "You haven't used a relay". Hence the fuse conks off. And ASC guy is a moron who said warranty has void, no such gadgets/electricals come under warranty.

Yeah as Nano said go for branded horns, ROOTs are best suited for Indian bikes IMO. Hella, yes the most powerful horn but u ll kill a heart patient near u

If you do it right nothing will go for a toss. I have fitted Roots vibrosonic 3.5A dual horns for P180. It running successfully for the past 2 years just need regular tuning once in 3 months with stock battery 4 years of age. I made it clear to take a seperate 16ga wiring from the battery with 10A fuse inbetween connected with Roots melody maker cum relay. Its a electronic relay cum Music maker. From the original wiring terminal I took the positive and connected to the relay as per the illustrated diagram mentioned in the relay. I fixed the horn in lieu of stock horn. Roots vibrosonic really work wonders for the lane cutter and dumb drivers, very useful tool for the highways