Best horns on a ride that I have ever experienced was the '81 Yamaha Seca 550. They were by and far the loudest factory horns I have personally experienced. They kill the CB1100 horn.
Guess I forgot to mention the grips. Cheapest I've seen. I replaced them with Grab On grips,much better. Oh,and I had the horn disconnected and replaced it with a Denail Blaster air horn. Now that's a horn!.
Fortunately, many Forum folks have upgraded one or both. So there are options available and they appear thoroughly described in many corners of the Forum database.