ProStar air horn question, Heavy-D?

Took the Grover off and took it in my shop and did some testing. It needs 80 psi to sound right.
Took it apart and the spring on the diaphram was rusted bad.
Cleaned it up,Cut just a little of the spring off to lower the tension.
Installed it back on the truck and it sounds good!
I ordered a rebuild kit for it for 9 bucks also just so i can play with spring tension a little more.
It actually gave it a deeper tone too.
Good old Ebay!

 

The only thing inside this horn was the thin metal disc and a spring.
The tension on the spring determines when the disc opens under pressure so i shaved a little of the spring off on the bench grinder.
I played with air pressure from 60 to a 100 psi.
It first took about 85 to 90 psi to sound right but after the spring mod it works from 60 to 150 psi.
The more air the louder it gets.

The rebuild kit was 9 bucks on Ebay so i have it coming to do more testing and tweaking...lol.
Right now it does work with the stock air supply from the truck.Deep tone and pretty loud.

This is an older model Grover with a 24 inch bell.

I get this down good i may have to build a few for our other trucks.
All of our drivers hate that VW horn...