I installed a set of PIAA 600Hz/500Hz on my i3.
This is a sound test of stock vs the PIAAs. https://dl.dropboxusercontent.com/u/17299176/mybmwi3/test.mp4
Instructions: https://dl.dropboxusercontent.com/u/17299176/mybmwi3/i3horn.docx
This is a sound test of stock vs the PIAAs. https://dl.dropboxusercontent.com/u/17299176/mybmwi3/test.mp4
Instructions: https://dl.dropboxusercontent.com/u/17299176/mybmwi3/i3horn.docx