I was actually thinking of tweaking the horn itself. Like adding mass to the back of the horn or opening the horn and treating the paper with something. I remember reading about these tweaks but do not remember the specifics.

I do know if these physical horn tweaks will get the exact change that I am looking for, and neither do not know exactly how to do them...

but... I will at least attempt the mods with the resistors.

Thanks much to GarMan and Gumby