Born Third Syllable

[KenBolton]

I have two professionally rebuilt horns. Neither makes the complete Ahaa-ooh-gaa sound. I’ve assured lubrication, grounds, adjusted from one extreme to the other as well as consulted with the rebuilder to no avail. They either produce the first two syllables or a squawk. I know one diaphragm is repro but have no knowledge of the other. Please advise me as to next steps.

Of course the title should read “Horn”!!