White dot on terminals. Is this the positive or negative...?

[GM]

With the horn loading a 9v would be less of an issue.

Right, and a good way to check diaphragm condition because if it can't handle a ~5-10 W transient attack depending on its output impedance, its replacement time IME even if used in a HIFI/HT app.

GM

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Brilliant idea for testing the polarity of a hf-driver while still on the horn. Thanks for sharing it with.

You're welcome, but can't claim credit for it. I learned it from my childhood DIY audio mentor/next door neighbor who in turn had learned it while in the military and no doubt in my mind that it dates to the earliest days of electrically amplified sound reproduction and maybe even earlier in some other app such as for finding air leaks.

GM