What Value Of Potentiometer Should I Try?

[Ham]

I'm modifying an old "over the ear" radio shack pair of headphones for metal detector use. I'm only going to use one headphone. I would like to connect a volume control, (potentiometer) but do not know what value(s) of pot to try. I do not know the impeadance of the single headphone speaker. Any suggestions would be appreciated.

[Skippy]

Not much to go on, there, but I would say 100 ohms would be a reasonable choice. Good luck.