Installing a 3-prong attinuator?

[Old Guy]

Being naive, I would have guessed that using connections 2-3 would simply act as a variable R?

What is the purpose of connection #1? Is it some sort of negative feedback?

If you dope out the circuit, there is a series resistance and a parallel to "ground'. As the series resistance goes up, the parallel resistance drops.

Think it thru. An 8 ohm speaker with a 4 ohm series resistor is 12 ohms. Referring to Ohm's law...24 Ohms in parallel is needed to bring it back to 8.

So you attenuate more, and have 8 ohms in series (16 total)....16 in parallel gets you back to 8.

Get the idea? As series goes up, the parallel has to go down.

You can calculate and put in fixed resistors...many do.

For the math impaired, a parallel resistance calculator...for the series value just add.

PARALLEL RESISTOR CALCULATOR

As was aptly put "approximately 8 ohms". there are no perfect components. Fixed resistors are closer to ideal than variable, since to be 'perfect' a variable would have to "track' exactly, and none do. Also, if you go fixed, you can hand select components.