speaker to headphone jack conversion/hack

I Know Almost Enough

Oh goodness... with solid state power amplifiers... and amplifiers capable of driving loudspeakers are called power amplifiers... I THINK there are two types of circuit.

One type of power amp needs to be terminated in the designed impedance, which would be 4 to 16 ohms, or else the transistors will overheat and burn out.

But there are types of power amp circuits that load into any impedance...

UNLESS I'M WRONG!

To be safe you maybe want to feed each channel into a 16-ohm 2 Watt resistor.

The way you have it shown is not correct. The resistors must be across the outputs from + to - to load the output amp.

Then 2 MORE resistors, about 1k Ohms wired as shown in your picture to isolate the input line from the power of the amp output.