You are correct. On the Gen 1 there is a single mono audio wire going straight to the mono speaker, with no 3.5mm jack.

The converter you posted looks like a bit of overkill. Wouldn't something like this be just as good? https://www.amazon.com/Rockford-Fosgate-RFIF2SW-Speaker-Adapter/dp/B00G352P2C/ref=psdc_3236443011_t1_B00I4EF1BC