Hi guys, I'm not very skilled with electronics and hoped you could help answer this.
I have a stereo setup and my old passive sub no longer works. I decided to just get a new powered sub. The new sub says it's 4 ohms, but my two satellites are labelled 6 ohms. So is this an ok mismatch for my receiver?
I'm running this setup in parallel and my receiver can handle as low as 4 ohms.
Yes, the rating of the driver in the sub doesn't really matter since it will not be powered by your receiver. If you are running the speaker wiring through the sub to give the sub a signal that will not change the load your receiver "sees". It would be better if you could connect the speakers directly to the receiver and connect the sub to the "sub out" on your receiver, but if that isn't possible just make sure the sub you buy supports getting the signal from the speaker signals.
My receiver does not have a sub out feature, so it will be receiving its signal from the speakers. I see that the receiver won't see the same load as the sub is powered, so I assume it's a safe setup as long as the sub is on with receiving its signal from the speakers?
It's a perfectly safe setup. It would be no different than running just your receiver and speakers with no sub. The fact you are passing the speaker signals through it won't affect the impedance or load your receiver sees.