Aux cord to RCA converter?

[Tharp Daddy 25]

The speakers on my old Altec system died recently, so I picked up a new set of speakers the other day. But the new speaker's subwoofer, compared to the old one's, is extremely weak. Sadly, though, the old subwoofer uses RCA inputs while the new one has a single Aux jack input. Is there any cable or way that i could swap out the old subwoofer for the new? I would like to not have to return them, but it's so weak that my music feels like it has no kick.

[Rooster69 18]

I am pretty sure that both the "phono" jack and the "head phone" jack are simple two wire setups. You should easily be able to splice one to the other. Bottom line is that neither are digital connections.