I currently own a set of Edifier r1280db and am looking at buying a subwoofer. However, I have the older model version of the r1280db's which don't have a sub out port, so don't know how to connect them. I'm still new to audio/speakers, so I don't really know what I'm doing. If it helps I was probably going to buy this sub

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If it ins't clear I'm going for a budget audio setup