I am curious why a subwoofer high-level cable has three cables which are connected left positive, right positive and left/right negative... If it is receiving two separate AC signals (left and right speaker) and has itself only one speaker (as my MJA Ref. 100 has) then does it just combine the two signals - is it that left and right speaker signals must be as near as dammit the same at lower frequencies..? Also, why two positive connections and only one negative..? Some clarification to ease my restless and tormented mind, please.