All you need is regular 2 wire speaker cable(2 conductor).
To get that extra piece of wire that runs between the two terminals for series wiring is to cut a chunk of the 2 conductor speaker cable off and just use 1 wire. No need to pay extra for the 4 wire unless you want to. It is kind of a waste though unless you are trying to do something else I am missing.
2 conductor speaker wire will pull apart easily so you can just use 1.
Edit I see you have two diferent diagrams of two different amps. One has 2 connectors and one has 4. If your amp only has 2 connectors you would only need 2 conductor speaker wire.
HTPC, Sony 40es, 120" Silver Ticket, 7702mkii, Sunfire Amp 225w, JBL 590, JBL 520
PSA XS30, Seaton Submersive, 2 Um-18 8cf sealed, Outlaw Ultra x 12, Kappa Pro 18LF, BFM Tuba 60 horn, B&C 18TBW100 6cf 41hz, 34hz, 28hz tune
iNuke 3000 & 6000 DSP's, Crowson Motion Actuator
Last edited by bscool; 09-10-2018 at 09:38 PM.