Tributaries - 4BA - Series 4 Bi-Amp Speaker Cables (Pair) Tributaries 4BA is a high-performance Bi-Amp Speaker cable made by hand. The 4BA is designed with two 14AWG and two 16AWG High Conductivity Oxygen-Free (HC-OFC) copper conductors that are terminated with Series 4 Banana Plugs or spade lugs. The conductors have a unique individually insulated dual-gauge configuration for superior sound clarity. The 4BA is terminated with red & black banana plug or spade lug connectors. The wires are secured by dual screw terminals to solid gold-plated brass Series 4 Banana Plug or spade lug connectors.