I have a friend, a former concert pianist, who has one of the best systems I've ever heard. He has some pricey interconnects and even a power cable or two, but I asked him once what speaker cable he was using, it looked sort of rugged. He said, "You won't believe me if I tell you." So he told me anyway, and I tried it, and it's the best speaker cable I've ever heard. I've sent some to friends and they love it too. It's 8 AWG stranded THHN combined with (yes, really) 18 AWG 5-conductor copper sprinkler cabling, with one conductor snipped and the other four twisted together in pairs for positive and negative. You can parallel the two or use them separately for bi-wiring, which I do--the 18 AWG for the highs and the 8 AWG for the lows. For termination I use large copper offset lugs, snipped to make spade lugs. Or you can get large-size screw-on banana plugs. I strap them together with cable ties.
I like Blue Jeans cables, especially their interconnects and digital spdif, they just sound NORMAL. But I like this rig better than their speaker cable. Cost about $100 for a 15 foot pair, and you can buy both cables in bulk from Amazon and save some money. How do they sound? Big, rich, smooth, open, plenty of detail but absolutely no fussiness or phasiness. That's my free tip for the day. ;-)