Is it safe, for mine and the speakers sake, to hook up more than one set of wires to a single set of ports?

I have three JBL decent sized speakers, about 2 foot by 1.5 foot, and i am hooking them up to my tv, two are hooked up but i want to add a third. The tv has 4 ports, 2 red 2 black, and a set of red and black for right and left. Is it safe to have two speakers hooked up to the one set of those 2 ports? If not, is there a way to get around this and hook up the 3 safely without possible damage to anything and without having to buy anything else?