On my mixer, which is a 22 year old peavey mixer, the back has a left and a right speaker output, and each of them have paralllel outputs. Do both of the parallel outputs go to one speaker?
no. It just means you can hook up more speakers, ie. 2 speakers on the left and 2 speakers on the right. You can hook one speaker up, and the other parallel output can sit unused. It's only when you hook up 2 on each channel, since they are in parallel, the impedance load it sees from hooking 2 speakers/cabs will be halved, ie. 4ohm speaker + 4ohm speaker in parallel = 2ohm load. Since it's probably a SS powered mixer, a lower impedance would increase it's output power on each channel, left and right. Just don't go below it's rated impedance, it will usually be labeled somewhere what not to go below.