Ok, I found a Harbinger 12" powered speaker for pretty cheap and bought it to use as a monitor. When I tried it out last night, it sounded like crap when fed from the mixer (through the aux outputs). But when I plug my mic directly into it, it sounds great. So I'm losing something somewhere along the way. Our mixer is a Behringer ub2442fx. By no means am I well versed in mixers and setup, but I thought it was as easy as plugging your speaker into the aux outputs and voila! - monitors. Also, I'm using 14 guage speaker cord. Any help, advice? Thanks!
Use a balanced shielded cable like this.