I have a spare Audioengine a5 passive speaker that I would like to use. It only has the binding post, but I think a banana plug fits into it. I was wondering if I could somehow Frankenstein a set up with banana plugs on one end and a single 3.5mm jack to go into a phone on the other end, without amplifying it. I saw a video on Youtube where a guy ghetto-modded some wires and successfully powered a passive speaker without an amp assuming the right resistance. Is it safe and doable?