Quick question: what type of "av cable" did you have connected between the splitter (plugged into your TV's headphone jack) and the Y-cable (plugged into your speaker's AUX input)?
The issue could be any of the items in the chain: TV volume setting, TV headphone output, splitter, A/V cable, Y-cable, AUX input on speakers, speaker volume setting, and/or (and this isn't mean to sound insulting, as it applies to all of us) you.
Some things that I'd do to troubleshoot the issue:
1. Try turning the volume up on the TV to see if that gives you anything (I'm assuming that the TV's speakers get shut off when you plug something into the headphone jack).
2. Figure out if the headphone jack on your TV actually works. If you don't know that it does, you could plug a set of headphones into it to check it out, or you could plug your speakers directly into it.
3. Figure out if the AUX input on your speakers actually works. You could plug something that you know should work into the AUX input.
4. Figure out if all of the cables are actually working. If the headphone jack works and the AUX input works, try removing some of the splitters/cables between them - assuming that you have the right cables to directly connect them.
Just some things to get you started.