TV's audio settings (via configuration) is set to mono or simulated stereo? Or the Y-adaptor is not situated properly? Normally it works by the metallic plug contacting particular portions of the input, which then sends signals to the respective speakers.
But I'm surprised--your TV doesn't allow for a component cable arrangement? Nor do your speakers?
Well the generally connection for these speakers (being computer speakers) is your typical 3.5mm headphone jack which is meant to go directly into your sound card. However, since I have multiple devices including my PC hooked up to my TV, I figured it would be wise to use that connection into my TV's audio output so whatever plays through the input will go through my speakers. The output unfortunately is component/RCA, which means I had to convert the signal from RCA to the mini-jack. Apperently my right speaker didn't appreciate this.
So now what I'm doing is using a direct connection for my PC and using male male RCA cords for my TV's output on the additional aux on my speakers. Hopefully this works, otherwise I may very well be SOL if I decide to jump on my consoles.