Speakers not detected by monitor

[Mottom17]

I have my ps3 connected to my computer monitor (Asus VH236H) through hdmi cable. Everything works fine there and I get sound through my monitor's speakers. Then using the audio input in the back of the monitor I plug in my speakers so the sound comes out of those. The first time I did this it worked. The next day I unplug my speakers and plug it back into my computer. Now I try to plug it back into my monitor but it seems like it's not working. Even with my speakers plugged in the exact same way, the sound is just coming out of my monitor. They work fine when plugged into my computer but they're ignored when plugged into my monitor when it should be giving me sound that my games on ps3 are giving off. I've tried messing around in the ps3's sound settings but I'm pretty confused there. I didn't change anything since so I have no idea what's wrong and why it isn't working now. Any help or insight would be appreciated. Thanks in advance.

 

[getochkn]

Are you sure it worked the first time? You are plugging your speakers into an input. That doesn't work. An input is as input, not an output. The circuit doesn't allow it to output audio. I don't see anyway this would work, or know how it ever did. Maybe you thought sound came out of it and it was really from the monitor, because inputs don't output.

 

[Mottom17]

Are you sure it worked the first time? You are plugging your speakers into an input. That doesn't work. An input is as input, not an output. The circuit doesn't allow it to output audio. I don't see anyway this would work, or know how it ever did. Maybe you thought sound came out of it and it was really from the monitor, because inputs don't output.

Yes I plugged my speakers into the back of my monitor where it say "audio-in" and the sound came out of my speakers. I know this because it sounds a lot different from my monitor and I could adjust the volume levels using my speakers. I don't know the exact model number of my speakers or whatever but on it, it says klipsch THX. I have a subwoofer connected to both my speakers and tower. Then when I want audio from my computer I plug the speakers into there. The first time all I did was plug my speakers into the back of the monitor and it worked immediately. I get sound/video on my monitor from the ps3 using the hdmi cable but I'd much prefer my speakers. Is there another way I'd be able to get sound from my ps3 to my speakers?
Edit: The only other thing on the back of my monitor is something labeled SPDIF.