Acer Blue 6920g and Bose problems, help!

I recently bought a Bose Companion 2 Series II multimedia speakers which I connected to my Acer Aspire Blue 6920g laptop. The sound that came out of the speakers is terrible. There's this annoying "wave" like tone wherein the speakers (it seems) is trying to level out all the sounds coming out of it. Once the bass sounds kicks in, the vocals or higher pitch sounds are subdued and gets drowned. What you hear is a "wave" like rhythm as if all the sounds (instruments and vocals) are trying to out do each other. Sorry, I am having a hard time expalining the problem but I hope you all got what I mean.

I don't think the speakers are the problem. If I connect them to my Ipod, the sound is fantastic! I've connected them to a couple of other MP3 players and they sound great. In my laptop, I've tried playing MP3 files using winamp, GOM player, Windows Media Player, Nero, itunes and VLC player, but the problem is still there. Turning on "equalizers and surround sound" makes the problem worst. Anyone of you have any ideas what seems to be wrong? BTW, the speakers are connected to the earphone jack. If I listen through my earphone (instead of the speakers), the sound is great.

 

Check sound setting in control panel, check weither its on headphone or desktop speaker setting ?

 

The setting is already for speakers. It's really weird since I get this "wave" like output/sound from my speakers. As if the speaker is trying to level out all the sound coming out of it. This "wave" like sound does not happen when the speakers are connected to other sound source like an Ipod. This wave like sound does not also occur if I just use the on board laptop speakers or if I use an earphone. The sound is great.