My speakers sound like the sound is playing underwater

I've had my speakers for less than a year and recently they have been acting temperamental, sound goes in and out, one speaker sounds much lower than the other. And now they both sound like they are playing underwater. What's happening? How can i fix it? We just bought a new Asus computer - it didnt come with speakers so we just hooked up the old ones from our HP PC. Initally there was a ton of feedback, but now they sound like they are playing underwater with all internet feeds. When I run the "test" everything is fine except that even on the highest volume they arent particularly loud. I have run all the tests and driver updates - no problems found there. Help - I only have one day to return the computer if that is the problem