Cristant Smith

I bought a 2008 Ford Edge Limited awd about 7 months ago and all of the sudden the bass is starting to come in and out. The treble is fine but it goes from sounding decent to sounding like it's being played through a tin box. I was going to try to replace the stereo but thought I'd see if there's a simple fix for this. Everything else works for the radio, lights, buttons, satellite, CD. It's just the audio portion of it that the bass comes in and out. Any ideas or help would be appreciated.