I just bought a pair of AKG K545's yesterday. The included cables are only 3 feet, so I picked up a 6.5 foot extension to use with my computer. When the 545's are used with the extension, the vocals disappear, and the rest of the sound is crackly and sounds like it's underwater. The cable works fine with other headphones. What is the issue here? Not sure if this is posted in the correct location.