I purchased a Sony Htib about 3 or 4 years ago. It came with some small speakers so I upgraded them to a pair of Bose 301's and changed the rears to some bigger Sony speakers from another radio, and kept the center speaker the same. The problem (which I just noticed about 2 or 3 months ago) is that when I use the test tone feature on my receiver I get noise out of two or three speakers at the same time. For example the left front and the left rear will make noise at the same time. What could be causing this?