I have a older 4 ch US Acoustics amp that I bought used & has wired to some jbl got 6x9’s. It sounded pretty good for a while then one speaker got very scratchy sounding, it felt like the voice coil was dragging inside the magnet, I figured the speaker was bad, replaced with punch 4 way 6x9’s and after about 5 minutes of playing the same channel did the same thing! I swapped input rca and problem stayed with the speaker so do I have a bad output channel? Could I bridge the 3/4 and nod not mess up other speakers?