One workaround is that you can disconnect the subwoofer so that it does not come into picture at all. But then you will be getting sounds only from your speakers, which will be like the other normal laptops. You can not disconnect the subwoofer from the system. For actually disconnecting the subwoofer, you need to open the back panel, the RAM box, there you will see a white coloured plug coming from the subwoofer side and connecting to some chip. Just gently pull open that plug (the plug remains there though not connected to anything), then place the cover and screw it. Now there won't be such grinding noise. I even don't know that my woofer is damaged or it can be repaired. Do share if you get any real solution to this.