Thanks for informations Timrhu. I was trying to look for the help from Audio Physic. It took weeks but there was no luck to get any respond from them. I looked closer inside the bad sound speaker cabinet. It turned out that the cable inside looped around and touching the cone, I straighted the loop and making sure it will not falling back to touch the cone. Whew !!......That is it.
Again thanks Timrhu.
Again thanks Timrhu.