I don't know if this method has been used before, but I just repaired a speaker from a DAC90A with total success. The voice coil was off centre & rubbing as the fabric centring ring had come unstuck. Initially I tried to release the cone from the frame using various solvents but all I managed to do was pull off the thick cardboard trim. I then decided to take a chance and go for broke - I disconnected the 2 wires on the rear of the cone from the voice coil and then, using a sharp craft knife, cut round the perimeter of the cone. Once this was done the cone came out easily. After cleaning the frame I ran 5mm of silicone sealant right round the edge of the frame just adjacent to the fixing rim. I put a little JB weld (slow cure epoxy) round the edge of the fabric ring and then refitted the cone with 3 fine card spacers inserted between the pole piece and voice coil former, spaced at 120 degrees. I gently pressed the edges of the cone into the silicone until it sat evenly all the way round. It was the n left overnight. The next morning I removed the spacers and was pleased to fid the cone moved in & out without rubbing. I resoldered the voice coil wires and tested the speaker. Much to my surprise It works fine. So one refurbished speaker at very little cost.
