Speaker cloth cleaning and restoration

I thought I would share the method I used for speaker cloth cleaning which worked very well on my  TELEFUNKEN OPUS 1955 model.

The cloth was initially extremely dirty and considerably darker in the areas where the speakers are and I find it extremely unsightly to be able to see the outline of the speakers underneath.

The procedure was as follows.

1. After appropriate disassembly the speakers were removed leaving just the wooden board with the cloth
2. Removal of the cloth: This is the most time consuming  part as it was glued quite firmly and to remove it without damage was difficult. Starting at the edge and by digging my finger  underneath the cloth was slowly and carefully removed just a little at a time. Great care must be taken as if the cloth is pulled from a distance with any threads still stuck to the board these could easily be pulled out from the cloth ruining it. Soaking in water first has been reported to be of assistance but I did not find it to make any difference.
3. Washing – this was done carefully by hand in warm soapy water. The cloth was then rinsed and blotted by laying on a towel and placing another towel on top, then allowed to dry on a flat surface.
4. The result was a cleaner cloth though the areas where the speakers were were still clearly visible.  
5. Bleach. To remove the stain and give uniform appearance the cloth was soaked in a solution of chlorine containing bleach, blotted off with towels and the bleach solution allowed to dry off. Care must be taken as too strong a bleach can dissolve the fabric so it is suggested to  start with a very dilute solution and increase concentration if necessary.
6. The result was a cloth of uniform but pale and yellowed appearance.
7. To restore appropriate colouring the cloth was soaked in a solution of black tea. Again it is suggested to begin with a dilute solution and make more concentrated if necessary. Blot with a towel and allow to dry on a flat surface. The tea will actually wash out to some extent if made too dark however the less handling and wetting and drying of the delicate fabric the better.  
8. The result was a clean cloth very close to original appearance.
9. A note on cloth replacement. Initially I fixed the cloth just around the edges without gluing over the whole surface in contact with the board. This may be adequate for some applications however for the high powered OPUS the vibrations caused the cloth to rattle against the board quite audibly. I therefore had to take it all to bits again and refix with a film of glue all over. The glue was applied to the board, allowed to partially dry before carefully and uniformly attaching the cloth.    

 

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