Ok now that's got your attention>
It's really a case of failing memory. I dragged the sub out of the corner it has been in for many years to have a good clean.
Looking through the port on the bottom I was shocked at the size of connection braid I had used when I made it, still better too big than too small:
It was evidently some spare earthing braids I had got at then time of manufacture.
Shot of the complete sub, it is a 10 inch driver to give a indication of scale.
For those of a certain experience you might recognise the legs used on the bottom of the sub.
It's now re-oiled and back in it's corner for a good while longer