Work continued on getting the music system back in shape. One thing, glad we hadn't contacted the supplier of the speakers to complain about the lack of new plugs to hide the holes for the screws to say nothing about the differences between the old and new speakers.
We opened the box containing the second of the interfaces today. What did we find? A container of plugs - for hiding the holes for the screws. And, of course, two sheets of paper describing exactly how to extract the old speaker cores and how to insert the new ones - with minimal impact to the speaker frame.
We had opened one of the boxes containing the interfaces before going to work on the speakers, just not the other one.
You would think by now...