I am repairing two 15" Tannoys of the Gold series. A $5k unit if we
could get them.

Un oscillation in a cassette deck I was using, produced a very lowed
sound that damaged the speakers.

One of them has 6 turns of the voice coil, lose and can be glued back.

On the old days I used to repair speakers using the same type of glue
that was used on the assembling of models. A type of glue that use
acetone as a solvent.
Today we have better types of glue like epoxy and I believe the harder
the glue the better the performance, the disadvantage is that using
epoxy will make a future repair very difficult.

Any suggestions ?

The coil on the second speaker is open and in very bad shape. I am
looking for a replacement.

Tannoy does not carry parts for this type of speaker but there is a
place in England that will sell me a cone assembly for about $300 usd.