[Phlogiston]

Also

When removing the woofer (tweeters can stay) be careful : if 37-690 is the same in the way the acoustic arrangement is, there is a large buffle wooden cone under the he woofer so when pulling it out, maneuver it such that the wood cone doesn't damage the woofer's paper cone.
Also take the same precaution when replacing the woofer.

Before replacing, inspect the wooden cone for cracks: they do fall apart and the loose piece could damage the paper cone. Did in mine.

Yeah, you can't see it until it is too late - unless your grillcloth is gone.