Is it a rattle or a broken connection? One of the leads from the woofer coil to the post may have an intermittent break which can sound like a rattle when it cuts out. One way to tell is to use a continuity tester and manually move the cone. If the tone stops and starts then you will have to find the break because it will only get worse. Depending on the location the break may be repairable with MG Chemicals 8331 Silver Conductive Epoxy Adhesive. Usually the death rattle means you need a replacement woofer.
Or it could be loose screws somewhere.
Thanks for the info. I’ll probably solder the voice coil connection if it’s that. Good idea for something to check!
The real issue is getting the damn grill cloth off to take a look. They should have made the grills removable, at least from the front! Plus, the connector arrangement creates an additional issue with wiring, so I’m using two pairs of 8’ Cherry MEGA Snakes (9-gauge equivalent), but that’s another story.
These sound way too good for the “problem woofer” to have a rubbing coil. Sadly, I’m all too familiar with that. It might be a loose mounting screw like you said, or the surround might be unglued in a small area (how to fix that?).
I base this on the sound when varying the volume while playing 40 Hz and other close frequency sine wave test tones. It’s ok until excursion gets large, which is why your coil connection theory makes the most sense so far.