Large Advents (1974) woofer pops with deep bass.

Here ya go!

 https://www.simplyspeakers.com/advent-replacement-woofer-p001-31858.html

Uh, considering they're almost 50 yrs old you may want to consider buying something newer ...

Uh, considering they're almost 50 yrs old you may want to consider buying something newer ...

Yea, if the speaker driver is 50 years old, it probably needs new surround’s, however you can get replacements online usually at pretty good prices. Check out Dayton. I’ve used their woofers in projects a couple of times and been very happy.

All the best.

The LA of 1974 would have a Masonite ring with a 9” paper cone in a 12” basket, designed that way specifically to prevent bottoming.  So either the inverted foam surround is perforated or there is another air leak somewhere…or you are overdriving them.  They should handle a 125W amp easily, but you may have more.  Are you boosting the low end?  Don’t. People used to stack pairs to increase their output.  They had impressive bass but there are limits!