[JohnR]

I'm not sure if this might be a Lab topic but... if you "bottom" a sub, is it likely to get damaged? Or does it just "deal" with it?

[craig sawyers]

The main problem is if it jumps out of the gap (ie in an outward direction).  If it fails to return because the voice coil former catches on the magnet rim you can burn it out pretty quick. 

It is more common for a reflex cabinet, because there is nothing to control the cone excursion, so record warps, or weird infrasound that is on many CD's (possibly air conditioning flutter in the studio at a few Hz) are not controlled well.  If you have a reflex you really need to put an electrical LF cut at the plate amp or whatever electronic crossover you are using at maybe 10Hz, or maybe a bit lower.  If it is closed box, it is very difficult to get a modern driver to bottom or jump out - you have to abuse it pretty badly.  All you need to do is put a tiny hole in the cabinet (a millimeter or to) - if it is truly sealed, as the temperature of the air changes it pushes the driver in and out with a DC excursion and can cause problems.

[*Scotty*]

When a woofer hits the back plate the potential is there for the voice coil former to crumple like an aluminum beer can. If it crumples it may easily start rubbing on the pole piece or seize up entirely. Sometimes it hits and you get a pass and nothing detectable happens, but sooner or later damage will result.
Scotty

[mcgsxr]

No disagreement with what has already been suggested.

I used to run a Fosgate 12 in my BMW in a sealed box with 500w heading to it.  On bass heavy tracks like "Ray of Light" from Madonna, the woofer would clunk.  I beat on that sub for 2 years in that car, never giving it a second thought, as the nasty noises could not be heard in the cabin, only when you opened the hatch.

Frankly, a lot of it comes down to what the sub was designed for too.  In my case, that woofer was a competition SPL type with a huge spider and rolled surround.  It was capable of huge excursion, and got it.

A lighter, less robust woofer might suffer much more under similar conditions.

I imagine it is best to never have it happen, but I have lived through doing it over and over and ignoring it, and that woofer ran beautifully on OB years later.  I sold it to a guy that to this day beats on it in his winterbeater.

[Bob in St. Louis]

I'm with Mark. I've bottomed out my HT woofers for years, sometimes REALLY bad, and they have shown no sign of weakness.
I guess it all boils down to them being quality enough to take that beating.