FOH, I am all too familiar with bottoming out drivers
I have always been obsessed with the lows, but as I get further and further into this thing, it keeps getting lower and lower. I remember when i was obsessed with music that went down to 30Hz. Then it was 20Hz. 15Hz. I am at 5Hz and Id like to think Ill never get stupid and want 1-3Hz. 1/2 octave, 4X the displacement.
The former smashing into the bottom plate. The IB3s are tough, very tough. Aluminum. I initially had one 1B3 18 that I bottomed many times until it died, reconed it and it lasted a couple days because I had just gotten the EP4000s and really beat it up, then I got the two installed in the HT and an accident here, accident there over and over and they just kept on going. Then I got four for the van, accident here and accident there, never any issues. The van would still be fine, but because of my having more accidents in the beginning as I was getting to know the limits in that alignment, when i went to get TermLabed I didnt hold back. Every single frequency i brought up click by click until over excursion to get max SPL. I went into it knowing I would finish them off so that i could recone them and have fresh new cones with the knew knowledge of my limits. I ended up selling a pair of the blown subs, so I was going to recone the two HT 18s to replace those, and replace the HT subs with 22's. 22's got delayed yet again, never heard back from Nick at IA or Kevin at Exodus, and boy am I GLAD! So I purposely got carolous with the two in the towers to have some fun and bottom them to recone them.
So I reconed the four subs and they are in the towers, and 2 nights ago I ordered four more IB3 18's. So I will have a total of 8. BTW, the initial IB3 I had I used to test fit holes during the HT and van build, someone broke the motor on it in the process, otherwise Id have 9 IB3s.
When you bottom, you know. A tiny slight kiss isn't loud but clearly audible. But when you smack, it puts the fear of god into you. It is very loud, very frigtening.
You are very correct about electronics roll off, when I get to the single digits I have to really crank the receiver up. I do not need a HP filter, when I bottom out it is above tuning, not below. When I model them in WinISD I add two Linkwitz @ 10Hz to simulate rolloff.