Does anyone happen to have the T/S params from the original IB15 that had a phase plug? I can't seem to find them anywhere. I asked over at the AE board but haven't gotten a response yet and figured this may be faster as Thomas probably has them in a modeling program somewhere
If they have straight tapered vinyl cones you can probably assume Fs of 32Hz.
I measured my four with REW and a 100 Ohm series resistor and all are very close to 32Hz.
This is easily overcome with a +16dB boost 120/160BW @ 20Hz on the BFD. The surrounds/spiders are so stiff these drivers are still unburstable even with this massive boost. I used mine like this for a couple of years on the usual DVD torture implements. In fact I still do with my present 8 x 15" IB though excursion is no longer an issue. You can always work up to +16dB, at a dB at a time, until you are sure they wont hit the end stops on your loudest, bassiest films.
You will probably need a few minor trimming (cut) BFD filters to pull down the higher bass frequencies.
Thanks guys! I thought it may have been the one with "questionable" params but wasn't sure. I thought I had found a "deal" on some but then I found out they used to go for $99 each so not so much Oh well.