I am getting very worried somebody is going to break their IB trying to reproduce my own results.
Just in case nobody noticed the humps on the left of the graph are at around 12-13Hz! These measurements were made at 9 feet from my 4 x 15" IB.
The 12-13Hz hump increases from ~87dB to slightly over 100dB as the boost filters are applied. Though note that the ganged filters only rose by +7dB overall. That's a doubling effect.
This increase in output places considerable demands on the IB on real program material. Target level was only 75dB! That's over 25dB of gain at 12-13Hz over modest SPL target level in REW and at a very low frequency indeed.
Are you feeling lucky? Can your IB cope without self destructing if it finds a pure LFE sinewave effect at 8-15Hz on a film? Very few commercial subs can even reach these low frequencies at useful levels.
Do not assume that your own IB is indestructible on LFE when using ganged filters
whatever your previous headroom. The 8Hz component in the helicopter blades in Blackhawk Down may be your undoing and you would never even hear it before your drivers fell apart.
Please be very careful out there.