The F228Be are specced at 90dB sensitivity, so -3dB would be 87dB. Now from the Revel own spin seems that the F208 are around 87dB sensitivity and the F228Be maybe 1dB more but we don't know if the level there equals sensitivity, even if it is very close to Amir's one for the F208.
Anyways based on that Klippel spin I would say that for the F228Be the -3db is around @40Hz and the -6dB around 27Hz, look at the spin I have annotated. Sensitivity aside the F208 and F228Be are pretty much the same below 60Hz.
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