Originally Posted by Funky Waves
In theory the 5100 has less bottom end, but if you look at the models in the same size sealed box with the same power input they are within ~.5db from 10-50hz, its just that the 5100 has more efficiency/output over that(can be eqed down if room response requires it).
The difference in extension capability is really only as regards xmax and output capability.
Because it's more efficient it's more accurate to say that the 5100 rolls on w/increasing freq instead of rolls off w/decreasing freq.
I just looked at the spec's and the 5100 actually has a slightly more compliant suspension than the 5400, so it doesn't require more power to fight stiffness.
But with it's low Qe/high back-EMF it might require more amp voltage to get the same output at low freq.
What would really be interesting is to see if similar (both sealed or both ported) systems using each from 80 Hz down, and EQ'd to the same response, would be audibly different.