Black line = Peerless XXLS 830845 in a 1cf sealed box
Blue line = Ascendant Audio Atlas 12" free-air
Red line = Peerless XXLS 830845 free-air
XXLS is about ~5db more efficient than the Atlas 12". That's equivalent to almost 4x the power required for the Atlas to achieve the same SPL as the XXLS. Of course the XXLS needs a much larger sealed enclosure for the same QTC, but it looks and sounds fine in a 1cf box.
Also notice the upper end response of the XXLS is relatively flat, while the Atlas has a downward sloping response at 70hz.