the two FR specs just reflect the different FR range with respect to the 3dB and 6dB deviations. The 4B would need to be crossed over to a sub at a fairly higher point than the HTM-200SE....which has a +-3dB of 74hz. It also has sensitivity rating of 87dB as opposed to 84dB.....which roughly means it would take twice as much power to to drive the 4B to the same levels as the 200SE.