Magnepan vs B&W: Same specs, different bass?

Hey everyone,

I recently acquired a set of Magnepan 3.7 speakers which are rated down to 35 Hz, and I've been comparing them to my B&W 803S speakers (also rated to 35 Hz).  While I enjoy the big sound and clarity of the Magnepans, the B&W's blow the Magnepans away in the bass department in an A-B comparison test.

I figured this would be the case, but I can't explain why there's such a big difference in bass when the speakers have the same specs.  Can anyone explain?

B&W 803S specs:
35Hz – 22kHz ±3dB

Magnepan 3.7 specs:
35Hz- 40 kHz

Thanks,
Chris