near field vs far field mid woofer measurement

Hi

In my far field measurement is see a rise in amplitude at about 400hz. (attached)

The baffle dimensions are H:50cm; W:18cm.

if it is a baffle step, it is to late in frequency by 200hz according to the calculation.

F statr = (c/baffle width)/8

What do you think?
Driver: DSA135*8 5"
measurement distances are 1m and 20mm.
Pink is the near field. Orange if the far field.

Thanks
Ran
 

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F3(-3dB)=115/0.18m
F3(-3dB)=639Hz

It looks spot on to me. Lower the nearfield measurement to overlap the 200-300Hz region to far field and you are getting pretty good aproximation of anechoic performance of midwoofer (without port output though).
 
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