Hi LTD02, tuxedocivic,
first, thank you for the replies. I am not sure in what time should the break-in show a change, but 11 hours later with sweeps at cone amplitude about +- 5mm, the plots are exactly the same.
I am little confused about the comment to "be happy with that 'flat as a board' impedance response". It is my understanding that the Fs affects the Fb, i.e., the onset of mass control region where the speaker rolls off. It is modeled as Fb = 68 Hz with the advertised Fs and 83 Hz with the measured Fs. Thus, if I interpret the model correctly, there is a loss of SPL exactly where one does not want it. Am I misinterpreting?
I am measuring with a bridge and network analyzer. Are you saying that the Fs is driving signal amplitude dependent? If so, I will ask John at which amplitude he is measuring.