'Sounds' like ya'll aren't factoring in the amps used, which were ~matching impedance originally, decreasing down to vanishingly low by the time of the 'E'; so originally, driver impedance was listed as a function of network impedance and the VCs would have been wound to have a DCR/impedance that yielded the desired inductance to achieve the flattest, widest BW over some average power band. As output impedance dropped, the driver's impedance would become increasingly more dominant for a given Qts, power handling.

Note too that compression horns will add enough acoustical loading to raise the nominal impedance up to 2x Rdc over their pass-band, dropping back down when the horn unloads and only functioning as a direct radiator, so with a loading cap I?m not surprised its Rdc is considerably < a woofer?s ~12 ohms for a nominal 16 ohms impedance.

With re-cones though, I?d be surprised if GPA still has period correct coils for the early series or even much choice of nominally 16 ohm coils beyond the ~12 ohm ones for the 416, 515 where inductance should be ~the same, so it seems reasonable these are the ones used in 605, 604 re-cones.

WRT the XO point ?floating? between 1500-1600 Hz with the small horn, I assume this is due to how the XO?s alignment changes with driver VC design between models, which with re-cones may actually work out to yet something different if the original VCs aren?t used.

Short of GPA listing a customer?s options to choose from, one can only measure what one receives, which in some cases we know is well shy of the mark.

This ?E? plot should be in the ?ballpark? from around 300 Hz-up for most of the small horn 604s when driven with a typical SS amp: http://www.lansingheritage.org/image...itor/page2.jpg

GM