I stepped through your entire photo series beginning here:
http://pix.minirig.org.au/main.php?g2_itemId=1470
Beautiful job on the cabinet build; I savored every pic.
The PDS221 curve looks like classic power response above a 3.5 kHz mass breakpoint. It's linear monotonic, and should be amenable to Wayne's Pi-speaker HF compensation approach. Parse it out. Start with just the comp cap; if that's an 8-Ohm driver, your 2.5 uF value is too high and not rolling off the response high enough; pick a value that starts at just above 20 kHz, then set the slope with the resistor in parallel. That'll give you a perspective on how it works. Then add the resistor to common and adjust the pair according to what is required to balance with the core highpass filter and the woofer output. Refer to his attenuation chart here:
http://www.audioroundtable.com/PiSpe...ages/1278.html
Read through his tutorial if you haven't done that, and his posts on the subject in this thread, accessible via Advanced Search This Thread on his ID.
With 8-Ohm Selenium drivers, 1 uF is about the max value for C1, eWave's C3. Above that, there's no comp happening at the 20 kHz high end.
Footnote: One of your early schematics had the highpass inductor to common before the series cap. Not surprising that didn't work....
