Potentially there's another issue, this one not so easy (or cheap) to resolve. I suspected from the get-go that at least one of my drivers was reconed, due to the over-application of glue around the dust cap on one of the cones, and the absence of a part number stamped on the backsides.
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Compared to the JBL data, the impedance is not as smooth above 500hz, but it doesn't seem particularly bad either. As you've said in another post, the impedance notch at around 1k is a good indicator that the cone is aftermarket.
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I'm going to wait until I can conduct final FR measurements and listening tests before making any decisions. I paid about $300 for both drivers, and if they're good enough I'm inclined to keep using them.