OK, another idea run up the flagpole that nobody saluted. :-(
Here's one more. Since measurement systems can save a frequency response sweep to some kind of computer media, it seems a measurement system could also open up a previously saved file. So a manufacturer just needs to publish a readable file of the actual target response they want their speakers to get. Easy peasy...
Of course there probably isn't a standard format for response files, but how many flavors of that are there?
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Back to my "True Q" new improved empirical measured Q, I understand that some measurement systems can perform a sweep and then download the data from that sweep into a spreadsheet. If you do before and after (EQ) sweeps of a platform, you can then subtract those two sets of numerical values from each other to extract just the EQ difference signal. This difference signal, even for a small 1dB boost/cut will take the form of a common bandpass, with measurable -3dB points. This extracted EQ component will look like a BPF output and we can determine Q using the classic definition.
For the example of a boost EQ delivering roughly +1dB ( 1.1V) above the flat (1V) nominal signal, the extracted EQ term will peak at approx 0.1V and have -3dB points down around 0.07V.
Since EQ is often layered on top of other filters, this method subtracting two files seems most accurate, but for just measuring EQ relative to flat 0dB one might be able to directly compute it.
JR