As you probably know, any reputable driver will have a datasheet available. These sheets should include the 1W/2.83V frequency response & impedance curves for the driver. Much of the time, they are of crappy visual quality, but usable.
There is free digitizing software out there. I happen to like
Engauge Digitizer which is free, and allows you to specify semi-log & log-log scales. Paste in a screenshot of the response curves. You pick 3 points on the main axes (typically max Y, lowest X/Y, & max X), choose linear or log scales, & go to it. Visually picking points along the curve image, you can capture all of the "important" parts of it. With the axes specified, the picked points will usually work out perfectly. You can export it to a CSV file.
That's all good & nice, but if you actually want to manipulate the frequency response with simulated passive XO parameters, you need impedance & response values (Y's) at the
SAME frequency values (X's). That's why I wrote a custom app to do that. Capture all the important points on the screenshot, & export them to a CSV file. Do this for the frequency response & impedance curves if you want to do passive calculations. My app lets me specify the frequency intervals & step sizes (for example: 1Hz increments from 10Hz to 1000Hz, 10Hz increments from 1000Hz to 10kHz, 100Hz increments from 10kHz to 25kHz). This is accomplished with simple linear interpolation between the digitized points made by Engauge. Then you just paste the data into MS Excel, or equivalent, & you can start loading these suckers up with formulas.
So in case there was any confusion, the response curves in the first post are NOT from measurements, but rather based upon the datasheets for the drivers. Certainly, real-life response will be different.
Also, in a similar fashion, I digitized WinISD curves, correlated them to the actual driver response & interpolated on them to account for the effects of the enclosure in the computed response curve.
If there's interest, I can share the application I wrote. I might put a bit more work into it first, though, to make it more user-friendly. Apps you write for your own personal use are usually un-friendly to others since you don't have to put in any real "idiot-proofing" since you know all the quirks!
