This white paper is 26 years old and has very rudimentary measurements. There must be some independent data on the subject? For such an iconic brand, with such explicit claims, I am surprised I can't find any.
I have to say that test methods and data are very difficult to make universal and transferrable. I know many live by measurements, but ATC knows them too and knows how results can be flawed by process, environment or set up and yield conclusions that are not accurate. A non calibrated mic for example, would not reveal itself in the test. A flawed acoustic space would not reveal itself either. 20-20K measurement means nothing without the variation limits: +/- 10dB, +/- 6dB or +/- 2dB are all dramatically different tests in terms of value to the user. +/- 2dB can reveal some good info, but you still don’t know about the space or how the speaker was tested.
I remember the first time I saw a non smoothed HF driver response curve while at JBL. It was awful and my instant reaction was “ something is wrong”. Yet, the engineer explained probably for the 20th time today, this is the way they REALLY are and there was no error. A smart person not familiar with the test could make an incorrect assumption that this driver was not good compared to others because they did not know all the comparison driver tests were smoothed. Microphones are similar, the true response curve at +/- 1dB is not pretty at all! It looks all over the place. So manufacturers don’t print that because no one would buy the mic based on this +/- 1dB test. Make it +/- 6dB it looks a lot better, and in fact this has become “usable limit” in many live sound speaker tests. +/- 6dB also equals a 12dB swing at times, something very significant that you would easily hear. If the variation is not printed, it is NOT easy for the average buyer or user to recognize 20-20K does not compare to 20- 20K +/- 2dB in any way. You spend a lot of time trying to figure out why there is a 20dB null somewhere when this is normal, and the max variation on +/- 2dB would be only 4dB.
At TransAudio/Lone Mountain we use our AP 515X with all the acoustical software and a calibrated mic constantly at work to calibrate, measure and test ATC’s in the diagnose and repair or upgrade process. While we understand our measurements, I would not print them or rely on them as “proof” of specific virtue because our space has some acoustic anomalies in the LF band. One could get the idea from the tests its revealing a product flaw when in reality its the space or the mic or ?.
So that being said as background of why you don’t see more tests, what test do you want to see? BTW, the 26 year old white paper is still valid as drivers mentioned are still in production. The principles discussed are all still current.
Brad