It's a bad analogy or at least I really hope it's a bad analogy
ie a medical "pretest" is a test that is generally considered to provide sufficient signal to warrant being followed up by an entirely different test that is known to be more accurate but is invasive/expensive, in comparison this is just a low resolution version of the actual test where the resolution is low enough to render the results inaccurate enough to be simply wrong.
Well let's leave the medical discussion out of it for now
I would disagree that the resolution is so low that the result can not be interpreted. It was enough to pick up the difference in directivity between my horns and the woofer. And more importantly, the trend from the raw, unprocessed measurements is consistent with what I would expect to see if the woofers have a wider radiation pattern than the horns.
There is something even more remarkable with those measurements. If you look at the directivity index in this graph (green line):
You will see a sudden rise at about 13kHz. This shows the tweeter horn suddenly changing direction from wide dispersion to a beam.
When this was pointed out to me, I got a tape measure out and measured the diameter of the tweeter horn - 12cm. With horns, the lowest supported wavelength is twice the diameter of the horn, anything longer than that is not "horn coupled" and loses efficiency. So we have the lowest wavelength of 24cm, which corresponds to 1430Hz. The upper supported frequency is 3 octaves above the lowest frequency, so 11.5kHz, that is close enough to 13kHz (allowing for errors in my technique, not knowing the exact geometry of the horn, etc). Anything above the highest frequency is not horn loaded either, and it starts to behave like a beam. I was pretty amazed to see that this measurement was able to pick it up.
More practically, the bit I don't understand is, given it's an active speaker, is why you measured it as an entire speaker? and also why you added the moving mic bit which isn't really moving mic at all given it is just moving up and down?
If you are asking why I did not measure the drivers independently, it is because I wanted a rough comparison of the directivity of the horns vs. the woofers. I could do that by measuring the drivers independently, but that would give me twice as many curves to process, and the result would not be side by side in the same graph. I also wanted to see if my very steep crossover causes sudden changes in directivity, which it does. For me, this result is actionable - over the next few days, I will reconfigure the crossover between woofer/horn to something more gentle. I will repeat the measurements and post them here.
As for moving the mic up/down, my understanding of "MMM" is that you move the mic across the area that you want to cover. In a normal MLP MMM, the mic moves around your head. I wondered whether a vertical MMM would give me useful information, which it appears to do.
Look, I am far from an authority on any of this. I am sure that any of you know far more than I do. I am a tinkerer, after all this is only a hobby for me, I do not do it professionally. I often come up with hare brained ideas, which I only find out are hare brained in retrospect and after getting brutally savaged in ASR after discussing them
So I don't mind getting savaged, I am humble enough to know that some of my ideas are just plain stupid. If this one is stupid, then so be it. It cost me nothing to do, and it is "backyard science".