It only appears within particular presets, yes. The church IR’s seem to have more affected presets than other groups. But I haven’t gone through everything.
This is something I didn’t get into in my first post, as I was trying to keep it as simple as possible. But now that I have your attention, I’ll explain some of my findings, with accompanying screen grabs in Audacity. Hopefully this makes it clearer.
This is an image of the stereo B-format IR, of the Presidio Chapel. I have drawn a colored line after a few of the more substantial reflections in the IR. Remember, that channels 1, 2, and 3 represent B-format for the left source, and 4, 5, and 6, represent B-format for the right source. Now, notice that channels 4, and 6 align with each other, but not with any of the other channels within the IR.
In this second image, I have shifted channels 4 and 6 to a point in which all of the reflections roughly align as they should. But this obviously leaves an empty space, where all of the other channels contain the direct signal and initial early reflections. In channels 4 and 6 however, they are simply gone, completely cut off.
Continued in next post…