More details on each step and on the other stuff in the table-
1) With PAS, the angle between PA speakers is always the same as the angle between microphones. Using supercardioid (or hypercardioid) pattern microphones and pointing them directly at the PA is what maximizes pickup of the direct sound component as much as possible from the recording position. The first step after choosing a recording position is to measure that angle. Since they are the same, you can either meausure the angle between PA speakers or the angle between microphones. There are a few ways to measure. I’ve learned to measure distant angles quickly and relatively accurately by using what I call the “backyard astronomer / poor sailor method”. A balled fist held at arms length and viewed through one squinted eye covers approximately a 10 degree arc. Practice measuring a few known angles and you can perfect it pretty quickly. I need to kind of stick my thumb knuckle out a bit to get a full 10 degrees. Yes it looks funny when doing it. Smart-phone apps now exist which make measuring angles easily without looking like you are shaking your fist at the stage.
Alternately you might simply go ahead and set up the microphones, point them directly at the PA speakers, measure the angle between the microphones themselves, then readjust their spacing once you determine what that should be. You can measure microphone angles directly by whiping out a protractor or using an angleometer, use some creative oragami folding techniques to estimate angles, or a smart-phone app.
2) Consulting the table- If you understand the Stereo Zoom concept, here’s a few things going on here: The PA angle is the Orchestra Angle and on this table that’s always the microphone angle as well.. that’s what makes it PAS. The table is based around a Stereo Recording Angle which is around 10 degrees wider than the Orchestra Angle (the PA angle), which tends to be more appropriate in most cases rather than making the SRA exactly equal to the Orchestra Angle.
The options in the other rows for the same microphone angle are SRAs which are 20 degrees wider than the PA speakers, the same width as the PA and 10 degrees narrower than the PA. That information and the total SRA angle are indicated in the columns to the right of the one indicating the closest “standard” mic setup, which is just for reference. The one setup indicated on the table that equated exactly to a relatively standard near-spaced stereo pair configuration widely used by tapers is DIN (which maybe only a standard to tapers and not the rest of the world anyway), the others are approximate.
Yes, it is true that ORTF is only ORTF if it uses small diaphragm cardioids which have well behaved polar patterns angled 110 degrees apart and spaced 17cm. The squiggly line in front indicates “approximately” and the indication simply provides a general point of reference many users will be familiar with. [Edit- this referred to a previously posted table that I decided was more complicated than necessary. Unless otherwise noted, the values in the table above produce an SRA (Stereo Recording Angle) 10 degrees wider than the PAS angle, which seems to be about right in most cases. Details on this for anyone interested can be found this post, later in this thread.4) The configuration with black box around it corresponds to DIN.
5) The highlighted cells are those where the proportion of imaging resulting from level differences (ΔL) and from time-of-arrival-difference (ΔT) columns is approximately equal. Note that DIN falls in this category. Since tapers tend to use the DIN configuration frequently, I've highlighted alternate configurations which
may provide similar imaging qualities. Try it and let me know what you think.
6) Notice how wide the microphone spacings become with narrow microphone angles. As the angle between microphones gets increasingly narrow, the level differences between them decrease rapidly and they begin to behave more like omnis with regards to time-of-arrival stereo imaging, although more directional patterns will not behave like omnis at all in terms of direct/reverberant pickup ratio. It might be difficult to setup the wide spacings indicated on the table due to practical considerations such as the limited length of the microphone mounting bar, but since decent spaced omni recordings can be made with less wide spacings it may be acceptable to err towards spacings which are somewhat less wide than what the table suggests. However I doubt I’m the only one who likes omnis a few meters wide when recording from far enough away that the angle between PA speakers is only measures about 40 degrees wide or so. When you consider it from that perspective, setting up supercardioids about a meter apart with a 40 degree angle between them will begin to seem much more reasonable than it might have at first glance, even if it’s not always so easy to achieve.
