Actually, directly on axis of one of the capsules may be the worst
direction for a tetrahedral array. While it's true that otherwise you are
slightly off-axis for a given capsule, with whatever coloration that might
cause, I believe the non-coincidence problems of the complete array
overwhelm this effect. When pointing directly at one capsule, the distance
to each of the other three is the same, thus the peaks and notches caused
by phase differences all line up at the same frequency and become one
bigger peak or notch. When a source comes in between two capsules, the
distances in the array don't match so the peaks and notches spread out in
frequency and help to smooth each other out a bit. Of course, the
calibration filters for tetrahedral mics attempt to correct for this
effect, but those filters more closely match the diffuse field average of
all directions than the more extreme results in the direction of one
On Tue, Sep 11, 2018 at 8:21 AM James Mastracco <***@verizon.net>
> I've love to see pictures of the chapel and the mic placement.
> > Hi Folks
> > Is it better to align performers to capsule axis, to get the best
> > frequency, and noise performance from those directions, then rotate the
> b-format encode afterwards?
> > I am recording at Union Chapel, with tetrahedral mics, and spot
> > The final output will be stereo and HOA.
> > I usually just position tetra mics as normal (upside down and
> > end-fire), but it occurred to me that it may be better to align the
> > capsules to performers (where possible).
> > All performers will be spread out horizontally on an equilateral
> > triangle, with the main tetra on a corner.
> > The main decode will be stereo, but I want to capture the acoustic of
> the place, and do a HOA mix.
> > Best
> > Steve
> > _______________________________________________
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> Best regards,
> James mailto:***@verizon.net
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