PASHKULI I vehemently disagree with a lot of what you write, especially your axiomatic way of saying things are true when in fact a lot is just your opinion.
Was the metal frame a necessity? Sure. Does it affect the sound? Sure. Is that part of the piano sound? Yes. Would removing its effect change the sound? Yes.
You don’t like the piano sound, as we’ve discussed, go build a new instrument.
I fed specifically my points of disagreement to an AI and asked it to produce a Binto Pyramid consultative response based on what I know to be true.
Fair correction on one thing: my final sentence put a paraphrase in quotation marks about the 200Hz deal. It wasn’t intended as a verbatim quotation, and I should not have formatted it that way.
But the paraphrase didn’t come from nowhere. Your exact words were that, with omnis, there are phase issues depending on “pointing parallel, 90° or worst is 180° to one another”.
You now say “position change (not rotation!)”. That’s a different claim — and one I agree with. Moving a microphone changes direct arrival times and the reflection field.
But that happens across the spectrum. There still isn’t a physical boundary at 100 or 200 Hz above which two signals suddenly become impossible to time-align.
A fixed delay produces a phase shift proportional to frequency. Higher frequencies are actually more phase-sensitive to a given timing error because their wavelengths are shorter.
What is true is that two microphones around a piano in a room aren’t simply delayed copies of one another. Different positions capture different mixtures of piano radiation and reflections. Therefore a single delay cannot make their complete waveforms identical.
That’s exactly the distinction I was making.
Filtering unnecessary LF is a perfectly valid way to reduce spectral overlap and recover headroom. But that’s a mixing/filtering decision, not evidence of a 100/200 Hz phase-alignment boundary.
DPA’s own material is quite explicit (and those guys know a thing or two about recording): stereo techniques intentionally use time differences between microphones, and DPA also describes time-aligning support microphones to main arrays to reduce comb filtering — with the appropriate delay depending on the room and reflections, not on a 200 Hz cutoff.
More importantly, though, you haven’t addressed the points I actually find more interesting: the directional radiation of an anechoically recorded grand, or why modifying the lid/frame should count as obtaining a “purer” piano rather than modifying the source.
