On 2011-06-20, umashankar mantravadi wrote:
years ago i had asked (several times) this same question and never got a satisfactory answer. i thought of two alternate systems. one where the sphere is about seven or eight inches across, and the other where the sphere is just large enough(about an inch) to mount the capsules. never tried to build either of them
Just as I've wondered for a long time about automatic, approximative and purely numerical solutions to the decoder problem, the same goes for the mic array. Can't we somehow optimize the mic array and whatever baffles plus other obstacles it might contain?
As you say, we already know mounting mics on top of an opaque sphere is superior to a free standing differencing scheme. Not only because Fons and other have argued for the theoretical singularity of the latter scheme. But also because of the related, practical, empirical fact that that sort of thing tends to regularize the encoding equations -- something Gerzon already talked about when referring to Gaussian quadrature in the literature over the development of the original SoundField.
Can't we take such physical optimization beyond simple symmetrical structures such as the ball, now that we have all this computing power? Especially in the context of mixed order, semi-pantophonic systems?
Looking at the highly developed theory of sigma-delta converters, it's all about dividing the labour between what analog and digital domains do best. In mic design, the analog side would be about placing various, perhaps even highly intricate, obstacles among the mics, so as to make the eventual array perform better in average, as an aggregate, and in a way more susceptible to digital post-processing. Do we have *any* theory on how to optimize for this, jointly, between the physical and digital domains, then? If not, it sounds like a weighty dissertation to me. :)
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