SNR wouldn't have been my initial concern because I have some wee-tiny electrets that have (purportedly) +10 dBA noise--pretty low for a small capsule. When I think of the "classic" multi-polar mics such as the AKG-414, the multiple patterns are often derivatives of back-to-back diaphragms sharing a common stator (I think... not a mic expert here). In comparison, ribbon mics (Coles, Royer, vintage RCA, etc.) are figure-of-eight (or bi-directional) because of their pressure-gradient design. Cardiod condenser and dynamic mics have rear venting for delay/cancellation (delay using materials of varying density, not merely time-in-air delay), hence their directional characteristics. So... Having directional characteristics provides direction-dependent output levels for each of four mics. Spacing, of course, provides a time difference component for computing direction. The ideal is no inter-capsule spacing (= zero time delay). Tightly spaced omnis are just that... omni... and wouldn't have discernible time or level differences unless there's *some* time difference or pressure difference. Sound intensity probes rely on a phase (and level) difference to determine the vector quantity of sound power (SPL alone being a scalar quantity). So, based on acoustical signal processing and beam forming described by, for example, Vorlander, I was curious whether the *new* surround mic used such processing to create four virtual subcardiods that would also serve as the equivalent *A-format* mics. Any single mic, or average of all mics, would be the omni component. For mics such as the AKG 414, the electrically and acoustically combined response yields one polar. So, I was really wondering how four omni mics could provide unique info for multiple directions. A highly-directional mic can be created using omnis and beam forming, but not a *series* of directions at a given instant. Now, scratching my head, there's no reason that multiplexing among the mics couldn't be used to create rapidly-changing patterns that are akin to interleaved quad channels. That is to say, only one direction is picked up at a time, but the derived direction changes swiftly enough that it appears to have four *directional* mics (is this a new idea... it just came off the top of my head... most of what I think up has been done.) I just found the technology interesting/curious, and wondered where it might deviate from the Soundfield mic to the point of being a unique design. One aspect of a patent is that the invention be unique.
Above post in response to:: If one regards the subcardioid as made up of omni and figure of eight components, is it not the case that the ambisonic XYZ signals of the Soundfield Mic are derived solely from the figure of eight components? Further, if this new mic relies on omni capsules, how will it not suffer from the signal to noise ratio problem of Blumlein's method of deriving stereo from two omnis? David -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130420/8684942d/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
