Okay, so it works in principle although we haven't yet determined how well and if good enough for our purposes. Can better establish that after some tests. Until then, I'll go ahead and jump right to the "ideas for use" driving my interest in this.
I've posted about my wish for a truly miniature fig-8, ideally PIP/low-voltage powered. I'd use it as the Side channel in a Mid/Side pair with a DPA miniature omni, cardioid, or supercard Mid, probably with both mics mounted in one of the hard-rubber DPA boundary-mount disks, modified to accept the Side mic. I could use two miniature DPA cardioids to form the fig-8, and for that to fit in the boundary mount I'd probably need to remove the short interference tube grids from the DPA miniature cardioids, which I suspect wouldn't cause a problem. Alternately as this thread explores, I might be able to use two DPA omnis to form the fig-8. Both options would be small enough, but neither is attractive due to the increased channel channel count needed for the pair - to do it that way I'd need 3 channels total for the Mid/Side pair, one for the Mid and two for the Side channel. The clever scheme DPA mentions requires only 2 recorder channels, but only works into a balanced input. It uses two DAD6001 XLR adapters or the equivalent, one for each mic, connected in parallel through a passive summing adapter with pins 2 and 3 swapped on one of the inputs to achieve a differential sum of the two, into a single balanced mic input on the recorder.
That requires three mics into two balanced recorder channels for a Mid/Side stereo pair. But I've an idea that would use only two omnis into two unbalanced recorded channels-
If placing two miniature omnis on either side of a small baffle, say about the size of a typical fig-8 diaphragm is able to produce a fig-8 Side channel good enough for what I want to do, I may be able to reduce the channel count needed for a M/S pair back down to just 2 AND use a small recorder with unbalanced inputs. To do that the two omnis would be recorded to individual channels. Afterward on the computer, those two channels get summed with polarity inverted on one of them to create the Side channel. But in addition to that, both channels could also be summed without inverting polarity to create the Mid channel. With appropriate gain adjustment I'd then have both Mid and Side channels.
Conceptually that works best if a small baffle (typical fig-8 diaphragm size would be acceptable) between coincident omnis is able to create a fig-8 which is good enough. If some spacing between the pair is required either instead of, or in addition to the small baffle in order for to form a sufficiently good fig-8, that complicates the summed Mid channel pattern. Can probably get away with a little bit of spacing but not too much.
Taking that where I would..
I would use this to record anywhere from one to four Mid/Side pairs. The simplest two-pair / four-channel application would use them in place of a typical pair of mics worn on either side of the head. Doing so would provide for the choice of any desired polar pattern afterward. In addition, if choosing a pattern more directional than omni, separate forward and rearward facing patterns can be produced. Same principle of operation as the Schoeps KFM360 system.
I like recording using four baffled/boundary-mounted 4060/4061 omnis facing in the four cardinal directions. I've written a bit about doing that here at TS, but not nearly as much as I do about other, open taping techniques. The ultimate goal is to extend each of those four omnis into a Mid/Side pair. Would require eight recorded channels rather than four, but allow for M/S manipulations that would provide increased control over stereo image by working the front-facing and rear-facing M/S pairs, and even better control over front/back direct/reverberant balance and overall sensitivity pattern of the entire array. I currently have some welcome control over that via how much rear-facing omni is added to the mix, but this would add front/back directivity control via the side-facing pairs as well (KFM360 like).
Although I prefer using a baffle larger than my head for this, all of the mics would easily fit into a hat. If a bit of spacing works instead of, or in addition to a fig-8 baffle that's small enough, each M/S pair wouldn't be much thicker than a single 406x. All the mics could even fit into a hat band or a sweat band, early Mark Knopfler style.
I have some testing to do when I can get around to it.
Topic: Omnis to figure of eight (Read 2314 times)