With a tetrahedral ambisonic type mic, the capsules are cardioid. This
configuration allows you to simulate 3 Mid Side (each along a different
axis, x, y, z) + 1 Omni. The benefit to the tetrahedral config is that
all capsules are nearly at the same point.
You can get the same effect without a tetrahedral array. If you don't
care about the 3rd dimension (height), you can use two Mid Side mics + 1
Omni (two sennheiser MKH 30s and one MKH 20). Three mics can be placed
close enough like so:
http://ambisonic.info/practical/recording/mainColumnParagraphs/06/image/Hal=
liday-Nimbus-1-tiny.jpg
Note that the omni is in the middle and MS are vertical with one being
rotated 90 deg from the other. This will give you full 2D horizontal
surround able to decode on any 2D loudspeaker array.
Ambisonics aside, you can of course create great recordings with a bunch
of omni (or cardiod) microphones. Just envision each microphone as a
speaker, then during playback, position the speaker at the same relative
angle (both horizontal and vertical) as the mic was during capture. The
standard stereo recording techniques should be considered with thinking
about the distance between microphones.
Some people don't like Ambisonic reproductions. I have and have not. I
will say that the best electroacoustic imaging and sound quality I've
heard was from a SoundField Mic replayed over a bunch of Genelecs.
Some people don't like MS either. Ultimately, it depends on the
situation and recording subject. I think the greatest benefits for MS
and Ambi is 1) flexible decoding and 2) good to great surround
experience with few amount of audio channels.
peace,
Charles
On 8/26/10 6:30 PM, Marcus Buick wrote:
>
> [Four 4060s aligned in a tetrahedral pattern will provide the basis for
> ambisonic surround ~Bernie]
>
> My greatest respect goes out to one of (in not the) finest nature
> recordist
> ever. Please allow me to contest you on this one, Bernie.
>
> From my understanding of ambisonics in studying Michael Gerzon=E2=80=99s
> http://www.audiosignal.co.uk/Gerzon%20archive.html work though the
> years is that
> the four capsules in the tetrahedral array are not only aligned
> symmetrically,
> but electronically as well. This electronic calibration gives the four
> diaphragms four distinct pickup patterns:
>
> 1). Top/Bottom figure-8
> 2). Left/Right figure-8
> 3). Front/Rear figure-8
> 4). Omni for pressure
>
> The 4060 is an omni mic, and without the proper electronics, four
> omni=E2=80=99s that
> close to one another will create and image rife with time-alignment
> issues,
> phantom reflections, and an overall muddiness that is not akin to the
> point-source algorithm Michael so beautifully describes. I own eight
> 4060=E2=80=99s,
> and would gladly reconfigure four of them for ambisonic use, if only I
> could
> figure out how to do so.
>
> ~Marcus
>
> ________________________________
> From: Bernie Krause <
> <chirp%40wildsanctuary.com>>
> To:
> <naturerecordists%40yahoogroups.com>
> Sent: Thu, August 26, 2010 7:51:14 AM
> Subject: Re: [Nature Recordists] Re: Surround Sound / Wildlife Recordings
>
> Four 4060s aligned in a tetrahedral pattern will provide the basis for
> ambisonic surround that can be delivered by anything from 3 to over
> 150 channels. And, yes, the surround provided by an MKH 30 and two 40s
> facing opposite directions (used by Martyn, Chris Watson, and a few
> others) provides a wonderful double MS result that can likewise be re-
> programmed in an ambisonic configuration. The beauty of the double MS
> configuration is that only three channels are needed.
>
> Bernie
>
> On Aug 26, 2010, at 6:48 AM, Martyn Stewart wrote:
>
> > I actually had a chance to use the DPA surround setup on a project
> > and was very impressed with them. I'm told they are the same
> > capsules as the 4060's. I use normally 2 MKH 40 back to back with 1
> > MKH-30 effectively.
> >
> > Martyn
> >
> > Martyn Stewart
> > .........................................
> > www.naturesound.org
> > www.soundofcritters.com
> > .........................................
> > 425-898-0462
> >
> >
> > Sent from my iPad
> >
> > On Aug 26, 2010, at 6:19 AM, clay <
> <dan.cesonrocks%40gmail.com>> wrote:
> >
> >> On Thu, Aug 26, 2010 at 8:29 AM, corticalsongs
> < <corticalsongs%40yahoo.com>
> >> >wrote:
> >>
> >>>
> >>>
> >>>
> >>>> Any thoughts on using surround sound for wildlife? Are the mic
> >>>> specs
> >>> suited to wildlife?
> >>>
> >>> I would say that all you need is 4 mics to start. As far as I can
> >>> tell the
> >>> fancy surround mics are all pretty noisy right now, perhaps thier
> >>> intended
> >>> use was the concert hall or foley stage. If you are recording a
> >>> jungle at
> >>> night, they would be fine, but as Dan pointed out, they are
> >>> probably too
> >>> noisy for most quiet places in North America.
> >>>
> >>> David
> >>>
> >>> __._,_.
> >>>
> >>
> >>
> >> I was thinking three mics would work, if one were Figure-8, plus
> >> front and
> >> rear facing cardiods?
> >>
> >>
> >> There is something called a Tetramic that might be useful, but still
> >> relatively noisy.
> >>
> >> http://www.core-sound.com/TetraMic/1.php
> >>
> >> clay
> >>
> >
> >
> > ------------------------------------
> >
> > "While a picture is worth a thousand words, a
> > sound is worth a thousand pictures." R. Murray Schafer via Bernie
> > Krause
> > Yahoo! Groups Links
> >
> >
> >
> >
>
> Wild Sanctuary
> POB 536
> Glen Ellen, CA 95442
> 707-996-6677
> http://www.wildsanctuary.com
> <chirp%40wildsanctuary.com>
> Google Earth zooms: http://earth.wildsanctuary.com
> SKYPE: biophony
>
>
>
|