Hi Justin,
If I had a pair of good super-cardiods, I would be inclined to try them hea=
d spaced, perhaps parallel, with a sound absorbing baffle in between. The e=
ffect would be a narrowly focused, front and rear layered soundscape. I am =
imagining a perspective from the bank of a woodland lake with the the forwa=
rd focus on a subject in the tree canopy, and the rear lobe focused on some=
sounds at the water's edge.
John Hartog
rockscallop.org
--- In "ajustend" <> wrote:
>
>
>
> John,
>
> Yes, I also find it very strange that in all of my research of MS stereo =
mic'ing techniques almost nothing is mentioned about stereo-image side swap=
ping when using a super-cardioid mid. In fact, before trying it myself, the=
only thing I read about using a super-cardioid pattern for recording in MS=
was that many people liked it for it's improved "focus" and off axis atten=
uation (with the MKH50/30 combo being second in popularity to the MKH40/30)=
.
>
> Being a recordist who does a ton of mono recordings for SFX purposes I th=
ought I saw the purported value in this statement. But, it seems, the big m=
istake in my thinking (and I am curious about other's thinking on this topi=
c as well) was that the Mid mic would continue to act like a forward facing=
mic in a stereo MS setup, when it actually does NOT. When the Mid and Side=
signals are decoded into stereo the end result is IDENTICAL to an equivale=
nt XY setup (shown very clearly with diagrams in this paper: http://www.rib=
bonmics.com/pdf/technique.pdf) which means that the solo Mid super-cardioid=
mic's off axis rejection is actually only helpful when listened to alone o=
r when the MS stereo signal (decoded or not) is played back in mono.
>
> It seems to me that in stereo recording you are basically nullifying the =
advantage of a super-cardioid's off axis rejection and are instead only giv=
ing yourself: 1) smaller recording angles (as John stated in his example of=
a rubber band stretching), and 2) the potential for throwing rear lobe rec=
orded signals into the opposite stereo speaker during playback. Therefore, =
I really do not see any advantage of using a super-cardioid mic over a card=
ioid for coincident stereo recording.
>
> I have been reading over the Manfred Hibbing "XY & MS Stereo Recording Te=
chniques" paper today and have been very impressed by the information it pr=
esents about these interchangeable coincident stereo setups. I have found s=
ome very lucid quotes in regards to my original post:
>
> (these are from the polar plot comparison section of the paper, looking a=
t XY recording angles)
>
> about Cardioid
> "Due to the fact that cardioid microphones record sound from all directio=
ns in phase the audio recorded from the rear is not side inverted."
>
> about Super-cardioid
> "Supercardioid microphones invert the phase of any signal originating 120=
degrees or more off the microphone axis." Therefore, "At [XY recording] a=
ngles below 120 degrees the signal recorded from the rear are side inverted=
and above 120 degrees they are not."
>
> Very cool! So, as has already been mentioned in this thread (thank you Mi=
chael Raphael), it is the phase-inverted rear lobe of the super-cardioid mi=
crophone that is causing these stereo imaging problems. If I had a pair of =
MKH50's setup in an XY configuration and attempted an equivalent 360 degree=
walk around test I would (it seems) experience the exact same thing.
>
> -Justin
>
>
> --- In "rock_scallop" <john_hartog@> wr=
ote:
> >
> > Hi Justin,
> > It is interesting, in the many times super-cardiod has been mentioned o=
n this group as a possible option in an MS setup, the expected convolution =
of the stereo image has not really been explored until now.
> >
> > In your localization test, I heard something similar to what Jos=E9 des=
cribed - though for the sake of interpreting the effect I will assume a the=
oretical L/R symmetry for this array configuration.
> >
> > The frontal stereo image becomes expanded, and the maximum perceived wi=
dth occurs somewhere between 10 and 2 o'clock. At 11 to 1 o'clock the image=
seems stretched from 60 degrees on location to around 90 degrees in playba=
ck. In this frontal wedge, the relative side to side localization of subjec=
ts might be fairly accurate. Though I think it is like stretching a rubber =
band: as the width is expanded the depth becomes thinned. To the sides an=
d back, including 10 and 2 o'clock and beyond the image becomes severely tw=
isted.
> >
> > All arrays distort the image in one way or another, so I am not discoun=
ting super-cardiod MS as useful technique for stereo nature recording - tho=
ugh be extra careful with any content outside the angle of focus.
> >
> >
> > John Hartog
> > rockscallop.org
> >
> >
> >
> >
> > --- In "freitojos" <josefreitas81@> w=
rote:
> > >
> > >
> > > In my stereo speakers in a equilateral triangle 2mts 90=BA speakers.=
12 was 0=BA in front, 1 was 45=BA my right 2 35=BA right, 3 20=BA right 4=
10=BA right 5 10=BA left 6 was as 2 but far away 7 was 20=BA left 8 was 25=
=BA left 9 30=BA left 10 45=BA left and 11 12 0=BA in front.
> > > I hope this helps,
> > > Jos=E9
> > >
> > > --- In "ajustend" <ajustend@> wrote=
:
> > > >
> > > >
> > > >
> > > >
> > > > Here is a link to the recording I made:
> > > >
> > > > http://soundcloud.com/justinmullens/ms-test-mkh30-50-handsofclock
> > > >
> > > > -Justin
> > > >
> > > > --- In "J. Mullens" <ajustend@> w=
rote:
> > > > >
> > > > > Hi, this is my first post to Nature Recordists.
> > > > >
> > > > > I have just added an MKH 30 to my collection in order to expand i=
nto MS
> > > > > recording and am experiencing very bad imaging (side swapping) wi=
th the
> > > > > setup when the sound source is located in certain places behind t=
he
> > > > > microphone.
> > > > >
> > > > > To clarify, I am *not *trying to record a surround signal using a=
stereo
> > > > > mic setup, but I *am *interested in maintaining a correct left-ri=
ght stereo
> > > > > image. When I use an XY setup, or an XY mic like a BP4025, anythi=
ng on the
> > > > > left side of the mic (in front of it or behind) will playback out=
of the
> > > > > left speaker. Using the MKH30/50 combo this is not the case.
> > > > >
> > > > > Here is the test I conducted: Set the microphones up in the middl=
e of an
> > > > > open field so that I can walk in a full circle around it. I start=
directly
> > > > > in front of the M/S setup, about 15-20 feet away, and walk in a c=
lockwise
> > > > > direction around mic calling out each position on the clock face.=
12 is
> > > > > directly in front, 1, is to the right of that, 3 is directly to t=
he right,
> > > > > 6 is directly behind, 9 is directly to the left side, etc.
> > > > >
> > > > > Here's the problem, when I get to the 4 & 5 o'clock postions (rea=
r right
> > > > > side) the sound source swap sides and sounds like it is coming fr=
om front
> > > > > left. And the exact opposite happens to the 7 & 8 o'clock positio=
ns
> > > > > sounding like they are coming from the front right.
> > > > >
> > > > > Again, any source originating in the 180 degree arc in front of t=
he setup
> > > > > performs beautifully and the stereo image is perfect. It only hap=
pens to
> > > > > sounds coming from behind the mics, and if a sound source is maki=
ng a
> > > > > constant tone you can actually hear it jump diagonally across fro=
m one side
> > > > > of the stereo field to the other as it enters these rear right & =
left areas.
> > > > >
> > > > >
> > > > > After asking around it has come to my attention that the closer y=
our Mid
> > > > > mic is to a pressure-gradient mic (figure 8 polar pattern), the m=
ore of a
> > > > > rear lobe you have, and thus the more chance you have of that rea=
r lobe
> > > > > picking up sound in the opposite channel. This definitely explain=
s how, and
> > > > > why, I could be experiencing side swapping.
> > > > >
> > > > > Since I've never used an MS setup with a pure cardioid mic I am w=
ondering
> > > > > if the same thing happens... For those using a Sennheiser 30/40 =
MS setup:
> > > > > does this happen? Do you have side swapping in the 4-5 o'clock an=
d 7-8
> > > > > o'clock positions?
> > > > >
> > > > > Nature recording is, for me, one of the areas where a really accu=
rate
> > > > > stereo image in a 360 degree circle around my recording location =
is
> > > > > critical. I am always pointing my mics at the source I am recordi=
ng, but
> > > > > having sounds behind the mic appearing in opposite channel is jus=
t weird.
> > > > > How do the MS recordists on this forum deal with this?
> > > > >
> > > > > Thanks!
> > > > >
> > > > > -Justin
> > > > >
> > > > >
> > > > >
> > > >
> > >
> >
>
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