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Author Topic: M/S with two Figure 8's  (Read 1316 times)

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Offline Derp1

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M/S with two Figure 8's
« on: November 09, 2023, 05:12:36 PM »
Anyone have any experience with a figure 8 as mid? Ive had good luck with cards, hypers and omni's but Im thinking about trying this from a "tapers section" type distance this weekend.
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Offline mepaca

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Re: M/S with two Figure 8's
« Reply #1 on: November 09, 2023, 05:20:29 PM »
Yes, It effectively turns it into a Blumlein setup with the ability to widen or narrow the stereo pattern. Also, it does not reverse the patterns from front to back as Blumlein does. I have also used an omni for the mid channel for a 2 lute concert.

Offline heva

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Re: M/S with two Figure 8's
« Reply #2 on: November 11, 2023, 03:18:16 PM »
It’s the first method using (bi)directional mics as described/patented by Alan Blumlein

Offline Gutbucket

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Re: M/S with two Figure 8's
« Reply #3 on: November 13, 2023, 10:44:05 AM »
Maybe more info than you want!..

M/S using a fig-8 mid decodes to X/Y Blumlein.

A Blumlein pair is fully omnidirectional in the horizontal plain, with no forward sensitivity bias. It's just as sensitive to sound arriving from the rear and sides as it its to sound arriving from the front. Think of it like an omni in that sense.  Because of that it typically works best in a good sounding room from a recording position relatively close to the source, in order to avoid having the recording dominated by hall reverberence.  From a "taper section" type distance I'd use a cardioid or supercardioid Mid, as that will provide more forward sensitivity bias which is likely needed from a recording position that is further back. 

Generally, a fig-8 Mid works in the same way any other M/S arrangement.  The one thing that is unique about it is that because both Side and Mid are fig-8 patterns, only the inclusive angle between the virtual X/Y pair changes as you alter the Mid/Side ratio.  The pattern of the virtual crossed pair will always consist of a pair of virtual fig-8's. This is different than any other Mid pattern where the virtual pattern morphs between whatever the Mid pattern is (at 100% Mid, mono) and 180° angled fig-8's (at 100% Side). 

At a 50/50 ratio, a Mid/Side pair using a cardioid Mid provides the most forward bias, decoding to something like a virtual pair of 90° crossed supercardioids.  A supercardioid Mid at 50/50 ratio will decode to something with a bit less forward bias, more like a pair of 90° crossed hypercardioids, and will sound more Blumlein-like.  That little bit of forward bias might be just enough to help with needed clarity if the recording position isn't really close enough or the room good sound enough for Blumlein to shine. 

To complicate this a bit, from a distance, the apparent width of the stage and PA is going to be narrow, so it might actually work best to use a supercardioid Mid to get the needed clarity, along with a Mid/Side ratio of less than 50/50, which will narrow the angle between the virtual pair and thus increase forward bias at the expense of some stereo width, somewhat compensated for by the change from cardioid to supercardioid Mid.

In general I prefer coincident pair stereo from closer recording positions, where its possible to get sufficient angle between microphones without them being pointed overly far off axis, and configurations that rely more on spacing along with less angle between microphones, from recording positions that are further away, unless doing something like combining both approaches in an array.
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Offline Gutbucket

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Re: M/S with two Figure 8's
« Reply #4 on: November 13, 2023, 10:49:56 AM »
Yes, It effectively turns it into a Blumlein setup with the ability to widen or narrow the stereo pattern. Also, it does not reverse the patterns from front to back as Blumlein does. I have also used an omni for the mid channel for a 2 lute concert.

Sorry, but the bolded part is incorrect. With a fig-8 Mid, image placement of sound sources behind the recording position will be flipped right/left upon stereo playback, just like with Blumlein. 

But (conversely)..

Using an omni Mid, the placement of sound sources behind the recording position will not be flipped right/left upon stereo playback.  When altering ratio, the angle between the virtual microphone pair always remains 180° and does not change, but the virtual polar pattern morphs between omni at 100% Mid (mono) and 180° angled fig-8's at 100% Side.

So they behave oppositely in that way, yet are similar in that both a fig-8 Mid and and omni Mid will produce a stereo pair that has omnidirectional horizontal sensitivity without any forward bias.  If you need forward sensitivity, use a cardioid or supercardioid Mid.
« Last Edit: November 13, 2023, 10:53:40 AM by Gutbucket »
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Offline ArchivalAudio

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Re: M/S with two Figure 8's
« Reply #5 on: December 03, 2023, 04:04:24 AM »
While it's not M/S using two Figure 8's  one of my favorite arrays is the "Faulkner" array, which is two figure 8 microphones spaced at 20cm  pointing straight ahead. I usually run mine  (Milab DC 196's ) @ 36 cm and slightly angle the front lobes of the 8's toward the left and right. this gives a overall full sound space it is a wonderful way to run a pair of Figure8's
see:
http://www.sengpielaudio.com/TonyFaulknerPhasedArray01Engl.pdf
and this
https://martinmitchellsmicrophones.wordpress.com/2022/03/17/the-faulkner-phased-array-another-useful-stereo-microphone-technique/

for example

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Offline voltronic

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Re: M/S with two Figure 8's
« Reply #6 on: December 03, 2023, 06:03:32 AM »
While it's not M/S using two Figure 8's  one of my favorite arrays is the "Faulkner" array, which is two figure 8 microphones spaced at 20cm  pointing straight ahead. I usually run mine  (Milab DC 196's ) @ 36 cm and slightly angle the front lobes of the 8's toward the left and right. this gives a overall full sound space it is a wonderful way to run a pair of Figure8's
see:
http://www.sengpielaudio.com/TonyFaulknerPhasedArray01Engl.pdf
and this
https://martinmitchellsmicrophones.wordpress.com/2022/03/17/the-faulkner-phased-array-another-useful-stereo-microphone-technique/

for example

Thanks for linking that article with the original 1981 HFNRR writeup TF did. I had not seen that before.
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Offline heva

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Re: M/S with two Figure 8's
« Reply #7 on: December 03, 2023, 01:56:10 PM »
Do note that TF also writes about adding a center blend to the 20cm spaces pair of fig8s

Offline voltronic

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Re: M/S with two Figure 8's
« Reply #8 on: December 03, 2023, 04:44:49 PM »
Do note that TF also writes about adding a center blend to the 20cm spaces pair of fig8s

I saw that. Very interesting given the close spacing of the array to start with.
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Offline Gutbucket

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Re: M/S with two Figure 8's
« Reply #9 on: December 04, 2023, 11:42:51 AM »
I usually run mine  (Milab DC 196's ) @ 36 cm and slightly angle the front lobes of the 8's toward the left and right. this gives a overall full sound space it is a wonderful way to run a pair of Figure8's.

Similarly I've long thought near-spaced fig-8's might be an attractive technique for concert tapers, because the fig-8 pattern should be able support a narrower spacing / angle combination than any other pattern.  Sort of narrow Blumlein with a bit of spacing to compensate for less angle.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline EmRR

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Re: M/S with two Figure 8's
« Reply #10 on: December 04, 2023, 08:33:12 PM »
I like to refer to the words of Rolo 46 over at Gearspace, who recorded classical and TV/Film sound:

Quote
M carries the weight of the music
S provides space and the stereo field info
As long as M is within its critical distance you will render an effective stereo image
Omni M is wide angle, little proximity, close critical distance
Card M is portrait, medium proximity, medium critical distance
Fig 8 M is telephoto, hi proximity, long critical distance.

Quote
What is Critical Distance? In every room, there is a distance (measured from the talker) where the direct speech and the reflected (or reverberant) speech are equal in intensity.


Stage versus PA sound will shift what's desired, depth of room and back wall slap will shift what's desired, etc.

I find MS with 8's to offer greater options when needing to narrow the image to reduce ambience.  Usually.  Sometimes PAS is what you want, and with clean/quiet sounding rear image, coincident 8's at the appropriate PAS angles will sound closer than other directional patterns, with better bass, and cleaner than short shotguns. 
« Last Edit: December 09, 2023, 06:08:20 PM by EmRR »
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Offline Gutbucket

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Re: M/S with two Figure 8's
« Reply #11 on: December 05, 2023, 10:05:16 AM »
^ That's excellent!

Only clarification I'd note is that distance is relative. "Long critical distance" isn't really that far, at least in terms of audience and section taping.. although a PA does dramatically extend the critical distance. ..and it skips over my go-to taper Mid, which is a supercardioid, producing a sort of forward-biased Blumlein, arguably more "telephoto" than a fig-8 Mid.

I recently picked up a short M/S AT shotgun to try in its place.. although part of my interest is in how well it's  fig-8 Side channel (derived from back to back cardioids I believe) compares to the Naiant X8S I'm using.  So I intend to try my go-to supercard as Mid with that AT shotgun Side as a point of comparison as well.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline grawk

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Re: M/S with two Figure 8's
« Reply #12 on: December 05, 2023, 10:19:19 AM »
my concern with fig 8 as the mid is the rear lobe puts the room way more in play
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Offline Gutbucket

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Re: M/S with two Figure 8's
« Reply #13 on: December 05, 2023, 12:17:02 PM »
Yeah, that's why I feel a supercard mid is more "telephoto-ish" than a fig-8 mid... at least out near or beyond the critical radius where managing the direct/reverberant ratio becomes the most important thing.

I think a lot in terms of how the combined pattern of Left and Right together pick up reflected and reberberant engergy from the whole room, and in that sense a figure-8 mid produces a combined sensitivity pattern which is omnidirectional overall*.  Some degree of forward bias in that overall combined sensitivity pattern is really valuable most of the time.

[*edit- well, it's omnidirectional when a 50/50 M/S ratio is used.  More relevant is that the front/back sensitivity bias of the combined sensitivity pattern using a fig-8 mid remains equal regardless of ratio - it just shifts from omnidirectional to ellipsoid to figure-8 shaped as less Side is used]
« Last Edit: December 05, 2023, 04:26:35 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline EmRR

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Re: M/S with two Figure 8's
« Reply #14 on: December 09, 2023, 06:06:01 PM »
my concern with fig 8 as the mid is the rear lobe puts the room way more in play


it really depends on the space....sometimes the rear is like a black hole and there's nothing there. 

Plus...again...add an omni in between and now you have horizontal only ambisonics if you want it. 
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Recorders: Zoom F8n, Sony MZ-R50

 

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