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Author Topic: Honey, I broke the M/S array(?)  (Read 1044 times)

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Offline voltronic

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Honey, I broke the M/S array(?)
« on: November 08, 2023, 08:39:34 PM »
I had a very strange result after using a friends pair of 414s in M/S. See the link to GS below for the whole explanation and samples. Does anyone have any idea what could have happened?

https://gearspace.com/board/remote-possibilities-in-recording-amp-production/1417064-what-went-wrong-m-s-array.html
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Offline lsd2525

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Re: Honey, I broke the M/S array(?)
« Reply #1 on: November 09, 2023, 08:58:30 AM »
i know you had the polar patterns set correctly; is it possible that you had the mic positions reversed?
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Offline goodcooker

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Re: Honey, I broke the M/S array(?)
« Reply #2 on: November 09, 2023, 09:41:13 AM »

I gave this a quick listen this morning in the headphones - not a critical listen but with a good pair of Beyerdynamic DT880s.

The sound field seems bunched up on the right in the Gerzon array sample (that I assume is your "control" sample) also. I thought at first that since the piano intros the piece that it was located to the right and that's why but after the choir starts it still seems to "lean to the right" in both the OG MS sample and the Gerzon array sample. It may just be how it sounded in the room and if you were there your brain corrected for the imbalance.

Was this straight into an F6? Have you checked your settings like gain and pan in your deck?
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Offline rocksuitcase

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Re: Honey, I broke the M/S array(?)
« Reply #3 on: November 09, 2023, 10:46:05 AM »
volt,
perhaps another more experienced mic guy will pitch in her, but to me this sounds like a classic, the fig 8 polar pattern has "degraded" inside one or both of the mics. This IS possible with multi pattern mics in a few manners. 1] the electronics are messed up with the selector switch and omni sounds great but fig 8 does not (opposite sides of the selector switch 2] The capsule(s) itself may be degraded 3] XLR connector damage (as in wire slightly unsoldered, etc), although would probably manifest with other symptoms.
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Offline voltronic

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Re: Honey, I broke the M/S array(?)
« Reply #4 on: November 09, 2023, 03:56:20 PM »
i know you had the polar patterns set correctly; is it possible that you had the mic positions reversed?

Good thought, but no. See photo confirming the mid mic was set to cardioid (not great resolution but it's the center selection on a 414).
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Offline voltronic

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Re: Honey, I broke the M/S array(?)
« Reply #5 on: November 09, 2023, 03:59:37 PM »

I gave this a quick listen this morning in the headphones - not a critical listen but with a good pair of Beyerdynamic DT880s.

The sound field seems bunched up on the right in the Gerzon array sample (that I assume is your "control" sample) also. I thought at first that since the piano intros the piece that it was located to the right and that's why but after the choir starts it still seems to "lean to the right" in both the OG MS sample and the Gerzon array sample. It may just be how it sounded in the room and if you were there your brain corrected for the imbalance.

Was this straight into an F6? Have you checked your settings like gain and pan in your deck?

I'm curious to hear if you have the same impression listening on speaker / monitors and especially if you feel that way on Lullaby, which is a capella. The piano was hard right, pass the right boundary of the choir. Sopranos left, Basses right, Altos center, tenors behind Altos.

Yes, direct into F6 and I've had two channel pairs ganged together since the day I've owned the unit. I will fire it up and double check though.
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Offline voltronic

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Re: Honey, I broke the M/S array(?)
« Reply #6 on: November 09, 2023, 04:01:11 PM »
volt,
perhaps another more experienced mic guy will pitch in her, but to me this sounds like a classic, the fig 8 polar pattern has "degraded" inside one or both of the mics. This IS possible with multi pattern mics in a few manners. 1] the electronics are messed up with the selector switch and omni sounds great but fig 8 does not (opposite sides of the selector switch 2] The capsule(s) itself may be degraded 3] XLR connector damage (as in wire slightly unsoldered, etc), although would probably manifest with other symptoms.

The first two situations were what I was suspecting.

I just texted my buddy who's going to drop off the mics and cables tonight so I can do some controlled testing.
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Offline Gutbucket

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Re: Honey, I broke the M/S array(?)
« Reply #7 on: November 09, 2023, 05:25:53 PM »
Started replying after listening on headphones this morning and got pulled away, so some of what is below has been covered, such as the questions about source layout and Mid pattern.  Gotta run now, without time to edit what I typed earlier. My first thought was same as Rock's in wondering about the symmetry of response of the fig-8 pattern (as its a dual diaphragm type)..


A few baseline questions: 
What was the physical layout of chorus and piano in relation to the microphone position, and where specifically was the Mid pointed in relation to that?  What pattern as used for Mid?

My initial observations (on SoundPros SP-HP1 headphones, may check on Senn HD650 tonight)-
In the Gerzon I hear piano right and chorus distributed across the stereo image, with some specific women's voices weighted more strongly to the left.  I like the delta-t / phase content from the near-spacing, although I hear the Gerzon as generally right heavy, and slightly weak in the center.  Makes me wonder what the spaced omni pair sounds like as a point of comparison.  The delta-t / phase content content somewhat makes the general right heaviness less problematic than it might otherwise be in a coincident array.

The Mid/Side is less wide overall and more center-heavy, which is expected from a Mid/Side pair (somewhat depending on Mid pattern).  But agreed that there is some oddness going on.  Your panning correction may be partly correcting the baseline weighting also apparent in the Gerzon.

Have you taken a look at it using a goniometer (lissajous display / vector display)?  You know, the spaghetti looking visual display?  That's likely to be of help in digging deeper here.  Advanced versions differentiate by frequency range, but you could use a typical one after a peaking parametric EQ filter (inverse notch filter) and see what happens on the display as you sweep the frequency around to get an idea of what's going on by frequency range.

This may get some eye rolls, but I carry a small dog clicker in my recording bag.  I don't always use it, but when I get a chance its useful and fun to walk all the way around the recording position clicking at each of the 12 points of the clock (and announcing the positions when possible).  The resulting short test recording can be very useful for diagnosing problems like this, and how actual directions translate in the playback imaging.  Started doing that when working up surround methods, but its very useful for stereo too.
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Offline goodcooker

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Re: Honey, I broke the M/S array(?)
« Reply #8 on: November 09, 2023, 05:52:41 PM »
Regular people call this a Phase Scope - "You know, the spaghetti looking visual display?"- so do the people at Steinberg.

I use the Phase Scope full time in Wavelab6. I'll have a look at it tonight when I give a listen to the a capella piece and the other over the monitors. I try to be cognizant of how my brain will interpret the stereo image (like the piano intro on the right making me think the whole performance is off center because of first impression) even though the scope and other data shown in my editing software doesn't support what I'm hearing (or interpreting what I'm hearing).
« Last Edit: November 09, 2023, 10:49:28 PM by goodcooker »
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Offline voltronic

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Re: Honey, I broke the M/S array(?)
« Reply #9 on: November 09, 2023, 08:22:00 PM »
First some setup points:

Choir was in a 2-row arc, with Sopranos left, Altos center, Basses right, and Tenors behind Altos and slightly right of center. Piano was far right, behind the Bass side of the arc. So to my ears, everything sounds as it should with the Gerzon pair though I agree with Gut it may be a bit center-light. I might post these excerpts with the wide omnis and just the mid cardioid after I can get a balance that sounds decent.

I just did some testing (copying below from GS):

OK, I just finished some tests. First I did what you just suggested, and can confirm that the nulls are quite deep on both mics when set to fig8, so nothing seems wrong there. I used a GAC-3 single channel cable direct into my MOTU M2, recording in Reaper to remove the cable and recorder variables.

Then I tested the TGS-02 cable pair (all good), set up a M/S array and did a walk-around recording, announcing the different positions. It came out perfectly. Direct to DAW, two mono tracks decoded using a manual matrix.

I repeated the second test recording to my F6, imported the tracks into Reaper, and decoded with MSED. Perfect once again.

I checked my photos to make sure I hadn't swapped cable channels at the mics, and then thought I should confirm I hadn't swapped cables at the recorder. So I ran the test a third time, and even though I got the expected phase cancellation, L/R still imaged correctly when decoded.

So the mics are fine, the cable I used was fine, and my setup was correct at the concert.

I am at a loss as to why the concert recording came out so badly.
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Offline Gutbucket

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Re: Honey, I broke the M/S array(?)
« Reply #10 on: November 13, 2023, 12:54:07 PM »
I intended to take another listen and potentially a deeper look over the weekend but didn't find the time.  Any additional insight since last Thursday?

Regular people call this a Phase Scope - "You know, the spaghetti looking visual display?"- so do the people at Steinberg.

Your statement implies the folks at Steinberg aren't regular people.  ;)

The visual oscilloscope type "spaghetti display" (or alternately a point cloud or color field type display) visualizing the changing phase relationship between two channels with a degree of visual persistence goes by a few different names.  Searching both "audio goniometer display" and "audio phase display" will immediately bring up images of what we are discussing. The terms are used interchangeably.
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 voltronic

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Re: Honey, I broke the M/S array(?)
« Reply #11 on: November 13, 2023, 07:46:33 PM »
I intended to take another listen and potentially a deeper look over the weekend but didn't find the time.  Any additional insight since last Thursday?

Not really; it's quite a mystery. Many variables have been eliminated, and the mics test perfectly at home. If you look back at the GS thread, one user suggested that there might be intermittent polarization voltage to the rear diaphragm which sounds plausible but I can't replicate the symptoms. Maybe it's behaving while I'm closely examining it?

 I'm looking at my photos from the concert again, and I have that mid cardioid pointed dead straight ahead. There's no explanation for what is pulling the image so strongly off-center.
I am hitting my head against the walls, but the walls are giving way.
- Gustav Mahler

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