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Author Topic: XY Greater than 90 Degrees?  (Read 1574 times)

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Offline Gutbucket

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Re: XY Greater than 90 Degrees?
« Reply #30 on: January 20, 2020, 01:53:18 PM »
With regards to adjustment of Mid/Side ratio of an X/Y recording (as well as direct recording in Mid/Side), I think it helps to think of the actual pickup pattern of the physical microphones and the setup angle between them, verses the virtual microphone patterns and angle between them which result from the Mid/Side ratio used.  If the Mid/Side ratio is altered, the virtual patterns and angle will differ from the actual microphone patterns and X/Y angle.

Using the term virtual helps keep the relationship between the physical microphone configuration and the virtual output configuration straight in my mind.

Bringing this back around to the original topic..
I found one of the most interesting things to mess around with when listening back to an ambisonic recording is changing the virtual microphone pattern/angle relationship.  With an ambisonic recording, the stereo output produced is always some virtual X/Y stereo pair. Output can be thought as being a choice between various combinations of a virtual pair of microphone patterns and inclusive angles between them.  What makes it different than Mid/Side in this respect is the inclusion of the omni microphone 3rd or 4 channel which effectively allows one to change virtual angle independently of virtual pattern, and vice-versa.  So one can hear what changing the virtual angle between microphones sounds like while the virtual pattern is held constant.

For example, one can choose a pair of virtual cardioids and play with various angles between them without altering the cardioid pattern.  Alternately one can hold the virtual angle between microphones constant while adjusting the shape of the virtual pickup patterns.

Doing this with "typical taper scenario room recordings" I found I generally ended up gravitating to virtual pickup patterns which landed somewhere between supercardioid and hypercardioid, with a typical inclusive angle of anywhere from around 110 to 120 degrees or so.  With cardioids I needed a 130-140 degree angle in an attempt to achieve a similar stereo-width and ambient-openness, yet the microphones were then typically too far off-axis from the source.   A subcardioid pattern with a 150 degrees or so angle seemed to work better than cardioids most of the time, and I'd frequently find myself going back and forth between virtual super/hypercard-like patterns with a more narrow angle between them and virtual subcardioids with a wide angle between them, homing in on what sounded best.

I ended up thinking a lot about a seemingly inherent "cardioid compromise" that defines the less attractive region between the above points on the continuum of X/Y patterns and angles. A few times I combined the two, using a wider angled pair of virtual subcardioids for low frequencies transitioning to a pair of more narrowly angled virtual hyper-cardioids at high frequencies.
« Last Edit: January 20, 2020, 02:14:22 PM by Gutbucket »
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Offline Gutbucket

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Re: XY Greater than 90 Degrees?
« Reply #31 on: January 20, 2020, 02:13:19 PM »
^My intention in posting this is not so much as an endorsement of ambisonics, but rather as a way to share what was for me a rather enlightening exploration of the general relationship between X/Y pickup-pattern and microphone angle.  Pretty much the only time I ended up liking a 90 degree virtual angle was with very hypercardioid-ish pattern that approached figure-8. 

Interestingly, I generally liked a somewhat smaller angle than the standard 90-degree specified as Blumlien for crossed fig-8s, sometimes as narrow as 70 degrees.  That helped better define a solid center, yet most of the time overall pickup of crossed-8s didn't provide enough forward sensitivity bias in typical taper scenarios, and something between supercardioid and hypercardioid tended to work better.
« Last Edit: January 20, 2020, 02:27:00 PM by Gutbucket »
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Offline EmRR

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Re: XY Greater than 90 Degrees?
« Reply #32 on: January 20, 2020, 03:17:25 PM »
^ yup to that.
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Offline DSatz

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Re: XY Greater than 90 Degrees?
« Reply #33 on: January 20, 2020, 07:19:49 PM »
^ yup to that as well.

Despite certain ideal properties, in my work it has been rare that Blumlein was the most fitting solution. It has a relatively narrow stereo pickup angle, yet requires closer placement to the sound sources than most other types of setup because of the large amount of room sound that it naturally picks up--the rear lobe of a figure-8 being equally as sensitive as the front lobe, of course. And of course the closer you get to your sound sources, the wider the angle they represent from the microphones' point of view.

--best regards
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Offline vantheman

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Re: XY Greater than 90 Degrees?
« Reply #34 on: February 07, 2020, 05:24:29 PM »
I took the XY 110 rig for a spin last weekend in Las Vegas for Van Morrison. All in all I’m pretty happy with the results, you can check it out here: https://drive.google.com/drive/folders/12u6Kxxg9-95TfLRjAPyYh5BwKnjxkzLg

I was front row balcony dead center in line with the center stack, and you’ll see that the music is pretty center heavy. It’s almost like a M/S recording, so mastering it was pretty straightforward once I realized this, as it harkens back to my MV88 days.

In this case I dropped the low mid range frequencies of the sides by about 6db, in an attempt to reduce the chatter, which isn’t all that bad to begin with. I lost hardly any musical information by doing this, maybe just a tad bit of “air”.

What I’m wondering is, what if anything did I really gain by going with 110 instead of 90? Yes, there is a nice stereo effect with the audience off to the sides, but I found myself wanting more center. Do you find that too? Due to where I was positioned, I only stood to capture one stack anyway.

These are things I’m considering before he comes up to Oakland next week. My approach for those shows will be pretty similar, just thinking about mic angle.
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Offline Gutbucket

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Re: XY Greater than 90 Degrees?
« Reply #35 on: February 10, 2020, 01:13:03 PM »
Sounds good here, listening on cheap Samsung phone headphones straight out of the computer.

What I’m wondering is, what if anything did I really gain by going with 110 instead of 90? Yes, there is a nice stereo effect with the audience off to the sides, but I found myself wanting more center. Do you find that too? Due to where I was positioned, I only stood to capture one stack anyway.

I suspect the 110 angle helped achieve the "nice stereo effect with the audience off to the sides" aspect you describe. I don't detect any lack of center, but I'm not listening over speakers where I'd prefer to make that kind of critical judgement.

If you plan to re-adjust stereo width in post with a M/S ratio adjustment anyway, you can let the geometry of the recording location relationship to the PA be the biggest influence in determining the X/Y microphone angle. Capture maximum clarity by keeping the microphones angled so that they are relatively close to on-axis from the PA source(s), then adjust virtual angle afterward to achieve the wider stereo effect with the audience off to the sides, but limit the ratio readjustment to the extent that sufficient center clarity and focus is retained.

If you are in a recording position where most of the energy is coming from a single PA stack position in front of you, a narrower (say 90 degree) X/Y angle combined with increasing Side ratio afterwards to achieve a similar perception of width as recording with a 110 degree X/Y angle and no ratio readjustment might be a good bet. 

Just remember to keep both the actual X/Y microphone angles and the ratio readjustments made afterwards within a reasonable range.  This method of optimizing for one aspect when recording, then optimizing for another when mixing afterwards can work quite well until it is pushed overly far.  In order for you to be able to increase either Side or Center contribution later, there has to be a sufficient amount of it in the raw recording ito start with.  If you were to start with a zero-degree X/Y angle because that would place the microphones on-axis with the only significant PA stack located directly in front of you, the recording will have no significant Side information at all, and there will be no Side information captured that you can emphasize later.
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<<

 

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