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Author Topic: Three mics - two cards XY and one omni. Working?  (Read 822 times)

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Offline Popmarter

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Three mics - two cards XY and one omni. Working?
« on: June 02, 2021, 02:37:13 PM »
Picture this.
 >:D situation. Typical 500 people venue, black box. Hanging PA and some on stage.
Cards in XY setup and one  omni mic above it. FOB.

XY could be a bit thin, lacking low end, they say. Not sure if that would be the case in this scenario. If so, would a third omni mic help in this situation? Or be necessary? Any experiences?
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Offline fireonshakedwnstreet

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Re: Three mics - two cards XY and one omni. Working?
« Reply #1 on: June 02, 2021, 04:33:32 PM »
I did this in an awful room (bar) for the same reason and debated whether or not to even use the omni in the final mix. I ended up mixing it in -10 db. I knew there would be a lot chatter so ended up recording just the background noise and used noise reduction -3db and it seemed to help. You also have the option of EQing the bass up (or putting a warm plugin) on the cards. I'd say more channels is more options!
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Offline Gutbucket

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Re: Three mics - two cards XY and one omni. Working?
« Reply #2 on: June 02, 2021, 07:34:34 PM »
Well, you can always record it all to separate tracks and figure it out if it was worthwhile later by playing around with it in various ways.  You don't have to use it all.  I'm a big proponent of that. Its a good way to learn what works and what doesn't.

It makes sense to low-pass the omni afterward and just use it to fill in where the cardioid response drops off.  No one will call you crazy for doing that.  But it may not be that useful in an awful room.

If you aren't low-passing the omni you'll get a lot of monophonic reverberance.  A cardioid pattern is 50% omni and 50% bi-directional, so you have a lot of omni already without any spacing between coincident X/Y elements to decorellate the reverberant pickup. You really need to increase the angle between X/Y cardioids to compensate even without the omni, but that's problematic in a bad room. 

In general if I was recording an omni too and not low-passing it I'd want to space the cardioids out more than I would otherwise..  and if I did that I'd feel free to use less angle between the cardioids in a Point At Stacks arrangement that would be likely to work much better in an awful room.  In a bad room I'd Point At Stacks with sufficient spacing between mics to compensate for the narrow angle.. regardless of any omni or not (and probably not). 

If stuck with X/Y for whatever reason, consider vertical spacing on the stand, with the omni up a lot higher than the X/Y pair.  That will decorellate the high and mid frequency room pickup of the omni in comparison the the X/Y pair at least.
 
 
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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 crackmc

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Re: Three mics - two cards XY and one omni. Working?
« Reply #3 on: June 02, 2021, 10:47:59 PM »
i’ve been toying with the idea of running split omnis w/ a cardioid in the center
or AB hypers with an omni in the middle
or a pair of __________ in a ___________ config with a __________ in the middle
…and encoding them to mid-side


i’ve been mildly obsessed since seeing the Reaper YouTube tutorial mid-side video
you'll love it
it's a way of life

Offline dyneq

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Re: Three mics - two cards XY and one omni. Working?
« Reply #4 on: June 02, 2021, 10:50:40 PM »
Since we’re talking LTO (less than open), I agree with Gutbucket that PAS with cards would work well. I use this method with a fixed distance and angle and try to position where the angle matches the stacks. If you can maximize proximity effect by getting closer, you will have more to work with in post.

Full PAS thread for reference (thanks, Gutbucket!):
https://taperssection.com/index.php?topic=167549.0

Offline Gutbucket

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Re: Three mics - two cards XY and one omni. Working?
« Reply #5 on: June 03, 2021, 09:58:04 AM »
^ I like dyneq's approach.
I overlooked the OP comment that this is a >:D situation, so the option of placing the omni high above the X/Y pair is obviously out.

I'd say go with near-spaced PAS cardioids from the center of the sweet spot up front if you can.  If X/Y, move a bit closer without placing yourself forward of the horizontal high-frequency radiation pattern drop off of the PA, which essentially defines the forward edge of the sweet spot.  That position will best fit the wider pickup angle of X/Y, and the proximity and impact there with a predominance of direct-sound will make the tendency toward a more monophonic ambient pickup and the need for the omni to extend bass response less important.


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 Popmarter

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Re: Three mics - two cards XY and one omni. Working?
« Reply #6 on: June 05, 2021, 04:35:19 AM »
Thanks for the replies. I read the PAS piece from Gutbucked, excellent although bit too dufficult to understand complete.

I was running into some phase issues running PAS as mics (nevaton) were rather close to each other (10 cm). so i might try XY someday to see that fix things in those situations.
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Microphones: Nevaton MC59/S (cards); Milab VM-44 Links (cards), AT853 7.4mod (cards); AT831 (cards); Nakamichi CM300 (all CP's); Soundman OKM II Rock Studios
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Offline Gutbucket

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Re: Three mics - two cards XY and one omni. Working?
« Reply #7 on: June 07, 2021, 12:10:54 PM »
Here's the basic gist:

In less than ideal acoustic situations, it pays to make efforts toward getting the clearest recording of the PA as possible.  Good clarity is more important than a nice wide stereo image.  Easiest way to do that is get closer, and point a pair of directional mics directly at the PA speakers.  When you do that you'll find that in many situations the resulting angle between the microphones isn't very large, often less than 90 degrees.  So in the interest of making an even better recording with decent stereo qualities in addition to good clarity, it helps to use more spacing between microphones to compensate for the overly narrow angle between them.  The whole improved PAS thing is all about determining the most appropriate spacing based on whatever the angle between mics ends up being when you point them at the PA speakers.  As the angle becomes narrower, the spacing becomes greater, and vice-versa.  That increased spacing helps to improve the stereo qualities.  It can also help reduce problematic phase interaction problems.  It will at least shift the comb filtering around in frequency, possibly making it less audibly problematic.

X/Y takes that the opposite direction.  Because there is less spacing between microphones (none at all), phase differences between channels are minimized.  Ideally you would want to use increased angle between the microphones to retain good stereo qualities, but that may point the microphones well outside the PA making clarity suffer.   However, if you find that a coincident X/Y configuration solves the phase interaction problems that may be more important to you than getting a wider stereo image.  If you are okay with the more narrow/monophonic stereo quality that results from X/Y using a relatively narrow angle needed to keep the mics pointed toward the PA so as to retain clarity, no problem. You might then play with how wide you can angle the mics while still retaining sufficient clarity from the PA.
« Last Edit: June 07, 2021, 12:29:34 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 heathen

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Re: Three mics - two cards XY and one omni. Working?
« Reply #8 on: July 06, 2021, 06:01:36 PM »
Can you set up the omni so that it's on the other side of your body from wherever the XY mics are?  Like using your body as a baffle between the XY pair and the omni?  Maybe that could help create another type of decorrelation.  Also since the low frequencies you're trying to cover with the omni aren't all that directional, it shouldn't matter if the omni is, for example, mounted on your back.

Maybe this is completely stupid.  Just an idea.

Also, with good mics I can't imagine why XY would lack low end compared to any other coincident or near coincident configuration using the same mics.
« Last Edit: July 06, 2021, 06:03:15 PM by heathen »
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Offline Gutbucket

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Re: Three mics - two cards XY and one omni. Working?
« Reply #9 on: July 07, 2021, 10:14:27 AM »
^That's an unusual configuration that could be fun to play around with.

Things to try with it:
>Easiest is simply balancing the X/Y channels, then bring up the level of the omni channel room/audience/low-frequency-extension/front-back-dimension-feel to taste.  Might be entirely happy with that. If the omni doesn't help just leave it out entirely.  This is how I use my 4-channel baffled omni recordings, only difference being that instead of an X/Y pair in front I substitute a baffled L/C/R omni arrangement.

>Fancier could be splitting up those roles by duplicating the omni signal to two mono channels and applying low-pass filtering to one and high-pass to the other.  Low-pass frequency/slope and level set to effectively extend low-frequency response of the directional X/Y mics.  High-pass frequency/slope and level set by ear to whatever works best for adding appropriate room/audience/ambience/front-back-dimension feel.

Both approaches take advantage of the low frequency phase correlation and higher frequency phase decorellation between the X/Y pair and the body-baffled rear-facing omni.

..and do so via complementary mechanisms- as frequency decreases past a certain point, both the size of the torso baffle and the spacing between the X/Y pair and omni become acoustically insignificant and phase is more closely correlated, yet as frequency increases, both spacing and baffling become acoustically significant, decorrelating the phase relationship. The omni acts as a coincident omni at low frequencies and like a rear-facing near-spaced cardioid at high frequencies.
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 DSatz

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Re: Three mics - two cards XY and one omni. Working?
« Reply #10 on: July 07, 2021, 04:00:24 PM »
heathen wrote:

> with good mics I can't imagine why XY would lack low end compared to any other coincident or near coincident configuration using the same mics.

The total amount of low-frequency pickup would be the same, but whatever is picked up in the two channels will be exactly in phase with each other due to the arrival times being the same. The more you space the microphones apart, the less that will be so.

Back in the days of vinyl LPs, the lack of low-frequency phase differences between channels was considered a cardinal virtue, since it helped prevent records from skipping (vertical modulation encodes difference information, and in the RIAA curve the bass is substantially boosted so that it can be cut in playback to reduce turntable rumble). But if you're not recording for release on vinyl, or for FM radio where you might feel that you need to be "mono compatible", I recommend some "creative conflict" in the low-frequency phase situation. It helps the whole feel of the recording with respect to the space it was made in.

You may know that I'm, I think the technical term is "old". When I started recording professionally, it was for vinyl LPs and FM broadcasts. But the freedom to space your microphones apart is one of the real advantages of a digital recording and playback medium. Now that we've had such things for almost 40 years, I'd say it might be time to take advantage of that advantage.
« Last Edit: July 07, 2021, 04:02:38 PM by DSatz »
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