Become a Site Supporter and Never see Ads again!

Author Topic: X/Y vs. A/B (dis)advantages?  (Read 389 times)

0 Members and 1 Guest are viewing this topic.

Offline vibrioidxire

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 24
  • Gender: Male
  • Where am I?
X/Y vs. A/B (dis)advantages?
« on: June 20, 2022, 02:52:14 PM »
Sorry in advance if it’s been discussed before!

I’m pretty novice when it comes to understanding microphone positioning, figuring out the best signal-to-noise ratio in an environment, etc.. I was able to make a makeshift mount for my SP-CMC-4U mics where I can choose between X/Y and A/B positioning. I’ve read some other threads that X/Y is something to avoid, but I think it would help me point towards a P.A. stack. I’ve always liked how the internal mics of the ZOOM H4n Pro sounded (at least tuned to 120°), so I’m wondering if the X/Y position is worth it or just stick to the A/B setup?
Mics: SP-CMC-4U (4.7k mod) (c, h caps) - Shure MV88, SM57 (2x), & SM58.
BB's: SP-SPSB-10
Recs: Sony ICD-SX2000, Roland R-07, Zoom H4n Pro

Offline aaronji

  • Site Supporter
  • Trade Count: (8)
  • Needs to get out more...
  • *
  • Posts: 3487
Re: X/Y vs. A/B (dis)advantages?
« Reply #1 on: June 20, 2022, 03:58:39 PM »
XY is for cardioids and leverages level differences to create a stereo effect. AB is for omnis and uses varying time of arrival to achieve stereo recordings. For most people here, near coincident configurations are employed with directional microphones to harness both level and time differences. The whole thing gets pretty complex, but maybe start with this article from DPA's Microphone University. The Stereophonic Zoom paper by Michael Williams (it's been posted to the site, but I can't find it; link here) goes into some depth. There are tons of threads discussing the merits (or lack thereof) of various configurations and in which situations they might be best used.

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (15)
  • Needs to get out more...
  • *****
  • Posts: 14740
  • Gender: Male
  • "and the rowers keep on rowing!"
Re: X/Y vs. A/B (dis)advantages?
« Reply #2 on: June 20, 2022, 04:22:46 PM »
^Good advice as always.  Below was being typed as that was being posted..

Quote
I’m wondering if the X/Y position is worth it or just stick to the A/B setup?
I suggest you do neither!

X/Y is a coincident microphone pair configuration.  That means both microphones occupy (ideally) the same point in space, which in practical terms means placed as close together as possible, typically one positioned immediately above the other.  Mid/side is another example of a coincident microphone pair configuration.  Because both microphones occupy the same point in space, coincident arrangements rely solely on the microphone's directional pickup pattern in combination with the angle between micrphones to produce a form of stereo based entirely on level-differences between the two channels.  This type of stereo works on the same basis as the pan control on a mixer or balance control on a playback stereo unit in how it effects stereo image by way of level.

A-B generally implies a relatively wide-spaced configuration.  Both microphones are spaced a significant distance apart rather than attempting to occupy the same point in space.  Omnis are generally used for this (partly because due to their omnidirectional sensitivity pattern, an angle between them will not create significant level difference and thus would not generate significant stereo in X/Y). There is no default spacing distance implied by A-B, but typical spacings are from a couple feet apart up to 10's of feet apart (~50cm to meters).  3 feet or 1m  apart is pretty common.  This arrangement produces time-of arrival differences between channels.  Sounds which arrive from direclty in front, above, behind, or below (more technically, the plane which is at a right angle to an imaginary line drawn between the two microphones) will arrive at both microphones at exactly the same time.  However, sounds originating from off-center over toward one side or the other will reach the microphone on that side first, producing a time-of-arrival difference between the two channels.  This is a different type of stereo cue than level difference.  A-B arrangements may also produce level differences, oviously so with angled directional microphone patterns, but even with omnis due to one source being closer to one microphone than the other.  However the configuration is primarily used for generating time-of-arrival stereo.

These two methods are very different in the type of stereo information they produce, the result of which upon playback of the resulting stereo recording is a different type of sound, stereo image, and overall feel. Both can and are used to make good recordings. 

Some advanced 4-channel microphone arrangements combine two pairs of microphones, one setup as a coincident-pair, the other as an A-B pair, in an effort to combine the best of both.

However, there is an easy way to combine some of the attributes of both approaches while using only a single pair of microphones.  That's what a near-spaced stereo microphone pair arrangement is intended to do.  Directional pattern microphones with an angle between them are used in combination with a relatively small amount of spacing between them, but not as much as would typically be used for A-B.  In this kind of arrangement the stereo microphone pair generates both level-differences and time-of-arrival differences.  In this case it is the combination of pickup pattern, angle and spacing that determines the particular balance of stereo cues.  One can work the balance between more of one cue and less of the other while retaining approximately the same apparent stereo width on playback by trading angle against spacing.  Cool huh?

This kind of near-spaced arrangement is probably what will work best for you.  The near-spaced pair approach is the most common one used by tapers employing external microphones, and for good reason. When you hear or read about stereo microphone pair configurations by the name of ORTF, NOS, DIN, DINa, etc, those are all near-spaced configurations which use slightly different combinations of pickup pattern, microphone angle, and spacing.  Plenty of tapers settle on one near-spaced configuration that they use all the time, such as cardioids in DIN, supercards in DINa or whatever.

But to really take charge of things, you can adjust the angle and spacing between the two microphones to specifically fit each recording situation for best results.  The easiest way to do that is to use the Improved PAS Method in which you point whatever microphones you have directly at the PA stacks (or just outside them) and adjust the spacing between microphones to the value indicated on the table found here- https://taperssection.com/index.php?topic=167549.msg2087409#msg2087409.

To really dive deep into how microphone pickup pattern, angle and spacing work together and can be played off each other to advantage, check out the Stereo Zoom paper. You'll find it here- https://microphone-data.com/media/filestore/articles/Stereo%20zoom-10.pdf.  It may take a few readings for it to really sink in.  The Improved PAS table is really just a made-easy way to apply the Stereo Zoom concept, oriented specifically toward concert taping.  It was designed to keep things as simple as possible while optimizing a near-spaced PAS (Point At Stacks) microphone arrangement for best results.
« Last Edit: June 20, 2022, 05:28:30 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 vanark

  • TDS
  • Trade Count: (29)
  • Needs to get out more...
  • *****
  • Posts: 8085
  • If you ain't right, you better get right!
    • The Mudboy Grotto - North Mississippi Allstar fan site
Re: X/Y vs. A/B (dis)advantages?
« Reply #3 on: June 20, 2022, 04:25:02 PM »
You don't need to run XY to point at the stacks. If I'm running PAS (which I do from time to time), they are generally in the 15-20 cm apart range (distance between my thumb and first finger is 17 cm and my thumb and pinky finger is 20 cm).

Some of us when running low profile (are we talking about low profile or open here?) do our best to get the mics pointed towards the music in any configuration possible. Mine (hypers or cards) are generally A-B pointed forward and I'm very satisfied with the results.
If you have a problem relating to the Live Music Archive (http://www.archive.org/details/etree) please send an e-mail to us admins at LMA(AT)archive(DOT)org or post in the LMA thread here and we'll get on it.

Link to LMA Recordings

Link to Team Dirty South Recordings on the LMA

Mics: Microtech Gefell M21 (with Nbob actives) | Church Audio CA-11 (cards) (with CA UBB)
Pres: babynbox
Recorders: Tascam DR-60D | Tascam DR-40 | Sony PCM-A10 | Edirol R-4

Offline aaronji

  • Site Supporter
  • Trade Count: (8)
  • Needs to get out more...
  • *
  • Posts: 3487
Re: X/Y vs. A/B (dis)advantages?
« Reply #4 on: June 20, 2022, 04:37:57 PM »
One other approach which we have all neglected to mention is that you can also use a baffle between the mics to create differences between the stereo pair. I think the most commonly employed baffling technique used by tapers is "HRTF" (Head Related Transfer Function) in which omnis are baffled by the users head (that is: one microphone on each side of your head), which creates level differences by blocking sounds of a head-sized wavelength from one side or the other. There are other ways of doing this, such as using a dummy head or a Jecklin disk, but the principal is the same.

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (15)
  • Needs to get out more...
  • *****
  • Posts: 14740
  • Gender: Male
  • "and the rowers keep on rowing!"
Re: X/Y vs. A/B (dis)advantages?
« Reply #5 on: June 20, 2022, 04:56:15 PM »
You don't need to run XY to point at the stacks.

And you typically wouldn't want to use a coinincident arrangement such as X/Y when pointing at stacks anyway.  That's because when pointed at stacks the angle between microphones will typically be rather narrow, and the implication of a rather narrow angle is that more spacing is required between the micrphones to compensate.  You mentioned liking the 120-degree X/Y option of the built-in mics on the Zoom you've been using. That's makes sense and is a good angle for X/Y in general, but you'd need to be extremely close to the stage before a 120 degree angle between microphones places the microphones on-axis with the PA stacks. And even then, you are likely to find yourself outside of the good coverage angle of the PA. But if that's were you find yourself recording from and it sounds good there, go for it.

When stealthing, other things more important than good stereo imaging need to be prioritized, so best to get those things in order first.

Baffled approaches generally fall under the near-spaced category, yet loosen or remove the constraints dealing with pickup pattern and the angle between microphones.
« Last Edit: June 20, 2022, 05:07:32 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 vibrioidxire

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 24
  • Gender: Male
  • Where am I?
Re: X/Y vs. A/B (dis)advantages?
« Reply #6 on: June 20, 2022, 07:37:25 PM »
Wow, really in-depth answers. Thanks everyone.

Now about the question "(are we talking about low profile or open here?)" by vanark, low profile. There's a venue in specific that I go to quite often and I'm pretty much trying to make the best out of a bad situation, with the bad situation being the P.A. system. Normally venues around here have gorgeous line array systems that face the crowd and give a really good sound all around (usually), but this venue doesn't have the greatest system.

I have only ever managed to get a good sound out of this place is if the mics are pointed right at one of the overheads or the vocals will come out distant, or won't pick up at all. My idea of a X/Y config was that if both mics were pointed at one P.A., the sound would be a little better than other ones, but seeing Gutbucket's response helped me think otherwise.

I've attached a picture of said venue's speakers. Not the best angle, but gives a pretty good look. I usually try and stand in the middle, but the right side is louder than the left, and good ol' moshpits occur.
Mics: SP-CMC-4U (4.7k mod) (c, h caps) - Shure MV88, SM57 (2x), & SM58.
BB's: SP-SPSB-10
Recs: Sony ICD-SX2000, Roland R-07, Zoom H4n Pro

Offline Gutbucket

  • record > listen > revise technique
  • Trade Count: (15)
  • Needs to get out more...
  • *****
  • Posts: 14740
  • Gender: Male
  • "and the rowers keep on rowing!"
Re: X/Y vs. A/B (dis)advantages?
« Reply #7 on: June 21, 2022, 09:45:38 AM »
In that situation these other more important things take priority over the particulars of the stereo microphone configuration:
1) Position yourself in the best sounding spot, with a direct line of sight from microphones to PA speaker(s)
2) Mount the mics as high as possible
3) Orient them so as to be pointed directly at, or at least in the general direction of the PA speaker(s)

A typical arrangement will be both mics pointing directly forward using you as a baffle in the middle, alternately whatever near-spaced combination of angle and spacing fits.

Once recording in your spot, close your eyes while listening to the apparent L/R balance.  Using your ears not eyes, rotate as necessary to center the apparent image and achieve an even balance of loudness Left / Right.  This means you will usually be rotating so as to directly face the loudest source, even if it's not in the center.  Don't try to compensate for a visually off-center location by turning toward the opposite side, doing so will only further aggravate any off-center balance.
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)

 

RSS | Mobile
Page created in 0.04 seconds with 30 queries.
© 2002-2022 Taperssection.com
Powered by SMF