Topic: Wide cardioid/subcardioid spacing and angle

[Gutbucket]

If you do want to try option 4), given the mics in your sig-line I'd probably run the CM4's in standard ORTF or NOS in the center with the OM1 omnis three or four feet out to either side of that as a wide flanking pair.  If you have available to you mics that are a bit more directional, I'd use those in the center as they allow for less spacing and angle (X/Y works great in the center when combined with a more open pattern wide pair, even if you don't like X/Y on its own) and use the CM4s as the flanking pair.

[Gutbucket]

Like wforwumbo, I'm a strong proponent of running a known baseline config along with whatever new config is being tried. Its really the best way to really figure things out.  And believe me, I totally get the desire to keep things simple and easily managed by recording using a single pair of microphones.

But I'm also a strong proponent of running mic arrays which use more than two channels.  Checht and others are doing that to great advantage.  Three or four channels is enough to leverage those advantages.
^
Unfortunately these two things are somewhat at odds because the second requires additional channels and setup all by itself, so running that and a known-good stereo config at the same time for comparison takes a bit more more stuff and effort.  Entirely doable with your 6 channel recorder though.


Also agreed with "centering the auditory image".. which I recommend doing by ear rather than by eye whenever possible (likely not possible when setting up on stage).  The "pointing at the snare" thing is less about actually pointing the mics at it and mostly about positioning the mic array so that there is a direct line of sight from the snare to the mics, without the rest of the drum-kit or anything else getting in the way of that direct sound path, as general best practice when recording on stage or from the stage-lip.  It's helpful in picking up the musically important transient snap of that anchor instrument cleanly and clearly with less potential for it sound buried in stage sound.  Going further, pointing a mic directly at the snare does become applicable when the array includes a center mic or Mid/Side pair, and helps further with clarity and center solidarity by using the sound of the snare drum to help solidly anchor the center of the playback image.  Of course when using a typical 2-mic stereo pair arrangement (or an arrangement with an X/Y pair center) rather than a single center mic or M/S pair, its a lot less likely that one of the mics will be pointed directly at the snare, unless the drummer happens to be positioned way over to one side.  IME, the important thing regardless of the mic array used is getting that clear line of sight to the snare when possible, which often means shifting slightly to the right (stage left) rather than setting up directly centered in front of a centrally placed drum-kit.  Moving slightly off center in that way can also help by keeping the mics out of the "wind puff" that sometimes emanates from the hole in the front skin of the kick drum, if there is one, and if the mics are close enough to be effected by it.  I've felt that puff from around 8 feet away. 

In any case, whenever I walk in and take a first look at the instruments on stage arrangement with the intent of setting up to record on the stage or at the stage lip, one of the first things I do is look at placing my recording setup in such a way that it has a clear line of sight to the snare drum.  Achieving that is not the end-all be-all, but is usually simple enough to arrange and an easy thing to take advantage of.

[edit for readability and to add..] ^ That said.. If the Jazz Is Dead line up and stage arrangement are the same as when I caught them last fall, you'll have the two guitarists positioned at either end of the stage, with Steve Kimock stage right and Bobby Lee Rodgers stage left. Pete Lavezzoli on drums was setup bit stage-left of center next to Bobby, and with his snare on the left side of the kit it may be somewhat masked by the rest of his drum kit as viewed from a center stage-lip mic position.  But don't worry about that, it will sound just fine from there.  Yet another advantage of the four mic arrangement discussed above which incorporates a narrow center pair + a wide flanking pair is that it's likely to place the wide mics more or less in front of the two guitar positions, with the one on Bobby's side having a clearer line of sight to the snare.

However you do it, have fun and make great tapes!

[wforwumbo]

1) Record using the same mic config, then try making a slight mid/side ratio adjustment afterward, reducing the level of Mid and increasing the level of Side.  This quite literally decreases the level of the center portion of the image.  It will also make it sound wider because there is less center content than before.  Tread lightly and listen carefully when you try it though.  Too much is going to sound bad (due to the classic non-coincident pair mono-compatibly problem), but just enough might do what you want without apparent audible problems.  This option keeps your mic config unchanged, making it easy to nail it in the same way you've done previously on the day of the show, but first give it a try on one of your past recordings using this same mic config that sound a bit too center heavy to you to determine if it is going to do what you want without making things worse.

2) Angle the mics apart more but keep the spacing the same.  This reduces the level of the center due to less pickup pattern overlap - sound sources near the center arrive at each of the two microphones somewhat more off-axis where they are less-sensitive. This is actually similar to 1) in what it does, except for being implemented at the physical microphone level, which avoids the potential mono-compatibility problems of changing the M/S ratio afterward. The change in the microphone configuration itself produces less Mid content and additional Side content. This should work well for you when recording on-stage or at stage lip with the CM4s for a couple reasons: The off-axis response of subcards tends to be smooth and natural, so even though the mics are pointed farther away from the sources in the center the center part of the image should still sound clear and natural.  And, when recording on stage or at stage-lip, the sources will tend to to be spread out across a wider angle, so a wider mic angle makes sense because the mics are still mostly on axis to the ensemble, unlike a recording position far back in the room where the mics would end up pointing at the side walls.  This is may be the best way to go because it's a better way to approach it than 1), yet doesn't alter your current microphone config much, making it simple to walk in and nail it the day of the show.

3) Space the mics apart significantly more, and angle them less.  This actually increases pattern overlap, yet can still reduce the level of the center because each microphone is further away from the central sound sources.  It will also change the image distribution, pushing sources that were near center a bit farther out toward to the sides of the playback image, which perceptually can sound like there is less level from the center.  This one sort of takes advantage of the proximity and wide positioning of the sound sources on stage - a quite different acoustic situation than a recording position out in the audience.  The decreased angle between mics will also reduce level of audience and room sound somewhat.  You will definitely need to use more spacing between the mics to compensate for the narrowed angle between them, because otherwise the center image would get louder rather than quieter [edit to correct oops] as with 2).  Additionally, the wider spacing will provide improved audience and room sound - not only will the mics be somewhat less sensitive to audience pickup due to their angle, the larger spacing will help de-emphasise pickup of individual audience members, and the room/reverberant pickup will tend to be more open and natural sounding.  Implementing this is going to be more of a gamble though, because you are changing both angle and spacing, balancing one against the other.  It's also a bit more complicated in that it may require two separate mic mounts (two clamps or short stands).  But when you do nail it, it can pay off nicely in this kind of situation. 

4) Get the advantages of 3) and a lot more, with way less gamble, by using 3 or 4 microphones total, placing the third mic or a 2nd pair in the middle - this is what Checht is talking about.  It does require more stuff and work, but dramatically increases the likelihood of nailing it.  To properly integrate the additional mic(s) in the center you'd need to significantly increase the spacing and/or angle of the wide pair, more so than in 3).  The additional mic positions and increased spread/angle of the wide pair will provide a more even pickup of all sources on stage AND provide you with a small but welcome degree of control over instrument and image balance afterward.  IME, in this way you gain a lot more leeway in setup since the actual spacing and angles between microphones are less critical, while achieving both a tight, well-anchored center AND a nice wide image width and sense of space at the same time (aspects that are otherwise often contradictory), as well as gain the ability to make the center louder or softer afterward, allowing you to dial it in just right.

I won't say "don't do it" but in the interest of adding to discussion I'd like to put heavy asterisks around 1) and instead say "proceed with extreme caution" as this is likely to distort (or outright destroy) phase and time information for mic pairs that are not coincidental, and this distortion will occur in a manner that cannot be recovered without the original un-MS'd tape. I have done 1) myself before with results that satisfied me, but it required a very gentle adjustment and constant checking against the original un-edited tape before I convinced myself I was not causing more problems than I was solving with this method.

2) and 3) chase after the overall intuitions of stereo zoom. Once you find a spacing that you are happy with, 3) slowly morphs into 2) and a lot of this thinking becomes general intuition for me as a a taper, shaped by experience.

I also want to advocate here for XY cards/hypercards/supercards/fig8s or MS with a directional mid mic (I think card + fig8 sounds magical), especially if you are running more than one pair. It allows for extreme flexibility in post as MS processing is now a is a lossless transform that does not distort information.

To my ear, the major problem with coincidental tapes is that the auditory image never extends outside of the speakers (or, if I'm listening on headphones, outside of my head). That's why I like running a second pair of mics outside of the center coincidental pair, then mix down in post. It's very easy to get a great sounding recording with this method since the binaural cues between spaced pairs in AB and a coincidental pattern don't interfere too heavily with each other if the spaced pair is far enough away from the coincidental pair.

[Gutbucket]

Good warning on 1).  Listen carefully. Just a touch may do the trick, and probably best used as a correction for an existing recording.  At least testing on an existing recording made using the same mics and config can help determine where the threshold of doing harm rather than good lies.

To my ear, the major problem with coincidental tapes is that the auditory image never extends outside of the speakers (or, if I'm listening on headphones, outside of my head). That's why I like running a second pair of mics outside of the center coincidental pair, then mix down in post. It's very easy to get a great sounding recording with this method since the binaural cues between spaced pairs in AB and a coincidental pattern don't interfere too heavily with each other if the spaced pair is far enough away from the coincidental pair.

Yes. I relate much of that "nothing outside of speakers or head" to insufficiently low diffuse field correlation.  The reverberance needs sufficiently randomized phase.  Sufficient spacing provides that in spades, while a coincident center pair provides pretty much the opposite- highly correlated sharp imaging with a solid center.  When appropriately combined the two are so nicely complementary, like flip sides of the same coin. IME It's a real art and significantly more difficult to achieve the same using a single pair. Kudos to those who can.

And yes! Sufficient space between the center pair and the wide pair is an important key to that working, yet also represents the primary practical difficulty of it for most tapers.  I probably harp on that too much around here, but one of the biggest problems I find with attempted multiple-microphone arrays is that the mics are all too often too close together to play nicely with each other. Its difficult to arrange for enough spacing between the center pair and the wide pair for this to really shine.  At least it's easier to achieve on stage or at stage lip than it is out in the room on a single mic stand.

[vantheman]

Just seeing all these generous replies now, and typing from a phone so it’s harder to pinpoint certain quotes, but #1 is something I’ve been trying to dabble with very recently actually. I use Ozone 9 a lot, invested in it early in my journey with a coupon having already purchased RX7. What I was looking for was a feature to control gain in mid/side, and they don’t quite have that feature. I can do it with compression but I don’t want to do that at the expense of those precious drum transients. I achieved it somewhat indirectly in RX7 using music rebalance to turn down the drums, located in the center, by a few db. If there is a recommendation for a different tool to control gain in mid/side I would love to hear it!

I agree it’s a delicate operation, and I think deciding whether it’s necessary depends heavily on whether vocals are present. From a first person point of view of someone observing a small club show from the front of the stage, drums just are naturally pretty loud, so I tend to leave it that way if I can, and not mess with history, if there’s nothing else that needs to be centered in post, like vocals.

Having observed the very strong center using wide ORTF with the CM4s, at least in the scenarios where I apply them, I recently invested in the SRS hybrid config bar for CM4, but haven’t been able to use it yet. From memory that’s 30cm at 110 degrees.

For the Jazz is Dead project, pending permission, space and my sense of the roo, I’ll have to decide on the day of the show what to deploy. I am liking this suggestion -

If you do want to try option 4), given the mics in your sig-line I'd probably run the CM4's in standard ORTF or NOS in the center with the OM1 omnis three or four feet out to either side of that as a wide flanking pair.  If you have available to you mics that are a bit more directional, I'd use those in the center as they allow for less spacing and angle (X/Y works great in the center when combined with a more open pattern wide pair, even if you don't like X/Y on its own) and use the CM4s as the flanking pair.

And maybe run my AT853 hypers (or cardioid) in XY, and run my CM4s in “hybrid”. A total of 6 mics with one 4 mic array and another 2 mic array. Try and see how the omnis mix with the CM4s, worst case scenario mix them with the hypers. Will also give me a chance to see how the wider hybrid spacing works. I’m liking this idea quite a bit actually. Thanks again for all the food for thought, as usual.

[DuctTaper42]

Try and see how the omnis mix with the CM4s, worst case scenario mix them with the hypers. Will also give me a chance to see how the wider hybrid spacing works. I’m liking this idea quite a bit actually. Thanks again for all the food for thought, as usual.

I, admittedly, don't have much input regarding the rest of your post but I have been experimenting with 4 mic arrays using a pair of Omni1s (maybe not exactly the same but as close as can be) and a pair of CM4s to great success. Listening to each individually there are subtle, but noticeable differences, both entirely usable on their own, but when mixed together they compliment each other incredibly well to create a nice, full reproduction of the source.

I have not yet had the chance to try it with AB spaced omnis + near coincident CM4s, so far I have had to keep fairly compact so what I've found to work nicely is the omnis Healy or similar (usually 20-30cm/150-180deg depending on venue and location) and the CM4s about 30cm/60deg that I saw someone mention earlier in this thread. Mounted on one bar (I use 15mm camera rig equipment with a round bar and clamps made for them, sacrifices some ease of setup for flexibility) I have the Omnis in the front of the bar and the CM4s on top. The capsules for each side end up roughly coincident which I'd be curious to know if that may help with phase issues. The omnis get some stereo imaging thanks to the slight HF directionality being pointed in opposite directions and while it does tend to need a bit of a HF bump in post on its own, all the info is still there, and when mixed with the CM4s, adds a lot of richness to the bass. I've tried this method outdoors from about 60' from stage as well as indoors, but only from stage lip so far (in full disclosure, for the stage lip attempt I had the CM4s and omnis on separate bars, omnis clamped lower on the mic stand and the CM4s on a boom arm angle backwards and mics angled up to try and get as much direct PA source as possible; looked funky and perhaps less than optimal deployment but mixed with the omnis and sbd had a nice result). If I get the opportunity to try indoors from deeper in the audience I'll still give it a try, for science, but could see it being likely that the omnis would be mixed in much lower to avoid too much chatter and room reverb.

All this to say... The Line Audio Omni1s and CM4s seem like they were designed to compliment each other well and in my experience they certainly do.

Edit: just realized it's hard to spot the omnis in the second pic with how cluttered it is but you can see one of them in front of the head on the snake skin drum and the other slightly left of it

[Gutbucket]

#1 is something I’ve been trying to dabble with very recently actually. I use Ozone 9 a lot, invested in it early in my journey with a coupon having already purchased RX7. What I was looking for was a feature to control gain in mid/side, and they don’t quite have that feature.

Look for a simple stereo width function.   That's typically doing an L/R>M/S conversion and back to L/R again, with a change of M/S ratio in the middle step.  Otherwise there are plenty of free M/S plugins that will do it.  Here's one- https://www.voxengo.com/press/voxengo-msed-3-0-free-mid-side-encoder-decoder-plugin-released-311/

I can do it with compression but I don’t want to do that at the expense of those precious drum transients.

I get that. L/R stereo compression will tame all dynamics equally, but if the most dynamic stuff is drums in the center, you'll hear it working there the most, and preserving good transients is a critical compression-related thing. Alternately a compressor running in Mid/Side mode, using a different compression ratio for Mid vs Side, will make the same kind of M/S ratio change as a stereo width control, except it does so dynamically. The same caveats about making a M/S ratio adjustment of a non-coincident stereo mic pair still apply, but because it will only be changing the M/S ratio momentarily whenever the compressor threshold is exceeded, you might get away with a bit more reduction in Mid level before hearing phase problems in comparison to a simple static ratio change. 

I achieved it somewhat indirectly in RX7 using music rebalance to turn down the drums, located in the center, by a few db. If there is a recommendation for a different tool to control gain in mid/side I would love to hear it!

 
That's a much higher-level way of going about it which has the potential of working better if the routine works well without artifacts and its only the drums that are overly loud in the center.  Same "listen carefully" applies of course.

Having observed the very strong center using wide ORTF with the CM4s, at least in the scenarios where I apply them, I recently invested in the SRS hybrid config bar for CM4, but haven’t been able to use it yet. From memory that’s 30cm at 110 degrees. [..] For the Jazz is Dead project [..] maybe run my AT853 hypers (or cardioid) in XY, and run my CM4s in “hybrid”. A total of 6 mics with one 4 mic array and another 2 mic array. Try and see how the omnis mix with the CM4s, worst case scenario mix them with the hypers. Will also give me a chance to see how the wider hybrid spacing works. I’m liking this idea quite a bit actually. Thanks again for all the food for thought, as usual.

One of the advantages of a coincident pair (X/Y or M/S) in the center is that you can readjust it's stereo width using an M/S ratio tweak all the way down to a mono Mid if you want, without incurring any phase problems.  You can then dial in whatever width happens to work best in combination with the wide-spaced pair.  This works best with an actual M/S pair (100% Mid is cleaner), but works with X/Y as long as they are closely coincident and angled reasonably, say the typical 90 deg total. 

[Gutbucket]

The capsules for each side end up roughly coincident which I'd be curious to know if that may help with phase issues.

Phase interaction problems tend to manifest when two mics which will be mixed together are neither perfectly coincident nor spaced widely enough apart. "Almost-coincident" or "near-spaced" is where phase problems between two or more mixed channels becomes more likely. The safest bets are "all or nothing" - either fully coincident, or spaced apart widely.

That said, if that configuration is working for you without problems, no problem.  It can be difficult to achieve sufficient spacing.

Just how coincident / how far apart?  It's wavelength related- at close spacings any phase interaction issues occur at high frequencies, so if the mics are close enough but not perfectly coincident, any phase interaction problems may manifest high enough in frequency so as to be not easily perceived.  As the spacing grows larger the frequency region where potential problematic phase interactions may occur is lower. It tends to be most problematic at mid-range frequencies where our hearing is most sensitive, and becomes less problematic above and below that.  It also depends on the similarity of content in the two channels and the degree to which the two are mixed.  If one of the two channels has limited frequency content in the problematic phase region, there will be little there to mess with the content from the other channel. If the content in both channels is very similar, mixing the two channels together at equal level can be more problematic than adding just a touch of one to the other.  Making a Mid/Side ratio adjustment changes the mix between the two channels, which is that's the basis on which the warning about it above is made, and why just a tiny bit of M/S tweaking might work without causing the same problems that a larger ratio change would.