Topic: Wide cardioid/subcardioid spacing and angle

[DuctTaper42]

Howdy folks,
TL;DR I was wanting to inquire the hive mind on techniques y'all use for wide cardioids.

I have been using my new Line Audio Omni1s for the past couple months and am loving them, even when I used them inside an arena for Billy Strings last week @AB 2' I am happy with the results (will be posting in kickdown central soon). Understandably sounds a bit reverberant but wasn't nearly as muddy as I expected. So far I've had them set up ranging from 12" spaced and angled out maybe 30deg at a small, intimate outdoor show, to 3' AB at a festival and have been happy with all of the results so far, though admittedly I don't have the most discerning ear for stereo imaging. (Yet?)

Even though I've just recently gotten them I am already brewing future purchases (gotta have a couple rigs in case of a multi-stage festival riiiiiight??  ) and the Line Audio CM4s are one of the mics in consideration. While so far it hasn't bit me too bad I'm thinking the bit of rear rejection would be helpful for less than ideal circumstances. I don't mind a bit of room noise and think I'd rather have some room noise if it meant I maintain the natural reproduction of being there.

Short story long... How do y'all typically set up wide cards? AB? Improved PAS? Radio station standards designed for cards? Combination of all of the above? If it varies based on type of venue I'd be curious to know.

Thanks

[aaronji]

I usually space my DPA4015 wide cards at about 30 - 35 cm and 75 - 90 degrees, depending on distance/SRA (which are related). Try this tool https://sengpielaudio.com/HejiaE.htm to see where the wide cards reproduce the SRA of cards or other patterns.

[C.Clark]

What I normally do is space minimum 1 foot and up to 4 feet.  I find myself running PAS sometimes and then other times doing an angle between 60 and 90 degrees.  Kind of depends on how far from the stacks and if the PA has a lot of bass or not.  The more bass, the less angle I use.  I also find that the closer I get to the PA, in smaller venues, the more likely I am to run PAS.  Hope that helps!

[morst]

I have not gotten very creative. Ran wide cards in the house once as a test but didn't hear an improvement over the cardioids.
https://archive.org/details/Steepwater2016-10-05.B-KM143


I tried them on stage, downstage lip, with mics near each other, and it was OK but I tried again the next night with them spread wider and liked it a lot more in terms of getting two different signals to work with when I split them apart.


So now I usually run Neumann KM143 wide cards on stage, split wider than 6' if possible, aimed at snare drum for a regular rock band setup with center drummer.


Best if mixed with SBD feed, and if I have that I'll go low, under the wedges so my mics dont pick up much if any stage vocals. Leave that for the SBD mix.
Here's one without the SBD feed, more jazz than rock but plenty loud.
https://archive.org/details/Nolatet2018-06-06.KM143-FLAC2448/Nolatet2018-06-06t14.flac


Another result without a board feed is this mix of cards in the house plus wides on stage
https://archive.org/details/MonksOfDoom2018-05-20/MoD2018-05-20t09.flac


Gotta admit I like to go with a setup I'm confident in... Experimentation is important, but on the day of the show I just wanna nail it.

[Gutbucket]

Use a somewhat wider spacing than what you like when using cardioids, or use the same spacing and a wider angle between mics.  The open pattern makes the angle between mics somewhat less critical than when using tighter more directional patterns.  Off-axis response will tend to sound more natural than with a tighter pattern so there is more freedom in angling the pair somewhat wider than you otherwise might.

You might think of them sort of as directional-omnis.

[Gutbucket]

Attached is the latest Improved PAS write up.  To make it easier to use, the useful part is now presented as a list of mic setup diagrams arranged by PAS angle, rather than the former table of figures. The other change is that in addition to standard 2-mic Improved PAS it's now extended to also include 3-position PAS - for the use of 3 mics with single mic in the center, or 4 if using a coincident X/Y or M/S pair in the center (those two mics share the same center position).  If only interested in standard 2-mic PAS for subcards, just ignore ignore the 3-position stuff.  I've been meaning to start a new thread on this, just haven't made the time.

The 2-mic PAS part is based on the same data as the older table version, originally derived using the Sengiepelaudio.com on-line calculator tool that aaronj linked in his post above.  So you'll get the same answer if referring to the older Improved PAS table, the new PAS diagrams, or the online Sengiepel tool. The 3-mic PAS part of it is based on data from the online Schoeps Image Assistant tool which is capable of handling both 2 and 3 mic-position configurations. The 2-channel solutions derived from it are very close to those from the Sengiepel tool but are based on a more extended data set. It also provides additional information and control options (some of which are a bit hard to find, burred in the menu).  However, Image Assistant is less straightforward for most folks to use than the Sengiepel tool.  Additionally, I used a slightly different way of determining the appropriate offset between the PAS and SRA angles, some details of which are mentioned in the write up, and which I plan to discuss in the future thread in more detail.

[Gutbucket]

I totally agree with morst when he says "Gotta admit I like to go with a setup I'm confident in... Experimentation is important, but on the day of the show I just wanna nail it."

In that regard I consider the improved PAS stuff relevant for taping from out in the audience.  Taping on-stage or at stage-lip is a different deal.  Improved PAS still works in those situations, but very different approaches can also work and may work better.   The acoustic situation there is quite different and makes for additional options when up close.

I also find that the closer I get to the PA, in smaller venues, the more likely I am to run PAS.  Hope that helps!

This is very interesting to me, please tell me more.  A primary intent of Improved PAS is to make the most of the very typical less-than-ideal taper situation of recording from farther away.

[goodcooker]

Farther away from the source I tend to do more separation and less angle and up front or onstage the opposite - more angle and less separation.

Some examples
15 feet from the band unamplified jazz small listening room- https://archive.org/details/JVidacovich2019-06-25.MBHOka300.flac - DINa 17 cm 90 angle
Back of the floor medium venue 1000 cap loud blues rock - https://archive.org/details/tabbenoit2021-06-12.flac24.mbhoka300 30 cm 75 angle
At FOH 50ft from stage small venue ~400 cap loud blues rock - https://archive.org/details/rrfb2023-08-12.cm3.portico.mr1/rrfb2023-08-12mr1t07.flac 25 cm PAS
Big outdoor festival at FOH enclosure 150 ft from stage reggae - https://archive.org/details/matis2018-06-02.MBHOka300.flac/matis2018-06-02t07.flac 25 cm PAS - IIRC I tightened up my usual wider outdoor spread since there was little room to be had so small footprint and high wind

[DuctTaper42]

Greatly appreciate all the feedback so far, has been enlightening and as I could've guessed... it varies. My initial inclination was a bit of a mid-point between AB and near-coincident, angled arrays, something like a 2-3' spaced PAS so nice to see I wasn't tooooo far off the opinions of others.

The more bass, the less angle I use. 

I'd also be interested in further detail on these comments. When there's more bass do you not want the mics pointed directly at the source in attempt to attenuate it some to prevent the bass from overpowering the other frequencies? With the CM4s specifically, it appears that the lower frequencies have the least amount of rear rejection so I could see wanting to maximize what attenuation it does have while still making sure the sound is relatively on-axis.

I also find that the closer I get to the PA, in smaller venues, the more likely I am to run PAS.  Hope that helps!

Is this in order to ensure the max sensitivity is facing the source rather than stage/crowd noise? and by "closer to the PA" do you mean strictly closer to the stage or lateral moves as well if you're not able to set up in the center?

So now I usually run Neumann KM143 wide cards on stage, split wider than 6' if possible, aimed at snare drum for a regular rock band setup with center drummer.

Aimed at the snare as in angled inward? So that each mic is picking up it's respective side of the audio while keeping the drummer centered between the two as it was in reality?


I appreciate the other comments as well, I'll spend some time checking out the links, tools, and tapes when I can so I can get a sense of the differences between circumstances and resulting tapes.

Thanks all

[rocksuitcase]

it appears that the lower frequencies have the least amount of rear rejection

Acoustically, frequencies below approximately100 Hz are too lengthy to be "localized" to one side or the other using most microphones no matter the configuration. e.g. a 40 Hz wave is 1/4 length at about 40 feet, so to pick up the full wavelength you need to be 160 feet away. However, most recording principles use mic distances less than that. Of course live music is not white nor pink noise so it behaves a bit less "uniformly".
In summary, human hearing does not perceive separation between Left and Right at frequencies below approximately 100 Hz.   

[morst]

So now I usually run Neumann KM143 wide cards on stage, split wider than 6' if possible, aimed at snare drum for a regular rock band setup with center drummer.

Aimed at the snare as in angled inward? So that each mic is picking up it's respective side of the audio while keeping the drummer centered between the two as it was in reality?

Yep, pointed inwards. Although now you have me thinking about it! PAS = Point At Snare lol

[Gutbucket]

The snare is the tempo and snap focal point!  Love good, clean on-stage drum transients which give a live performance a enhanced sense of more lively life.  That's the stuff that doesn't translate the same through the PA.

Yeah the outward angling of a traditional stereo pair doesn't necessarily apply in the same way to wide-spaced stage-lip / on-stage setups positioned relatively close to the on-stage sources distributed across the stage.  Maybe more like sampling a bunch of individual but interacting soundfields on stage, rather than sampling a single combined and more coalesced one out in the room.

[Gutbucket]

it appears that the lower frequencies have the least amount of rear rejection

Acoustically, frequencies below approximately100 Hz are too lengthy to be "localized" to one side or the other using most microphones no matter the configuration. e.g. a 40 Hz wave is 1/4 length at about 40 feet, so to pick up the full wavelength you need to be 160 feet away. However, most recording principles use mic distances less than that. Of course live music is not white nor pink noise so it behaves a bit less "uniformly".
In summary, human hearing does not perceive separation between Left and Right at frequencies below approximately 100 Hz.

My understanding is that within the frequency response limits of the microphone, it remains sensitive to low frequency pickup regardless of its distance from the source and need not be placed a 1/4 wavelength or more away.  And a directional mic that does retain its directional polar pattern down to the lower limit of it's response (not all directional mics do) retains its directional sensitivity down there.. which is what the shape of the polar pattern plot at low frequencies indicates (assuming an accurate plot). If not the polar plot would go omni at low frequencies.. or would need to indicate the distance from the source at which the measurement was made, like a frequency response plot. Rather, I think the issue is room acoustics behavior and human hearing perception. 

Consider:
It is common to place a kick drum mic inside the small volume of the drum itself, and measure speaker response in part by placing the measurement mic directly at the outlet of the bass-reflex port.

One can produce/reproduce low frequency energy even if the wavelength is considerably longer than the dimensions of the room itself.  Subwoofers in cars are a good example.  But that energy is "all pressure" without any "directional vector" component.

Human perception of source direction is grows increasingly weak at lower frequencies and is more or less inconsequential below 100Hz, but human perception of low frequency modulation and bass "movement" persists.  "Mono" correlated bass tends to sound dimensionless and "in head" where as "stereo" decorellated bass sounds spacious and can have a sense of movement to it even if it doesn't indicate any direction of the source.  This is one of the reasons I so dig spaced omnis for live music.

/nits

[rocksuitcase]

^^^^^^^
Not to go too far OTS, I should have said: psychoacoustically vs acoustically
I was trying to explain to the OP why he may not perceive bass differences the way he does higher frequencies.

So I agree here with you and is what I was speaking to: "Rather, I think the issue is room acoustics behavior and human hearing perception.

As to what you say about human hearing capable of finding distinction, or "stereo imaging" lower than 100Hz, my experience agrees with that. However, there is a fair amount of literature which claims "trained listeners" will distinguish characteristics in similar musical pieces which "untrained listeners" may not. A very well regarded FOH engineer told me "it's not always what you hear, but what you don't hear I find fascinating"     

[Gutbucket]

No doubt.  In regards to "it's not what you hear, but what you don't", the perceptual masking thing is fascinating to me.  That some of the lossy-compression codec stuff can be as perceptually benign as it is while throwing away so much information is a good example. It's like a good magician, slight of hand, a skilled con man - successful because the con-man knows how the mark's mindset and leverages that to advantage without the rube noticing.

Even more fascinating to me is a subset of this- the stuff we don't consciously notice or realize we hear, yet still effects us in some deep way.  That's what I fear is lost with lossy compressed music that's otherwise perceived as being fully transparent.  A loss deeper than the diminishment of perceivable qualities which trained listeners might be able to pick out.  A stealing away of the stuff we don't actively notice, yet somehow makes us feel different.

/ot

[wforwumbo]

To address OP first: I have run my subcards between 27 cm up to 1 meter, angled between AB (0 degrees) and 110 degrees. For amplified music, my ears prefer a spacing of 30 cm and anywhere from 30-75 degrees. The most commonly used mount in my gear bag is 30cm/60deg. I can try to get you some tapes if you'd like, off the top of my head here's one already on archive:

https://archive.org/details/fruitbats2023-05-17.mk21.flac16

My experience is that my subcards really want to be on axis with the PA. I got em dead on into a v3 for a phish show in 2022 and that tape came out sublime - I'll upload a song from that to give you an idea of what these narrower angles and spacing give with subcards.

^^^^^^^
Not to go too far OTS, I should have said: psychoacoustically vs acoustically
I was trying to explain to the OP why he may not perceive bass differences the way he does higher frequencies.

So I agree here with you and is what I was speaking to: "Rather, I think the issue is room acoustics behavior and human hearing perception.

As to what you say about human hearing capable of finding distinction, or "stereo imaging" lower than 100Hz, my experience agrees with that. However, there is a fair amount of literature which claims "trained listeners" will distinguish characteristics in similar musical pieces which "untrained listeners" may not. A very well regarded FOH engineer told me "it's not always what you hear, but what you don't hear I find fascinating"     

To allow a healthy dose of skepticism, that literature always uses stimuli we do not find in nature, in controlled conditions. Imaging below 100 hz absolutely exists - as evidenced by the fact that no engineer sums their mixes to mono below 100 hz. The idea that no imaging or spatial cues happen below 100 hz comes from mix engineers who discovered that panning bass and kick drums would cause weird phase cancellation in the stereo fields and appear to make those instruments weaker. That's more of a coherence thing, and binaural coherence is much more complicated of an argument than stereo/binaural cue perception at low frequencies. Keeping bass panned center helps prevent odd phase artifacts from muddying or confusing the mix.

[Gutbucket]

[...snip] For amplified music, my ears prefer a spacing of 30 cm and anywhere from 30-75 degrees. The most commonly used mount in my gear bag is 30cm/60deg.[...]

^Was thinking of this last week while posting, hoping you might join in.

There is a second aspect in play which that may hint at. What's uncertain is how much of each is attributable to one's ear and preference.

I feel one side of the mic pair spacing "coin" is image distribution, sense of space and how diffuse the reverberance sounds, and the other is how spacing effects frequency response in a secondary, stereo aspect kind of way.  That is, the frequency response of each individual microphone remains unchanged regardless of how far apart the pair is spaced, however, the response of the pair in sum is partly effected by the spacing between them via interaction with the vector of the wavefront.. and maybe with the distribution of modal pressure nodes. I say secondary stereo sense because unless some processing step along the way includes some sort of summation of the two independent stereo channels, this summing does not actually occur until stereo playback, and happens "in air" with speakers and maybe "in head" with headphones.  Its a ripple in the summed response due to comb filtering and is definitely audible, but is unlikely to be clearly identified as a frequency-response thing unless actively listening while making a change in spacing, in which case it is quite easily heard.  Its tangentially related to the mono-compatibility issue.

I've long wondered how wide the variance in taper preference might be in determining one's preferred spacing for a pair of mics, given this (conscious or not) weighing of the two different aspects.

tl/dr: The effect of mic pair spacing is tonal as well as spatial.

[wforwumbo]

So I can do one better for this thread... I've uploaded two recordings of the same show, from the same spot, in the same configuration (30cm/60 degrees), with different microphones/chains. The mk21 subcardioid recording is Schoeps mk21 (30cm/60 Degrees) > Schoeps KC5 > Schoeps CMCC5 > Grace Lunatec V3 > Sound Devices MixPre-6 (aux in, channels 5/6 @ 24/48k); the mk4 cardioid recording is Schoeps mk4 (30cm/60 Degrees) > nbob KCY > Naiant PFA > Sound Devices MixPre-6 (mic in, channels 3/4 @ 24/48k). The mics were clamped right next to each other, one atop the other. This is Phish's Walls of the Cave from 9/3/22.

https://drive.proton.me/urls/AMXPD3GHZR#uj1F0LbjCKbj

This is my favorite mk21 tape I've made so far to-date.

[Gutbucket]

That's certainly most helpful to the OP. That recording and our discussions about it are exactly what I had in mind!

But in regard to the summed response ripple thing, since both pairs used the same spacing that will produce the same frequency response effect on both of them.

What I'd really love to hear is the same show, recording position, mics, and angle, but several different spacings.  Even then it might be difficult to clearly identify the difference in response attributable to the ripple in the summed response, since the change in spacing will also effect the imaging and diffuse field correlation simultaneously. 

Now if someone were to somewhat rapidly slide one of the mics along the bar during the recording, the summed response ripple thing would be immediately obvious to any listener.  I say that because I did this with omnis years ago to get a better empirical understanding of how differences in spacing effects the sound and image.  During the relatively rapid change of position the ripple becomes obvious from the flanging effect of the movement shifting its frequency centers. After becoming aware of it in that way, the difference in static response between various positions becomes more easily perceived.  But actually doing that means intentionally sacrificing a recording.  Maybe something to try at a meh opener.  ..or maybe it works the same when testing in front of the stereo, I've not tried that.  Best to make a relatively swift slide between the various spacing positions (that's what makes the flanging effect obvious) noting each position, either verbally on the recording or via time-stamps, and sticking with each position long enough to get a good feel for the sonic differences of the other aspects - the difference in static response, imaging, and diffuse correlation.

Curious about your thoughts about all that.

Years ago there was a tread here at TS about a few different stereo pair robot mic bars able to remotely adjust angle/spacing.  Not really practical use type things but more like university project type stuff.  I recall some youtube videos which included sound and video of one shifting back and forth between configs - you could see each config and hear the sound the entire time.  I may search for those and see if I can hear the summed response flange effect while the mics are moving and the static response differences when still.  If I find a good example I'll post a link here. As I recall most were changing angle at the same time though, complicating things.

[DuctTaper42]

     

Really appreciate the discussion, off topic and on, here. Lots to mull over and explore further but this is shaping up be a nice little repository of info that accomplished exactly what I'd hoped of not only helping me get a good idea of what you seasoned vets do in practice with this particular, perhaps less common, polar pattern, but also creating a easily searchable thread for future learners to find without having to dig through numerous threads in search of those nuggets of gold. Y'all rock 

[DuctTaper42]

And as my own attempt to add this repository, there is significant discussion of spacing and angle in the Team Line Audio thread here: https://taperssection.com/index.php?topic=172445.0 especially since the CM3/4 are much more commonly used on this board than the OM1/Omni1.

A particularly detailed response from Voltronic:

What's generally the preferred pattern for CM3? I have a pair I've never used but can pickup a Shapeways.

Most of the classical people on GS like NOS (30 cm / 90 deg), and that's what I started with as well. Now, my go-to is the SRS "Hybrid" which is the same 30 cm but opens the angle up to 110 deg.

If you use the Sengpiel visualization tool, you can see the SRAs for these arrangements. Select NOS, then change the mics to Subcardiod. For the "hybrid", select ORTF (note the SRA), change to subcardioid, then the spacing to 0.3 m. You'll see the SRA is very close to ORTF with cardioids.

To give you an idea what these sound like, here are some of my samples. NOS was used for Ubi Caritas. Hybrid was used for Road Home, Rise Up, Joyous Occasion, and Innisfree. I think I used "Wide ORTF" for the rest, which is only 21.5 cm at 110 deg. I don't use that spacing anymore, as I found the wider spacing to sound better with these mics.

Keep in mind that this what I recommend for acoustic ensemble recording, which is what I do. For amplified music, other people here will have better advice.

[wforwumbo]

I heartily agree with Voltronic at a high level, and like him I love using the sengpiel visualization tool when explaining stereophonic zoom. Stereo zoom in my opinion is the most effective tool I can effectively experiment with when taping. Once I have a mic pair pattern and set up under my fingers, it's simply a matter of deploying what I think works in a given taping set up.

There is a significant difference in the equation when we are discussing amplified music - and the room acoustics of spaces normally used for amplified music. Recording the sound field of unamplified music and how we binaurally perceive the performing ensemble/the room acoustics is a very different deck of cards than capturing what is effectively an oversized stereo in enclosed space (we are only rarely blessed to operate in a free field, and this is precisely why subcards and Omnis shine in big meadows).

I'll also reinforce that every taper has our own personal preference, and that's okay too. If there were a "right way" to do things, we would all agree and trust one taper to run their mics and the rest of us would be one large patch chain.

And as my own attempt to add this repository, there is significant discussion of spacing and angle in the Team Line Audio thread here: https://taperssection.com/index.php?topic=172445.0 especially since the CM3/4 are much more commonly used on this board than the OM1/Omni1.

A particularly detailed response from Voltronic:

What's generally the preferred pattern for CM3? I have a pair I've never used but can pickup a Shapeways.

Most of the classical people on GS like NOS (30 cm / 90 deg), and that's what I started with as well. Now, my go-to is the SRS "Hybrid" which is the same 30 cm but opens the angle up to 110 deg.

If you use the Sengpiel visualization tool, you can see the SRAs for these arrangements. Select NOS, then change the mics to Subcardiod. For the "hybrid", select ORTF (note the SRA), change to subcardioid, then the spacing to 0.3 m. You'll see the SRA is very close to ORTF with cardioids.

To give you an idea what these sound like, here are some of my samples. NOS was used for Ubi Caritas. Hybrid was used for Road Home, Rise Up, Joyous Occasion, and Innisfree. I think I used "Wide ORTF" for the rest, which is only 21.5 cm at 110 deg. I don't use that spacing anymore, as I found the wider spacing to sound better with these mics.

Keep in mind that this what I recommend for acoustic ensemble recording, which is what I do. For amplified music, other people here will have better advice.

[Gutbucket]

^ And that's what Improved PAS is all about.  It's just Stereo Zoom applied to the taper situation of recording amplified music from an audience position.

All it really does is suggest the optimal spacing between a pair of mics that are pointed directly at the PA speakers. 

[Gutbucket]

All it really does is suggest the optimal spacing between a pair of mics that are pointed directly at the PA speakers.

To tie this in to the somewhat obtuse blather I was spouting earlier in the thread - "optimal" in this case refers to clarity, direct/reverberant ratio, image distribution and sense of space.  Stereo Zoom does not address that secondary stereo summed response thing at all, which is going to vary along with the different spacings it suggests. 

I personally feel clarity, direct/reverberant ratio, image distribution and sense of space are more important (putting me squarely in the Stereo Zoom camp), but different ears may value different aspects, which is why I mentioned the secondary effect on response.

[checht]

Very interesting theoretical basis for various techniques. I'm gonna just answer the initial tldr:

Howdy folks,
TL;DR I was wanting to inquire the hive mind on techniques y'all use for wide cardioids.

Outdoors and indoor venues with good sound/room, I run my mk22s OMT4, 4' spaced with mk41s x/y PAS in the center.
Indoor venues with questionable sound, I run the 22s wide ORTF.
Love the results. Simple enough even for me.