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