Topic: Running more than 2 mics

[HealthCov Chris]

I've done it all and still do it all.  For this discussion I will assume we are referring to taping indoors on a stand from the soundboard area.  Onstage or festival situations are conducive to more diverse configurations.  These days I always run a pair of cards in NOS and hypers in some form of PAS (lately 25cm @ 70deg).  It is so easy, light, and low profile with actives and SRS mounts...so why not.  I post all mic pairs on their own and have typically mixed the pairs together.  I can hear all the differences and am usually left wanting something more from the individual pairs.  The cards offer more bass and a richer sound field but lack some focus that the hypers bring. The hypers lack some of what the cards offer.  I know this is not new info to you all.  However, with lots of critical listening lately, I feel that the mix of the two stereo pairs are not hitting my sweet spot either.  I can hear how they may step on each other's toes a bit and prevent their best qualities from shining through together. Recent experimentation with a center channel (hyper or shotgun) has seemed to work for me.  Any phasing and/or cancellation caused by mixing in the center channel is outweighed (to my ears) by the addition of center focus, which usually equates to cleaner vocals.  Often that is what everyone fails to consider..."Does that additional channel/s benefits outweigh the downfalls?".  This question is personal to the taper.  The "Physics" argument is all well and good, but we do not record in a vacuum.  There are so many variables in a given concert recording scenario that influence the raw product, I feel comfortable saying anyone not taking them into consideration is perhaps making the most aggreges error in judgement.  To say that a certain configuration is the best for every scenario may be too simplistic.  What works best in theory is not always what works best in practice. The "less is more" statement is also inaccurate or you would be recording with a single mic.

So Yes, I am on a slightly more minimal trend by cutting down from 4 mics to 3.  This would finally justify my picking up a MixPre-3ii.  But heck, I may rather be moving up from 4 mics to 5 since I hate to lose the pair of hypercards because you never really know which pair will shine that night.  Regardless, I view this as my hobby and the quality of my pulls equate to the degree of effort and concern I have for that particular piece of work.  It is my effort, my time, and my money so I will do what makes me happy and not pee in your beer if you do something different. 

[goodcooker]

I've done it all and still do it all.  For this discussion I will assume we are referring to taping indoors on a stand from the soundboard area.  Onstage or festival situations are conducive to more diverse configurations.  These days I always run a pair of cards in NOS and hypers in some form of PAS (lately 25cm @ 70deg).  It is so easy, light, and low profile with actives and SRS mounts...so why not.  I post all mic pairs on their own and have typically mixed the pairs together.  I can hear all the differences and am usually left wanting something more from the individual pairs.  The cards offer more bass and a richer sound field but lack some focus that the hypers bring. The hypers lack some of what the cards offer.  I know this is not new info to you all.  However, with lots of critical listening lately, I feel that the mix of the two stereo pairs are not hitting my sweet spot either.  I can hear how they may step on each other's toes a bit and prevent their best qualities from shining through together. Recent experimentation with a center channel (hyper or shotgun) has seemed to work for me.  Any phasing and/or cancellation caused by mixing in the center channel is outweighed (to my ears) by the addition of center focus, which usually equates to cleaner vocals.  Often that is what everyone fails to consider..."Does that additional channel/s benefits outweigh the downfalls?".  This question is personal to the taper.  The "Physics" argument is all well and good, but we do not record in a vacuum.  There are so many variables in a given concert recording scenario that influence the raw product, I feel comfortable saying anyone not taking them into consideration is perhaps making the most aggreges error in judgement.  To say that a certain configuration is the best for every scenario may be too simplistic.  What works best in theory is not always what works best in practice. The "less is more" statement is also inaccurate or you would be recording with a single mic.

So Yes, I am on a slightly more minimal trend by cutting down from 4 mics to 3.  This would finally justify my picking up a MixPre-3ii.  But heck, I may rather be moving up from 4 mics to 5 since I hate to lose the pair of hypercards because you never really know which pair will shine that night.  Regardless, I view this as my hobby and the quality of my pulls equate to the degree of effort and concern I have for that particular piece of work.  It is my effort, my time, and my money so I will do what makes me happy and not pee in your beer if you do something different.

I do cards NOS and a center mic quite often in larger indoor venues when I'm towards the back. I almost always end up mixing in some of the center mic.

[Gutbucket]

If either of you guys have access to a fig-8, consider adding that to the single center microphone position to form a Mid/Side pair.  That works particularly well in the above described situations as it does not change your currently preferred 3-microphone arrangement, yet allows you to add as much Side as the situation calls for afterward by ear.. which might be none at all, but you gain that option.  That's a big reason why this is my preferred 4 microphone arrangement and the one I recommend to other folks.

If you don't have a fig-8, consider trying X/Y in the center position.  That does change your primary arrangement slightly, yet retains a coincident "single position" in the center.  A typical 90-degree X/Y angle is likely good, but to hedge the bet in light of what you know you like currently, you might try a rather narrow X/Y angle to start (say no wider than PAS), which will be close to what a single highly directional center microphone pointed directly ahead provides, but with a bit more stereo interest.  Similar to the tweaking how much side you use in a Mid/Side pair, you can always pan the X/Y pair closer to center instead of hard Left/Right to get something closer to what a single microphone pointed directly forward would be doing.  With X and Y panned full center, you form a virtual single microphone pointed directly forward again, although with a wider pattern than either of the individual X/Y microphones.  The wider the X/Y angle, the wider the pattern of the virtual forward facing center microphone. 

However, with lots of critical listening lately, I feel that the mix of the two stereo pairs are not hitting my sweet spot either.  I can hear how they may step on each other's toes a bit and prevent their best qualities from shining through together. Recent experimentation with a center channel (hyper or shotgun) has seemed to work for me.  Any phasing and/or cancellation caused by mixing in the center channel is outweighed (to my ears) by the addition of center focus, which usually equates to cleaner vocals.

This correlates to what I hear as well, and why I frequently campaign for the use of a single microphone position in the middle (either one microphone or a coincident pair) between a somewhat wider than normal near-spaced pair, rather than combining two near-spaced pairs together.  This often gets push back from other tapers at TS, because many prefer a near-spaced pair to an X/Y pair when used by itself, myself included, but the important difference in this case is that center pair is no longer being used by itself in isolation.  Instead it combines better with the near-spaced pair without "stepping on each others toes" as much as two near-spaced pairs will tend to do.  The same argument applies to using a single microphone in the center.  Most will prefer an X/Y pair over a single mono microphone when listened to by itself.  So not liking X/Y by itself is not really relevant to its use in combination with a near-spaced pair, or with a wider spaced omni pair.

When recording using more than two microphones the interaction between channels that are mixed together cannot be avoided or ignored and has a big influence on the outcome.  Limiting that complexity to just three positions in space greatly improves the odds of everything working well in the mix without problems.  Using a coincident pair in the center position does't increase the phase-interaction complexity any more than a single microphone in the center, but in my experience increases the odds of achieving a good sounding recording by adding an additional degree of flexibility and control.

[JiB97]

pic of a time i ran the AT "line cards" PAS and a single AKG ck8 short shotgun in the middle

[goodcooker]

I think a few of the folks around here are bantering about the term "phase" and how it relates to what we do without really understanding what it means.

The only way to be "in phase" when using more than one microphone at one time is to make them completely coincident (located at close as possible to each other in physical space). When we are using 2 mics to make a stereo pair that are near spaced there is "out of phase" action creating partial reinforcement or cancellation of the two sources. This is inevitable when using spaced pairs. I like the sound of spaced mics and like it when I see a good amount of "scattering" on the phase scope that I use 100% of the time when I'm mixing. Managing what happens with phase correlation between multiple sources is as much art as it is science. Don't get lost in the details. All sorts of techniques can produce great results.

There's a nice article using layman's terms and easy to understand concepts here at the Fabfilter website -
https://www.fabfilter.com/learn/science-of-sound/phase-what-is-it-and-why-does-it-matter
This one is neat too - good basics here to provide some terminology for discussion without being overly technical - https://www.fabfilter.com/learn/science-of-sound/wave-theory

[Gutbucket]

Good points. "Phase" in audio is a funky thing, frequently misunderstood. The guy that does the Fabfilter videos on youtube is generally an excellent resource as well. 

Phase meter tools are good way to visually check and confirm what's going on.  Generally, there are two kinds.  The first is a simple looking meter that ranges from 0 to 1 indicating the degree of phase correlation between two signals. Here is a good write up on that kind of phase metering with respect to spaced microphone pairs- https://www.soundonsound.com/sound-advice/q-what-are-my-phase-correlation-meters-telling-me

The other type, the one goodcooker mentions, is a Lissajous display which presents a "spagetti pattern" or "cloud of points", providing more intuitive information about the stereo nature of the relationship.  This was originally done using an oscilloscope.  Here's a more in-depth write up which includes good info on this type of metering- https://www.sweetwater.com/insync/phase-meters-can-help-mixes/

Generally for taper recordings, a nice round blob of dancing spaghetti on that type of display while the music is playing represents a good stereo signal.  The direct sound content is generally more phase correlated (more in-phase) between the two channels and tends to excite the blob vertically, while the reverberant / ambient content is preferably mostly decorellated and excites the blob more horizontally.  It's the dance between the two that creates good stereo interest.  Taper recordings can, will, and generally should have more decorellated content in comparison to most studio recorded stuff.  This helps to best portray the "you are there" live performance aspect, and serves to sort of audibly separate the audience reaction and hall sound from the direct arriving sound from the stage and PA. Its okay for the blob to "go wide" during the break between songs when the content is primarily hall and audience sound. We don't need to worry about LP needles jumping out of the groove, yet decent mono-compatibility remains important. 

[Gutbucket]

Here are a few bullet points that come to mind about phase in regard to audio signals:

• Phase describes a relationship between signals - a single signal has no "phase" at all.
• Explanations of phase generally describe the relationship between two steady state sine waves.  But that's not what music is like.  Music is neither steady state nor a single sinewave.
• Phase is not the same as polarity. Polarity is an inversion of the waveform, without any time-shift, and an inversion of polarity affects all frequencies equally. Phase is a time-shift of one waveform verses another which affects the interaction between the two, and that interaction will vary with frequency. A specific time shift will create a 180-degree phase relationship at a certain frequency and even multiples of that frequency (which is still not the same as a polarity inversion, as it takes time for this interaction to occur), but shifts the phase relationship of all other frequencies by differing amounts.
• A perfectly implemented coincident stereo microphone pair arrangement (X/Y or Mid/Side) will produce no phase difference between channels.  But those which use microphone patterns that have a rear lobe will produce some polarity inversions between channels.
• Any spaced stereo pair of microphones will produce phase differences between channels.  That phase relationship is always complex, varying with frequency, angle of arrival, and the spacing distance between the microphones.
• But any spaced stereo pair of microphones will also produce signals that are in phase.  The in-phase signals occur for sounds that arrive from directly in front, directly in back, above or below (from anywhere along the median plane

 
I suspect it is that last point that makes spaced microphone configurations work well - sources in the dead center of the soundfield will be in phase, and those close to center more in phase than sources located farther out to the sides.. collectively, the reverberant sound which arrives from all directions equally ends up being more decorrelated and thus gets reproduced more diffusely, while the stuff in the middle is more correlated and in-phase.

Optimized spacing between a stereo pair of microphones provides both of those things.

I think the most useful way to setup and use a combination of more than two microphones is with this relationship in mind.  That's what the combination of a wide-spaced pair plus a center coincident pair does particularly well, while keeping the phase interaction complexity from getting out of hand. The two channels of the center coincident pair are fully phase-correlated, producing no phase-difference between its two channels.  That pair provides the clear, sharp imaging needed for good reproduction of the direct sound from stage and PA.  It does that very well, but doesn't do as great a job translating the space, openness, reverb, and "liveness".  The wide pair provides that, via the more decorellated phase relationship between its channels (a good reason to go wider with this pair than you otherwise would if it were used alone).  In this way the two pairs are different enough that they won't tend to step on each others toes, yet will be more likely to complement each other - each providing more of what the other lacks.

[Organfreak]

I record pipe organs in large churches using an omni pair spaced at 1 meter distance. That works well, except for organs placed so high that my stand (6 meters high) is not tall enough to get the mikes close enough to the pipes and I get too much acoustics. See picture.
A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

[voltronic]

I record pipe organs in large churches using an omni pair spaced at 1 meter distance. That works well, except for organs placed so high that my stand (6 meters high) is not tall enough to get the mikes close enough to the pipes and I get too much acoustics. See picture.
A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

Instead of the same bar, I would follow Decca's advice and place an ORTF pair of "detail cardioids" much closer to the pipes than your omnis. See attached picture from the Recording in the Decca Tradition book.

What stand are you using that goes 6 m? I don't think it's the Manfrotto 269 HDBU since that one goes over 7 m.

[Organfreak]

I record pipe organs in large churches using an omni pair spaced at 1 meter distance. That works well, except for organs placed so high that my stand (6 meters high) is not tall enough to get the mikes close enough to the pipes and I get too much acoustics. See picture.
A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

Instead of the same bar, I would follow Decca's advice and place an ORTF pair of "detail cardioids" much closer to the pipes than your omnis. See attached picture from the Recording in the Decca Tradition book.

What stand are you using that goes 6 m? I don't think it's the Manfrotto 269 HDBU since that one goes over 7 m.

Hello Voltronic, thanks for your reply. I could not find the Decca tree attachment?

I made a combination of 2 stands: A K+M aluminum stand and a K+M fishing pole (I thought K+M 24645 and K+M 23783). The aluminum stand has a top section of 30 mm. The fishing pole has a bottom section of 30 mm (foam removed). I took out the top section of the aluminum stand and inserted the fish pole instead. Secured the bottom section of the fish pole after inserting through the clamp with some tape windings to prevent accidental pulling out during set up. This makes a very light weight stand, small size in collapsed state, maximum length 6 meters but sturdy and stable enough to support a bar with 4 mics.

For a Decca tree set up the stand may however not be stable enough, I am both technician and performer and the stand can be unattended while people are walking around during church visits... Catholic churches are always open for public.
To get an idea of the huge dimensions: The ceiling of the church in the picture above is at least 20 meters high. My 6-meter stand did even not reach to the balcony below the organ. So placing a pair of ORTF much closer to the pipes is impossible for my equipment.

The SRA (Stereo Recording Angle) for an omni pair at 1 meter distance is 60 degrees (as per the Neumann app "recording angle calculator"). The SRA for an ORTF pair is 96 degrees. Should the SRA's of two pairs on the same bar match eachother?

[Gutbucket]

A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

The real-world answer will be to try a few different things, listen carefully and decide how well it works or not. 

The SRA (Stereo Recording Angle) for an omni pair at 1 meter distance is 60 degrees (as per the Neumann app "recording angle calculator"). The SRA for an ORTF pair is 96 degrees. Should the SRA's of two pairs on the same bar match eachother?

The part I've bolded above is a question I think about frequently.  I've found no clear answer to this yet.  As far as I can tell the answer is.. maybe.. but not necessarily.. sometimes best if not.

Here's one thing: Even if SRA of two pairs is the same, the image distribution within the SRAs of the two different configurations is going to be somewhat different.  How much does this matter?  Probably depends on the situation and content.  With an organ recording where image is generally diffuse, probably not as much as other things where sharp imaging is expected.

Here's another thing more fundamental altogether: Mixing the two pairs together will produce a new SRA that is going to be different than that of either pair in isolation.

One take away is that when introducing an additional pair in the middle, it can be a good idea to try spacing the omnis more widely.  The best solution may end up being anywhere from the same 1 meter width you are currently using up to twice as wide at 2m.  Using the Schoeps Image Assistant visualizer you can see this for yourself by switching between a two microphone configuration and a three microphone configuration that both use the same spacing between the wide pair, noting how the introduction of a third microphone in the center effects the SRA.

Here are a few guidelines from my experience: If you don't have the ability to monitor and adjust the setup prior to recording, you can reduce the chances of bad phasiness occurring by using a coincident pair arrangement in the middle between the omnis instead of a near-spaced pair.  That reduces the phase interactions to three different microphone positions in space rather than four.  Sorry for being repetitive about this, but its a fundamental issue that becomes important when one cannot monitor and readjust things prior to making the recording.   A near-spaced pair can certainly work in the middle, its just more likely to have issues when mixing the two pairs together which you won't be able to discover until after you mix them.  Its also less likely to be problematic because it is combining two stereo pairs that behave sufficiently differently from each other - one producing stereo cues based strongly on time of arrival differences, the other solely on level differences - making them less likely to "step on each others toes".

Somewhat OT but related-
I'm currently working on a 3-position version of the 2-channel stereo Improved PAS table I posted at TS years ago.  The idea of the original Improved PAS table was to create a list of stereo microphone pair spacing/angle combinations for various Orchestra Angles (OA - which for PA amplified things is the PA angle) where SRA is always equal to OA (more precisely, OA + 10 degrees).  This simplifies the optimization of a microphone configuration from a restricted recording location which may be more distant than desirable by pointing the microphones directly at the outer edges of the source, ensemble or PA and adjusting the spacing between the microphone pair based upon whatever the angle between them ends up being.  The new 3-position Improved PAS table extends this to microphone arrays of 3 or 4 channels, 3 if using a single microphone in the center, 4 if using a coincident pair in the center.

^ A couple general takeaways I've noticed while working this up are:
The spacing between the wide pair is always larger (up to twice as wide as mentioned).
The center single microphone or coincident-pair is typically best placed about 20cm forward of the wide pair.

If you end up trying a few different things, please let me know what ends up working best for you.

[voltronic]

I record pipe organs in large churches using an omni pair spaced at 1 meter distance. That works well, except for organs placed so high that my stand (6 meters high) is not tall enough to get the mikes close enough to the pipes and I get too much acoustics. See picture.
A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

Instead of the same bar, I would follow Decca's advice and place an ORTF pair of "detail cardioids" much closer to the pipes than your omnis. See attached picture from the Recording in the Decca Tradition book.

What stand are you using that goes 6 m? I don't think it's the Manfrotto 269 HDBU since that one goes over 7 m.

Hello Voltronic, thanks for your reply. I could not find the Decca tree attachment?

I made a combination of 2 stands: A K+M aluminum stand and a K+M fishing pole (I thought K+M 24645 and K+M 23783). The aluminum stand has a top section of 30 mm. The fishing pole has a bottom section of 30 mm (foam removed). I took out the top section of the aluminum stand and inserted the fish pole instead. Secured the bottom section of the fish pole after inserting through the clamp with some tape windings to prevent accidental pulling out during set up. This makes a very light weight stand, small size in collapsed state, maximum length 6 meters but sturdy and stable enough to support a bar with 4 mics.

For a Decca tree set up the stand may however not be stable enough, I am both technician and performer and the stand can be unattended while people are walking around during church visits... Catholic churches are always open for public.
To get an idea of the huge dimensions: The ceiling of the church in the picture above is at least 20 meters high. My 6-meter stand did even not reach to the balcony below the organ. So placing a pair of ORTF much closer to the pipes is impossible for my equipment.

The SRA (Stereo Recording Angle) for an omni pair at 1 meter distance is 60 degrees (as per the Neumann app "recording angle calculator"). The SRA for an ORTF pair is 96 degrees. Should the SRA's of two pairs on the same bar match eachother?

Hi There,

Sorry about that - the relevant pages are attached.

Just to be clear, I was not referring to a Decca Tree at all (I think that would not work well here), but other specific techniques Decca engineers have used for organ recording as shown/described in the attachments. You will see that the near cardiods are not very close to the omnis. Besides the setups shown in the Haigh/Dunkerley book, I've seen other engineers do something like fig. 14.2 but with the distant pair used even if there is no division at the opposite end of the church. Sometimes another pair of omnis; sometimes subcards facing away from the organ.

I understand the height issues with the huge church you are recording in. Is there any way you could position your close detail pair actually ON the balcony where the main case is located? If there's a rail, I'm picturing a clamp setup with your K&M pole.

[Organfreak]

A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

The real-world answer will be to try a few different things, listen carefully and decide how well it works or not. 

The SRA (Stereo Recording Angle) for an omni pair at 1 meter distance is 60 degrees (as per the Neumann app "recording angle calculator"). The SRA for an ORTF pair is 96 degrees. Should the SRA's of two pairs on the same bar match eachother?

The part I've bolded above is a question I think about frequently.  I've found no clear answer to this yet.  As far as I can tell the answer is.. maybe.. but not necessarily.. sometimes best if not.

Here's one thing: Even if SRA of two pairs is the same, the image distribution within the SRAs of the two different configurations is going to be somewhat different.  How much does this matter?  Probably depends on the situation and content.  With an organ recording where image is generally diffuse, probably not as much as other things where sharp imaging is expected.

Here's another thing more fundamental altogether: Mixing the two pairs together will produce a new SRA that is going to be different than that of either pair in isolation.

One take away is that when introducing an additional pair in the middle, it can be a good idea to try spacing the omnis more widely.  The best solution may end up being anywhere from the same 1 meter width you are currently using up to twice as wide at 2m.  Using the Schoeps Image Assistant visualizer you can see this for yourself by switching between a two microphone configuration and a three microphone configuration that both use the same spacing between the wide pair, noting how the introduction of a third microphone in the center effects the SRA.

Here are a few guidelines from my experience: If you don't have the ability to monitor and adjust the setup prior to recording, you can reduce the chances of bad phasiness occurring by using a coincident pair arrangement in the middle between the omnis instead of a near-spaced pair.  That reduces the phase interactions to three different microphone positions in space rather than four.  Sorry for being repetitive about this, but its a fundamental issue that becomes important when one cannot monitor and readjust things prior to making the recording.   A near-spaced pair can certainly work in the middle, its just more likely to have issues when mixing the two pairs together which you won't be able to discover until after you mix them.  Its also less likely to be problematic because it is combining two stereo pairs that behave sufficiently differently from each other - one producing stereo cues based strongly on time of arrival differences, the other solely on level differences - making them less likely to "step on each others toes".

Somewhat OT but related-
I'm currently working on a 3-position version of the 2-channel stereo Improved PAS table I posted at TS years ago.  The idea of the original Improved PAS table was to create a list of stereo microphone pair spacing/angle combinations for various Orchestra Angles (OA - which for PA amplified things is the PA angle) where SRA is always equal to OA (more precisely, OA + 10 degrees).  This simplifies the optimization of a microphone configuration from a restricted recording location which may be more distant than desirable by pointing the microphones directly at the outer edges of the source, ensemble or PA and adjusting the spacing between the microphone pair based upon whatever the angle between them ends up being.  The new 3-position Improved PAS table extends this to microphone arrays of 3 or 4 channels, 3 if using a single microphone in the center, 4 if using a coincident pair in the center.

^ A couple general takeaways I've noticed while working this up are:
The spacing between the wide pair is always larger (up to twice as wide as mentioned).
The center single microphone or coincident-pair is typically best placed about 20cm forward of the wide pair.

If you end up trying a few different things, please let me know what ends up working best for you.

Thanks Gutbucket, this makes sense. For me, having two omnis and two cards, only XY will be possible to make a coincident pair between the spaced omni mics. Placing of the middle pair 20 cm forward of the wide pair may be possible by careful bending of the aluminum bar in the horizontal plane.
My monitoring option is just listening back via headphones at recording location.
-Is that 20 cm forward position not introducing other phase problems? The sound will hit the middle pair just before hitting the spaced mics.
-Do you have suggestions for the angle between the XY mics? As my Rode NT55 card capsules can sound a bit bright/sharp, sound wise I would prefer rather 110 degrees than 90 degrees.

[Organfreak]

I record pipe organs in large churches using an omni pair spaced at 1 meter distance. That works well, except for organs placed so high that my stand (6 meters high) is not tall enough to get the mikes close enough to the pipes and I get too much acoustics. See picture.
A solution may be to place an extra pair of cards on the same bar.
Should this extra pair be a standard DIN or ORTF configuration or should this extra pair match the SRA of the omni pair?

Instead of the same bar, I would follow Decca's advice and place an ORTF pair of "detail cardioids" much closer to the pipes than your omnis. See attached picture from the Recording in the Decca Tradition book.

What stand are you using that goes 6 m? I don't think it's the Manfrotto 269 HDBU since that one goes over 7 m.

Hello Voltronic, thanks for your reply. I could not find the Decca tree attachment?

I made a combination of 2 stands: A K+M aluminum stand and a K+M fishing pole (I thought K+M 24645 and K+M 23783). The aluminum stand has a top section of 30 mm. The fishing pole has a bottom section of 30 mm (foam removed). I took out the top section of the aluminum stand and inserted the fish pole instead. Secured the bottom section of the fish pole after inserting through the clamp with some tape windings to prevent accidental pulling out during set up. This makes a very light weight stand, small size in collapsed state, maximum length 6 meters but sturdy and stable enough to support a bar with 4 mics.

For a Decca tree set up the stand may however not be stable enough, I am both technician and performer and the stand can be unattended while people are walking around during church visits... Catholic churches are always open for public.
To get an idea of the huge dimensions: The ceiling of the church in the picture above is at least 20 meters high. My 6-meter stand did even not reach to the balcony below the organ. So placing a pair of ORTF much closer to the pipes is impossible for my equipment.

The SRA (Stereo Recording Angle) for an omni pair at 1 meter distance is 60 degrees (as per the Neumann app "recording angle calculator"). The SRA for an ORTF pair is 96 degrees. Should the SRA's of two pairs on the same bar match eachother?

Hi There,

Sorry about that - the relevant pages are attached.

Just to be clear, I was not referring to a Decca Tree at all (I think that would not work well here), but other specific techniques Decca engineers have used for organ recording as shown/described in the attachments. You will see that the near cardiods are not very close to the omnis. Besides the setups shown in the Haigh/Dunkerley book, I've seen other engineers do something like fig. 14.2 but with the distant pair used even if there is no division at the opposite end of the church. Sometimes another pair of omnis; sometimes subcards facing away from the organ.

I understand the height issues with the huge church you are recording in. Is there any way you could position your close detail pair actually ON the balcony where the main case is located? If there's a rail, I'm picturing a clamp setup with your K&M pole.

Thanks, this is a lot of useful information I did not see up to now. Nice book to ask for my next birthday .
If I read chapter 14.4, it seems moving the cardioids forward is specifically done to highlight a choir section of the organ and just adding more detail allows the cardioids remain sitting on the same bar as the omnis?
I try to keep my set-up as easy as possible.

[Gutbucket]

[snip]
-Is that 20 cm forward position not introducing other phase problems? The sound will hit the middle pair just before hitting the spaced mics.
-Do you have suggestions for the angle between the XY mics? As my Rode NT55 card capsules can sound a bit bright/sharp, sound wise I would prefer rather 110 degrees than 90 degrees.

With the omnis spaced 1 meter apart, an approx 20cm forward center pair spacing is not likely to alter the complex phase relationship between the omnis and center pair in a way that is problematic.  Generally, the center pair fwd spacing should be greater when the omni spacing is smaller, lass when wider. In the modeling and in my experience 20cm seems to work well across a wide range of cases. Positionong the center coincident pair somewhat forward of the omnis helps in aligning the imaging which results from the interaction between the coincident pair in the center and the omni over to one side, and vice versa for the center coincident pair and omni on the other side, without requiring any application of delay.

This is meaningful because in addition to the stereo image interaction between the left and right channels of the each separate individual pair (the omni pair, the coincident X/Y pair), there will also be stereo interaction between the left omni with the right center drectional microphone, and the right omni with the left center directional microphone.  These subsequent secondary pairs produce their own SRAs, which complicates things. Pushing the center pair forward by ~20cm or so helps to get these secondary SRAs to "hand-off" from one to the other across the center more so than simply overlaping, miminizing potentially conflicting imaging cues.

That said, the nature of organ music will tend to downplay imaging and emphasise steady-state tonal aspcts more so than other types of music, so tweaking the relationship between the three separate microphone positions in space in your situation my be more about finding the right tonal interaction, than optimizing image.

Use whatever X/Y angle you are most comfortable with and sounds best to you. Because I can alter the frequency response of that pair with EQ, and its stereo width with a mid/side ratio adjustment, I tend to choose X/Y angle based on how on or off-axis from the source I want each microphone if that pair to be in terms of center clarity and direct/reverberant ratio.

110 degrees is entirely reasonable.  If you find you want a bit more direct definition and clarity from that pair, narrow it up and adjust its EQ to comoensate if it gets too bright.