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Author Topic: "Variable Fixed-Configuration Stereo Bar" - thoughts?  (Read 1635 times)

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Offline melontracks

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"Variable Fixed-Configuration Stereo Bar" - thoughts?
« on: May 16, 2019, 11:34:33 AM »
My first foray into open taping after many years of stealthing was this past Sunday. I really enjoyed the freedom of not having to wear my recording gear. Ha! I tried to pay attention to my setup routine so i could improve it at future shows. Aside from managing to lose one of the clips that came with my brand new AT4041s, my biggest gaffe was trying to set up a stereo-pair of mics on a stereo bar using a ruler and a protractor. i wasted a solid 15 minutes dicking around trying to get it "just right." Having two variables (separation and angle) where changing one changes the other is maddening. Being brand new to this, I would like to try out many of the different configurations (ORTF, DIN, A-B, etc).

People make rigs to hold specific mics in specific configurations, but I wanted something that would let me lock the mics down quickly in a number of arrangements, depending on what i wanted to try. Last night, I built this from a piece of aluminum plate and some cheap shockmounts:



I had bought the shockmounts for another purpose, then noticed that they had a couple of threaded holes in the top of the mount that take M4-.70 bolts. I should have probably cut the plate longer, but this was just a prototype. So far, I have it drilled so I can run ORTF, DIN, NOS, and a 30cm-spaced A-B pair. I could pepper the plate with an unlimited amount of holes for a great variety of placements. I've labeled them with the config and spacing.



This thing removes the angle variable, so all you need is a cm ruler to space the capsules. It's really fast, and requires only a screwdriver and a minute or two to completely re-arrange. I need to come up with a better spacer than the miniature sockets i'm using, but that's a detail.

Aside from the fact that the mics tend to sag a little if they're hanging too far out one side or the other, i haven't identified any liabilities. I was wondering if the plate itself might present acoustic problems. I could skeletonize it, but would rather not bother. I searched around for similar homebrew stuff and was surprised i didn't find anything. What might I be overlooking here as far as potential problems?

Thanks.

One more pic:


Offline DSatz

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #1 on: May 16, 2019, 12:27:22 PM »
That's some nice-looking metalwork. I agree that it can be difficult and time-consuming to get the angles between capsules the way you want them to be, and anything that simplifies the process and reduces errors is very welcome. That's why for some configurations, I use fixed stereo bars that set the angle and spacing between capsules on active cables so that there's no ambiguity.

--The acoustic effect of a rigid, flat surface depends on how large it is, how far your capsules are from it, and sound wavelengths. As a rule of thumb, any rigid surface or solid object with dimensions half a wavelength or larger should be kept several wavelengths away from the capsule. High frequencies are the most vulnerable to physical interference, because their wavelengths are the shortest.

How big is a wavelength? If you use 1100 ft/sec as the speed of sound in air, then a wavelength at 1100 Hz = one foot. At 11 kHz (ten times that frequency) it's one-tenth of a foot, or just 1.2 inches. So if we just consider just the central part of your mounting plate by itself (ignoring most of its length, in other words), that's already half a wavelength or more for all frequencies above about 2 kHz.

So its potential for physical interference with sound is considerable, and you really do need to keep your capsules away from it. I would suggest six inches or more so that its solid angle in the sound field around your capsules won't be large. If you build another version of this plate, I suggest that you try to reduce its depth (the dimension that looks as if it's maybe 3 to 4 inches in the current version) but most of all, keep your capsules away from the flat part.

--best regards

P.S.: If those are cardioid mikes in the center--for coincident cardioids, I would really urge you to try a wider angle between your capsules unless a near-mono recording is required for some reason. Cardioid just isn't a sharply directional pattern.
« Last Edit: May 16, 2019, 12:39:58 PM by DSatz »
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Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #2 on: May 16, 2019, 12:49:21 PM »
Nice work.

Consider making a few of these, or otherwise figure out a way to extend the spread of the omnis for any situation where you are able to run them wider, which will be advantageous for taper situations.  I'd double it to 60cm or better 1m, and if mixing the omnis with with the X/Y pair in the middle, 1 to 1.5m or even more will often improve things significantly.  One way to increase omni spacing to something wider than the bar itself is to point the omnis outwards in opposite directions to either side, so that the capsules are cantilevered outwards past the ends of the bar when placed in the shock-mounts.  Would be easy to set that up by making another pair of mounting holes in-line with the bar at either end.  Such a 180 degree opposed arrangement of the omnis also leverages their slight high frequency directionality in a way which helps compensate somewhat for an otherwise overly narrow omni spacing.

I commonly use heat-shrink over the aluminum bar-stock parts I make for my taping rigs.  It provides a tough, resilient, hard-rubber optically flat-black surface, decent acoustic damping, and deforms just enough when bolting through it to friction-lock both the part and screw in place so as to resist rotation.  Requires a diameter large enough to slip over the bar prior to shrinking, and works best if you shrink it onto the bar prior to drilling the holes.  I  clean it up by sanding down the heatshrink which extends past the ends until flush with either ends of the bar using a standing belt-sander.  The bar-sock I use is narrower in width yet thicker than that pictured above, which increases resistance to bending while somewhat reducing the acoustic interaction issues Mr Satz mentions.

I don't think you need to worry much about resonance of the bar, especially with the mics suspended in shock mounts.

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Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #3 on: May 16, 2019, 01:36:18 PM »
I strongly concur with Mr Satz's post script comment on increasing the X/Y angle using cardioids to greater than 90 degrees as long as your intent is use of that pair on its own.  And I strongly recommend your own experimentation with other stereo configurations to learn what they sound like in the situations in which you record.  That's the best way to really learn about two-channel stereo microphone arrangements.

But be aware that complications arise when mixing two or more two-channel microphone arrangements together, especially if they are in close proximity to each other.  That pretty much throws much of what works for 2-channels alone out the window, and X/Y angle is a good example of that.  If mixing with omnis, I usually prefer a center pair X/Y angle which is 90-degrees or less, in combination with a wider omni spacing.  The near-mono (but not quite) nature of that center X/Y configuration blends nicely with the omnis without conflict, providing tight X/Y stereo imaging across the center of the image while the wide omnis provide an immersive ambient "stereo-ness" which a cardioid X/Y setup tends to lack regardless of angle.

Because of that, if you wish to play with mixing both microphone pairs at some point, you might consider positions for 45-degree X/Y for combination with wide omnis, as well as 90-degrees, and say 110-120-degree X/Y for a pair of stereo cardioids on their own.   

At that point, a productive approach that works especially well for typical taper recording positions which are not close to the stage is to choose whichever angle places your cardioid or supercardioid X/Y pair closest to on-axis with the main PA speakers.  Then afterwards while mixing with the omnis, re-adjust the stereo width of the X/Y pair to whatever works best by ear, using a stereo-width-adjustment plugin that does L/R>Mid/Side>L/R type adjustment.

Apologies for jumping ahead, just attempting to lay out something of a roadmap to keep you out of the ditch.
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Offline melontracks

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #4 on: May 16, 2019, 03:46:58 PM »
So its potential for physical interference with sound is considerable, and you really do need to keep your capsules away from it. I would suggest six inches or more so that its solid angle in the sound field around your capsules won't be large. If you build another version of this plate, I suggest that you try to reduce its depth (the dimension that looks as if it's maybe 3 to 4 inches in the current version) but most of all, keep your capsules away from the flat part.

this bar is about 6cm deep. I think after I make others, I'll cut this one out to suit some specific configurations. My options for bar shapes are pretty unlimited, as I'm cutting them from a large plate of aluminum with a jigsaw. I'll put more specific thought into future designs. I went with 6cm on this one because it was pretty much the narrowest bar that would still permit a parallel pair of A-B mics with the threaded holes in the shockmounts being where they are (41.2 mm apart).

I commonly use heat-shrink over the aluminum bar-stock parts I make for my taping rigs.  It provides a tough, resilient, hard-rubber optically flat-black surface, decent acoustic damping, and deforms just enough when bolting through it to friction-lock both the part and screw in place so as to resist rotation.  Requires a diameter large enough to slip over the bar prior to shrinking, and works best if you shrink it onto the bar prior to drilling the holes.  I  clean it up by sanding down the heatshrink which extends past the ends until flush with either ends of the bar using a standing belt-sander.  The bar-sock I use is narrower in width yet thicker than that pictured above, which increases resistance to bending while somewhat reducing the acoustic interaction issues Mr Satz mentions.

I like this idea! Man, the bar I have has 3/8 thread on the thumb screws, so i had to use 3/8 to 5/8 adapters to connect to the stock mic clips, and BOY did they want to spin. Ha!

I strongly concur with Mr Satz's post script comment on increasing the X/Y angle using cardioids to greater than 90 degrees as long as your intent is use of that pair on its own.  And I strongly recommend your own experimentation with other stereo configurations to learn what they sound like in the situations in which you record.  That's the best way to really learn about two-channel stereo microphone arrangements.

Thanks for all this good advice. I guess I need to read up on the X-Y 90-degree card pairing. I was under the assumption that you wanted the capsules to be as perfectly coincident as possible to avoid potential phasing. As far as having four mics on the stand at the same time, I probably should have posted different photos; i don't really foresee doing that much, if at all. Mostly, i just wanted to see how much junk I could mount after i built it, and get a feel for what would physically interfere with what, and when spacers would be needed. I expect to build a few of these for different general purposes.

Thanks again for the input!

Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #5 on: May 16, 2019, 05:02:11 PM »
I guess I need to read up on the X-Y 90-degree card pairing. I was under the assumption that you wanted the capsules to be as perfectly coincident as possible to avoid potential phasing.

That is correct, any coincident microphone setup arrangement should aim to have the microphone diaphragm elements as coincident as possible in the vertical plane
regardless of the angle between the two microphones.  With the capsules arranged so as to be coincident with each other, there is no partial phase difference between the signals of both channels. This applies to Mid/Side setups as well as X/Y.. and to Blumlein crossed fig-8's (which can be run either way, as X/Y or M/S).

If you are setting this up for use of a single stereo microphone pair at a time, perhaps make 2 or 3  X/Y setup positions providing something like: 105, 117 and 130 degrees or there about. And if you make a few omni bars, I'd suggest something like the 30cm you already have, 60cm and 90cm.  Won't hurt to try +/- 90 degree sideways pointing omnis as well, to determine for yourself how that sounds different than forward pointed omnis.

Quote
As far as having four mics on the stand at the same time, I probably should have posted different photos; i don't really foresee doing that much, if at all. Mostly, i just wanted to see how much junk I could mount after i built it, and get a feel for what would physically interfere with what, and when spacers would be needed. I expect to build a few of these for different general purposes.

That's a good approach and establishes a strong foundation for really getting to know how different stereo-pair microphone configurations sound. 

Things start to get complicated quickly when multiple microphone pairs placed in close proximity are mixed together, so its good to resist such temptations until you get a strong handle on how single pairs behave.  It's not a simple linear 2+2=4 type of combination as many expect.  This is one reason why when tapers discuss using two pairs of microphones on the same stand with the intent of mixing them together, I suggest they use a coincident pair between a wide-spaced pair, with the coincident pair angled narrower than one would ever typically want to do if using that pair alone, and the wide pair spaced something like twice as wide than one might want if that pair were used on its own.  This represents a heavy modification of what works well for a single two-microphone configurations, yet totals only three microphone positions in relatively close proximity to each other (2-channels are coincident in the single center position) rather than four which would be the case if trying to mix two near-spaced pairs or a near-spaced pair + omnis.
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Offline heathen

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #6 on: May 16, 2019, 05:45:19 PM »
There are some very nice bars out there that make setup in different configurations easy, but all those I know of are pricey (Grace, etc.).
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Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #7 on: May 16, 2019, 06:28:51 PM »
^ OT, but I long dreamed of an articulated pantagraph-like bar that automatically changes angle verses spacing, based on the Stereo Zoom data for a particular pickup pattern.

I've seen videos of exotic computer-controlled electrical actuator driven remote-controlled contraptions which do that, but I'm imagining a simpler mechanically geared "rack and pinion" arrangement.. sort of a steam-punk love-child of a Grace spacebar, spirograph, slide-rule menage-a-toi!  Any clockwork makers on board?
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Offline melontracks

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #8 on: May 17, 2019, 11:12:57 AM »
If you are setting this up for use of a single stereo microphone pair at a time, perhaps make 2 or 3  X/Y setup positions providing something like: 105, 117 and 130 degrees or there about. And if you make a few omni bars, I'd suggest something like the 30cm you already have, 60cm and 90cm.  Won't hurt to try +/- 90 degree sideways pointing omnis as well, to determine for yourself how that sounds different than forward pointed omnis.

I'll set up those alternate angle X/Y setups on this bar, and the "variety of omni arrangements" will be my next bar. Dumb question: if omnis are truly omnidirectional, does it actually not matter what direction they're pointed? Most of what I read implies this, though anecdotally, i feel like i can perceive a difference. If omnis on stage or right in front are well-positioned space as much as 6-feet apart, it stands to reason that a 20-foot-long bar on a stand in the back of the hall would be a practical thing to have, right?   :hmmm: Could be hard to get in the car. Ha!

Things start to get complicated quickly when multiple microphone pairs placed in close proximity are mixed together, so its good to resist such temptations until you get a strong handle on how single pairs behave.

Is this strictly a phasing problem, or is it about the stereo "image" you get when all four mics are on a single plane relative to the sound source? I'm fine with "it's complicated." Just curious, if it's not too involved.

There are some very nice bars out there that make setup in different configurations easy, but all those I know of are pricey (Grace, etc.).

^^This! Pricey, indeed. I understand what it takes to make a precise piece of equipment, but I marvel at the price of Grace's stereo bars, though they are pretty sexy. Even if you were machining them one at a time by hand, it's hard to imagine a piece of metal with a couple of thumb screws in slots costing $500. Not disparaging it...it's just out of the question for me. Total cost of this thing I'm tinkering with so far is $42. (4X$9.99 for the smallrig shockmounts off of amazon and a bag of bolts from Lowe's).

I long dreamed of an articulated pantagraph-like bar that automatically changes angle verses spacing, based on the Stereo Zoom data for a particular pickup pattern.

Honestly, if I had a better understanding of Stereo Zoom, I think I could pull it off. I've built all sorts of nonsensical stuff, and my nephew is an aerospace engineer. When he's back in town, I'll talk to him about it. As I understand Stereo Zoom, there's a range of "correct" angle/spacing configurations for any given Stereophonic Recording Angle (SRA) depending on considerations of angular distortion and the ratio of direct to reverberant sound. I get lost in those considerations. If there were a "best" (or at least most-frequently useful) answer to dealing with them, it would simplify things. I think I could build a pantograph-like bar (a pantobar?) for a specific mic type (I'd just stick with cardiod) that would either A) cover the range of configurations for a specific SRA, or B) cover the range of SRAs for a particular "most desirable" solution for angular distortion and ratio of direct to reverberant sound.

Does that make any sense, or am I completely wrong? I think between my nephew's design skills and my so-so fabrication, it could be do-able. A computer animation of a pair of lines representing the mic capsule positions through the ranges of either A or B based on the curves in Williams' SRA diagram would probably be the starting point. Which sort of bar would be more useful? I'm assuming "B." I think I understand your saying "based on the Stereo Zoom data for a particular pickup pattern" to imply that my assumption is correct. For example, a "B-type" bar might be one that "Is infinitely adjustable for a pair of cardiod mics positioned for an angular distortion value (ADV) of 5 for SRAs between +/-90* and +/-50* and an ADV of 4 between +/-50* and +/-30*" but I have no idea what that ADV should be. Those values keep the ADV out of the "bad" zones for reverberation limits...I think.  I could also be completely off-base.

Offline DSatz

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #9 on: May 17, 2019, 06:01:07 PM »
It's probably easiest to understand Prof. Williams' work if you imagine an acoustic performance by musicians on a stage in front of you. The farthest-left and farthest-right sound sources are some distance apart from each other, so imagine a straight line connecting them. Then draw straight lines from those two points to your recording position. You now have a triangle with yourself at one of its angles--and you're facing what we hope is a pretty-much-symmetrical left-to-right arrangement of sound sources.

Now consider, as a parallel situation, your home stereo system. Assuming that you have two loudspeakers some distance apart, and you sit or stand (or lie, or kneel, or dangle from a chandelier) at one corner of a triangle as you face those speakers. The assumption is that this triangle will be approximately equilateral. And the assumption is that during playback, you want the relative positions of the original sound sources to seem to originate from places in or between the two speakers, corresponding to the relative positions that they actually occupied during the performance.

If the angle that you faced in the hall was 60 degrees, for example, then the geometrical correspondence between performance and playback will be 1:1, if you have achieved this ideal. If the original performers occupied a much wider angle with respect to your recording position, then that wider angle will be squeezed (proportionately) down to the 60 degrees that you have during playback. (If the original performance was much narrower, that's a bit of a special case, because in general it sounds very unnatural to stretch the angle by much--you get "the violin that ate Manhattan" effect which can be, um, rather disconcerting ...)

All of his charts and graphs and magical incantations are aimed at (a) getting the stereo image to occupy the intended width in the space between your speakers, including the speaker positions themselves as endpoints if that's what you want, and (b) keeping those angles proportional--i.e. whatever sound source was in the center, if it was really only as wide as whatever was on (say) the far left, it shouldn't play back sounding as if it was much wider or much narrower than whatever was on the far left. "Everything in proportion" (geometrically speaking) is the idea.

He is also very much concerned with the pickup of reverberant sound, both quantitatively and qualitatively. But that's maybe too much to go into here; I just wanted to set out the basics.

(By the way, I've known him for years from numerous meetings at AES conventions. He's a quick, funny, warm-hearted guy with twinkly eyes, who seems to be well liked and respected by those familiar with his work. And by no means is he the stereotype of a theoretician who only juggles numbers and equations and doesn't listen; he does a large amount of live recording and is constantly tinkering and experimenting with different recording and playback arrangements. Last I heard, he was heavily into 7.1-channel systems, for example.)

--best regards
« Last Edit: May 17, 2019, 06:13:02 PM by DSatz »
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Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #10 on: May 17, 2019, 09:32:56 PM »
Quote
(If the original performance was much narrower, that's a bit of a special case, because in general it sounds very unnatural to stretch the angle by much--you get "the violin that ate Manhattan" effect which can be, um, rather disconcerting ...)

It happens that much of Taperssection style audience recording falls into this special category, as the total angular width of all sound sources on stage and the PA speakers to either side of it, quite often constitute an angle of less than 60 degrees as viewed from the recording position. The narrow "orchestra angle" as viewed from the recording position, plus the use of narrower angles between the microphones in an attempt to to keep them closer to on-axis with the source, reducing sensitivity to the sides and rear, is what leads to microphone spacings which would seem inconceivably wide in more typical recording scenarios.

That, along with other unusual acoustic attributes of PA reinforcement make recording from an audience perspective a rather strange subworld compared to most other forms of music recording.
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Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #11 on: May 17, 2019, 09:57:37 PM »
A decade or so ago, a taper friend who always uses the Point At Stacks microphone setup commented that other tapers were nuts for using stereo microphone configurations which angle the microphones more widely than the edges of the stage, such that the microphones point off axis (think ORTF with a 110 degree angle between microphones from a perspective where the stage is less than 50 degrees wide). Gesturing toward the stage he said, "the music we want to hear is coming from that way, why point the microphones at the trash cans and exit doors on the sidewalls?"  I admitted he had a good point, and attempted a brief explanation of the how the angle/spacing relationship between microphones is linked and affects stereo imaging, the difference in off-axis response behavior of various different microphones, and other standard recording stuff, but he just shook his head and was having none of it. 

Years later I realized via experience he was right.. at least with regards to addressing the most important aspect of a relatively distant audience recording- the qualitative sense of clarity, reverberance, and impression of distance versus proximity (granted, he didn't state his case in those terms at the time).  Good proportional imaging qualities are far less critical to a "reasonably good" AUD taper recording and a luxury by comparison, and most tapers don't care to dive too deep into microphone setup and acoustic theory.  This eventually became the incentive for me to work up the Improved PAS table which specifically applies Mr. Williams work to the popular PAS technique.  A technique which originally came into being as a sort of grass-roots-experience-derived taper setup for AUD taping which did a good job of addressing that most important aspect when recording PA amplified performances from a distance, but never really took good imaging and stereo qualities into much consideration. I realize most tapers will never actually use the wider spacings suggested in the table for narrow PAS angles, but it at least provides a non-theoretical easy-to-read entry point into the general trend of stereo microphone pattern/spacing/angle relationships via a simple lookup table.

I never intended to try and influence that taper friend's method too much with my ways, yet occasionally suggest he give wider spacings a try to complement the 40 degree-ish PAS angles he typically uses.

Mr Melon, enjoy your experimentation with various stereo microphone setups, there is much you will discover which can be applied widely to all forms of recording.  Yet also keep in mind that in a number of significant ways taper audience recording can be quite different than most other forms of recording, and it is all those other forms of recording for which you will find reference material, including this website.  Have fun, keep an open mind and follow your ears.
« Last Edit: May 17, 2019, 10:06:22 PM by Gutbucket »
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Offline DSatz

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #12 on: May 18, 2019, 12:16:10 AM »
Hmmm: I would have said that you were right and that your taper friend was wrong. As you pointed out, the angular width of the sound sources is often relatively small in the type of recording that we're talking about. But narrowing the angle between microphones in a coincident or closely-spaced pair doesn't increase the proportion of direct sound in the recording by very much. To a much greater extent, rather, it makes the two channels of the recording much more similar to one another than they were before--which pushes the recording toward mono.

A more appropriate response, if it's possible, might be to put more distance between the microphones, to use microphones with greater directivity (if you're not using supercardioids already), and/or to use microphones with a moderate upper-midrange elevation.

The "violin that ate Manhattan" effect is caused by putting the microphones too close to the sound source(s) in an attempt to widen the image. That removes the solo instrument (or other narrow source) from the context of the space that it's in, and instead "brings it into your living room" where it wasn't invited. So that is really not a risk that most tapers will ever run.

--best regards
« Last Edit: May 19, 2019, 06:37:00 AM by DSatz »
music > microphones > a recorder of some sort

Offline melontracks

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #13 on: May 18, 2019, 01:47:03 PM »
I'm glad the conversation has gone the way it has here. Good stuff, and I have a better understanding of what I should be heading toward in getting what I want from my mic arrangements. I like the Improved PAS approach (especially that the angles and spacings are spelled out for me, instead of me having to guess at a number of variables. Ha!). When I was setting up at the show last sunday, i thought "well, the stage is small, but the hall is really short, so i'm actually still pretty close to the stage in the back of the room" but was a little flummoxed when i discovered that the entire "orchestra angle" from where i stood was 50 degrees, or +-25 degrees...which isn't even on Williams' diagrams.

Looking at the specs for Improved PAS, I see i'm going to have to build a sectional bar for that, so i'm carrying two 2-foot pieces that assemble onsite instead of a single 4-footer. :)

I had observed that virtually all wisdom available online about live recording assumes you have the option to set up pretty close to the performers, and that very little of it speaks to audience-based recordings, which seems kind of odd, i guess, until you consider who the pros would be conducting their research for.

Chris

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #14 on: May 19, 2019, 07:08:01 AM »
Chris/melontracks, yes. The research projects of Williams, Sengpiel, Wittek, (etc., e.g. less formally Griesinger) are based on assumptions such as:
  • open recording, with a free choice of the number, type and positioning of microphones, and maybe even some leeway to position the performers ...
  • ... of mostly "acoustic" (unamplified) sources, especially classical music ...
  • ... by professionals schooled in the technology of recording AND in the prevalent aesthetic of recording such material (as in the German "Tonmeister" approach) ...
  • ... in spaces designed above all for clear, pleasant, well-balanced sound, according to the kind of material that is being performed.
These are/were researchers with deep roots in European musical, technical and intellectual traditions, in other words. American hobbyists who mainly record amplified rock 'n' roll, generally from the audience position, often in venues where acoustics are a secondary consideration if that, don't necessarily know or care about those traditions. Undoubtedly that leads to large amounts of "re-inventing the wheel".

But the lack of a constraining tradition can also free the imagination. It prompts many people to experiment and develop their approaches based on careful listening to the results--a very real form of old-fashioned practical science. I think, for example, that Benjamin Franklin would approve.

Hobbyists are also free to care more--even primarily--about their own enjoyment of the experience of recording. And that includes some complex psychological and social factors. Some people are drawn to the status (real or imagined) of being a person who makes recordings, or who makes them in a certain way and/or with a certain type of equipment. This can lead to an odd kind of identity politics and niche-seeking.

To which all I can say is, in this world there are plenty of worse things.

--best regards
« Last Edit: May 21, 2019, 01:49:32 AM by DSatz »
music > microphones > a recorder of some sort

Offline melontracks

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #15 on: May 20, 2019, 12:00:22 PM »
But the lack of a constraining tradition can also free the imagination. It prompts many people to experiment and develop their approaches based on careful listening to the results--a very real form of old-fashioned practical science. I think, for example, that Benjamin Franklin would approve.

But hobbyists are also free to care more--even primarily--about their own enjoyment of the experience of recording. And that includes some complex psychological and social factors. Some people are drawn to the status (real or imagined) of being a person who makes recordings, or who makes them in a certain way and/or with a certain type of equipment. This can lead to an odd kind of identity politics and niche-seeking.

To which all I can say is, in this world there are plenty of worse things.

--best regards

Agreed! I've seen a bit of that in the forum here over the years. Ha! People can certainly have strong opinions. For me, one of the more interesting aspects of open taping is that it lets me quantify qualitative observations to some degree...something almost impossible with stealth taping. I know that having precise configurations based on established techniques and wisdom won't magically translate to a pleasing recording, but it let's me track what worked and what didn't like a recipe. Start with something known, throw it away if it doesn't work, tweak it to your liking, changing just one variable at a time.

Having that sort of control is imperative if I'm ever going to get to where i want. I'm not very good at winging it.

To that end, I'm working up a second stereo bar. My idea with this one is that it will accommodate Gutbucket's Improved PAS positions for cardiod mics from DIN-equivalent down to 30-degree PAS angle, and on the flipside will have simple 30 - 60 - 90 - 120cm spaced brackets for A-B omnis. It's long enough that i'm designing it to fold in half for travel and storage. Here's a couple of pics of what i have mocked up so far.







I haven't yet decided whether to tack the brackets in set positions or attach them with a screw. I'm leaning toward tacking them, as it would be really hard to thread a hole in this light-gauge square tubing that I could crank a screw down hard enough to actually hold it in place

Chris


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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #16 on: May 20, 2019, 01:28:04 PM »
I know that having precise configurations based on established techniques and wisdom won't magically translate to a pleasing recording, but it let's me track what worked and what didn't like a recipe. Start with something known, throw it away if it doesn't work, tweak it to your liking, changing just one variable at a time.

Best advice I can give for undertaking this kind of Ben Franklin empirical approach while actually recording live performances is to record two microphone setups from the same position at the same time whenever possible: Your current "known good" microphone arrangement as a control, and an alternate setup you wish to compare against it.  This is really the only good way I've found to sufficiently constrain the other variables and enable a really useful listening comparison of just that single aspect under test.  If recording different setups one at a time over the course of different performances, there are simply too many other variables in play. 

Second word of advice is that for hobbyist music taping, practicality reigns over everything we do.  More often than not, we are unable do whatever we might like, which is why we find ourselves recording from further away to begin with.  A big part of solving the taping puzzle is working within the constraints of what we are allowed to do and not do, and determining what is practical within those allowances.

Cool to see your prototype bar laid out like that.  It's a great visual indication of a wide range of angle/spacing relationships which will all provide about the same resulting recording angle, yet produce different stereo aspects. It also makes it easy to visualize how pantagraph-like articulation would work for a single mounting position that could be moved outward along a fixed bar, or more ideally, how angle would change as the bar was telescoped out to increasingly wider positions.  However, even with a center break, the size of that bar may make it unwieldy and impractical.  Maybe consider making it 3 or 4 pieces, so you can leave out the wider mounting options and run it more compactly when necessary.
« Last Edit: May 20, 2019, 02:42:24 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #17 on: May 20, 2019, 01:29:11 PM »
If recording different setups one at a time over the course of different performances, there are simply too many other variables in play. 

This is so true and cannot be emphasized enough.
Recordings on LMA: https://archive.org/search.php?query=taper%3A%22Lucas+Lorenz%22
Mics: Core Sound TetraMic | AT4031 | AT AE5100 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pre: CA9200 Decks: Zoom F8 | Roland R-05

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #18 on: May 20, 2019, 05:24:45 PM »
Best advice I can give for undertaking this kind of Ben Franklin empirical approach while actually recording live performances is to record two microphone setups from the same position at the same time whenever possible: Your current "known good" microphone arrangement as a control, and an alternate setup you wish to compare against it.

I had thought of that. For example, I'll be taping a standard rock ensemble at the Echoplex on June 6. That place is an oddly-wide hall that holds just under 800 people. I thought I'd set up with a wide omni a-b pair and a pair of cards in the appropriate Improved PAS arrangement on this new bar. I understand that I probably won't be able to make a matrix recording using these two inputs, but the two independent should be okay. This Sunday i'll be taping a singer-songwriter at McCabe's Guitar shop (small, standard rectangular room with maybe 100 seats) and was thinking of doing something similar. I think it'll be just two guys with vocals for both, one with a guitar, one with a fiddle. In each case i'd be doing something completely new to me, but i'd get two tests for the price of one. In both cases, i'll try to get a line out from the board if i can, as well.

Maybe consider making it 3 or 4 pieces, so you can leave out the wider mounting options and run it more compactly when necessary.

I had thought of that. The total length of the broken down bar is almost exactly the same length as my Photek stand when it's completely collapsed, so i was figuring i'd just strap it to that. I'll definitely be hitting it with some flat black spray paint. I'm a little concerned that venues might think it's a little obtrusive, it's so long. Ha!

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #19 on: May 20, 2019, 06:06:52 PM »
Right. A bigger constraint is what the venue will allow and what you can do without aggravating them, the band and support people (sound and light guys), and other patrons, rather than what you are able to carry and setup.

You can use the two recording comparison technique to immediately compare the qualities of your first recordings, but where it really becomes valuable is by leaving one of the setups unchanged on future recordings.  The unchanged setup becomes the standard against which subsequent changes are judged.  That's important because the unchanged setup will sound somewhat different each time based on all the other variables.  Only after confirming over time that an alternate setup is consistently closer to what you want should you make that on the standard against which other changes are judged.  Of course you don't have to do it that way, but it provides the control which makes this kind of comparative approach especially valuable.

Since you have to start somewhere, given the setup you have pictured, I'd suggest starting with DIN (20 cm / 90-degrees) as your standard, as it is something of a standard near-spaced configuration for tapers (even though its not an official German DIN standard).   And it's a relatively narrow spaced setup so you can run it anywhere you can raise a microphone stand.
« Last Edit: May 20, 2019, 06:11:24 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #20 on: May 20, 2019, 08:59:14 PM »
Hmmm: I would have said that you were right and that your taper friend was wrong. As you pointed out, the angular width of the sound sources is often relatively small in the type of recording that we're talking about. But narrowing the angle between microphones in a coincident or closely-spaced pair doesn't increase the proportion of direct sound in the recording by very much. To a much greater extent, rather, it makes the two channels of the recording much more similar to one another than they were before--which pushes the recording toward mono.

A more appropriate response, if it's possible, might be to put more distance between the microphones, to use microphones with greater directivity (if you're not using supercardioids already), and/or to use microphones with a moderate upper-midrange elevation.

Exactly these ingredients in combination..

Let me try and clarify why I came to understand how my taper friend was correct in a vitally important way, at least with respect to something more fundamental than what I was trying to explain to him at the time.  Apologies in advance for what may be a long post.  I acknowledge my susceptibility to identity politics / niche-seeking to the same degree as anyone else here at TS, although I try to I approach it as more of a high level gestalt engineering exercise applied to this unusual type of hobbyist music recording.  A type of recording which has not been rigorously explored in the same way more typical professional methods of recording have.  And because of that I especially value alternate points of view on any of this!

My current understanding is that both my friend and myself were correct, albeit about different things, and he was getting at something more fundamental with regards to recording a PA amplified band from an audience position than I.  My realization that followed was about determining the appropriate hierarchy for prioritizing these things and addressing them in a logical order. 

There is no substitute for an appropriate recording position, yet we can still seek to make the best of a compromised situation.  The questions are: To what degree can we compensate at all?  What is the most important thing to optimize?  What can we actually do about it?  Then, having identified and addressed the most important aspect, what's the next most important aspect and what can be done to improve that without messing up the more-essential thing?

A pair of microphones is only able to sample the sound field which exists at that location.  As such, a recording made from an acoustically distant location cannot escape being dominated by reverberant far-field sound, regardless of the microphone technique used.  Unless we can mix in a feed from the SBD, which is the addition of content from microphones placed close to the source(s), we are more or less stuck with the basic sound balance present at the distant recording position. 

In such a situation it is advantageous to arrange things so as to get the sound of interest as clear and proximate as possible.  It's difficult to enjoy a recording when one can't make out the lyrics or hear the musical phrases clearly.  Those things are more important than good stereo aspects.  A clear mono recording is more enjoyable than an otherwise unintelligible stereo recording*.  Clarity and proximity are more fundamentally important than stereo aspects.

Let's start by reducing the problem to making a mono recording using a single microphone and recording channel.  A microphone with a moderate upper-midrange elevation helps with clarity when recording at a distance, so let's start with that.  Next what pickup pattern is appropriate?  Say I choose a highly directional microphone like a quality supercardioid which, on average, favors sound arriving from the direction in which I point it over all other directions. In which direction should I point it?  Will I hear a difference if the single directional microphone is pointed away from the stage and towards the back wall, towards a side wall, or toward the stage and PA sources?  Its pretty self-evident that I want to point the microphone in the direction of the sound source regardless of my distance from it. That helps because even though the level of sound arriving from any direction is essentially the same as any other due to the distant recording position, the quality of sound arriving from the direction of the source will be somewhat more clear than that arriving from other directions.  Not necessarily by very much (a consequence of being far away), yet enough to make pointing the microphone toward the source a meaningful improvement.  If anyone really does doubts this, I can provide samples of identical supercardioid microphones pointed directly toward the stage, directly away from the stage, and directly toward the sidewalls, all made simultaneously from a distant recording location. The differences in most cases are easily audible, although sometimes not as significant as many may expect.  Otherwise I may as well use a less directional microphone that is likely to have smoother off-axis response, a more extended low frequency response, and is less susceptible to handling/wind noise like say an omni.  Which I would if I could only place the microphone close enough.

For the same reason, It's also important that the directional microphone I use have a well-behaved off-axis response that differs from it's on-axis response ideally only in level, but not significantly in frequency response.  Because again, the soundfield energy at that distant location is arriving with pretty much equal level from all directions, so the microphone really needs to sound good across all angles of arrival.

Okay, I've now addressed the most significant issue as best I can, by pointing a well behaved directional microphone at the source.  Next, how might I introduce a second microphone channel to make this into a suitable stereo configuration without overly compromising the more important thing I've just achieved?

I can add a second supercardioid facing directly toward the stage, AB spaced from the first like I would arrange a pair omnis.  This produces time of arrival stereo like a pair of omnis without compromise to the first aspect.  But because ensemble on stage fills some small angle as viewed from my distant recording location, and because the PA speakers are a major contributor of the sound and are typically placed on either side of the stage, I choose to point the Left supercardioid directly at left PA speaker and the Right supercard at the right PA speaker.  Now both microphones remain on axis with the primary sources, but now have some angle between them, as determined by the width between PA speakers and my distance from them.

Once I know that angle, I can determine the optimal spacing between the two microphones based on the collective work of Williams, Sengpiel, Wittek, etc. which has been made easier by referring to the Improved PAS table.  This is also good because any angle between microphones will reduce the need for as much spacing between them, making the setup more practical while at the same time introducing some welcome degree of of level-difference stereo in addition to time-of-arrival stereo.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline Gutbucket

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Re: "Variable Fixed-Configuration Stereo Bar" - thoughts?
« Reply #21 on: May 20, 2019, 09:34:09 PM »
A clear mono recording is more enjoyable than an otherwise unintelligible stereo recording*.  Clarity and proximity are more fundamentally important than stereo aspects.

* It is ironic that although the mechanics of making a stereo recording is more than twice as complex as making a mono one, and the mechanics of making a surround recording represents yet another jump in complexity beyond the simple addition of more microphones, recording channels and supporting gear, it is considerably more difficult to make a mono recording with good perceived clarity and proximity than a stereo one.  Likewise it is easier to make a surround recording with good perceived clarity and proximity than a stereo one. In each case the separation of elements to more reproduction channels provides additional cues for our ear/brain to do it's thing a little bit more like it would when exposed to the original soundfield, even though all of these reproduction methods fall far, far short of reproducing it. Thank goodness for our willing-suspension-of-disbelief that allows the illusion of spatial audio reproduction to work at all.

It's easy to jump to stereo and disregard mono, yet better stereo can be built atop a solid foundation also able to support mono.  When thinking about the hierarchy of what is most important for good stereo I think it's helpful to start with the mono recording situation even if one never plans to actually record that way.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

 

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