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Author Topic: Ambient sound & Jecklin disc for quad?  (Read 3224 times)

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Offline m326

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Ambient sound & Jecklin disc for quad?
« on: November 21, 2020, 06:47:50 AM »
Hi all, I know what end result I want - but I don't know how to get there.

Let me explain.. I like relaxation recordings, especially nature based ones but often the music puts me off. I want to be able to record my own nature sounds with the idea of having random bird calls from various places in the room, a rustling in the leaves here and there, an animal scampering... you get the idea. Quiet and peaceful, no music & no dogs barking!

With my Dr100 I have made some progress with dual stereo recordings, Reaper is set up for 5.1 audio - but only using 4 channels. The resulting .wav file is then converted to .mp4 which then gets copied to my NAS and played through Plex to my Sonos PlayBar & 2 surround speakers. Not an ideal process or setup for outputting small signals. I would really like to have more discreet speakers placed further apart, any opinions or alternative (budget conscious) hardware recommendations on this?

I have made a Jeckin Disc which seems to work well for me with good stereo separation using a pair of EM172 omni's.

This Christmas I'm getting a Zoom F6 recorder and am contemplating getting a set of 4 matched EM272 XLR microphones. Beings the Jecklin Disc was successful, has anyone tried to make a quad version of it? It seems to be an obvious thing to try - or are there better solutions out there?
I would think that, looking downwards onto the discs & seeing a cross, the microphones would need to be located much more centrally and perhaps because of this, the discs need not be so big? In my current disc, the mic supports are removable which means it packs flat, a quad version would be much bulkier and wind noise protection will add further to this, perhaps reducing portability.

Thanks in advance for your comments and help, I'm fairly new to the audio scene.. technical wavelengths go straight through my skull  ;)

Offline heathen

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Re: Ambient sound & Jecklin disc for quad?
« Reply #1 on: November 21, 2020, 11:22:28 AM »
It seems like you're asking about playback setups and recording setups.  I'm pretty much just a two channel stereo guy when it comes to playback so I can't be much help there.  With regard to the recording setup, have you considered an ambisonic microphone?  If the Zoom F6 has an ambisonic mode like the F8, then something like the Sennheiser ambisonic mic would be a nice fit because the Zoom ambisonic mode is specifically designed to work with the Sennheiser mic ( it will also work with other ambisonic mics, though some mics like the Core Sound TetraMic don't let you take full advantage of the Zoom ambisonic mode capabilities).

For multiple mic setups, maybe look into things like IRT Cross and other arrays specifically intended for capturing ambience.
Mics: AT4050ST | AT4031 | AT853 (C/SC) | Line Audio CM3 | Sennheiser e614 | Sennheiser MKE2 | DPA 4061 | CA-14 omni Pres: CA9200 | DPA d:vice Decks: Zoom F8 | Roland R-05

Offline m326

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Re: Ambient sound & Jecklin disc for quad?
« Reply #2 on: November 22, 2020, 04:01:29 AM »
Thanks for your reply heathen.
Although ideal, the Sennheiser mic is way out of my budget. The IRT cross idea is something I will research.. but again cost of mics for what is an occasional hobby idea would be a limiting factor, hence my more DIY approach.

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #3 on: November 22, 2020, 09:53:47 AM »
I like primo Em172. I think they are great for nature recordings. I don't know if you have another use for FX6. If you only use it with Em172, maybe a Tascam Dr2d + Church audio preamp would suffice.

It is good idea to use four baffled omnis.  EDIT: Cross baffle with omnis in the corners is good idea. It should be similar to four coincident directional microphones. Also when the omni is placed in a corner, the direct/reverberant sound ratio increase and also the S/N ratio increase (the directivity and the improvement is only for frequencies where the baffle works). It's nicely explained by Gutbucket here https://taperssection.com/index.php?topic=186619.0
A baffle as a four sides box should be also good. When you use a box, you introduce a time difference into the signals.
The smaller the baffle, the higher frequencies will get around it. The larger the baffle, the lower frequencies are blocked and also, in the case of a box, the greater the time difference.

Wait if Gutbucket joins. He experimented with 4 baffled microphones and also his oddball technique is very similar to it. I think he is also one of the few here who has done recordings for surround playback. Once, when I was inspired by Gutbucket and his oddball microphone technique, I pinned 4 microphones on me - a pair on the my shoulders, one center forward, one center backward. It was at a concert. But I wasn't in a good place, the microphones on the shoulders hadn't enough separation to create space for mixing in the center microphones (I am mixing only for stereo playback). But I would like to try 4 baffled microphones again. I need to get some bigger inconspicuous box.

Oddball microphone technique:https://taperssection.com/index.php?topic=191953.0
I can't find it now, but I know that someone sent a picture from a recording studio - a large box of transparent plastic that served as a baffle, with musicians sitting around.
« Last Edit: November 23, 2020, 07:26:59 AM by kuba e »

Offline m326

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Re: Ambient sound & Jecklin disc for quad?
« Reply #4 on: November 25, 2020, 04:32:07 AM »
Seems the EM172 stocks are depleted now, EM272 being an almost direct replacement.
I originally bought a Clippy EM172 stereo pair with 3.5mm jack plug and was quite impressed by them so when I bought my DR100 I got a XLR pair of 172's with XLR.. another improvement in sound.
The F6 has been purchased and wrapped for Christmas - so no changing that now. Must admit though, I'm a bit concerned about the reports that say the DR100 has quieter preamps.

Thanks for the info and links, I'm trying to take it all in.
Over the holiday period I'm going to make and try a cross baffle, I have all I need for it but I need to think of a way to make it fold flat for more portability.. 3D printer to the rescue no doubt.

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #5 on: November 25, 2020, 10:18:10 AM »
I mixed two things together. The baffle may be rigid - 'boundary microphone' and the baffle may be damping - 'Jecklin disc'.

'Boundary microphones' in corners of a cross.  Edit: I thought more about it. It should work. The cross should be 90 deg (theoretically, problems arise at angles lower than 45 deg) and the microphones have to be placed exactly in the corners to avoid unwanted reflections. It's interesting. When I find plexiglass, I'll try it. A rigid baffle as a box or sphere is also fine. In all cases, the boundary microphones must be placed directly on the baffle surface to prevent unwanted reflections. And the rule of amplification and the improvement of the direct/reverberant ratio should apply to the frequencies at which the baffle works. Which can be a disadvantage when the baffle size is small. Because only the high frequencies are amplified, the low frequencies remain unamplified.

'Jecklin disc' as a cross. The material of the baffle must dampen a lot to prevent reflections. Then you don't have to put microphones right in the corners, they can be in the space between the baffle. The farther from the baffle, the smaller its influence. I think Jecklin discs in the cross is fine.

The third possibility is that you install the omnis in spheres, this will increase their directionality. When you have individual omnis in separate spheres, you can easily place them in space.
https://schoeps.de/en/products/accessories/filters-pads/ka-40.html
https://reverb.com/item/28102645-schoeps-kfm6-sphere-stereo-microphone

For a basic idea of ​​what frequency the baffle will affect, it is possible to use an approximate relationship - the baffle will affect sound wavelengths that are as long as the baffle dimension and shorter. E.g. a baffle of 60 cm will start to affect frequencies from 570Hz (wavelength 60 cm) and higher.

I am writing here what I have read here on the forum. Try waiting for someone who has experience with it to advise more.

You have a very nice present for Christmas!
« Last Edit: December 01, 2020, 01:05:44 PM by kuba e »

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #6 on: February 08, 2021, 12:06:11 PM »
I must've overlooked this thread until today. Its right up my alley. I do a lot of suuround recording and I agree with most of what has been posted previously. Following are a few thoughts and clarifications from my experience-

First bear with me through a breif philosophical underpinning, as I think a rudemenatry inderstanding at that level really helps to point the way at each practical step.

I consider live music performance and environmental ambient recording, via either 2-channel stereo or multichannel surround, as all being rooted in capturing the sound arriving directly from the sourc(es) and the indirect diffuse sound that arrives from all directions. Those are the basic things that must be in balance. With 2-channel recording we generally arrange things to achieve a good set balance of those things via the recording location, microphone pickup pattern, stereo mic'ing cofiguration, etc. With a multichannel microphone arrangement, we can set things up in ways that achieve a less compromised pickup of each of those aspects and allow a degree of freedom over how they are combined for 2-channel reproduction, or manipulated for discrete multichannel playback,  after the initial recording was made.

Practical things-
I find good capture of surrounding ambience generally requires space between the microphones, and that the direct sound component from each individual source is not being picked up by all microphones (there is minimal direct sound in at least some of the other channels). That means some spacing combined with some directionality imparted by microphone directivity or baffling.

Ambisonic mics are compact and convenient and a 1st order ambisonic microphone is great at capturing direct sound from all directions and retaining directional info. But they are not great at conveying the diffuse ambience that gives one the  distictive realistic feeling of "being there" immersed in the sound environment.  You need some space between the microphones for that.  Sure folks use them for ambient recording, but that is mostly about convenience and/or VR compatibility, rather than representing an optimal approach

The IRT cross is a great starting point for that and what I'd recommend if using 4 cardiods or supercards for the type of ambient recording you are doing. If using 4 omnis, use a similar spacing to IRT cross with baffles to produce directionality. Mounting to the surfaces of a box works well. Mounting to four sides of your torso does too. A cross-shaped intersecting Jecklin disk will work, as will two of them separated by a fore/aft baffle. They may provide sharper direct sound imaging, but a box is simpler and effective. You essentially want sufficient directionality/spacing between each adjacent pair of microphones similar to that of a 2-channel recording atrangement. That means any two opposing channels in a 4-channel ambient pickup arrangement is angled twice as wide and spaced twice as much as a typical 2-channel arrangement. With that in mind, using 4 omnis, I'd use a box before choosing a sufficiently large beachball sized spherical or vertical round column baffle, but use what you have available.

For ambient recordings an L,R,Ls,Rs (quad format) recording and reproduction works well. For things like music where there is a definite forward direction I prefer to turn that 45 degrees (L,C,R,S), which achieves better front/back differentation,  imaging across the front, and keeps the loud front arriving sound in the front. For LRCS playback it helps to distribute the S channel to as many surround speakers as possible.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #7 on: February 08, 2021, 12:25:07 PM »
Any of the essentially symmetric 4 channel microphone arrangements above are picking up both the direct sound from a specific direction as well as diffuse sound from all directions. For sources in front the C channel contains the primary direct sound, with a bit less in L,R, and the the S channel exclusive of the direct sound as much as possible, where as the ambient component of that sound is picked up bu all channels.  For any source located behind the recording position it is the opposite situation. And the same goes for sources to the far left and right.

Playback of these recordings can be really impressive. I've recorded frog choruses in the back yard and then immediately played them back in surround inside the house and it was astoundingly transporting. Walked around the block with the windows open and from all sides it souned like the house was filled with frogs. Walking the street in back the actual frogs were stimulated to join in, creating a super croaker chorus. Good fun
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #8 on: February 11, 2021, 05:40:19 PM »
I will also have to get surround playback one day. The frog concert must be enjoyable.

Do you know how the boundary layer behaves on the sphere? Is it the same as on the flat surface?
I like the boundary layer theory. Acoustic boundary layer reminds me of the boundary layer in aerodynamics. In aerodynamics, it is explained by the boundary layer why objects have resistance in a fluid stream. The resistance is determined by a thickness of the boundary layer. The aerodynamic boundary layer is also separated from object at high velocity. This could be compared to an "acoustic shadow". Although one is a wave, the other a flow, there may be some distant resemblance.

It seems useful that a boundary layer microphone amplifies direct sounds over diffuse sounds. This would be good for audience recording. It is a pity that a large surface is needed for this. All those boundary microphones that are on a smaller board have 6db drop for lower frequencies. There are probably also problems with the polar pattern in this transition.

Offline DSatz

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Re: Ambient sound & Jecklin disc for quad?
« Reply #9 on: February 11, 2021, 11:03:08 PM »
kuba e, exactly so--the surface that a boundary microphone is placed on has to be large w/r/t the wavelength of the lowest frequency that you hope to capture with it, or else you'll just get a 6 dB shelving rolloff somewhere in the range. Crown used to show their PZMs on music stands; PZMs on piano lids were commonplace at one time; et cetera ad nauseam.
music > microphones > a recorder of some sort

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #10 on: February 12, 2021, 10:47:53 AM »
kuba e, I certainly see parallels between aerodynamic and acoustic boundary phenomena, although I dont really know how truely analogous they are or how far the analogy holds.

Similar to what you describe, at the acoustic boundary surface above the corner frequency determined by the area of the bounary there is no velocity component and only pressure component w/r/t a wave front arriving perpendicular to the surface. There will be incresing velocity component for acoustic wavefronts as they ecounter the boundary at angles approaching parallel rather than perpendicular.

A sphere or vertical column boundary will produce the smoothest polar response above the corner frequency determined by the area of the boundary, while a flat sided box with corners will make for a somewhat tighter pattern in each direction, and a 4-pointed star shaped boundary tighter still, each with increasing boundary gain.  If the boundary is acoustically absorbent across that frequency range, the polar modification remains but there is less boundary gain.

I've made lots of recordings using 4 omnis in a cross formation without any baffles or boundaries (other than using 2" sphere attacments on each microphone), increasing the spacing to about a meter (3') between oposite sides to compensate. The result is somewhat less specific directionality of the direct sound but a very enveloping ambient sound that might work very well for the OP's stated intent. It is certainly practically easier to setup and transport without use of a central boundary or baffles.. unless you are the baffle.. or if their happens to be something already in place that can be used as suitable boundary/baffle such as a column or big tree trunk or rock or something.
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #11 on: February 12, 2021, 03:34:15 PM »
Thank you for your comments.

I asked about the difference between the sphere and the flat surface because I was thinking about recording with the ball as in the link. When someone records with this ball or dummy head, are the high frequencies also increased by 6db because boundary layer? Is it corrected by eq?
https://reverb.com/item/28102645-schoeps-kfm6-sphere-stereo-microphone
https://taperssection.com/index.php?topic=187681.msg2336073#msg2336073

Edit: I thought about it more. There is probably no analogy between the boundary layers. The aerodynamic boundary layer is formed due to friction. But the theory of aerodynamics, where friction is not considered (potential flow), should be similar to acoustic.

The analogies are interesting. I remember, I was unable to understand electricity at school. I only understood electricity when I learned hydrodynamics. The whole basics of electricity- voltage, resistor, current, capacitor, coil - can be learned to compare to water - pressure, velocity, resistance.
I remember when I was learning aerodynamics, there is another interesting analogy. It was used before when there were no computers. Older models in aerodynamics neglected friction because it has simpler equations. And friction-free fluid models and electricity are described by the same type of equations. This was used in practice. A conductive plate was taken and a non-conductive material was pressed into it, for example in the shape of a wing profile. Voltage was applied to the plate and the voltage potentials around the non-conductive part - the wing profile - were measured. And then these voltage potentials were recalculated to pressure and velocity potentials in aerodynamics. In this way, the wing lift could be roughly estimated.
Maybe there is something similar in acoustic.


« Last Edit: February 12, 2021, 05:26:33 PM by kuba e »

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #12 on: February 13, 2021, 09:38:28 AM »
I tried to figure it out. I mistakenly thought that the dummy head is just for creating an 'acoustic shadow'. But the dummy head also uses boundary layer reinforcement.
And my second misconception was that the gain in the boundary layer is the same for all directions. But that's not true. The maximum gain is for perpendicular directions only. And conversely, the sound in the tangential direction is not affected by the boundary layer.
« Last Edit: February 13, 2021, 09:41:04 AM by kuba e »

Offline DSatz

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Re: Ambient sound & Jecklin disc for quad?
« Reply #13 on: February 13, 2021, 10:20:41 AM »
Now that is really interesting, and makes general sense although I haven't seen or heard it mentioned before. The polar response patterns of boundary-layer microphones have always been represented by their manufacturers as if they were simply the original patterns "cut in half" at the boundary. But from what you say that should not be so; rather, the relative "selectivity" of the directional pattern should be emphasized by the boundary effect to some extent, even if only by a few dB, sharpening the patterns somewhat.

I'll try to find out more about this; I don't have the educational background to know about it on my own, nor the time right now to experiment. As I said, the way you're describing the situation (which makes sense enough to me) is at some variance to what I've always seen (and for Schoeps' technical literature, translated). As you may know, some of the leading microphone manufacturers offer not only special-purpose microphones--or more often nowadays, capsules designed for boundary-layer placement with extension cables for existing modular amplifiers, and/or accessories that facilitate the placement of their existing microphones and/or capsules on a boundary layer (Schoeps example shown below). And decades ago Shure used to offer an interesting little tripod stand for near-floor mounting of microphones (scan from an old catalog page also attached, from long before Crown made "PZMs" into a thing).

I've used both as problem-solvers in situations where the visual obstruction of a microphone stand couldn't be tolerated, as well as in one political situation of another kind that I can tell you about. I can't say that they worked any sonic miracles beyond allowing me to make somewhat decent recordings; 3 dB increase in sensitivity and reduction in diffuse-sound pickup is nice, of course, but only a modest effect overall.

--best regards
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Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #14 on: February 13, 2021, 11:19:47 AM »
I'm just guessing, I don't want to cause any confusion.

I have wanted to use a boundary microphone for a long time to record lectures. I wanted to put it on the floor (it's yoga, we sit on the floor during lectures). But now I'm not sure if it will have any advantage, because the lecturer is further and sound hits the microphone at a small angle. On the other hand, if the angle of incidence into the boundary layer does not matter, then a correction should be made to the dummy head recording. But these are just my imagines, it may be completely different in reality. I'll try to read something about it on the internet. If I found out more, I would write.
« Last Edit: February 13, 2021, 11:29:14 AM by kuba e »

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #15 on: February 16, 2021, 04:29:10 PM »
A directional microphone oriented more or less tangentially along the surface of the floor, in your case angled upward toward the lecturer but still close to the floor, may not benefit from significant sensitivity increase, but the arrangement should reduce the effect of the floor bounce interfering with the direct path arrival- addressing the "hollow sound" issue mentioned in the lower red-boxed portion of the Shure literature in DSatz's post above.  Placing the arrangement on a yoga mat probably won't hurt.

You may recall my previous posts about on-stage taping using directional mics positioned very close to the stage floor.  I think the reduction of floor bounce lead to increased clarity in those situations.  Those mics were angled upward at angles of 45 degrees or less toward relatively close drum kit and acoustic bass sources.  Noted and certainly related, although I'm not sure of all the details of the underlying phenomena, was the unusual and exceptional clear projection and pickup across larger distance of the guitar amplifier cabinet placed directly on the hardwood stage floor and projecting tangentially across it toward to the microphones.  Perhaps that was doubling the effect by it's application at both the source and receiving end of things.

On the frequency-selective sensitivity increase of a stereo sphere baffle like the Schoeps KFM6 using flush-mounted omnis in the +/- 90 degree positions, the maximum sensitivity increase should occur at +90 degrees in one channel and -90 degrees in the other.  That is in combination with the sensitivity decreasing shadowing effect toward the opposite direction across the same frequency range.  Because of that I imagine the averaged response across all directions is likely to be flat for each channel or close to it.  And I imagine the response along the median plane (source at 0 or 180 degrees), which is on-axis with respect to the stereo array but 90 degree off axis to either microphone, to be flat as well.  DSatz, please correct me if I'm incorrect about this.  Any additional information you have access to regarding the response of KFM6 would seem quite applicable to these questions.

The first stereo recording array I purpose-built after finding Taperssection 15 years ago was modeled on the KFM6, although modified as a boundary-mounted 7" diameter hemisphere mated to a larger diameter flat disk, intended to be placed on the floor, on a stool or a table rather than a full sphere placed in free space.  It was designed for recording instructor lectures, demonstrations and performances in a classroom setting at an acoustic guitar camp, as well as something I could place in the center of a circle of players, optionally housing the preamp and recorder within the hemisphere to form an easily portable all-in-one device that would fit into a guitar gig bag front pocket.   It worked well, yet was best when the sources were relatively low to it's 'horizon' such as the players seated on the floor itself, or with it placed on a table or high stool.  It lost directional differentiation as the angle to the sources grew higher, similar to how our own directional hearing becomes less differentiated for sources with significant elevation above the horizontal plane.

The original discussion is here - https://taperssection.com/index.php?topic=70134.msg939807#msg939807  I dubbed it Boundrisphere. Unfortunately it looks like the photos were stripped from that thread and I cannot find one of it on this computer, but I still have it at home if you'd like me to dig it up and take a photo. [edit- Hmm, I now see them again and am inserting a few from that thread below]





« Last Edit: February 17, 2021, 10:19:47 AM 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #16 on: February 17, 2021, 10:04:26 AM »
Apologies for getting OT w/r/t the OP, but to follow up on my reply to kuba e-

You may recall my previous posts about on-stage taping using directional mics positioned very close to the stage floor.  I think the reduction of floor bounce lead to increased clarity in those situations.  Those mics were angled upward at angles of 45 degrees or less toward relatively close to the drum kit and acoustic bass.  Noted and certainly related, although I'm not sure of all the details of the underlying phenomena, was the unusual and exceptional clear projection and pickup across a larger distance of the guitar amplifier cabinet placed directly on the hardwood stage floor and projecting tangentially across it toward to the microphones.  Perhaps that was doubling the effect by it's application at both the source and receiving end of things.
^
Below are photos of this from three different evenings recording a jazz trio.  The mics aren't close enough to the floor to achieve boundary effect through the highest audible frequency range, but no high frequency comb-filtering was apparent.  The guitar cabinet mentioned can be seen to the right and was farther away than seems apparent in the photos, partly because it was placed further away from the front of the stage than the drums and bass, and partly because the microphone array was intentionally not centered directly in front of the drum kit but positioned to the right of it (stage left) for increased proximity to the acoustic bass (amplifier-reinforced) and to avoid having the mics directly on-axis with the kick drum.  The 3 large diameter diaphragm ADK TL microphones in the small-format triangular decca tree-like arrangement on the stage were set to a supercardioid pickup pattern.  The room/audience/ambience/surround microphones clamped just below the stage-lip facing out into the room are Microtech Gefell supercardioids.







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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #17 on: February 17, 2021, 12:02:55 PM »
Congratulations, you overcame Schoeps. I like the ears you made to the ball. The musicians certainly liked the ball too.

Yes, that's a good note. Boundary microphone's  advantage is avoiding reflections from the floor. I will experiment with it more. I will try the microphones on the stand and on the ground. I will see how the reflections from the ground affect the recording.

Thank you for nice photos and explanation of onstage recording. It is beautiful setup. Photos are very good for creating an idea. Maybe the recording went also well because the cabinets were placed on the floor, so the microphones were at the same level.

Unfortunately I didn't find much information about sound boundary layer. I only found a mention that the width of the boundary layer depends on the frequency and that the gain of 6db only applies to sounds incident perpendicular to the surface. This is really just a guess, but if I recalculate it by simple relations for ideal flow (without friction), the gain in the boundary layer for sounds at an angle of 30 degrees would be only 1.5db. Anyway, this is not important. It is important to avoid reflections from the floor. I'm looking forward to trying it and being able to compare boundary and classic settings.
« Last Edit: February 17, 2021, 12:14:14 PM by kuba e »

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #18 on: February 17, 2021, 01:08:34 PM »
Don't know about overcame.  A modified emulation inspired by Schoeps, and based upon the same underlying principles, I'd say

Most of the times I've used "standard" boundary mounting involved attaching the miniature omnis directly to the back wall of the room facing the stage, in a spaced A-B arrangement.  That produced a more advantageous direct/reverberant ratio in the resulting recording with better clarity and less low frequency "muddiness" than using directional microphones placed a similar distance away from the stage (perhaps a meter or two in front of the back wall - either way, more distant from the stage than desirable).  As the only option was to record from back there or not at all, the boundary mounted omnis placed on the back wall produced the best result in that situation.  If I could have moved closer and used directional mics in a typical arrangement I would have chosen that.  I tried this same back wall boundary-mounting arrangement in the onstage recording scenarios pictured above.  Ironically it picked up too much direct sound from the stage for the room/audience/ambience/surround channels role.  Moving them to the front wall underneath the stage facing out into the room did work well as an alternate configuration to using the MG supercards.

Also, along with other directional microphone arrangements for the trio above I tried boundary mounted omnis on the stage surface facing upwards, but preferred elevating the omnis a few feet above the stage and ultimately preferred the L/C/R directional microphone arrangement pictured above which I stuck with for the remainder of the series.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #19 on: February 18, 2021, 08:00:50 AM »
Don't know about overcame.  A modified emulation inspired by Schoeps, and based upon the same underlying principles, I'd say

I meant it's a very good job and it has style. I understand that Schoeps had to make black ball on the stick, because it's dark at concerts and they don't want it to be seen. But for lectures or workshops, your ball is better, it's happier. It is easier for musicians to accept it.

Also, along with other directional microphone arrangements for the trio above I tried boundary mounted omnis on the stage surface facing upwards, but preferred elevating the omnis a few feet above the stage and ultimately preferred the L/C/R directional microphone arrangement pictured above which I stuck with for the remainder of the series.

This is good information that is worth experimenting with the height of the stand when recording onstage. I like onstage recording, but I haven't tried this yet.

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Re: Ambient sound & Jecklin disc for quad?
« Reply #20 on: March 11, 2021, 04:02:10 PM »
Thanks for you input guys, some of the terminology is rather foreign to the newbie me :-) but I'm sure will be helpful to me.

Bit of an update on my project.. I spent the whole of January in hospital and they kindly gave me Covid while there but when able I've been busy.
My idea of a quad went up by one to include a centre channel. I cut 2 x 12" discs from foam board and glued them together for the base. I then cut 5 radial dividers again from foam board and spaced them according to the mic's position, in hindsight I should have arranged the angles differently as the L, C and R channels occupy exactly 180 degrees and the surround channels the same. I would have preferred the L & R to gain an extra 20 degrees or so. Holes were made near centrally in the base for the mics and a quick test revealed the surfaces were too reflective so the interior surfaces were covered with 2.5mm fun foam (it's what I had left over from another job).
To offer some support for the wind protection fabric I 3D printed a set of different sized circles (rings) which were siliconed into position. The prototype was finished off by; reading up on making parachute gores and making a dome shaped wind protection cover out of 1" squirrel fur fabric. I didn't think I could create so much mess cutting that stuff!

The result is a really cool looking dome hiding a rather heath robinson contraption inside. I've only done a couple of outdoor test recordings - but not in ideal test conditions. I'm finding that the microphones are quite sensitive and pick up noise from quite far away  :shrug: and that includes noise form the bypass. On the plus side, wind protection seems to worth all the mess and effort. My next task is to get to grips with surround sound in Reaper, tutorials either seem too basic, incomplete or do way more than what I want to do with it  :help:

A couple of pictures:

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Re: Ambient sound & Jecklin disc for quad?
« Reply #21 on: March 11, 2021, 06:38:48 PM »
Nice work!  Very cool to see this actualized. This is very similar to what I was thinking about 10 years ago.  Hoping you didn't suffer that unfortunate illness too badly and are free of any lingering effects moving forward! A few comments-

Quote
Holes were made near centrally in the base for the mics and a quick test revealed the surfaces were too reflective so the interior surfaces were covered with 2.5mm fun foam (it's what I had left over from another job).

I'll start with this, as it makes for a logical continuation of the discussion of boundary-layer-effect in the preceding posts above.  The walls of your arrangement serve as both baffles that modify the directional pickup pattern of each microphone, and as acoustically reflective boundary surfaces which increase sensitivity and the ratio of direct to reverberant pickup.  Both of these effects will come into play above a particular frequency which is determined by the dimensions of the baffles and the area of the boundaries which they form.  Below that frequency, both the baffling and boundary effects are minimal.  Ok, so what are the implications of this?

A basic one is that boundary-mounting benefits from mounting the microphone as close as possible to a hard, acoustically reflective surface.  A baffle does not require the microphone to be close to it as long as the surface of the baffle is soft and acoustically absorbent within the frequency range in question.

Taken to the logical extremes, this means the microphones should either be mounted as deep into the corners as possible, or the baffles should be as acoustically absorbent as possible.  There are arguments for each approach.

To optimize the boundary effect, the surface of the boundary should be acoustically reflective (hard), and the microphone diaphragm should be mounted as close as possible to the boundary surface - flush embedded into it if possible.   It is the flush-to-the-surface mounting which avoids the problem of reflections off the boundary interfering with the sound reaching the microphone directly.  In your case there is not just a single boundary surface but three acting together to affect each microphone - two vertical wall boundaries and a floor boundary.  Ideally, the microphone should be mounted with its diaphragm as deep into the vertex as possible (buried as far as possible in the corner facing outward). 

It looks like you can easily get closer to that kind of arrangement without much trouble.  In your photo above it appears each microphone cable passes through a hole in the "floor panel" which is about the same diameter as the microphone itself and is positioned well back into the corner.  Try installing each microphone so that it barely protrudes through that hole, with its diaphragm facing directly upward, leaving most of the microphone body extending down below the "floor panel".  This will get the microphone element much closer to the vertex and reduce combfiltering from reflections off the boundaries. You may also notice increased high-frequency response as the microphone is moved closer to the vertex, which is the boundary effect working to a higher frequency given the closer-to-flush placement in the corner.  It might be that high-frequency boost nicely offsets the attenuation imparted by the squirrel fur.  If so, great.  If not you can correct for it with EQ, or play around with using foam and/or fur on the boundary surfaces.  If the microphone is placed flush enough to avoid comb-filtering reflections, making the boundary surfaces less acoustically reflective and more acoustically absorbent will reduce the sensitivity boost effect in the range in which the boundary effect is occuring.

Alternately, if the microphones are not flush mounted, you can make each baffle surface as acoustically absorbent as possible and rely on just baffle effect, like a multichannel Jecklin disk baffle. It will take a bit more than thin foam to effectively achieve this.  When I was playing around with Jecklin disk baffles, I made a bunch of tests to determine how much absorption I needed to reduce angle-of-incidence reflection across the frequency range in which the baffles were effective.  I initially thought I'd just use a layer of foam and fur, but ended up with a baffle core made from corrugated cardboard supporting a layer of cut-pile carpet, atop which I placed a layer of felt (further covered by fur) on each side.  In other words, it took a lot more than I first imagined it would to effectively damp reflections off a surface in close proximity to the microphone.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline Gutbucket

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Re: Ambient sound & Jecklin disc for quad?
« Reply #22 on: March 11, 2021, 07:33:51 PM »
Second-

Keeping the above in mind as you play around with the construction, consider whether you want some degree if time-of-arrival/phase difference between channels or not. In terms of stereo recording, this is the difference between a coincident microphone technique and a near-spaced one, and the same applies to a multichannel array such as this. 

With the microphones tucked as deep as possible into the corners, you effectively achieve a coincident array.  With them spaced away from the center, you have a near-spaced array. This is similar to how far the microphones are spaced from the face of a Jecklin disk.  Folks here at TS have made Jecklin-baffled recordings with the microphones tight up against the baffle as well as spaced farther away from it.  I like some spacing myself, but the more spacing the larger the baffle needs to be to effectively shadow the microphone on the opposite side to the same extent.

If you prefer near-spacing but want the microphones boundary mounted and avoid the need for acoustically absorbent baffles, you could make something that looks more like a star rather than an asterisk when viewed from above.  That pushes the inside corner between each point of the stair outward away from the center to provide near-spacing.  It would also allow you to place the microphone bodies inside the center of the star facing outward, rather than underneath with the diaphragms facing upward, while keeping the diaphragms tight in the corners.

If the overall diameter of the baffle remains the same, the larger you make the diameter of the center portion of the stair, the shorter each point of the star becomes.  Push it out far enough and you get a square (4 channels) or pentagon (5 channels) with outside corners instead of points and no inside corners.  Push it further still and you get a smooth cylindrical or spherical surface with the microphones flush mounted around it.  In that way you can trade off the degree of baffle-isolation between adjacent channels verses the spacing between adjacent channels.
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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #23 on: March 11, 2021, 08:08:16 PM »
Third-

Quote
I then cut 5 radial dividers again from foam board and spaced them according to the mic's position, in hindsight I should have arranged the angles differently as the L, C and R channels occupy exactly 180 degrees and the surround channels the same. I would have preferred the L & R to gain an extra 20 degrees or so.

This very much depends on what you want to achieve, what you are recording, and how you are playing it back.

If the primary goal is the sensation of immersion in the recorded acoustic natural outdoor environment, you'll do well to array the channels evenly around 360 degrees.  Reproduction will work best with your playback system arranged similarly with an even angular spacing between speakers all the way around.

In recording and reproducing live music events in surround, there is far more energy coming from the front, and a need to retain forward focus along with increased imaging clarity across the front. Much of the challenge in this case is keeping the energy from the front from bleeding into the surround channels, while at the same time limiting ambient pickup as much as possible from center channel so that the proportion of sound arriving directly from the sources of interest on stage dominate in that channel.  The Left and Right channels serve as intermediaries between the dry, forward focused center and the wet ambient surrounds, with a more-balanced distribution of both aspects.  So for surround recording of a musical performance with an audience, an angular distribution like you show above with the surround channels taking up a full 180 degrees or even more of the circle is likely to be advantageous. Likewise it might be helpful to narrow the acceptance angle of the center channel to less than that of the Left and Right channels.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #24 on: March 11, 2021, 08:15:41 PM »
If you are open to experimentation, I'd suggest comparing your 5-sided asterisk baffle arrangement with a flat-sided pentagonal box that has the same outside circumference and the microphones flush mounted in each face

I'd love to hear that comparison.
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #25 on: March 12, 2021, 11:18:35 AM »
You might do a web search for articles and photos from Mike Skeet, who was based in the UK and died in 2015.  He was a champion of home-built baffled and boundary-mounted microphone arrays designed for nature recording, experimented with and documenting numerous unusual configurations.  His contraptions and those built by others who were inspired by him are frequently referenced on nature-recording forums (or at least used to be, I've not checked in the last few years).

Here are a couple examples of commercial surround microphones using these techniques:

DPA 5100
A "bicycle seat" shaped microphone containing 5 baffled omnis-


Holophone
An egg-shaped hard-surface boundary with flush-mounted omnis arranged around the periphery-


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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #26 on: March 12, 2021, 05:07:35 PM »
Many thanks for all the info, lots of reading to do..
Worst thing about Covid was a lingering cough for weeks  :(
Regarding the pentagon, do you mean something like this (below)? Points are based within a 12" circle making the sides 7 x 7" with a mic mounted centrally in each face. Should the pentagon be enclosed top and bottom?
Next time I have the table saw out I can knock this up  :)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #27 on: March 12, 2021, 09:02:57 PM »
Yes, that looks promising.  I can't think of any reason you'd need enclose the top or bottom.

I don't know if that will really make any audible difference or not, but it might be beneficial to move the microphones up or down slightly to shift them away from the center of each face, and/or make each face a rectangle instead of a square.  Reason being that the distance from the microphone to the side edges will differ from the distance to the top and bottom edge, and that may help smooth the response around the corner frequency where the boundary effect imparts its high-shelf boost.  This is a phenomena akin to optimizing placement of a tweeter on the front of a speaker baffle.  Similarly, baffle-step-response in loudspeaker design is related to boundary-effect-response in this kind of microphone array design.

It's a minor detail though, and may not matter. Build it however is easiest and most practical.
« Last Edit: March 12, 2021, 09:24:29 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

Offline kuba e

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Re: Ambient sound & Jecklin disc for quad?
« Reply #28 on: March 13, 2021, 06:30:12 AM »
M326, great that Covid didn't cause you any trouble.

The pictures and comments are great. I'm curious to compare the original coincident asterisk to the pentagon. I don't have surround playback, but I wonder what you say about the difference.

I also can't think of why the pentagon can't be opened. Maybe it is good to enclosed it to avoid a sound in chimney (melusine) if you are recording in a strong wind. It also occurs to me that you will have to solve the windscreens. Maybe stick them on the board?

I was looking for details about the boundary layer. But I didn't find anything. So I wrote to Dpa if they could give me an example of a polar pattern for their boundary microphone. I also asked if they would have a document explaining the origin and behavior of the boundary layer. They sent me a message that this must be answered by a specialist and that it will take longer. If I get any information, I'll write here.
« Last Edit: March 13, 2021, 03:35:54 PM by kuba e »

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Re: Ambient sound & Jecklin disc for quad?
« Reply #29 on: March 14, 2021, 02:43:40 PM »
Made more progress on the pentaboundrythingy, twice I got the table saw out of the shed yesterday and twice it rained! That's UK weather for you.
While at it I made a top and a bottom, the bottom is fixed but the top is removable & has a carry handle. I'm thinking of perhaps adding something inside to deaden internal reflections.
Kuba, I have some 15mm acoustic foam which I'll wrap around it and cover with fur - it was a big squirrel  ;D
One of the pictures makes it look squarish, the last one is of another diy project on the go at the moment.

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Re: Ambient sound & Jecklin disc for quad?
« Reply #30 on: March 15, 2021, 06:12:50 AM »
It looks very nice. Thanks for the photos. I can't estimate if closing and filling in the pentagon is necessary.

I see you sealed the microphones in the board. That's good, I think that's important. You should probably pull them out a little. The microphone diaphragm should be at the same level as the board surface. It might also be enough to stick the windscreen just around the microphone. You probably don't need to wrap the whole pentagon.

The comparison of pentagon and star will be interesting. In addition to the coincident and spaced configuration, it will be interesting to compare how they affect high frequencies. At the asterisk, if you moved the microphones directly to the corners, you could get a higher gain for high frequencies. If I'm not mistaken, there should be theoretically a gain of up to 18db (3x6db - when microphone is in the corner of three solid surfaces). But the asterisk is made of damping material, it is difficult to estimate if the boundary layer will be formed and how it will behave. It may happen that the boundary layer does not form there and the baffles will only create the directionality of the microphone. The Pentagon has one solid surface, the gain for high frequencies will be 6db.
« Last Edit: March 15, 2021, 06:46:14 AM by kuba e »

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Re: Ambient sound & Jecklin disc for quad?
« Reply #31 on: March 15, 2021, 12:59:38 PM »
Solid construction!  Looks like the recorder will fit inside, which is probably one of the more appropriate metrics for determining the correct size.

Getting more technical about it and speculating about the most optimal spacing between microphones based on playback imaging-
The polar pattern of a stereo pair of microphones in combination with the angle between them and spacing between them determines the width of the auditory image heard at playback.  This relationship is explained in Michael William's Stereo Zoom paper and in his subsequent work and the work of others.  If one knows the polar pattern and angle between a pair of microphones, and there is a specific imaging playback width one wishes to achieve, the appropriate spacing needed to achieve it can be determined.

Refer to the Improved Point At Stacks table linked in my signature.  It applies in this case not because this baffled microphone arrangement is intended to be used PAS style for recording an amplified public address system with adjacent pairs of microphones pointed directly at the PA stacks, but because the table solves for the specific Stereo Zoom condition were the resulting image capture angle is the same as the angle between microphones (they typically are not).  It would be important in this case if you wished the directional imaging of each adjacent microphone/speaker pair segment to link-up accurately with its adjacent pair along the edges without either too much overlap or a hole in the middle.  To be clear- This is not necessary for achieving an immersive sounding recording that will effectively transport the listener back to that acoustic space.  It is only important if you want to achieve relatively accurate directional image placement of specific identifiable sounds across in the full 360 degree playback image when played back over 5 speakers arranged in a similar pentagonal arrangement.  In other words, don't sweat this unless its important to you to be able to be able to point in the exact direction of a specific croaking frog or squawking bird or whatever.

I'm not sure what polar pattern will be most closely approximated above the frequency where the baffle becomes effective, but lets assume it's essentially cardioid-like in that range.  There is a 72-degree angle difference between each adjacent face of the pentagon.  Given a pair of cardioids angled 72 degrees apart, the spacing between them which would be needed to achieve an approximate 72 degree wide imaging angle on playback is around 13-15" (30-40cm).  At lower frequencies where the baffle becomes ineffective and the polar pattern reverts to omni-directional, the necessary spacing would be more like 30" (77cm) or so between each adjacent pair of microphones.  That's a big baffle, and likely too large and unwieldy to be used effectively.  Fortunately, given the stated intent of these recordings, it's not critical to get this directional imaging aspect fully optimized.

For reference, with four channels and a square baffle there is a 90 degree angle between microphones, and the dimensions get smaller due to this increased angle.  In that case you'd ideally want a spacing of about 8" (20cm) between adjacent cardioids or about 26" (67cm) between adjacent omnis.
« Last Edit: March 15, 2021, 02:44:14 PM by Gutbucket »
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Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #32 on: March 15, 2021, 02:14:21 PM »
You can find specific references to 4 and 5 channel recording/playback arrays on pages 6 and 7 of this Michael Williams AES paper, available on his Multi-Microphone Array Design (MMAD) website here - https://www.mmad.info/Collected%20Papers/Multichannel/24th%20ICP%20Banff%202003%20Paper%20(16%20pages).PDF 

That indicates that in order to achieve seamless imaging across segments, the optimal spacing for 4 cardioids in a regular square arrangement with a 90-degree angle between pairs intended for 4 channel (quad) playback is 25cm (9.8").  For 5 cardioids in a regular pentagonal arrangement with a 72-degree angle between each intended for playback over 5 speakers arrayed in a matching pentagonal arrangement, the spacing is 39cm (~15" or so).

In addition to providing good correlation with the answer as derived from the Improved PAS table in the previous post, William's MMAD methodology and website helps in figuring and choosing between various microphone arrays, representing a good resource for this kind of thing.

William's MMAD website- https://www.mmad.info/
His original AES paper on recording and playback using regular 360-degree arrays (square, pentagon, hexagon, octagon)- https://www.mmad.info/Collected%20Papers/Multichannel/3157%20New%20York%201991%20(13%20pages).pdf
^His later work including the first paper linked above extends things to irregular shaped playback arrays with a specific front direction, as in the defacto standard 5 and 7 channel layouts.



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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

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Re: Ambient sound & Jecklin disc for quad?
« Reply #33 on: March 15, 2021, 02:25:23 PM »
Thanks for the continued interest and support  :)
 The microphones are now protruding about 5mm off the faces, I cut a smaller square of foam with the centre removed so nothing touches the mic elements and wrapped the whole lot with more foam.. which is quite effective at cutting down wind noise.
However, initially I was not so impressed with the sound. I look it into our garden, brick structures opposing each other, row of sheds behind and fence then road in front. It sounded so boomy and droney. Not good in an enclosed area. HP filter 60Hz.
I took it down our nearest woodland and got much better and more pleasing results this time with a 90Hz HP filter. It's a definite upgrade from my original which is comparison sounds sounds less defined and muddied. Recording (https://www.dropbox.com/s/vs5ylj4wuwd1ga2/F6_Tr_5edit.wav?dl=0) from today, recorded on F6 32bit float at 21db and gain adjusted up by 18db. The file is only the centre channel.
The string handle is more handy than I imagined, it allows hand holding of the device without introducing any handling noises.. but the whole thing is quite heavy, if the mics were 13 to 15" apart - it would be so much less portable for nature recording  :(
« Last Edit: March 15, 2021, 02:43:18 PM by m326 »

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Re: Ambient sound & Jecklin disc for quad?
« Reply #34 on: March 15, 2021, 02:57:21 PM »
In exploring that in the posts above I mostly wanted to address what's going on acoustically with this type of arrangement so that you and others following along are aware of the underlying phenomena driving things.  As mentioned, I don't think you need worry about getting the spacing between microphones optimized to achieve optimal discrete directional imaging and suspect the arrangement you show above will work nicely for the intended purpose.

One thing the exploration above makes clear is how increased spacing is a good idea as channel count goes up and the angle between adjacent sections grows smaller.  That corresponds with why a 1st order ambisonic single-point microphone (4 recorded channels) works well for mono or stereo output yet becomes increasingly less ideal for surround output as the number of playback channels is increased, unless one shifts to an exotic higher-order ambisonic system requiring twice as many or more channels.  A spaced array configuration which introduces time-of-arrival between microphones that can be increased as playback channel count increases overcomes this limitation with the use of standard 1st order pattern microphones, but is certainly less compact and portable.

Try the microphones with their housings completely flush to the surface as well and see if that makes much difference in response. It may not make much difference, or you might find you can sort of tune any appreciable high frequency resonances imparted by the arrangement in that manor.
« Last Edit: March 15, 2021, 05:16:16 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<< (note: This is a 1st draft, now several years old and in need of revision!  Stay tuned)

 

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