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Author Topic: Oddball microphone technique (OMT) - part 2  (Read 42703 times)

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Offline heathen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #330 on: March 06, 2019, 03:44:47 PM »
I actually had a small plastic tube that fit right over the antenna (from the dog's poop bag roll). 

I love this sort of ingenuity. 
Recordings on LMA: https://archive.org/search.php?query=taper%3A%22Lucas+Lorenz%22
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 IMPigpen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #331 on: March 06, 2019, 03:54:11 PM »
I actually had a small plastic tube that fit right over the antenna (from the dog's poop bag roll). 

I love this sort of ingenuity.

Haha, as an engineer, I've had to jury-rig stuff all the time with what's on hand.  So I thought about what I had that the antenna might fit through...Bic pen was a little too tight, but the poop bag roll was perfect fit, and it's hard plastic and just a little longer than the hole in the Impact clamp.  Perfect and free!   I could build two of the rigs for a grand total of $15.
Mics: Neumann KM184s; Naiant X-R omnis & cards; MM-BSM-7M omnis
Pres/Battery boxes: Naiant IPA; Sound Professionals SP-SPSB-6
Recorders: Tascam DR-60Dmkii; Tascam DR-40; Roland R-07
Cassette Transfers:  Nakamichi CR-1A->Tascam DR-60Dmkii
DAT Transfers:  Tascam DA-20mkii->Marantz PMD-670

My LMA uploads:  https://archive.org/details/@brandon_smith

**Have any old Strangefolk or Eddie From Ohio shows not on the LMA?  Let me know!**

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #332 on: March 06, 2019, 04:48:16 PM »
Right on, DIY improvisational engineering is the oddball way!

beegar- There are obviously lots of different ways to do this. My first thought for you is to find a coupling nut sized to fit the antenna studs.  A coupling nut is just a long nut with enough thread length that both studs will thread in fully from either end.  You then have something similar to what IMPigpen describes with the antennas connected directly to each other.

Lacking that, below is how I'd probably approach it using the antennas you have on hand. Do you have the capability to cut a piece of metal flatstock material and drill a hole in the middle? How about drilling three holes and making a couple 90-degree bends in the bar?

Two bars, one hole each, no bending, some gluing-
Imagine a 1-1/4" or so wide by 4" long (or whatever length the collapsed of the antennas are) piece of aluminum flat-bar with a hole in the middle sized to fit over the top stud of your stand.  Basically a 4" mic bar but with only the center hole in it.  Make two and sandwich the telescopic antennas between them, one oriented left, the other right, one placed just in front of the center hole, one just behind it. Hold the antennas in place (hold the sandwich together) by using construction adhesive or epoxy to glue them to one or both of the bars so they won't squeeze out from between the flat-bar "bun" like a slippery pickle. 

One bar, three holes, no bending, no gluing-
Use a single bar as above and plastic zip ties to mechanically secure either end of each antenna to the bar instead of using adhesive.  To do so drill 3 holes in the bar instead of one, each the same diameter (sized the fit over the stand stud), each positioned on the center-line of the bar, with the additional holes located near either end of the bar.  Secure each antenna to the bar by running plastic tie-wrap through the hole at one end, over the antenna, around the front or back of the bar depending on which antenna it is, and back through the hole. Do the same at the other end of the bar.  Then do the same for the other antenna, passing the tie-through the same holes but wrapping the opposite direction around the other edge of the bar.  Four zip ties in total, two on each antenna.

^Both those options create a more rigid, easily stand-mountable, permanent version of heathen's "opposed and duct-taped together" method.

One bar, three holes, + bending and thread tapping (or gluing)-
Make a shorter bar, with a hole in the center for the stand stud and a hole at each end sized to fit the threaded stud on the end of the antenna.  Thread the smaller holes to fit the thread on the antenna studs, or drill those holes slightly large and epoxy threaded nuts to the back side of those holes.  Put the bar in a vice and make a sharp 90 degree bend at end each end halfway between the holes.  You now have a U shaped bar which fits over your stand stud and into which the antennas will thread.  The U can open either upward or downward if there is enough clearance for the stand.  Best to keep the epoxied nuts on the inside of the U as long as the studs are long enough to pass through the bar and into the nuts.  That way the epoxy only keeps the nuts in place, and the nuts transfer the load to the bar.  If the epoxy fails with the nuts on the outside, the antenna falls.

^Without the antennas removed (unscrewed) this arrangement stows somewhat longer than twice the length of each individual collapsed antenna.  With the antennas removed it stows as three separate parts.  You could probably leave the center U portion attached to the stand or your clamp.
« Last Edit: March 07, 2019, 10:40:54 AM 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<<

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #333 on: March 06, 2019, 04:58:43 PM »
Back to heathen's question about center microphone pattern and L/R supercard spacing in an 3 channel OCT setup-

The primary relationship concerning spacing of the side-facing supercards is this: Narrower L/R spacing makes for a wider SRA - wider spacing makes for a narrower SRA.  It's the same basic relationship as in 2 microphone stereo configurations and there is no way around it.

What happens when other constraints require us to use a narrower L/R spacing than we might want? And what might we do to compensate?  If forced to go narrow with the L/R pair, try to keep the angle between them as wide as possible (+/-90 degrees / 180 degrees total).  That's because as the L/R pair is angled forward, additional spacing is required to compensate for the narrower angle. 

However, keeping the L/R supercards pointing fully sideways is likely to be contrary to what we'd really like when positioned far back in the room, because angling the L/R pair more forward is desirable to bring the on-stage sources and/or PA more on-axis, reducing the level of off-axis room and audience sounds arriving from the sides and back.  The problem is that in such a situation we want a narrower SRA AND a more-narrow L/R angle and BOTH those things require a wider L/R spacing.

If you retain the 180 degree angle between L/R supercards, you can narrow the spacing between a fully side-facing L/R supercard pair until they are only 22cm (~8-1/2") apart and retain good sector linking with the center microphone placed 10cm forward (requiring no delay or level manipulation of the center channel). Doing so results in a total SRA of 180 degrees.  That means the imaging window between the front playback speakers will encompass the entire front hemisphere as viewed from the recording position - a 180 degree arc of sound sources spatially compressed into the 60 degree arc between speakers. The sound sources on stage will be clustered tighter and more compactly into the middle of the playback image.  This makes for a more distant perspective in a geometric "imaging" sense than a narrow SRA that would spread out the stage-width sources until they more completely fill the arc between speakers (this aspect is why Michael William's titled his paper The Stereo Zoom ), but of course there are other psychoacoustic cues which relate to the perception of "closeness/distance" in addition to imaging perspective, and they may contradict the geometric imaging cues. Direct/reverberant sound balance and EQ balance are two among others.

Want to angle the L/R supercards forward 45 degrees?  We then need to increase the spacing of the L/R pair to 28cm and increase the spacing of the center channel to 18cm forward of the L/R pair in order to retain a 180 degree SRA, and retain decent sector linking.
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: Oddball microphone technique (OMT) - part 2
« Reply #334 on: March 06, 2019, 05:09:41 PM »
How narrow can we push it?

I've got Image Assistant up now, with L/R supercards spaced 31cm and angled a full 180 degrees apart.  I've switched the center microphone to a figure-8, as that is the only pattern available in Image Assistant which is tighter in front pickup than supercardioid, placed 8cm forward of the L/R pair.  In the taper world one might use a shotgun in the center with good reason, yet a fig-8 will be better behaved with regards to stereo imaging which is what Image Assistant is primarily about.  This produces an SRA of 138 degrees, which is still wide, but considerably more narrow than 180 degrees.
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: Oddball microphone technique (OMT) - part 2
« Reply #335 on: March 06, 2019, 05:37:05 PM »
The sideways versus forward-angling thing with the L/R supercards helps explain one reason why a considerably wider spacing is desirable for omnis when we introduce a center microphone as opposed to a pair of spaced omni's alone.  In terms of image linking at least, if one cannot arrange for optimal omni spacing, it can be advantageous to switch more directional omnis, subcards, or cardioids pointed sideways which will reduce the spacing requirement somewhat.  However, one gives up other advantages of spaced omnis when doing that, such as low bass sensitivity. 

This in one reason I suggest folks point their omnis sideways for OMT when the spacing they can achieve between them is limited, as it gets as much spacing as possible by using the mic bodies to extend the capsules out slightly farther and at the same time takes advantage of the slight top end directionality of most omnis.  Side facing subcards or cardioids can reduce the spacing requirement further if necessary.

I don't have subcardioids, but I'd not hesitate to use them facing 180 degrees apart in place of omnis, if I could not otherwise achieve as much omni spacing as I'd like.
« Last Edit: March 07, 2019, 10:46:04 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<<

Offline rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #336 on: March 07, 2019, 09:52:33 AM »
This in one reason I suggest folks point their omnis sideways for OMT when the spacing they can achieve between them is limited, as it gets as much spacing as possible by using the mic bodies to extend the capsules out slightly farther and at the same time takes advantage of the slight top end directionality of most omnis.
Here is a photo of what we chose to do after you recommended doing so. I would guess we gained a good 6-8 inches total further than the Manfrotto Triple bar's 30".
AKG ck22|460b outside; AKG ck8 fwd 0'; AKG ck61active rear 180'
« Last Edit: March 07, 2019, 09:54:04 AM by rocksuitcase »
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E|DPA 4060 SK
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #337 on: March 07, 2019, 11:20:34 AM »
Thanks for posting that photo and glad the arrangement worked well for you.

If you wanted you could probably gain an additional 6-8" by pushing the mic-bodies out further in the mounts, and you might gain a couple additional inches by pointing the swivel mounted capsules outwards instead of forward.

For those not be familiar with the ck22 omnis in the photo above, they are somewhat odd in that the microphone incorporates an internal end-plug which makes it more fully omnidirectional all all frequencies, even at very high frequencies were other omnis of the same diameter become more directional.  The 'pointy end' is blocked and sound enters trough ports running around the outer periphery of the capsule.  It is neither an end-address nor side-address microphone but an "all direction address" design, making it similar to miniature lavalier omnis which are fully omnidirectional due to their small size.  So for that particular microphone it doesn't really make much difference in what direction it is pointed..

But when using typical end-address omnis of a similar diameter as the ck22 I'd still suggest pointing them sideways whenever the spacing between them isn't as wide as desired.  That way their slight top end directionality becomes a feature making the most of the limited spacing - similar in a way to switching to side-facing subcards so as to leverage their directionality and make the most of limited spacing while still retaining strong bass extension, but to a lesser extent.
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 rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #338 on: March 07, 2019, 12:02:36 PM »
^^^^^^^^^^
Well, you got me. I should look for another snap which shows the ck22|460's mounted with bodies extended across the clips. Actually does get us several more inches on each side when we do it that way.
top: AKG ck22|460b outside omnis; AKG ck3|nbobs|Naint PFA fwd 0'; AKG ck61|nbobs|Naint PFA rear 180   (Steal Your Peach 2018-07-25)
middle: AKG ck22|460b outside omnis; AKG ck3|nbobs|Naint PFA fwd 0'; AKG ck61|nbobs|Naint PFA rear 180 (Fully extended the mic bodies in this one) (Adam Ezra 2017-08-16)
bottom: AKG ck22|460b outside omnis; AKG ck61 fwd 0';  3 channel OMT minus a rear mic; with no cables, testing on stand at home (before DnCo 2016-06-21)
« Last Edit: March 07, 2019, 12:08:50 PM by rocksuitcase »
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E|DPA 4060 SK
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline IMPigpen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #339 on: March 07, 2019, 12:17:37 PM »
Here are a few photos of my antenna rig.

1.  The antenna with eraser ends in the Impact clamp
2.  Just the antenna with the "poop bag" roll in the center taped for stability
3.  Electrical tape wrapped on the end to provide a snug fit for the eraser.
Mics: Neumann KM184s; Naiant X-R omnis & cards; MM-BSM-7M omnis
Pres/Battery boxes: Naiant IPA; Sound Professionals SP-SPSB-6
Recorders: Tascam DR-60Dmkii; Tascam DR-40; Roland R-07
Cassette Transfers:  Nakamichi CR-1A->Tascam DR-60Dmkii
DAT Transfers:  Tascam DA-20mkii->Marantz PMD-670

My LMA uploads:  https://archive.org/details/@brandon_smith

**Have any old Strangefolk or Eddie From Ohio shows not on the LMA?  Let me know!**

Offline heathen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #340 on: March 07, 2019, 01:30:45 PM »
Here are a few photos of my antenna rig.

1.  The antenna with eraser ends in the Impact clamp
2.  Just the antenna with the "poop bag" roll in the center taped for stability
3.  Electrical tape wrapped on the end to provide a snug fit for the eraser.

That is really slick.  Does the Impact clamp hold onto the antenna by just having a screw at one point?
Recordings on LMA: https://archive.org/search.php?query=taper%3A%22Lucas+Lorenz%22
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 rocksuitcase

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Re: Oddball microphone technique (OMT) - part 2
« Reply #341 on: March 07, 2019, 01:35:04 PM »
Here are a few photos of my antenna rig.

1.  The antenna with eraser ends in the Impact clamp
2.  Just the antenna with the "poop bag" roll in the center taped for stability
3.  Electrical tape wrapped on the end to provide a snug fit for the eraser.
+T!
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E|DPA 4060 SK
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline IMPigpen

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Re: Oddball microphone technique (OMT) - part 2
« Reply #342 on: March 07, 2019, 01:49:40 PM »
Here are a few photos of my antenna rig.

1.  The antenna with eraser ends in the Impact clamp
2.  Just the antenna with the "poop bag" roll in the center taped for stability
3.  Electrical tape wrapped on the end to provide a snug fit for the eraser.

That is really slick.  Does the Impact clamp hold onto the antenna by just having a screw at one point?

It does hold it with just the one screw.  I was prepared to wrap more tape around and/or add a little larger metal or plastic tube over it and tape that but it holds tight as is.
Mics: Neumann KM184s; Naiant X-R omnis & cards; MM-BSM-7M omnis
Pres/Battery boxes: Naiant IPA; Sound Professionals SP-SPSB-6
Recorders: Tascam DR-60Dmkii; Tascam DR-40; Roland R-07
Cassette Transfers:  Nakamichi CR-1A->Tascam DR-60Dmkii
DAT Transfers:  Tascam DA-20mkii->Marantz PMD-670

My LMA uploads:  https://archive.org/details/@brandon_smith

**Have any old Strangefolk or Eddie From Ohio shows not on the LMA?  Let me know!**

Offline ycoop

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Re: Oddball microphone technique (OMT) - part 2
« Reply #343 on: March 07, 2019, 02:04:55 PM »
Here are a few photos of my antenna rig.

1.  The antenna with eraser ends in the Impact clamp
2.  Just the antenna with the "poop bag" roll in the center taped for stability
3.  Electrical tape wrapped on the end to provide a snug fit for the eraser.

What are the erasers there for?
Mics: Avantone CK-1s, AT853 c+o
Pres: CA9100
Recorders: DR-60d mkII, DR-2d

Offline Gutbucket

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Re: Oddball microphone technique (OMT) - part 2
« Reply #344 on: March 07, 2019, 02:08:55 PM »
^ Very nice implementation, clean & simple.

Looking at the first photo posted above, it might be advantageous to slide the clamp left a touch.  That accomplishes two things- It centers the clamp's thumb-screw on the joint between the two antennas, where the threaded insert ends provide significant "hoop-strength" which keeps the tube from being crushed if you really crank down on the thumb-screw, and secondly centers the antenna-bar on a typical diameter stand upright, which is just a tweaky thing and of negligible acoustical significance.

The erasers are Moke's method of attaching small lav omnis.  He cuts a notch in the rubber wedge end to hold the mic cable.  Personally I never got that method to hold securely and just use a small square of gaffer tape.
« Last Edit: March 07, 2019, 02:11:10 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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