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Author Topic: Stronger T-bar extension for spaced omni's - boundary mounted DPA's  (Read 2649 times)

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Offline heesu

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So, my prior setup for outdoor venues has been running a 12" ruler w/ antenna extensions going each way, to get to around ~3'. With just mics like CA14's or DPA's, it was doable, though not the strongest setups.

Now that I have some DPA's, I'd like to be able to run them spaced, with the DPA boundary mounts. First time messing around with this, my current setup was just way too flimsy.

So I guess I'm looking for two things:
1. A t-bar that is either collapsable / extendable out to 3' that will be a bit stronger / not wilt.
2. Ideas for securing the boundary mounts. Gaff tape seems like the easiest, but other ideas area also welcomed.

These are the mounts I'm referencing, by the way: https://www.dpamicrophones.com/accessories/boundary-layer-mount-for-dscreet

thanks!

Offline capnhook

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #1 on: March 27, 2018, 11:16:52 AM »
I made a lightweight spread mount for my tiny CAFS omnis out of a screen-door tensioner...


« Last Edit: March 27, 2018, 02:49:17 PM by capnhook »
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BSCS-L->JB-mod [NAK CM-300 (CP-3)][TEAC ME-80 (CP-1)]->LSD2->CA CAFS-Omni->Sony ECM-907**Apogee MiniMe Rev. C->CA Ugly II->**Edirol OCM R-44->Tascam DR-22WL->Sony TCD-D8


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Offline capnhook

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #2 on: March 27, 2018, 11:29:32 AM »
You could attach the boundary mount with a small screw through the holes on the end of the tensioner rod..






Proud member of the reality-based community

BSCS-L->JB-mod [NAK CM-300 (CP-3)][TEAC ME-80 (CP-1)]->LSD2->CA CAFS-Omni->Sony ECM-907**Apogee MiniMe Rev. C->CA Ugly II->**Edirol OCM R-44->Tascam DR-22WL->Sony TCD-D8


"Don't ever take an all or nothing attitude when it comes to making a difference
and being beautiful and making the world a beautiful place through your actions.
Every little bit is registered.  Every little bit.  So be as beautiful as you can as often as you can"

"It'll never be over, 'till we learn."
 
"My dream is to get a bus and get the band and just go coast to coast. Just about everything else except music, is anti-musical.  That's it.  Music's the thing." - Jeb Puryear

Offline aaronji

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #3 on: March 27, 2018, 11:46:03 AM »
Just gaff tape the boundary mounts to the boundary you are using...

Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #4 on: March 27, 2018, 12:21:38 PM »
^ No boundary to mount them to.  As I understand it his intent is to suspend the mounts at either end of the bar atop a stand.   The mounts will serve as an Acoustic Pressure Equalizer attachment similar to a sphere attachment but with somewhat different properties.  So not boundary mounted per se, but using the boundary mounts as frequency and polar response modifiers.  I'd like to discuss the particulars of that more here, but first I'll post a bit on T-bars for small spaced omnis..
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #5 on: March 27, 2018, 12:25:50 PM »
Liking the screen door tensioner rod, Kev.  Nice repurpose.

Heesu, I'll point you to my oddball mic techniques thread in case you aren't aware of it, which began exploring ways of spacing DPA miniature omnis a decade ago- http://taperssection.com/index.php?topic=96009.msg1279052#msg1279052

It's a huge thread, so below are Cliff notes adn selected photos on this particular aspect-

I immediately gravitated to telescopic TV antennas as mic-bar, partly because they allowed me to achieve the width I wanted while being able to retract and fold without disassembly to stow and transport compactly.  The telescoping feature allowed me to adjust the spacing between the mics - both to experiment with the effect of various spacings, and to more flexibly accommodate various recording situations, going less wide than I might wish to when that was appropriate to the situation.  I've never found a superior option and still use variants on the TV antenna telescopic mic bar to this day.

Here's my first setup with a "T"-format telescopic TV antenna simply gaff-taped to a painter's pole-


On the later variants which I still use, the key was making the center connector part out of aluminum bar-stock, to which individual telescopic arms attach and which in turn attaches to the stand.  The upward angled flanges allows for a maximum range of vertical motion of the hinged antenna arms - they fold down and parallel to the stand for transport, up through horizontal to a maximum of about 60 degrees above horizontal-







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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #6 on: March 27, 2018, 12:28:12 PM »
There is a way to gaff tape the cables to the antennas beforehand which allows the antennas to be fully retracted or extended without disassembling everything-







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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: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #7 on: March 27, 2018, 12:43:32 PM »
This may seem too flimsy, but its capable of supporting a full 6' spread.  To avoid relying solely on hinge tension to keep the arms raised, I bent a portion of clothes hanger wire into a short support bar which attaches to the top of the stand stud and hooks under the antennas to brace them. Its stiff enough for good support but can be bent enough to make the angle whatever I want, and short enough that I just leave it on the stand at all times.  You can see it in this shot looking up from below-



..and in this shot looking down from above-




And that combination is stiff enough to support the antenna arms even when I added full-bodied pencil condensers gaff taped a foot or so out each arm along with the associated XLR cabling - quite a bit of weight on those TV antennas-

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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: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #8 on: March 27, 2018, 12:51:24 PM »
Anyway, hope that helps or at least sparks you own ideas.

I don't think your bar needs to be especially strong to do what you want to do with it.  For me its all about how to achieve the significant spacing I want (most spaced omni setups aren't wide enough IMO), while being as minimally visually intrusive as possible, providing the flexibility to accommodate various scenarios, and quick hassle-free setup/breakdown.


Happy to discuss what you might expect from your proposed unorthodox use of the boundary mounts if you like.
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 heesu

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #9 on: March 27, 2018, 01:20:03 PM »
Thank you Gutbucket! I had you in mind when I posted this, and while I've spent a good bit of time in the oddball thread...I couldn't quite come up with what I was looking for this time.

re: the boundary mounts - yes, I'm interested in using them in the way you mentioned. I don't know that they'll operate exactly as DPA intended them, but interested nonetheless. So to do that, and just for a more robust solution, I wanted to look at some other options for telescoping/extended split omnis.

Thanks capn hook as well - I will look into that option as well.

Offline aaronji

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #10 on: March 27, 2018, 02:37:54 PM »
Happy to discuss what you might expect from your proposed unorthodox use of the boundary mounts if you like.

Interesting; I didn't realize heesu meant boundary mounts with no boundary.  I am curious about the effect in that situation.  I would guess it is considerably less pronounced than an actual boundary or even an APE, particularly given the small size, and thinness, of the mount.  Angle must be an important factor as well, I would think.

Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #11 on: March 27, 2018, 03:31:47 PM »
I don't know that they'll operate exactly as DPA intended them, but interested nonetheless.

Definitely will not be operating as DPA intended.  But that doesn't mean it may not be useful or fun to mess around with.

I would guess it is considerably less pronounced than an actual boundary or even an APE, particularly given the small size, and thinness, of the mount.  Angle must be an important factor as well, I would think.

The frequency response effect of using the DPA rubber boundary mount disks (this way in free space, not attached to a larger boundary) will be more pronounced than an typical APE, or sphere baffle or whatever you want to call it, because the diameter of the boundary mount disk is larger than a typical APE sphere. Both frequency and polar response will be different because the edge of the disk forms a sharp boundary discontinuity.  A sphere is commonly chosen because it is a simple platonic solid with no edge and symmetrical in all axes.  And yes any of these kind of attachments which increase the physical size of the microphone will making it somewhat more directional but only in the upper frequency range where the attachment is "acoustically large" with respect to the wavelength.  So microphone angle will matter and hopefully that trait can be used to advantage.

« Last Edit: March 27, 2018, 04:39:36 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<<

Offline heesu

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #12 on: March 27, 2018, 05:22:53 PM »
Yeah, in a weird was as soon as I got my hands on the boundaries - I wanted to try this. Until I sell my CA14's I can still run them as a backup, but curious to see what kind of effect the boundaries have in this kind of setup.


Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #13 on: March 27, 2018, 07:18:45 PM »
Okay here's the basics on what varius shaped attachments on an omni microphone will do-
They basically work like boundary mounting does, but as a special case in that the boundary is tiny, may not be flat, and the shape of any edge comes into play.  Like "normal" boundary mounting, the size of the boundary determines the range of the effect. The larger the boundary, the lower the frequency range effected. In this case the boundary is very small, and will only affect a range of say 2kHz and higher.

Size of the attachment determines the center frequency of the on-axis response peak and shelf filter boost.  Shape of the attachment determines the how smooth or peaked that on-axis boost is, and the behavior of the response off-axis, due diffraction around the shape and off the edges of the shape back to the microphone element.

A round plate shaped attachment (such as the DPA disk will be when suspended in free-air) will produce a sharper response peak than a spherical attachment, and less-smooth off-axis responses.

A plate-shaped attachment is less common than a sphere, but has been used historically by some manufacturers.  Sennheiser is one I know of, although I can't remember the mic model. TS member and gear builder Jon (Naiant) used to offer an omni which he shipped with a wooden plate attachment (the Naiant X-W).  Below is what he says about it on his website http://naiant.com/x-w-specification/

"The X-W is an electret condenser microphone that uses a 6mm omnidirectional capsule with a 36mm pressure waveplate attached to the capsule mount. The waveplate, fabricated from instrument-grade ebony or bloodwood, provides an increase in on-axis high frequency response which enhances the directional response of the X-W. The X-W’s circuit incorporates equalization to restore the X-W’s on-axis response to nearly flat, with a 2dB presence peak centered at 6kHz.

The X-W thus has improved on-axis signal-to-noise ratio due to the acoustic gain of the waveplate. The 90 degree off-axis response of the X-W is approximately 7dB less than the on-axis response at 20kHz. The X-W exhibits practically no off-axis rolloff below 3kHz."
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #14 on: March 27, 2018, 07:19:59 PM »
For a deeper inquiry into the effect of attachments of various shapes-

First a link to an AES paper which is likely to be a definitive source on the subject - Diffraction Effects in High Quality Studio Microphones http://www.aes.org/e-lib/browse.cfm?elib=5902 I've not read it, couldn't find it freely available online, don't have an AES membership and am not paying $20 to download it directly from AES.  But if you have AES library access check that out.

The original research into this was done at Bell Labs back in the late 1930's - The Diffraction Produced by Cylindrical and Cubical Obstacles and by Circular and Square Plates
That study used speakers instead of microphones placed in various shaped enclosures, but the effect of acoustic diffusion around the shape is the same "going out" as it is "coming in".
Below is a figure from that paper which I've pulled from Stan Linkwitz's website (he's referred to it numerous times, I linked the image below from this page- http://www.linkwitzlab.com/Fitz/acoustics-mechanics.htm).  This shows on and off axis response when the source (or microphone) is mounted at the end of a cylinder, a cube, and a sphere.  These are larger baffles about 10" or more in size, but the effect scales linearly with frequency, so just look at the shape of the response curves and ignore the actual frequency indications, or mentally shift the frequency scale upward.  The important thing to note is the difference between the on and off-axis responses, how the response changes further off-axis and how the off-axis response curves are smoothest for a sphere compared to a cube or cylinder-

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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: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #15 on: March 27, 2018, 07:38:55 PM »
Before I started making my own spherical baffles, I considered making flat disks, but didn't think of using the DPA boundary mounts.  I was originally thinking of making plate baffles out of the clear plastic "dummy CDR"s which came atop a spindle of blank CDRs, which are somewhat larger in diameter than the DPA boundary mounts. I didn't try that for a few reasons, one of which being it would be a challenge to mount the mics in them such that the solid portion of the mic grid was flush with the front surface of the disk without any gap. That's critical.  A small gap or less than flush mounting will have an audible effect.  You needn't worry about that using the DPA boundary mounts since they are designed specifically for the mics with this in mind (the small opening is engineered to be the correct size to emulate flush mounting).  Actually one thing you might try is attaching the boundary mount disk to a CD or something to hear what effect a slightly larger diameter disk has.  The CD will extend the boundary edge another inch or so radially and lower the frequency where the effects begin somewhat.

I went with spherical attachments for a few reasons- Smoother response as described above, easier for me to make and less of a hassle to setup, less prone to damage and less visually intrusive.  Here's were I started discussing them in the Oddball Mic Techniques thread- http://taperssection.com/index.php?topic=96009.msg1338961#msg1338961
« Last Edit: March 27, 2018, 07:43:10 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #16 on: March 27, 2018, 08:32:11 PM »
Ran across this guy's blog searching today.  Pretty serious research into attachment shapes and measurement of the effects.  I'd like to figure out how to make these kinds of measurements to test some of my ideas and arrangements!

Here's his post on the measurement method and description of what he's doing.  I've not read through it in depth yet, but the part on how to read the plots is informative in understanding the measurements.  He shows polar response plots for an Earthworks omni without any attachment, with flat-faced cylindrical attachement of two different diameters, and a convex-faced cylindedrical attachment.  Ignore the polar phase plots on the right side, its the polar amplitude plots on the left which are of interest with regards to this discussion- https://recordingsofnature.wordpress.com/2011/02/12/visualisation-of-directional-frequency-response/

Here is his follow up post with detailed measurements of various cylindrical pressure attachment geometries on the Earthworks, all of the same diameter, but some with a concave, flat, or convex faces, and with varying degrees of microphone element flushness to that surface (some with the microphone protruding a bit some with it flush, some with it retracted into the hole in the attachemt by a few millimeters.  Quite ingenious use of a roll of 35mm film as variable geometry attachment- https://recordingsofnature.wordpress.com/2011/02/22/pressure-equalizer-geometries-and-directionality/

Also of interest to folks here may be his post with modified Jecklin-disk/dummy-head response measurements comparing various mic spacings from the surface and various surface materials- https://recordingsofnature.wordpress.com/2010/03/21/quasi-binaural-setup/
« Last Edit: March 28, 2018, 09:59:27 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 Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #17 on: March 28, 2018, 01:47:15 PM »
Well, sometimes you find things when you least expect to.
Objective of the morning: Find/learn about a Pintle tow hitch system.
Found:

https://www.homedepot.com/p/TowSmart-Solo-Hitch-Alignment-System-1280/206798835


Telescoping, extends from 10.5" to 43" each w/ hardish foam ball ends with 2.5" balls. Heavy magnetic bases.
« Last Edit: March 29, 2018, 09:42:58 AM by Moke »
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #18 on: March 28, 2018, 01:57:38 PM »
Ran across this guy's blog searching today.  Pretty serious research into attachment shapes and measurement of the effects.  I'd like to figure out how to make these kinds of measurements to test some of my ideas and arrangements!

\
Damn those Earthworks sure are sweet mics! Very interesting read on the first two links. As we have discussed it certainly makes for a "better" presentation if one can provide visuals AND even better he provides analysis of how to read/analyze his images.
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Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #19 on: March 28, 2018, 03:32:47 PM »
Damn those Earthworks sure are sweet mics!

They are.  Very much in the measurement omni camp, small capsule, low diffraction housing and very flat.  A "naked truth" type mic when used for music.

The aspects which make them somewhat less attractive for music tapers are are their power appetite, requiring more phantom current draw than most mics (from what I've heard, haven't used them myself), and that ruler-flat response which is probably going to need some presence-range and up high frequency boost to not sound dull and lifeless at taper distances.


https://www.homedepot.com/p/TowSmart-Solo-Hitch-Alignment-System-1280/206798835

Telescoping, extends from 10.5" to 43" each w/ hardish foam ball ends with ~2"(~+) balls. Heavy magnetic bases.

Nice find.  Can't tell from the photos or descriptions but they look like they may use larger diameter telescoping tubes than TV antennas, which would support more weight without sagging. Too bad they are chrome finished and not black.  The balls can be painted. Wonder if the magnet end screws off.  Lacks a built-in hinge at the fat end for folding that most TV antennas have, but not necessarily a deal-killer.

I should look into carbon fiber tubing again to see if I can put together a telescopic system from that.  When I've searched previously a few years back the only nesting tube options were for larger diameter tubes like for mic booms and things like that, with a minimum diameter of 1" typically and no less than 0.5".  I need something sized more like the tubes used for stunt-kites and drones.
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 Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #20 on: March 28, 2018, 07:10:21 PM »
Lee,
This is from the OMT thread, where I posted this same device.

Quote from: Moke
Do I ever leave anything alone?
Only in the bag, on the way home...

Found out:
Magnets just push out of the channels. This exposed mounting scheme of a pop rivet into the body of the tubing.
Determined: Childs play to mod further.
Pop Rivets will be removed, and machine screw replacements. At the magnet channel, matching all-thread connector ferrules will be attached so that the magnetic bases can be utilized, or, the machine screws can be used to connect the two spreaders into a single unit.
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Offline Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #21 on: March 28, 2018, 09:10:01 PM »
OK,... tearing them down, to build them back up.


4793: shows pop rivet
4794: no pop rivet. this is a very deep metal insert flange-lip press fitted into the lowest anchor section. I'm aiming for 1/4-20 male threads for this hole, w/ JB-Weld adhesive set.
4745: I intend to join the new spreader bar like the antique bar, but maybe a bit nicer finish.
4746+: size comps to my antique rabbit ear pair (vintage?)
« Last Edit: March 28, 2018, 09:12:00 PM by Moke »
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #22 on: March 28, 2018, 09:28:35 PM »
And,.. this just in: the base/anchor section fits the pass-thru hole of the Manfrotto mini clamp really well.
« Last Edit: March 28, 2018, 09:32:56 PM by Moke »
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #23 on: March 28, 2018, 09:55:58 PM »
really nice.  great use of the Trailer Alignment tool. I had to click the link to look at it. Never heard of such a thing! perfect adaptation of their product to the extension bar. kudos
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #24 on: March 29, 2018, 08:00:56 AM »
Love it!  What's under the yellow balls?
Neil
Mic's: AKG C214's, Line Audio CM3, AT4041SP, AT853 (C, SC, O), AT943 (C, H)
Pre's: Sound Devices MixPre 2
Rec's: Sony PCM-M10, Edirol R-44, Tascam DR60D MKii, Tascam DR70D x 2

Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #25 on: March 29, 2018, 09:03:01 AM »
From reading a few review comments on the Trailer Alignment tool it seems the balls screws onto a threaded stud at the skinny end.  Should be easily removable.

Way to make quick progress on this, Moke. Looks substantially beefier than the TV antennas yet still not overly large in diameter, so probably capable of supporting larger mics than the miniatures DPAs at a wide spacing, and very compact retracted.  Really nice how it fits perfectly into the Manfrotto mini clamp.

What material are the balls made of?  I can offer some advice if interesting in converting them for use as mic mounts / spherical baffles (APEs).
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #26 on: March 29, 2018, 09:17:11 AM »
The foam ball is flexible, but, quite hard. I have to push really hard with a pointed finger in order to distort the shape of the ball. I would call it closer to a reflective surface than an absorbing surface.
It is foam, not hard plastic. But it is quite a hard foam.
The balls are epoxied on, and do not appear to be removable.  I might take a tubing cutter, and cut them away, and, find some precision brass tubing to match the diameter, in order to make a sleeve that can used to remove or replace the balls as needed.

Neilyboy,.
It appears that the chrome extension at the ball is epoxied on. It does not rotate, and there is adhesive residue on the ball at the point, and a spot of it in another location on the ball.

Ball size measured at 2.5" this morning.
matches size of tennis ball, almost exactly.
« Last Edit: March 29, 2018, 09:50:36 AM by Moke »
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #27 on: March 29, 2018, 11:31:26 AM »
Maybe they changed the assembly since the review I read (where the reviewer discussed unscrewing the balls), or perhaps there's a threaded insert in the ball hidden under the glue.

2" is a bit on the large size compared to most spherical attachments, but that means the effect will start a bit lower in frequency (guessing around 1K or so) and will be a bit more obvious.  Could be advantages, and maybe just the ticket from further back  Definitely worth trying I think if anyone is interested in playing around with spherical baffle attachments.  Most spherical attachments are machined from hard plastic or wood, but I think what's important is that the surface is hard with respect to the frequency range in which the ball is functioning as a baffle, and that it be non-resonant across the full frequency ranges, so I think a firm foam ball with a smooth skin should work fine.
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #28 on: March 29, 2018, 11:31:47 AM »
I see two ways of mounting miniature DPAs to these balls.  The first and easiest would be to simply gaff tape the mic to the face of the ball so that the mic grid is held against the surface of the ball and the mic body is tangential to the surface.  I'd point the grid upwards if orienting the ball/mic combination directly forward or angled out +/-45 degrees.  Angled +/-45 degrees is how I run mine and what I'd suggest for folks using them as a spaced omni stereo pair alone at decent spreads.  If using the balls to help make the most of a situation where you are not able to space the mics as far apart as you might like (even though the telescoping bar allows for wider spacings) or if the intent is to use them in combination with a center mic or center pair, I'd suggest taping them to the outermost side of the ball (+/-90 degrees or 180 degrees opposed to each other).  Sort of a double mini-jecklin / dummy-head setup.  That will maximize the level differences.  In that orientation, this taped-on tangential mounting would then allow one to point the mic itself upwards or forwards by rotating the ball.  That probably won't make much difference, but may have some audible effect at the very highest frequencies.

The other more typical way of using the balls, and the method which would need to be used for any mic larger than the miniature DPAs is to make a hole through the ball for flush-mounting. Rather than drilling, which probably won't work well through the foam, I'd suggest either punch-cutting a hole through the ball with an edge-sharpened stiff metal or plastic tube, or melting a hole through it with a torch-heated rod or nail.  A red-hot nail head and a steady hand worked nicely for making holes in my Nerf hard-foam balls.  If the foam ball is compliant enough you might make the hole slightly smaller than the mic body so that it fits snuggly with no gap at the working end.  A section of plastic drinking-straw just larger enough to pass the microphone through, running most of the way through the ball but stopping just short of the surface where the mic peaks out will make it easier to thread the mic through.  If the ball surface gripping the mic body isn't enough to keep the mic in position, a short stick, tapered along its length (I use a piece of chopstick) inserted into the back end of the ball will wedge the mic cable in place without stress or damage.

To achieve variable angles, you can either make multiple balls and switch between them, or poke multiple holes through the ball through which the mic is inserted, or have multiple mounting points for the telescoping arm attachment around the ball.  Mine are setup with a single hole for the microphone and two different blind mounting holes which slip over the antenna button end with a simple interference friction fit.  That gives me options of pointing them directly forward (or behind) or +/- 45 degrees.  I should make another set of holes to orient closer to +/- 90 degrees parlty to accommodate overly narrow spacings, and to see if that offers any further improvement in combination with my center mics even at wide spacings.

The important part is to not have an opening larger than the mic body unless you stuff something in there to fill the gap, and not have the mic stick out or be recessed in the ball.  Ideally only the grid of the microphone should protrude past the surface of the ball, and the the ball's surface should align with the edge of the solid cuff portion of the grid.  It may seem that I'm contradicting myself in suggesting simply taping the mic to the ball, then getting overly particular about the fit in a through-hole, but gaps or small pockets produce more of an audible effect than the mic sticking out slightly.  Consider the difference in response produced by the long high-boost grid verses the short low-boost grid.  Thats a similar acoustic EQ difference produced by a difference of only a couple millimeters of air volume between the mic element and the grid opening.  Recessing the mic in the ball, or a gap around the mic is in some ways similar to changing to a longer grid.
« Last Edit: March 29, 2018, 11:33:41 AM by Gutbucket »
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #29 on: March 29, 2018, 11:46:48 AM »
It strikes me that these tennis-ball sized balls are not much different in diameter in comparison to the DPA boundary mounts.  Would be cool to hear a comparison of the two. 

If the yellow is too garish, a can of automotive spray paint intended for vinyl or fabric seats, tops and interiors remains flexible upon drying and is available in black or various shades of grey.
 
Photo of the chopstick cable wedge-


And a side-view of the wedged-in through-hole mic positioned so only the grid portion is sticking out-


Note- the ball in these photos was installed on the antenna arm with a direct-forward orientation of the microphone.  The ones I actually use are painted charcoal grey.
« Last Edit: March 29, 2018, 11:49:53 AM by Gutbucket »
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Offline Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #30 on: March 29, 2018, 11:50:35 AM »
Sarge just shakes her head in confusion as she watches the tear down,..

I had to pull with *all my might to break this bond.
*well, a strong hard pull, anyway.
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #31 on: March 29, 2018, 11:59:26 AM »
I might take a tubing cutter, and cut them away, and, find some precision brass tubing to match the diameter, in order to make a sleeve that can used to remove or replace the balls as needed.

Since they pulled off cleanly, you can probably just clean up the end of the arm a bit (for use without the balls) and leave it at that.   Then if you want to use the balls you can just push them back on using the existing hole and I expect they'll probably stay in place just fine from the elastic grip of the ball.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #32 on: March 29, 2018, 12:08:16 PM »
The second one came off even cleaner; but with a very loud pop.

What sort of mounting attitude are you looking for, on average,.. something like 0º straight forward?
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #33 on: March 29, 2018, 12:57:58 PM »
Depends on what you want to achieve.

> 0º equates to straight A-B, producing the maximum forward-facing direct-sound bias in the presence range and up.  I'm set up for but never played much with that, except on my center omni when I was doing the "Decca Diamond" setup - in which case the center ball-mounted omni was always 0º.
> 45º is what I use, which adds some left/right stereo difference across that HF range which is welcome with A-B omnis IMO, and retains much of the forward bias.  That's what I chose to use for Left/Right in combination with the center omni in search of more stereo info, but didn't dare to go wider angled at that time.  Something of a safe medium.
> 90º will maximize the left/right stereo difference.  I suspect especially useful for narrower spacings, and/or when center mics are used in combination, and gives up the forward biasing.  I'm no longer scared of going wider angled as I was back then, especially when there is a center mic or pair in combination.

With my 6 channel setup I now actually orient them so the 45º angle faces backwards.  That's because in this setup they are contributing ambience and low frequency pickup and pointing towards the back corners of the room provides a bit more HF differentiation between the forward and side-facing center mics.  I want their "presence" focus to be on the room ambience and audience reaction rather than the direct sound from in front.

Of course, using a sphere (or plate) attachment eliminates the "near-perfect omniness" of The miniature DPA omnis which is a characteristic of their extremely small size, replacing it with a form of limited range controlled directivity along with the modification in timbre.  That "near-perfect" omniness and flatter response is many times a positive attribute in itself. 

Options are good.
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Offline Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #34 on: March 29, 2018, 06:20:16 PM »
Updating in real time,....
The base anchor tube is not a good choice for tightening the set screw of the Manfrotto Mini, or, any other clamp.  I did so, very slowly and carefully, and still pocked it slightly. So, like the rabbit ear antennae pair, I'm going to rig a thread rod component to attach the pieces to gather, and, to give the clamp set screw something to bite into (steel walled thread rod ferrule connector)..

I've also found a slick way to convert the black plastic ends into a useable diameter for the #2 Pencil Eraser Mic Clips. But, I'll let the drama build before the great unveil.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #35 on: March 29, 2018, 06:27:13 PM »
The bases have been renovated, and ready for flat black spray paint.
1/4-20 thread rod ferrules and matching 1/2" flat machine screw
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #36 on: March 29, 2018, 06:51:47 PM »
Because I know the anticipation is killing everyone,... The new pencil eraser mic clip mounts.
I cannot show them mounted right now, as the spreader bars are set up with drying epoxy to set in a thread set.

This is some precision brass tubing stock; scrap from some of my past projects.  It is from nesting diameters of tubing.  This particular diameter fits the pencil eraser, and, also very nicely fits the O.D. of the black plastic spreader ends.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #37 on: March 30, 2018, 10:45:17 AM »
And, the finished spreader bar, mod'd for DPA4060 pair.
I'm going to slightly rework a couple of things now that the dry-fit has happened. but, this is essentially the finished bar:

4805: sections with 1/4-20 thread set added.  I used a nut on the threads to give me more surface area for the epoxy to embed.
4806: threads
4807: screwed to magnet bases
4809: thread rod couplers used to join the sections. This is one thing that I've already changed. I only need a single thrad rod connector; two is too long.
4810: Mic clips for DPA 4060 pair
4811: Kit  -> to mod, yet: I'm going to convert one of the magnet bases to a male thread post, as one of the spreader sections is going to be converted to female thread (screw shortened, and female ferrule to be added).
« Last Edit: March 30, 2018, 11:27:23 AM by Moke »
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #38 on: March 30, 2018, 10:53:13 AM »
Nice bit of kit you've put together there.

..in a 24 hour transformation.
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Offline dactylus

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #39 on: March 30, 2018, 10:57:52 AM »
^^

+T
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #40 on: March 30, 2018, 11:23:46 AM »
thanks, guys!  +'s

Sarge,... she rules the morning.
I'm going to hang some known loads on it later, like the cm3's, just to see how much it deflects under load.
The DPA4060 pair, I doubt they will even register. I think it will probably sag equally, just under its own load.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #41 on: March 30, 2018, 11:39:08 AM »
digging the purple eraser tips! Great project outcome!
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #42 on: March 30, 2018, 12:14:48 PM »
[chuckles]

And, a warning: FOR GEEKS ONLY!i!

The otherwise useless data stream of stress testing, and, how I otherwise abused a new toy.

Sarge is no longer confused by the events unfolding. She is now in the rolling of eyes mode=on.

4812: no load, except mic clips
4813: 4060's hanging at ends of spreader for maximum load
4814: 4060's properly mounted, cable load spread, with windscreens for max. load
4815: Abused  CM3's with 6' Belden 1804a Stubby XLR whip cables at ends of spreader
4816: With CM3 cable load spread out, and mics hanging at ends of spreader.
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #43 on: March 30, 2018, 12:22:11 PM »
Ha. Good woman you have there.

4815: Abused  CM3's with 6' Belden 1804a Stubby XLR whip cables at ends of spreader
^ cringes slightly.

4816: With CM3 cable load spread out, and mics hanging at ends of spreader
^ not nearly as bad. Copper wire and XLRs are heavy.

What's the total spread distance mic to mic?
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #44 on: March 30, 2018, 12:32:24 PM »
End to end is exactly 7' (well,.. 84.25" )
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #45 on: March 30, 2018, 12:38:52 PM »
Nice, that's pretty wide. Probably a TS record from a single stand.  I can get a bit over 6' with the TV antennas but usually tape it so the smallest several segments remain retracted since they are toothpick thin and end up closer to 5' or so - it's not a weight support issue with the 4060s as much as protecting the antennas themselves from accidental damage.

I wonder if there is some treatment which could blacken those shiny tubes.  Can't be a coating which would immediately scuff off or jam the telescoping action.  Would have to be a chemical or heat process or something (I used to heat-treat bright stainless parts to achieve a dark gold tone years ago in my sculptural metal fab days), but not anything which would damage or destroy the thing.

Although beyond the scope of your project, I've also long wanted to figure a way of running wiring internally through the telescopic arms for the ultimate telescopic arm setup. Would need to be a very fine spiral wire to fit and to slinky in and out sufficiently without jamming or stretching the wire.  A fine Litz wire coiled pair probably.  The metal tube could serve as 100% coverage shield.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #46 on: March 30, 2018, 12:50:56 PM »
I will normally use this with my other T-Bar, which reaches to around 37cm in total width.  I've typically velcroed my rabbit ears to the t.bar, which spreads the load out over that 37cm.
The clamp presents a hinge point, at the joing point of the spreaders; it also did this with the rabbit ears.
By spreading the load across the directional stereo bar, it solidly spreads out the load, and takes away the hinge point sag.

For now, i get to go play with my new scuffle hoe (triangular horizontal cutting blade to run a fraction of an inch below soil). I get to go cut a forest of wild/feral mustard plants that are trying to flower.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #47 on: March 30, 2018, 01:06:00 PM »
I wonder if there is some treatment which could blacken those shiny tubes. 
Maybe a very small sleeve of some black fabric that will scrunch up when the arms are collapsed?  As a bonus, one could probably run cables inside the sleeve.
« Last Edit: March 30, 2018, 01:26:21 PM by heathen »
Mics: Core Sound TetraMic | AT4031s | AT AE5100s | AT853s (C/SC) | Line Audio CM3s | DPA 4061s | CA-14 omnis | Studio Projects CS5
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #48 on: March 30, 2018, 01:14:23 PM »
As a bonus, once could probably run cables inside the sleeve.

Bet you could string CAFS omnis through the tubes.

No weight at all, +T
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #49 on: March 30, 2018, 02:32:53 PM »
Cables inside would present possible pinch/bind points.  Those only reveal themselves at home, in controlled testing [/sarcasm].
But, in reality, they only finish the outsides. Who knows what the inside would be?
In my drilling out of the mounting flange for the added thread set, that base flange is fully at least an inch deep+. I quit drilling before I drilled through it.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #50 on: March 30, 2018, 03:26:50 PM »
I sort of forgot where we started here.
With the balls.

4818:
This is how I normally rigged with the rabbit ears.  I spread them across my stereo bar, and velcroed them in tight.
These balls absolutely reject the gaffers tape. Gotta figure something out a bit more permanent.

4819/20:
Old worn out fishing waders get a new life as spreader bar, and t-bar storage
« Last Edit: March 30, 2018, 03:29:39 PM by Moke »
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #51 on: March 30, 2018, 03:37:52 PM »
The inside-the-telescopic-arms cable routing thing is mostly just a long-held fantasy setup of mine.  I've thought it through and don't see it as an easily achieved thing with my current TV antennas, but may pursue it if I eventually work up a carbon-fiber tube version, which would probably only have one or two telescopic sections per side instead of multiple sections.  For me, keeping everything pre-wired, the arms really only need to retract to a slightly shorter length than the stand to which they are attached collapses down to, and/or the most compact spread I plan to use once deployed.

It's conceptually doable as that's how many internally-wired overhead mic booms work, if on a larger scale with bigger tubes.

I wonder if there is some treatment which could blacken those shiny tubes. 
Maybe a very small sleeve of some black fabric that will scrunch up when the arms are collapsed?  As a bonus, one could probably run cables inside the sleeve.

That works.  Telescopic range is limited, but the wiring is well protected.. and it looks cool.  Photos of my Bear Creek setup used for way FOB and stage-lip recording in the "excitement zone", where I needed to be ready to yank and run if necessary, using Tex-flex expanding cable sheaving- http://taperssection.com/index.php?topic=96009.msg1713305#msg1713305




\

^ The shorter front-back antennae (non telescoping in the above configuration) were later shortened and support 4098 supercards instead of 4060s.



« Last Edit: March 30, 2018, 03:39:31 PM by Gutbucket »
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #52 on: March 30, 2018, 03:52:09 PM »
These balls absolutely reject the gaffers tape. Gotta figure something out a bit more permanent.

You might stick some more aggressive tape to the ball which adheres well to it, then stick the less-aggressive gaff-tape to that.  Or, if you spray paint the balls with fabric paint, gaff may stick better to that surface.

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Old worn out fishing waders get a new life as spreader bar, and t-bar storage

Totally dig your neoprene wader-bags.  I use the ones I got from you along with the Gefells years ago all the time to transport my larger mics.  Excellent well-padded protection!  You could easily market those things if you chose to.  Get some barefoot hippie chicks surfing below the cliff-home shrine of Jack O'Neill in Santa Cruz to sew 'em up for you.  Charge a premium for the shark-tooth distressed look.
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 Moke

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #53 on: March 30, 2018, 04:26:33 PM »
regarding the tape ism..
My mind keeps grinding on something like a bobby pin, or, light wire j-hook that can be pushed into the ball, and capture/hook the cable, and hold it that way.
I'm also looking at using the brass precision tubing as a core cutter, and cutting tunnels through the balls to route the mics through.
projects for another day.
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Offline Gutbucket

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #54 on: March 30, 2018, 04:46:39 PM »
That might work.  Similarly I use fat-headed sewing pins to affix hemispheric windscreens to the balls when needed. 

The screens are cut-down cheapo generic ball-mic foam screens sized for Shure SM-58 standard mesh-ball-head mics, which are the same diameter as my Nerf balls.  I cut-off the cuff-end of the windscreen which normally extends down the hand-held part of the mic somewhat, leaving just the hemispheric end, which covers half the Nerf ball to its equator perfectly, and secure it in place with three of four pins pushed through the screen around it's circumference into the hard-foam ball.   The omnis seem to become slightly more wind sensitive upon mounting on/in the balls, yet still not nearly as much so as directional mics.  Really only needed aloft outside in a breeze. 
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: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #55 on: March 30, 2018, 04:53:05 PM »
Neoprene pouches of all kinds! [chuckles]
I need to get out there and wear out another set.  I started wearing knee pads when I went fishing, as the wader knees always get pin holes. So, that slowed my needs down considerably; and i also got a bunch of shit about it, but, felt vindicated as I saw more and more people buying less and less waders on a particular Utah Fly Fishing discussion group. But, for a long time they had me nailed down as that tutu and knee pad wearing hippy fly flicker from cal.
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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #56 on: April 03, 2018, 10:08:54 PM »
OK,.. I took a piece of precision brass tubing, and ground a couple of horns at the end. I filed them into cutting edges, and chucked them into my drill.
I drilled three sets of holes. One set was at something near straight forward 0º. The other set were drilled parallel to the spreader, and emerged at the outer edge of the balls at 90º/270º.
One set of holes was to mount the balls to the spreader bar. I used the same diameter brass tubing that the eraser clips are mounted to, andd drilled those into the balls.
And the next tubing size smaller is a perfect fit for the 4060's. The easily slide through the tubes.

4824: DIY core cutter
4827: 90º end mount with mic in place
4829: main mounting tube, and, mic routing tube to 90º side mount
4833: 0º routing
4834/35: 0º forward mounting and routing
« Last Edit: April 03, 2018, 10:10:46 PM by Moke »
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Offline Limit35

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #57 on: April 04, 2018, 01:22:10 AM »
Nice, that's pretty wide. Probably a TS record from a single stand.  I can get a bit over 6' with the TV antennas but usually tape it so the smallest several segments remain retracted since they are toothpick thin and end up closer to 5' or so - it's not a weight support issue with the 4060s as much as protecting the antennas themselves from accidental damage.

I wonder if there is some treatment which could blacken those shiny tubes.  Can't be a coating which would immediately scuff off or jam the telescoping action.  Would have to be a chemical or heat process or something (I used to heat-treat bright stainless parts to achieve a dark gold tone years ago in my sculptural metal fab days), but not anything which would damage or destroy the thing.

Although beyond the scope of your project, I've also long wanted to figure a way of running wiring internally through the telescopic arms for the ultimate telescopic arm setup. Would need to be a very fine spiral wire to fit and to slinky in and out sufficiently without jamming or stretching the wire.  A fine Litz wire coiled pair probably.  The metal tube could serve as 100% coverage shield.

I have been thinking about this for quite awhile except one item above I haven't, but now it makes so much sense. I have built and rebuilt tent poles and thought this is where I need to go beyond extendable antennas. They are uniformly consistent in thickness and can be made to any size, one just cuts them and adds the end connectors.  There would be minimal sag in this system, which would look cooler if that means anything, and no rotation which I have had in the heat. Here's what I never thought about. The diameter of the pole compared to the diameter of the cord would easily allow the mic cable to be run through the tent poles. Obviously, mic cable cannot bend like the cord but one could run excess cable so there is a nice curve at the break points when one is packing/storing the rig. I use Naiant mics so dedicating a through pole mic and cable wouldn't be a big deal. The end connector would need to be cut and resoldered due to the inability to thread it through poles.

Depending on the poles, i.e. high quality tent poles, one could get a good spread with small omnis. It seems fussy, but for an easy 2-3m spread it seems like a possibility.

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Re: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #58 on: April 04, 2018, 09:14:01 AM »
Tent poles work well.   Good size, stiffness and disassemble-abilily.  I no longer run a second rig at fests, but a few times I made up a quick clamp-rig from a Windtech clamp, a discarded three section shock-corded tent pole, a spare pair of mics and recorder - pulled from a discarded tent and random stuff I had on hand back at camp.

I'd not worry about the internal cable routing unless/until you decide you want to run whatever setup you settle upon regularly.  If you do, I'd use tech-flex or some other cable sheath to protect the cable at the bends, maybe in a double layer.

Running cables along the outside of sectional (non-telescopic) poles I found it easiest to first attach the mics to each end, then hold the pole up in the air horizontally from its center, letting the cables dangle freely with its connector end(s) held together, then rotate the pole around its own axis (twist it) to spiral the cable around it.  The cable should spiral nicely and evenly inward from the mics in towards the center from each side.  Do the opposite to disassemble the mics from the pole.

Quote
^Nice.  Good flushness with minimal gap and just the grid extending.
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: Stronger T-bar extension for spaced omni's - boundary mounted DPA's
« Reply #59 on: April 04, 2018, 09:27:29 AM »
OK,.. I took a piece of precision brass tubing, and ground a couple of horns at the end. I filed them into cutting edges, and chucked them into my drill.
I drilled three sets of holes. One set was at something near straight forward 0º. The other set were drilled parallel to the spreader, and emerged at the outer edge of the balls at 90º/270º.
One set of holes was to mount the balls to the spreader bar. I used the same diameter brass tubing that the eraser clips are mounted to, andd drilled those into the balls.
And the next tubing size smaller is a perfect fit for the 4060's. The easily slide through the tubes.
+T     super good work on that mic mount in the ball.
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