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Author Topic: How A Shotgun Mic Works  (Read 1059 times)

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Offline Charlie Miller

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How A Shotgun Mic Works
« on: October 13, 2017, 01:16:50 PM »
I was doing some research on Schoeps shotguns and came across this page. It has some interesting info that some may find useful. Scroll down and check out the pics in the comments section.

https://randycoppinger.com/2012/04/05/how-a-shotgun-mic-works/

I've never seen an AKG C747 Shotgun mic before. Anyone ever seen one?

https://www.akg.com/Microphones/Shotgun%20Microphones/C747V11.html

« Last Edit: October 13, 2017, 01:21:34 PM by Charlie Miller »
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Re: How A Shotgun Mic Works
« Reply #1 on: October 13, 2017, 01:25:46 PM »
That's pretty interesting. Thanks!
Mics: ADK A51s; AT4041; Superlux S502; CK91 active w/homebrew BB; AT853; Naiant X-X; Nak 300's
Recorders: M10; DR-60D; DR-70D

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Re: How A Shotgun Mic Works
« Reply #2 on: October 13, 2017, 02:02:35 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.
Mics- AT 4041's, akg 460's ck 61's/63's/ck8's, akg active  couplings>naiant pfa's, naiant x-r's (cards,omnis). Pre- SD-302, naiant x-y amp, apogee mini-me X2, Lunatech V-3, Decks- R-44, dr-40,dr-100mkiii,  dr-03.....
ISO- pair of ADK a51 tl's

Offline Charlie Miller

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Re: How A Shotgun Mic Works
« Reply #3 on: October 13, 2017, 02:05:26 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408
Audio Engineer - Steve Kimock Productions


Schoeps CMC6/MK4 -> Lunatec V2 ->  Sound Devices 744T

Offline kindms

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Re: How A Shotgun Mic Works
« Reply #4 on: October 13, 2017, 04:09:50 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.
AKG414 XLS/ST> TCM-Mod Tascam HDP2
Musichall Mambo > VR-2's

Offline Charlie Miller

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Re: How A Shotgun Mic Works
« Reply #5 on: October 13, 2017, 04:15:01 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.

I'm running them for Phish NYE.
Audio Engineer - Steve Kimock Productions


Schoeps CMC6/MK4 -> Lunatec V2 ->  Sound Devices 744T

Offline kindms

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Re: How A Shotgun Mic Works
« Reply #6 on: October 13, 2017, 04:31:24 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.

I'm running them for Phish NYE.

Interesting. As a standalone pair or part of an array ?
AKG414 XLS/ST> TCM-Mod Tascam HDP2
Musichall Mambo > VR-2's

Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #7 on: October 13, 2017, 04:54:12 PM »
The original 'gun' mic was designed by Harry Olsen for use on the then new 'talkie' films (developed to be able pull the microphone back out of the frame) looked more like a classic sci-fi raygun than a shotgun.  It used multiple tubes of varying length arranged in a spiral cluster in front of the microphone element.  The later development of using a single slotted or otherwise vented interference tube achieved the same result using a single tube- simpler, more compact, lighter, lest costly- and that was the end of the multiple tube method

Although I've come across them in the past, I can't locate a photo of the original version, built by RCA I assume, as Olsen worked for them and developed the original RCA ribbon mics. I did find a photo of this DIY version which is similar-





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Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #8 on: October 13, 2017, 04:59:35 PM »
Check out the EV 643, largest interference tube mic ever-

The longer the tube the lower the pattern control. This ~7' long interference tube supposedly maintained a controlled shotgun lobe pattern down to ~700Hz.
Imagine a pair of these in the section!


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Offline Charlie Miller

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Re: How A Shotgun Mic Works
« Reply #9 on: October 13, 2017, 05:24:23 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.

I'm running them for Phish NYE.

Interesting. As a standalone pair or part of an array ?

probably stand alone. I'm very happy with how they sound. I think they'll be clearer than the MK4's. Plus this time I'm bringing my V2.
Audio Engineer - Steve Kimock Productions


Schoeps CMC6/MK4 -> Lunatec V2 ->  Sound Devices 744T

Offline obaaron

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Re: How A Shotgun Mic Works
« Reply #10 on: October 13, 2017, 05:55:17 PM »
Cool article thanks for posting. Im definitely going to be running my guns more often really like Mule pull with the 480/ck69 and the DJ Williams set from Adams ave came out grea with the 460/ck8 combo really impressd with both pulls
Mics:  Gefell M20,M21/sms2000/nbob | Schoeps MK4V/cmc6/nbob | AKG c460b/c480b/a60/Naiant actives - ck61,62,63,69 ;ck1,3,8;ck1x,2x,3x | AT853, AT933 | CA-11c,o
Pres: Naiant Littlebox | Tinybox | Shure FP24 | BMod Edirol UA-5 | Church ST-9200
Recorders:  Zoom F8 | Tascam DR-680 | Tascam DR-60D | Sony PCM-M10
Video: Canon VIXIA HF R42

**ISO** -   Schoeps mk22 set, JW Mod AKG 460 bodies, AKG CK1x and 3x singles

Offline Charlie Miller

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Re: How A Shotgun Mic Works
« Reply #11 on: October 15, 2017, 05:31:35 PM »
Found this:

https://www.quora.com/What-is-a-shotgun-microphone-How-do-they-work

I guess there’s a bunch of different sites with really cool info. Makes sense just never thought about it
Audio Engineer - Steve Kimock Productions


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Offline noahbickart

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Re: How A Shotgun Mic Works
« Reply #12 on: October 15, 2017, 09:57:04 PM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.

I'm running them for Phish NYE.

Charlie, if you want me to run the mk4> cmc6 rig for you, I'll have two extra channels on my Mixpre6....
Recording:
Capsules: Schoeps mk41v, mk4v, mk22, mk3 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Naiant Littlebox, Naiant IPA, Naiant PFA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10
Home Playback: Mytek DSD 192> Adcom SLC 505> Marantz Ma500 (x2)> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-400
Office Playback: Grace m903> AKG k701

Offline Charlie Miller

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Re: How A Shotgun Mic Works
« Reply #13 on: October 16, 2017, 12:54:08 AM »
Those c747's look pretty interesting. I just started messing with the ck-8's and have been enjoying the results with shotguns (short in this case) more than I expected. More lows than I had initially imagined I'd get out of them.

Just picked up a pair of 460/ck8 short shots and had the same findings as you.
http://bt.etree.org/details.php?id=595408

we have had the ck8's for years and would agree. I think probably one of the best shotguns you can have in your kit.

we run them with the knuckles on the bodies generally which helps keep the foot print a little smaller.

I'm running them for Phish NYE.

Charlie, if you want me to run the mk4> cmc6 rig for you, I'll have two extra channels on my Mixpre6....

Done! I have two free channels, just don't wanna deal with running 4 mics.
Audio Engineer - Steve Kimock Productions


Schoeps CMC6/MK4 -> Lunatec V2 ->  Sound Devices 744T

Offline opsopcopolis

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Re: How A Shotgun Mic Works
« Reply #14 on: October 16, 2017, 11:34:14 AM »
It's the same principle that differentiates directional mics from omnis in general.
Mics: Berliner CM-33, CA-14 card, CA-11 card & omni, AT-853, Sony ECM-907
Recorders: Tascam DR-60D, Tascam DR-05, Sony Hi-MD

Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #15 on: October 16, 2017, 03:25:03 PM »
It's the same principle that differentiates directional mics from omnis in general.

I don't follow, how so?

To my way of thinking interference tube (shotgun) mics are quite different because their directivity mechanism is not based on the same basic principle which governs all first-order patterns ranging from omni-directional through bi-directional.

One could mount an interference tube on a first-order capsule of any pattern (omni, subcard, cardioid, supercardioid, hypercardioid, bidirectional).  I could actually take one of the miniature interference tubes off my DPA 4098 super/hypercards and mount it on one of my 4060/61 omnis as the capsules and grids are the same diameter.  I've actually been meaning to do that for years and make some tests of the resulting miniature shotgun-omni but have never gotten around to it.
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Re: How A Shotgun Mic Works
« Reply #16 on: October 16, 2017, 03:25:50 PM »
was checking out the spec  sheet on those  AKG C747 s

the picture makes it look much larger than 5.4inches. thats a pretty compact shotgun mic. pretty cool
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Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #17 on: October 16, 2017, 03:37:10 PM »
FWIW, most shotgun mics are based around a supercardioid capsule, and exhibit standard supercardioid directivity at frequencies below the range where the interference tube becomes effective.  What made the gargantuan EV 643 remarkable other than it's monstrous size was that it retained the tighter front-lobe shotgun pattern down to ~700Hz before the standard supercard directivity took over below that.  The tiny DPA 4098 interference tubes which are only a couple inches long would probably only make the omnidirectional 4060/61 capsule directional above something like 10Khz or more (guessing), and is probably intended to fine tuning the directivity pattern of just the topmost octaves.

The other method of achieving greater than first-order directivity is via DSP - combining and manipulating the signals from more than one capsule, which is how the Schoeps SuperCMIT achieves such radical directivity with minimal artifacts using a relatively short interference tube.  They start with a supercardioid, made more directional at high frequences via the interference tube in the standard shotgun way, but also more directional at lower frequencies than where the tube is effective via DSP manipulation with a second rear-facing capsule located a few inches behind the primary capsule.

Otherwise, any shotgun directivity beyond that of the native polar pattern of the capsule is largely determined by the length of the tube.
« Last Edit: October 16, 2017, 05:51:04 PM by Gutbucket »
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Offline opsopcopolis

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Re: How A Shotgun Mic Works
« Reply #18 on: October 16, 2017, 03:52:32 PM »
It's the same principle that differentiates directional mics from omnis in general.

I don't follow, how so?

To my way of thinking interference tube (shotgun) mics are quite different because their directivity mechanism is not based on the same basic principle which governs all first-order patterns ranging from omni-directional through bi-directional.

One could mount an interference tube on a first-order capsule of any pattern (omni, subcard, cardioid, supercardioid, hypercardioid, bidirectional).  I could actually take one of the miniature interference tubes off my DPA 4098 super/hypercards and mount it on one of my 4060/61 omnis as the capsules and grids are the same diameter.  I've actually been meaning to do that for years and make some tests of the resulting miniature shotgun-omni but have never gotten around to it.

Sorry, didn't qualify that even a little bit hah.

I had just read this part of the third link:

Quote
A shotgun microphone operates on the principle of waveform interference. If you put a diaphragm at the bottom of a solid tube you will not have a shotgun microphone because you need the slots. It's the slots that are the reason for the tube in the first place.

Each of the slot openings is a point source of audio; there is a different location for each slot, so there is a phase difference for each of these point sources, resulting in constructive and destructive interference, enahncing on-axis sound and attenuating off-axis.

I was referring to the 'slots' in modern shotguns
Mics: Berliner CM-33, CA-14 card, CA-11 card & omni, AT-853, Sony ECM-907
Recorders: Tascam DR-60D, Tascam DR-05, Sony Hi-MD

Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #19 on: October 16, 2017, 05:49:12 PM »
Quote
A shotgun microphone operates on the principle of waveform interference. If you put a diaphragm at the bottom of a solid tube you will not have a shotgun microphone because you need the slots. It's the slots that are the reason for the tube in the first place.

Each of the slot openings is a point source of audio; there is a different location for each slot, so there is a phase difference for each of these point sources, resulting in constructive and destructive interference, enahncing on-axis sound and attenuating off-axis.

The bold part is incorrect.  It's the other way around.  The slots aren't the reason for having the tube in the first place, it's a way of using just one tube instead of needing a whole bunch of tubes without any slots.  You get the effect from two non-slotted tubes only in an extremely narrow frequency range determined by the difference in dimension between the two tubes.  Using a whole bunch of tubes of progressive lengths averages the large number of narrow-band effects across a wide enough frequency range to make an effective enhanced directivity microphone based on this phenomena - see the image I posted above of the DIY version of Harry Olsen's original enhanced directivity microphone featuring a great number of tubes arranged in a spiral bundle with the capsule at one end (longest tube in the middle, shorter tubes packed around it, all of them in parallel with the mic capsule at the back end).  I wish I could locate a photo of the actual RCA version of the microphone from sometime around the mid 50's.

The ingenious follow up innovation was to use a single tube with either a series of holes, slots, a long slit, or some other form of acoustic resistance along it's length to replace the bulky bundle of individual tubes.  The tiny interference tubes on the 4098 are made from fine metal screening formed into a cylinder.  The whole tube surface provides a uniform acoustic resistance along it's entire length.
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Offline Gutbucket

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Re: How A Shotgun Mic Works
« Reply #20 on: October 16, 2017, 05:56:57 PM »
Paper on the innovations of Schoeps's SuperCMIT from the Schoeps website (how it uses a second capsule in combination with DSP processing to increase directivity below the range where the interference tube is effective)- http://www.schoeps.de/documents/Paper_SuperCMIT_Development.pdf
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