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Offline DSatz

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Musings on shotguns vs rifles
« on: May 19, 2021, 06:14:36 PM »
Hi. I haven't had any training with firearms since a few minutes spent on a rifle range at a YMCA camp 60 years ago by now. I've long used the term "shotgun microphone" while being aware that in the UK, "rifle microphone" was the more common usage, at least up through the 1970s and 80s (not sure about since then). I'd heard the expression "shotgun approach" but ironically, didn't look up what it meant--in other words, I used a kind of shotgun approach toward understanding what a "shotgun approach" was.

Today I was listening to an audio book about human psychology (Daniel Kahneman's Thinking, Fast and Slow). It uses the term "shotgun" in a way that depends on the reader's awareness that this type of firearm suffers from a distinct lack of accuracy. I found that startling at first--then looked up "shotgun" on Wikipedia and found it amusing--since I've long been aware of the mistaken beliefs that many people seem to have about shotgun microphones. And now I think that the term is actually rather apt, not just visually. Shotguns are well known (in contrast to rifles) for the dispersion of the pellets that they deliver. They can't generally hit a target in a precise or focused manner, all the more so if the target is at any significant distance.

So part of the problem where microphones are concerned seems to be that people see shotguns, but imagine that they're rifles--maybe even some kind of computer-controlled super-rifle that exists only in the movies.

The metaphor breaks down after that, since like any other microphones, shotgun mikes respond to the sound field that exists at their location, not the one where you "aim" them. The sound has to come to them--and by the time that happens, if they're at all distant from the sound sources in a reverberant space, plenty of other sound is reaching them as well, which they aren't well equipped to cope with. Most people chronically underestimate (by a lot!) the amount of reflected sound that almost any non-close-up microphone will pick up in most live recording situations--and don't realize how weird and sucky the off-axis response of most shotgun microphones is beyond a narrow angle in the front.

In other words, microphones are of course receivers rather than sources--but people get fooled psychologically by their shape into thinking of them as being active only in the direction that they're pointed--which is far from being the fact.

--best regards
« Last Edit: May 19, 2021, 11:16:57 PM by DSatz »
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Offline crackmc

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Re: Musings on shotguns vs rifles
« Reply #1 on: May 19, 2021, 11:11:06 PM »
i often use the rifle/shotgun analogy when my non-taper friends ask me why i don't use them

i don't really consider the inaccuracy element so much, but in a nutshell i describe it like: shotguns are the perfect firearm for a very specific range of target...and i'm often not within that specific range from my target

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Offline voltronic

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Re: Musings on shotguns vs rifles
« Reply #2 on: May 20, 2021, 06:32:03 AM »
I always assumed the "shotgun microphone" term was given more for similarity in appearance than function.

Firearms sidebar: While most rifles should have greater accuracy at longer ranges than most shotguns, I disagree with the idea that shotguns are inherently inaccurate. You and the sources you are reading may also be assuming that a spray of pellets is all they can do, but you're forgetting about large, single rounds (slugs). I have seen 12 gauge slugs be accurate beyond 50 yards. You can also buy rifled barrels if this is something you do regularly, making it effectively a large-bore rifle in all respects. Then there is the common myth that you "don't have to aim" a shotgun when firing pellets of buckshot or birdshot. I can tell you as someone who does clay pigeon shooting that careful aim is absolutely required. Modern shotguns have come a very long way from the old short-range blunderbuss. Then there is the complex discussion about different barrel chokes and how they affect dispersion at various distances... you get the point.

Actually the more I think about it, chokes are a decent analogy for the directional nature of how the type of microphone we are discussing picks up. Take a look at these resources, especially the graphic from the first link which I'm including here for convenience. In my mind, a longer shotgun (mic) with increased diaphragm venting space to the rear is analogous to a full choke that has a more constricted pattern at shorter ranges.

https://1source.basspro.com/news-tips/hunting-gear/7692/guide-shotgun-choke-tubes

https://www.rem870.com/2012/05/06/shotgun-chokes-explained-cylinder-improved-cylinder-modified-full/



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Offline Gutbucket

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Re: Musings on shotguns vs rifles
« Reply #3 on: May 20, 2021, 12:06:28 PM »
I find it helpful to flip the primary understanding of the role of longish interference tube microphones away from thinking of them in terms of on-axis focus and "reach", instead thinking about them in terms of off-axis attenuation, the behavior of that attenuation, how that behavior does or doesn't suit what is being recorded, and how it might fit with whatever else is being recorded.

Rather than being about "focus", it's primarily about "rejection" and the qualities of that rejection. 

Shotgun mics are less sensitive to off-axis sound, yet they cannot attenuate off-axis sound completely and what is not attenuated tends to sound not as good as what one would get from a well-behaved directional microphone that does not use a longish interference tube.  It boils down to a trade-off between quantity and quality - Is the increased off-axis rejection worth the less natural off-axis pickup that comes along with it?  

For some applications the answer is an easy yes, and shotgun mics exist primarily to fill such roles.

Does it suit what is being recorded?-
For concert recording the answer is not an obvious and easy yes.  Our microphones are acoustically distant from the source so the sound-field at the recording position tends to be dominated by off-axis sound arriving from all directions.  The further back we are, the less dominant direct-arriving sound will be in the sound-field which exists at the recording position, making good off-axis behavior increasingly important.  And there lies a conundrum- off-axis attenuation becomes desirable, yet good behavior of that attenuation becomes increasingly important at the same time.  Because of this, the most straight-forward solution to the problem is to use a pair of directional mics that have good off-axis behavior - one of the important qualities which defining good "taper mics" IMO.  If recording using a single stereo pair at a significant distance indoors, I would choose good super/hypercardioids over shotgun mics.  My answer to the question above would be- "No, the increased off-axis rejection is not worth the less natural off-axis pickup that comes along with it, because the bad behavior is too audible and objectionable."

How it might fit with whatever else is being recorded-
If running additional mics, the answer becomes "Maybe". Bad off-axis behavior is not problematic if it isn't audible. Use in a mix with other channels that serve to mask audibility the off-axis problems can work, but only if there is sufficient difference between the positive aspects of what the shotgun(s) contribute to the mix and the level at which their problems become masked by the other channels. And there is not a whole lot of wiggle room there.  A quality super/hyper with better off-axis behavior may still work better.  But in the modern era when we can record each channel separately and adjust the mix by ear afterward, we at least gain the ability to tweak the balance within the wiggle room we have available.  It has a better chance of working at least.

Even without the ability to tweak it afterwards, the once popular GratefulDead section recording method of using pair of shotguns in combination with a single omni, mixed from 3 down to 2 channels ahead of the recorder was a useful technique. Besides extending low-frequency sensitivity for better bass, the good off-axis behavior of the omni served to mask the not-so-good off axis behavior of the shotguns.


Possible exception for good behavior-
I'd love to try Schopes SuperCMITs but they are well out of reach cost-wise. They have the unusual combination of both increased off-axis attenuation and better behavior of that off-axis attenuation in comparison to other shotguns, achieved by leveraging DSP processing within the microphone in addition to being of Schoeps quality with respect to their non-DSP'd off-axis behavior. The reason I'd like try them is totally rooted in their better off-axis behavior, both in terms of  quantity and quality.  And yet, if I ever did have the opportunity, I wouldn't use them as a single stereo pair, most certainly recording additional channels along with them to provide the ability to make the best of things in addition to the ability to listen to them on their own to see how well they might work alone.

As always, knowledge about how these things work, along with trying things out and listening for what works and what doesn't in practice is key.  That's the case for all forms of recording, but especially so for concert taper recording which tends to be atypical with respect to other types of recording.
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Online morst

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Re: Musings on shotguns vs rifles
« Reply #4 on: May 20, 2021, 04:51:50 PM »
Then there is the common myth that you "don't have to aim" a shotgun when firing pellets of buckshot or birdshot.
To be glib, you aim a rifle, you point a shotgun.

Offline fobstl

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Re: Musings on shotguns vs rifles
« Reply #5 on: May 20, 2021, 07:31:43 PM »
Then there is the common myth that you "don't have to aim" a shotgun when firing pellets of buckshot or birdshot.
To be glib, you aim a rifle, you point a shotgun.
That depends on what you are shooting at Morst. For flying birds, yes you point. But for things like turkey hunting you have to aim, at the head. You generally don't shoot turkeys flying unless you have done something wrong in your hunt. I have shotgun for turkey hunting with fiber optic sights and an extra full choke that you definitely have to aim to hit the small head of the turkey. Actually I missed one last week that started running off on me, tried to quickly point the gun instead of aiming and missed him.

Offline DSatz

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Re: Musings on shotguns vs rifles
« Reply #6 on: May 21, 2021, 03:52:41 PM »
voltronic, thanks. The main place I went to read up on shotguns was Wikipedia. The article there mentions that a single slug is an option, and it also describes the kind of choke that you described.

But I came away with the impression that those two techniques for achieving greater range and accuracy were "outside the mainstream" as far as the general use of shotguns is concerned--that the first thing that the term "shotgun" brings to mind for most people familiar with them is with the type of, I guess it would be ammunition, that consists of multiple pellets that diverge somewhat as they're fired. Do you think I was wrong to infer that?

--best regards
music > microphones > a recorder of some sort

Offline EmRR

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Re: Musings on shotguns vs rifles
« Reply #7 on: May 21, 2021, 04:16:58 PM »
I'll add the places my KMR81's have worked out best have been pretty close, as when used similarly to boom mics capturing dialog right off camera.  Seems counterintuitive to the general perception of purpose.   The times I've put them into a larger mic array at distance, they give one version of a particular 'focus', but it's not very natural.  I can maybe get a bit more vocal intelligibility out of an array with a PAS shotgun in a swim sounding room, but there's a definite limit of usefulness.  It seems to work better to have an ambisonic array or dual mid side array that can be steered in post to find the best focus. 

The sound of a pump shotgun being armed nearby is probably the most terrifying to an intruder, as you don't need much of a clue in the dark to hit a target.  You will need more drywall work though......
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Offline Gutbucket

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Re: Musings on shotguns vs rifles
« Reply #8 on: May 21, 2021, 05:20:36 PM »
^
Thanks for posting about your experience using them in that way.

Agreed on the greater value of the ability to tweak directional alignment in post with high precision while listening.   Although the analogy breaks down right out of the gate because sound is not projectile like, it strikes me that the comparison of pointing (shotguns) verses aiming (rifles) made earlier is analogous to visual pointing alignment of microphones during setup verses audible aiming of ambisonics or dual M/S in post.  Other than providing a direct-listening control loop, that also provides as much time as one wants before pulling the trigger - which may be both blessing and curse.
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Offline voltronic

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Re: Musings on shotguns vs rifles
« Reply #9 on: May 21, 2021, 08:04:33 PM »
voltronic, thanks. The main place I went to read up on shotguns was Wikipedia. The article there mentions that a single slug is an option, and it also describes the kind of choke that you described.

But I came away with the impression that those two techniques for achieving greater range and accuracy were "outside the mainstream" as far as the general use of shotguns is concerned--that the first thing that the term "shotgun" brings to mind for most people familiar with them is with the type of, I guess it would be ammunition, that consists of multiple pellets that diverge somewhat as they're fired. Do you think I was wrong to infer that?

--best regards

I wasn't trying to rain on your parade. And yes, what most people think of when they think of a shotgun is firing buckshot - the 9 or so large pellets that blow a hole through a door or a zombie or what have you in movies. I only was trying to correct one of the common hollywood gun myths that you don't have to aim or even sight down the barrel with proper form - people get hurt in the real world trying to operate a shotgun that way.

Slugs are not that exotic, but are very expensive (even before ammo prices skyrocketed with the pandemic). Choke tubes are extremely common though; any modern shotgun sold today comes with at least two. It's all about dialing in the amount of shot constriction you want at a certain range, and that was where I was thinking of the connection to shotgun microphones. The choke constriction is analogous to the length of the interference tube. Gutbucket has a better explanation though (as he usually does).
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Online morst

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Re: Musings on shotguns vs rifles
« Reply #10 on: May 22, 2021, 02:42:28 PM »
the common hollywood gun myths that you don't have to aim or even sight down the barrel with proper form
Oh yeah, one more bit I learned in high school gun club was you aim a rifle with one eye shut, but you keep both eyes open when shooting trap & skeet with a shotgun, because you need depth perception.
Tangentially, I learned when i worked in a jewelry store that when you use a magnifying loupe, you should keep both eyes open so you don't mess up half your face squinting all the time.

Offline voltronic

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Re: Musings on shotguns vs rifles
« Reply #11 on: May 22, 2021, 07:31:46 PM »
the common hollywood gun myths that you don't have to aim or even sight down the barrel with proper form
Oh yeah, one more bit I learned in high school gun club was you aim a rifle with one eye shut, but you keep both eyes open when shooting trap & skeet with a shotgun, because you need depth perception.
Tangentially, I learned when i worked in a jewelry store that when you use a magnifying loupe, you should keep both eyes open so you don't mess up half your face squinting all the time.

I actually tend to shoot clays with just one eye open as though I am using a rifle. It's the wrong way, but it's how I started shooting, and I tend to score quite well. I can't believe I never thought about the depth perception aspect though, and none of my instructors ever mentioned that.
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Re: Musings on shotguns vs rifles
« Reply #12 on: May 22, 2021, 10:32:44 PM »
you've been shooting the clays in mono!

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Re: Musings on shotguns vs rifles
« Reply #13 on: May 23, 2021, 01:11:47 PM »
The whole notion of shotguns having wide dispersion, even with bird shot, is vastly over exaggerated in the public mindset.  "You don't even have to aim" and that sort of nonsense.  Yes, there is dispersion to a certain degree when using bird/buck shot, but go to a range and try it out on cardboard targets and most people would be shocked at how tight the dispersion is at the type of home defense distances they have in mind.

That said, a shotgun is one of the most versatile guns a person can have.  I just can't help but address the widespread (no pun intended) misconception about how much the shot disperses. 
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Offline DSatz

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Re: Musings on shotguns vs rifles
« Reply #14 on: May 23, 2021, 02:05:44 PM »
heathen and voltronic, many thanks. That's pretty much what I'm trying to ascertain--the reality and (or perhaps, versus) the perceptions other people have about this type of firearm. The "segregation by lifestyle" in this country is so extreme that, just as I know only one person who voted for Donald Trump (that being my former mother-in-law in Texas, who is now in an assisted living facility), I don't personally know any gun owners. But I felt pretty sure that on this forum there would be people who could answer my questions.

I mostly didn't intend to talk much about microphone use, but of course "shotgun" microphones can be very useful for muffling* other, competing sounds that come from off-axis, when you're trying to pick up a sound source that's exclusively (or nearly so) on-axis. That's why their use can make perfect sense outdoors, or even indoors sometimes, to compensate for having to use a somewhat greater distance (i.e. just outside the film or video frame) than you would ideally choose to place a cardioid or supercardioid.

But to use them for picking up a sound source at a considerable distance in a reverberant space, when the same sound that's arriving on-axis is also arriving from many other angles in comparable amounts--they're just not designed for that (no microphone is), and they generally do poorly at it. Their extremely irregular off-axis response merges in with their on-axis response when that happens. (The ear/brain tends to integrate early reflections with the first-arriving sound for up to about 20 mS.)

If anyone gets a chance to watch a film or video being made, note how much trouble and effort a competent boom operator goes to, to keep the talent within a VERY narrow range of angles in front of a shotgun mike on a boom. That's not just for the sake of maximum sensitivity or even a "dry" pickup--it's also to keep the sound from the "talent" from getting in to the sides of the mike, which will color the voice or other sound in a way that is nearly impossible to filter out.

_____________
* edited later to add footnote: I say "muffling" rather than "suppressing" because an interference tube takes effect only above a certain frequency which depends on its length. Shotgun microphones are designed for intelligibility of speech pickup, which is largely a matter of the region above 1500-2000 Hz. To have narrow patterns for music including low frequencies, they would need to be 20 feet long or thereabouts. The only way around this limitation so far is for the microphone to use multiple capsules and fancy methods of combining their signals. A few manufacturers offer this, notably Sanken and Schoeps. But such microphones are extremely expensive and have operational peculiarities that the user has to work within; they aren't the all-purpose solutions that one might imagine them to be.
« Last Edit: May 24, 2021, 12:11:13 PM by DSatz »
music > microphones > a recorder of some sort

 

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