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Musings on shotguns vs rifles

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DSatz:
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.

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

crackmc:
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

voltronic:
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/

Gutbucket:
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.

morst:

--- Quote from: voltronic on May 20, 2021, 06:32:03 AM ---Then there is the common myth that you "don't have to aim" a shotgun when firing pellets of buckshot or birdshot.

--- End quote ---
To be glib, you aim a rifle, you point a shotgun.

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