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Author Topic: AKG 568 vent position.  (Read 973 times)

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Offline ts

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AKG 568 vent position.
« on: June 21, 2018, 10:09:57 AM »
Moving this question I asked in the yard. Pokahu says point the vents up. I point sideways. If you position the XLR ends like you would on any other mic the vents are pointing down, which makes sense for ENG work. So for what we do, what’s the best position? I suppose it’s also a matter of taste. Up would mean less crowd noise, down could be disastrous and sideways maybe neutral. What say you?

Offline Gutbucket

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Re: AKG 568 vent position.
« Reply #1 on: June 21, 2018, 03:13:07 PM »
Orientation of the vents in the interference tube matters for some shotgun microphones and doesn't for others.  For those where it does, it usually means a somewhat broadening high frequency pickup pattern toward the side with the vent openings.  More of a tone-flavor air and brightness thing than a major difference in off-axis rejection.  But there is no need to speculate about whether a particular shotgun mic has this attribute, nor rely on the hearsay of other tapers who may be using a particular orientation simply because that's how they've always done it, the justification for doing so seems rational and they report making sick tapes that way!  Better to figure it out what's really going on for yourself and get a feel for the specifics-

Plug in the mic, don headphones, hit rec/pause, and turn up the gain.  Speak into the microphone with it oriented perpendicular to your face (90 degrees off-axis). Continue speaking and listening while rotating the mic around it's primary axis but always keeping it pointed the same direction.  While doign this, listen for any change in timbre of your voice.  Note if the change of timbre corresponds with the orientation of the vents or not.  If it does change, make mental notes about how, in which way, and in general develop a ear for what is happening.

Once you have that kind of empirical knowledge of how your specific shotgun mic behaves, you can then think about how you want to use that trait to your advantage.   Also question those assumptions!  Check them by trying different rotational orientations in the otherwise same setup over the course of a few outings to determine if your assumptions works out the way you envisioned them or not.  Rinse-lather-repeat.
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Offline Walstib62

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Re: AKG 568 vent position.
« Reply #2 on: June 21, 2018, 05:49:18 PM »
https://www.soundonsound.com/sound-advice/q-how-do-shotgun-mics-work

Good article on the subject. There may be an "ideal" physical orientation of the tube vents in a given setting, but it would seem largely guesswork without knowing what frequencies are present at all sides of the mic at any given time. (And which of those are desirable or undesirable)

Offline pohaku

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Re: AKG 568 vent position.
« Reply #3 on: June 21, 2018, 05:51:41 PM »
My understanding has been that you don’t want to orient the vents downwards over the crowd. I use up, unless the room has a low ceiling.  If it does, then I orient the vents to the outside.  Gutbucket’s approach makes sense and is certainly more empirical than making assumptions about how the mic might interact with a particular room.
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Offline ts

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Re: AKG 568 vent position.
« Reply #4 on: June 21, 2018, 07:59:49 PM »
Orientation of the vents in the interference tube matters for some shotgun microphones and doesn't for others.  For those where it does, it usually means a somewhat broadening high frequency pickup pattern toward the side with the vent openings.  More of a tone-flavor air and brightness thing than a major difference in off-axis rejection.  But there is no need to speculate about whether a particular shotgun mic has this attribute, nor rely on the hearsay of other tapers who may be using a particular orientation simply because that's how they've always done it, the justification for doing so seems rational and they report making sick tapes that way!  Better to figure it out what's really going on for yourself and get a feel for the specifics-

Plug in the mic, don headphones, hit rec/pause, and turn up the gain.  Speak into the microphone with it oriented perpendicular to your face (90 degrees off-axis). Continue speaking and listening while rotating the mic around it's primary axis but always keeping it pointed the same direction.  While doign this, listen for any change in timbre of your voice.  Note if the change of timbre corresponds with the orientation of the vents or not.  If it does change, make mental notes about how, in which way, and in general develop a ear for what is happening.

Once you have that kind of empirical knowledge of how your specific shotgun mic behaves, you can then think about how you want to use that trait to your advantage.   Also question those assumptions!  Check them by trying different rotational orientations in the otherwise same setup over the course of a few outings to determine if your assumptions works out the way you envisioned them or not.  Rinse-lather-repeat.

Some shotgun mics having venting all around and some don’t. The 568’s have venting on only one side of the tube, while some high end mics like Neumann KMR 81’s and lower end like Nak CM 304’s are all around the tube. I can see how rotating the tube may have an effect on mics with half tube venting but don’t see how there would be any difference on tubes with all around venting. Although I do remember back in the day some CP4 fans saying “spinning the tube” made a difference. :P

Offline Walstib62

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Re: AKG 568 vent position.
« Reply #5 on: June 21, 2018, 08:04:11 PM »
Certainly misconceptions can come into play without a clear understanding of the subject matter.

Offline DSatz

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Re: AKG 568 vent position.
« Reply #6 on: June 21, 2018, 09:27:09 PM »
Walstib62, the article that you linked to is excellent. I wish that more people on this forum would read it, then read it again until it sinks in.

But why, one might ask, does the article not address the use of shotgun microphones in pairs for stereo recording? Perhaps it's because there's no such practice in professional audio to discuss. When professional recording engineers use shotgun microphones for stereo pickup, it's M/S stereo as a rule. Either they use special microphones from Neumann, Audio-Technica, Sanken or Sennheiser which have a figure-8 microphone built in to the same housing as the shotgun, or they attach a small figure-8 microphone for the "S" channel onto a single-channel shotgun microphone as shown in the attached photo.

Shotgun microphones have markedly different directivity at low and mid frequencies versus high frequencies, so for stereo recording with a pair of them, you'd need to angle and space them one way at low and mid frequencies, and a different way at high frequencies, both at the same time. Since that can't be done, the results are always a compromise in quality at a very basic level. It's just not something that professionals do as a rule.

--best regards

P.S.: The figure-8 microphone in the photo is positioned relative to the shotgun so that the two microphones' diaphragms are equally distant from sound sources in front of the pair.

P.P.S.: Stereo shotgun microphones, in order to align the two capsules on the same axis, generally implement the figure-8 pattern by means of a matched pair of side-facing cardioids, whose signals are then summed in opposing polarity.
« Last Edit: June 22, 2018, 09:30:50 AM by DSatz »
music > microphones > a recorder of some sort

Offline GDfan

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Re: AKG 568 vent position.
« Reply #7 on: June 22, 2018, 11:09:17 AM »
Moving this question I asked in the yard. Pokahu says point the vents up. I point sideways. If you position the XLR ends like you would on any other mic the vents are pointing down, which makes sense for ENG work. So for what we do, what’s the best position? I suppose it’s also a matter of taste. Up would mean less crowd noise, down could be disastrous and sideways maybe neutral. What say you?

I have had a couple pairs of these over the last decade and when I did some "The Dead" recordings in 09' I had the vents up. Since that time I have purchased a pair of right angle stubby XLR cables and when I used these recently the vents were down due to the cable I using being oriented down (right angle stubby). The recordings from 09 sound more open and the ones recently sound a bit dull if that is a good analogy.. I think if I were to use these again in the future I would use different cables so I could have the vents facing up (IMO).
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Offline Walstib62

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Re: AKG 568 vent position.
« Reply #8 on: June 22, 2018, 03:35:37 PM »
Moving this question I asked in the yard. Pokahu says point the vents up. I point sideways. If you position the XLR ends like you would on any other mic the vents are pointing down, which makes sense for ENG work. So for what we do, what’s the best position? I suppose it’s also a matter of taste. Up would mean less crowd noise, down could be disastrous and sideways maybe neutral. What say you?

I have had a couple pairs of these over the last decade and when I did some "The Dead" recordings in 09' I had the vents up. Since that time I have purchased a pair of right angle stubby XLR cables and when I used these recently the vents were down due to the cable I using being oriented down (right angle stubby). The recordings from 09 sound more open and the ones recently sound a bit dull if that is a good analogy.. I think if I were to use these again in the future I would use different cables so I could have the vents facing up (IMO).

I think there may be more variables than just the vent orientation in your above scenario.

Offline ts

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Re: AKG 568 vent position.
« Reply #9 on: June 22, 2018, 06:37:52 PM »
How come every shotgun thread turns into a you’re not supposed to use shotguns for stereo recording? We all know that. Someone, not gonna mention a name, made that quite clear in one of the GD Tapers Compendiums. However short guns seem to be used on a regular basis. The way I figure it is we are not all professionals. We are hobbyists looking to have fun and capture music at the same time. We don’t get paid. Maybe if we did we might pay attention to protocols. ::)

Offline DSatz

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Re: AKG 568 vent position.
« Reply #10 on: June 22, 2018, 10:17:22 PM »
ts, this thread has 10 messages in it so far. Nine are about how to use a pair of shotguns for stereo recording, while mine was mostly about how to use one shotgun plus a figure-8. I don't think that the thread has "turn[ed] into" "you’re not supposed to use shotguns for stereo recording".

I own four shotgun microphones, including one M/S stereo model; I use the mono shotguns mainly as spot mikes, for voiceover work, or very occasionally as the "M" microphone in an M/S pair. What I suggested was based on my own experience, and wasn't intended to be oppositional. When I really want to oppose something, you'll know!

--best regards
« Last Edit: June 26, 2018, 09:24:02 PM by DSatz »
music > microphones > a recorder of some sort

Offline Gutbucket

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Re: AKG 568 vent position.
« Reply #11 on: June 25, 2018, 09:58:06 AM »
Quote
How come every shotgun thread turns into a you’re not supposed to use shotguns for stereo recording?

Because that's generally true. 

There are good reasons why..
1) Typical near-spaced stereo configurations aren't recommended with shotguns.
2) Some stereo techniques are likely to work better than others.
3) Audience-perspective live music recording from a distance is different than most forms of professional recording.

We can discuss all of that stuff here.  Hopefully these kinds of threads help tapers make more-informed decisions when considering various approaches, which when combined with their own experience and listening preferences might make for better sounding tapes.  Do whatever you like, there is no taper police to come after you if you prefer to do it a particular way.  Only practical, theory-based, and real-world suggestions here - no hard-fast rules. 

Here are two setups using shotguns I can make strong arguments for (rather than simply substituting shotguns in place of standard first-order directional mics in near-spaced configurations)-

1) Coincident- Shotgun as Mid in a Mid/Side stereo-recording arrangement (as suggested above).
2) Spaced- Shotgun as Center microphone in an L/C/R stereo-recording arrangement.

..or better, a combination of those two approaches, such as as a Mid/Side pair in the center between widely-spaced omnis.

« Last Edit: June 25, 2018, 12:42:13 PM by Gutbucket »
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Offline spyder9

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Re: AKG 568 vent position.
« Reply #12 on: June 25, 2018, 12:03:20 PM »
Samples of C568EB shotguns, run in stereo, vents pointed out.  Discuss.

Radio City Music Hall (theater)
https://archive.org/details/bobandphilduo2018-03-03.r1.spyder9.flac16


BB&T Center (auditorium)
https://archive.org/details/deadandco2018-02-26.r1.spyder9.flac16

Offline Gutbucket

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Re: AKG 568 vent position.
« Reply #13 on: June 26, 2018, 12:42:03 PM »
Diggin' that Radio City pull.  Good "real-world" example of it working well. To me this is confirmation that audience-perspective live music recording from a distance is indeed different than other types of recording. 
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Offline illconditioned

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Re: AKG 568 vent position.
« Reply #14 on: June 28, 2018, 07:40:10 PM »
Samples of C568EB shotguns, run in stereo, vents pointed out.  Discuss.

Radio City Music Hall (theater)
https://archive.org/details/bobandphilduo2018-03-03.r1.spyder9.flac16


BB&T Center (auditorium)
https://archive.org/details/deadandco2018-02-26.r1.spyder9.flac16
Yep,   Sometimes shot gun point at stacks is a nice way to go.  Simple and gets the job done.
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

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