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Author Topic: The stereophonic zoom By Michael Williams  (Read 5430 times)

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Offline Chuck

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The stereophonic zoom By Michael Williams
« on: October 24, 2013, 10:51:20 AM »
http://www.rycote.com/images/uploads/The_Stereophonic_Zoom.pdf

A variable dual microphone
system for stereophonic
sound recording

Link to the topic README1st! Mic configs for dummies & LD mics, clamps + more, Stereophonic Zoom started in the Microphones & Setup section:
http://taperssection.com/index.php?topic=119057.0

Link to Michael Williams web site:
http://www.mmad.info/SOS_MMAD.htm


...this is obviously not my content. It's just link(s) to the paper that explains SRA in depth.
« Last Edit: October 24, 2013, 12:26:28 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: (2) Microtech Gefell M300, (2) AKG C 480 B comb-ULS/ CK 61/ CK 63, (2) CAD GXL1200 (cardioid and sub-cardioid capsule & electronics mod), (2) Audix M1290-o, (2) Micro capsule active cables w/ Naiant PFA's, (2) Naiant MSH-1O, (2) Naiant AKG Active cables, (2) Church CA-11 (cardioid), (2) CAD C9, (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Tascam DR-680, iRiver iHP-120 (Rockboxed & RTC mod), Denon DTR-80p

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline ScoobieKW

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Re: The stereophonic zoom By Michael Williams
« Reply #1 on: October 24, 2013, 10:56:17 AM »
Isn't Stereo Zoom a sticky by now? If not, it should be. This is essential stuff, especially when you are taping in a new venue.

Anyway, obligatory software tool links using the Stereo Zoom theory. The Sengpiel Audio app really helped me understand the relationship between time arrival and level difference in stereo imaging.

http://www.sengpielaudio.com/Visualization-ORTF-E.htm

https://play.google.com/store/apps/details?id=air.com.neumann.recordingtools

https://itunes.apple.com/us/app/recording-tools/id576702914?mt=8

Busman BSC1, AT853 (O,C),KAM i2 Chuck Mod (C), Nak 300 (C),
M10, UA-5, US-1800, Presonus Firepod

http://kennedy-williams.net/scoobiesnax/

Offline Chuck

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Re: The stereophonic zoom By Michael Williams
« Reply #2 on: October 24, 2013, 11:00:38 AM »
I didn't see it in here. So, I started the topic. I believe it's essential info for any recordist. If it's duplicated somewhere else let me know.
Reality is merely an illusion, albeit a very persistent one.

Microphones: (2) Microtech Gefell M300, (2) AKG C 480 B comb-ULS/ CK 61/ CK 63, (2) CAD GXL1200 (cardioid and sub-cardioid capsule & electronics mod), (2) Audix M1290-o, (2) Micro capsule active cables w/ Naiant PFA's, (2) Naiant MSH-1O, (2) Naiant AKG Active cables, (2) Church CA-11 (cardioid), (2) CAD C9, (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Tascam DR-680, iRiver iHP-120 (Rockboxed & RTC mod), Denon DTR-80p

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline audBall

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Re: The stereophonic zoom By Michael Williams
« Reply #3 on: October 24, 2013, 11:10:09 AM »
It's surely been discussed, but I don't think it was ever a sticky.

Is Fig 3 (cardioid) representative of all cards across the board? Fig's 4 and 5 (hypos and hypers) note "back attenuation of 10db", but Fig 3 does not. I'm assuming that means response at 180° versus 0° on-axis? If that's the case, my capsules are -20db and -23db at 180°. Is there a way to recreate these graphs according to our specific mics? I'd really only be concerned with SRAs of +/- 40-50°.

edit- correction
« Last Edit: October 24, 2013, 12:23:20 PM by audBall »

Offline Gutbucket

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Re: The stereophonic zoom By Michael Williams
« Reply #4 on: October 24, 2013, 11:39:30 AM »
It's already stickied at the top of the active Microphones & Setup section- http://taperssection.com/index.php?topic=119057.0 (this thread is in the knowledge base / archive sub-section)

There have been numberous discussions of it here at TS over the years.  A search will probably find a number of them, although some are burried in threads that do not have Stereo Zoom in the title I'm sure.

Michael William's website should be linked- http://www.mmad.info/SOS_MMAD.htm
The link there to microphone array design- http://www.mmad.info/MAD/Ch_n_cov.htm leads to a hyperlink-based interactive selector for choosing Stereo Zoom based configurations.  Run through it and download or print a PDF showing angles and spacing for your choice of mic pattern and SRA.  He has extended the Stereo Zoom to include not only two channel but up to seven channel microphone arrays.   Just pick how many microphone channels you want and follow the links.  Most here will simply use the 2-channel arrays, but the three (and four) channel arrays should be useful as well.  The straight three channel pages are not active, but you can determine three channel configs by running through the 5 channel links and simply ignoring the 2 surround channels.  Although designed for playback with the same number of speakers as mic channels, I've found that these mix down very well to stereo without problems, so they are good safe choices for 3 & 4 mic setups from one location with the intent of mixing to 2 channel, rather than just combining two seperate stereo pairs or guessing on an appropriate 3-mic setup.

I've personally found the site very useful for choosing between various appropriate 5 channel surround recording configurations, where the extention of the Stereo Zoom beyond just two mics gets complex.  I'll print several candidate configs out and choose between them.

All his papers may be downloaded at no charge (and are excellent reads I recommend for those interested) here, which is a page not linked from the home page- http://www.mmad.info/
« Last Edit: October 24, 2013, 12:06:45 PM by Gutbucket »
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Offline Gutbucket

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Re: The stereophonic zoom By Michael Williams
« Reply #5 on: October 24, 2013, 11:47:54 AM »
I'm assuming that means response at 180° versus 0° on-axis?
[snip]  Is there a way to recreate these graphs according to our specific mics? I'd really only be concerned with SRAs of +/- 40-50°.

Yes to the first question. 

You can compare otherwise identical cardioid and super/hypercardioid suggested configs to get a pretty good idea how mics with patterns that lay somewhere between the two will work.  Comparing the generic spacing-verses-angle curve plots for the various pickup patterns instead of the final configuration PDFs helps get an idea of the general trends going on too.
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Offline Gutbucket

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Re: The stereophonic zoom By Michael Williams
« Reply #6 on: October 24, 2013, 11:55:11 AM »
The Sengpiel Audio app really helped me understand the relationship between time arrival and level difference in stereo imaging.

The Image Assistant Java applet- http://www.hauptmikrofon.de/index.php?option=com_content&view=article&id=1&Itemid=40
at www.hauptmikrofon.de is another very useful tool for exploring and understanding that relationship.  It provides a lot more data and configuration flexibilty, but is not nearly as easy to interperate as the more straight forward Sengpiel App.
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Offline Chuck

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Re: The stereophonic zoom By Michael Williams
« Reply #7 on: October 24, 2013, 11:56:10 AM »
Thanks for providing the additional info Gutbucket & Lord Best Tools for the Job.  :coolguy:
« Last Edit: October 24, 2013, 12:45:27 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: (2) Microtech Gefell M300, (2) AKG C 480 B comb-ULS/ CK 61/ CK 63, (2) CAD GXL1200 (cardioid and sub-cardioid capsule & electronics mod), (2) Audix M1290-o, (2) Micro capsule active cables w/ Naiant PFA's, (2) Naiant MSH-1O, (2) Naiant AKG Active cables, (2) Church CA-11 (cardioid), (2) CAD C9, (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Tascam DR-680, iRiver iHP-120 (Rockboxed & RTC mod), Denon DTR-80p

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline DigiGal

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Re: The stereophonic zoom By Michael Williams
« Reply #8 on: October 24, 2013, 01:40:32 PM »
Adding links for iOS Apps by Engineered Stuff...

Stereo Mic Tools  https://itunes.apple.com/us/app/stereo-mic-tools/id572383335?mt=8

Mid-Side Mic Visualizer  https://itunes.apple.com/us/app/mid-side-mic-visualizer/id486145346?mt=8
Mics: AKG CK91/CK94/CK98/SE300 | Shure VP88 | Senn ME66/K6/K6RD Cables: Gotham GAC-4/1 "StarQuad" w/Neutrik EMC | Gotham GAC-2pair w/AKG MK90/3 connectors | DigiGal AES>S/PDIF cable Preamp: Sound Devices MixPre-D Recorder: Marantz PMD 661 Edit: 27"3.4GHz QuadCore i7 iMac | OS X Yosemite 10.10.5 | Wave Editor | xACT  | Transmission | Final Cut Pro X                                                            

Offline Gutbucket

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Re: The stereophonic zoom By Michael Williams
« Reply #9 on: October 28, 2013, 05:39:58 PM »
Just wanted to post a reminder that the SZ primarily deals with playback imaging between speakers.  It's a great tool and a fantastic way of understanding the relationship between mic pattern, angle and spacing, but it's not the end-all, be-all of recording.  It's a very good reference which can help recordists get a grasp on what is going on as well as offering specific setup configurations, yet there are plenty of other things going on which may or may not be more important than simply getting the SRA correct with an appropriate distribution of sources in the resulting image between playback speakers.  Don't forget there is more going on simply because the SZ offers specific setup suggestions.
 
Here's an interesting dichotomy I've become more consciously aware of with the Stereo Zoom-

The term "width" can refer to completely different, not necessarily related playback perceptions.  Adjustments to SRA image width are generally inversely proportional to a sense of ambient room width or feeling of spaciousness in the recording.

I think that may be why I find the SZ more applicable to directional mics and less so for omnis.  When choosing an optimal setup for omnis, other aspects become more important to me than acuracy of the stereo imaging.
« Last Edit: October 28, 2013, 05:47:56 PM by Gutbucket »
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Offline audBall

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Re: The stereophonic zoom By Michael Williams
« Reply #10 on: October 28, 2013, 06:01:03 PM »
This was posted before, but don't forget about the free Neumann SRA iOS app:
https://itunes.apple.com/us/app/recording-tools/id576702914?mt=8

 

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