MIC placement charts and formulas

[tsvisser]

You know those charts that show recording angles, mic placements, etc?

First off, is there a good resource that has downloadable / printable full size charts for A-B, X-Y, ORTF...?

Secondly, where are these charts derived from? I would ultimately be interested in knowing what the underlying formula used is for deriving these plots.

When it comes to M-S recording, there is no chart, because one of the main variables is the level that you mix in the -S +S signal into the mix. It occurred to me, however, if you only were concerned with the direct sound or first reflection, there must be some limitation to maximum stereo image with respect to the distance of the array to the source. If you array is too far from the source, the direct and first reflection audio would more or less be unidirectional and non-distinct and when you mix down, you would not get much stereo separation. Of course M-S is great for capturing room ambience, but if you wanted to capture a strong stereo image primarily of the performers, and not so much the room, what would your guidelines be for optimal recording angle for the array? It seems to me that anything more than 180 or +/- 90 would be too extreme, as the stereo images tend to be too exaggerated and unnatural, although could be great for a single acoustic instrument, while being less useful for a collection of instruments. 140 or +/- 70 seems like a good starting point for XY or ORTF and of course M-S is much less pinpoint accurate with the image at this angle than either XY or ORTF. Is there some optimal recording angle that anyone has found when doing M-S when your not so concerned with the room or hall ambience? Or should it just be accepted that M-S will always be a soft image?

[Martin Kantola]

Originally Posted by tsvisser

Secondly, where are these charts derived from? I would ultimately be interested in knowing what the underlying formula used is for deriving these plots.

Suspect that people have been using their ears more than formulas... which is the better way if there's a choice.

Martin
PS: "The Microphone Book" by Eargle has info like this.

[summer_room]

Rycote - Product Information

go to Tech Articles / The Stereophonic Zoom

plus
use your ears!!

-jon

[Karl Jackson]

To just play with the localization of various spacings and angles, you might check out Image Assistant 2.0. Ten minutes with the Image Assistant and a spreadsheet and you could have your own custom chart.

To look more into the math, look up papers by Helmut Wittek, Günther Theile, Michael Williams, or Geoff Martins.

kj

[David Rick]

For M/S recording, the key paper (with charts) was written by Manfed Hibbing of Sennheiser. I made my own two-page set of charts from this paper back before "cut and paste" involved a mouse. It's still in my location binder. The same binder has a two-page set of Williams stereo charts, done the same (old school) way.

Hibbing, Manfred. "XY and MS Microphone Techniques in comparison", J. Audio Eng. Soc., vol. 37, no. 10 (1989 October) pp 823-831.

You can order reprints from the AES Publications Page.

If you don't mind it being in German, there's a nice single page chart for spaced omni's (by Grammy winning engineer Eberhard Sengpiel) available here.

The main problem with Image Assistant is that it's a web applet, and I often don't have internet access on location jobs.

Please keep in mind that there are a many considerations besides sound stage width that enter into choosing a stereo microphone array configuration. There are generally a number of techniques that will acheive similar stereo spread, but each one will sound different. The art is in choosing the one that works best for the particular venue, ensemble, and composition.

David L. Rick
Seventh String Recording

[anechoic]

http://www.taperssection.com/referen...igTemplate.pdf