Topic: recording acoustic musicians sitting in a circle

[Gutbucket]

Does look like a nice low-key good time.

My apologies for getting this so far off topic..

Ambisonics does have important limits though: First, it's limited to coincident techniques, so unless used in combination with other microphones, any time-based stereo techniques are out. ...

In some ways, considering this a limitation is like saying that a cardioid mic is limited because it can't do stereo recordings. It really can, but it takes two of 'em!

As we've discussed in other threads, you can use two or more ambisonic mics to do time-based stereo techniques.

Sure, but the resulting multi-microphone recordings will no longer be ambisonic..  even though the feed from each individual ambisonic microphone is.  Ambisonics always deals with the soundfield and it's recreation at only a single point in space.

I feel it important to emphasize that ambsionics is not the end all be all of recording, even though it is indisputably an amazing and useful approach, and far more accessible than it once was thanks to tools like the relatively low cost ambisonic microphone Len has made available (The ambisonic microphone I use is his Core TetraMic).

However, if anyone reading is interested in all this somewhat arcane ambisonics stuff, there are some very costly and very heavy processing intensive ambisonic recording methods which do extend beyond the limitations of standard first-order microphone patterns.  Most of them deal with measurement and industry and aren't very suitable for music recording but I know of at least one which is.  It uses eight omnidirectional microphones arranged in a specific 2-dimentional pattern to derive virtual polar patterns of up to the 5th order, limited to the horizontal plane in this particular implementation.  Even though it uses multiple omnis distributed in space rather than four directional microphones arranged as closely as possible to the same point in space, its output is still limited to coincident patterns by the nature of ambisonic theory itself. Here's a link to the PDF from Trinnov Audio.

[cybergaloot]

Too bad I need to be elsewhere this weekend because this would probably be a good place to test things: http://pickersparadisepark.com/

"bout time Doug Oade's sleepy old hometown gits itself some culture.....looks fun.

I haven't seen or heard from him in quite some time.

[Len Moskowitz (Core Sound)]

Sure, but the resulting multi-microphone recordings will no longer be ambisonic..  even though the feed from each individual ambisonic microphone is.  Ambisonics always deals with the soundfield and it's recreation at only a single point in space.

Thanks for the very kind words about TetraMic.

If "ambisonic recording" means that a recording is made using only one ambisonic microphone, I think that's too limiting a way to think about it.

Ultimately, an ambisonic microphone is just another source of the audio tracks used to playback a recording. Its decoded output can be mixed with other sources of audio, which might include fixed pattern mics or other ambisonic microphones. In the final mix there should be no way to know whether the source of the audio is an ambisonic microphone or a fixed pattern mic.

Let's imagine we were recording an orchestra. We could position an ambisonic microphone behind and above the conductor and decode its output to - let's say, Blumlein. In post-production we could mix that with the output of another microphone - say a fixed-pattern hypercard spot mic positioned close to a soloist.

Or we could use two ambisonic microphones. One would be set up as before - behind and above the conductor, and decoded to Blumlein. The second ambisonic microphone could be positioned close to a soloist and decoded to hypercard.

The two resultant recordings would be near identical (though I say kind of proudly that it's very possible the second might have a better hypercard). Whether either of them is an "ambisonic recording" is really irrelevant, no?

The same goes for ORTF or other spaced arrays created by using more than one ambisonic mic.

'Nuff said.

[Gutbucket]

Aesthetically, I fully agree that it doesn't matter what labels are placed on all this other than subjective things like "good sounding" and "believable or not" with regards to the end result.  Music recording and playback is all about the creation of an illusion anyway.  However, from a technical perspective (this is something of a technical recording forum after all) what you describe above is two ambisonic recordings, the first decoded to two channel stereo, the second decoded to single channel mono, which are then mixed together in two-channel stereo non-ambisonically.  The end result is a two-channel stereo recording.

The distinction is important in differentiating what techniques are used and how to go about manipulating things, rather than describing the quality of the result perceived by a listener.  It's an important one in a technical discussion of how the equipment is used and the recordings are made.

Nothing stops us from using all these tools creatively.  I've made numerous recordings using a stereo decode from the TetraMic plus a spaced pair of omnis.  The resulting recoding is 2-channel stereo and not ambisonic.  Part of it was made ambisonically, part of it made as A-B spaced omnis stereo.  The ambisonic portion left the ambisonic domain when I chose one particular stereo decode of it.

I could describe alternate mixing options for your two ambisonic microphone scenario, done within the ambisonic domain without first decoding from B-format, which would be an entirely different procedure and have very different sonic implications.  Unless played back over an ambisonic loudspeaker array, the resulting output would most likely be decoded to stereo, multi-channel, binaural, or whatever for listening and would at that point no longer be ambisonic.  These are important distinctions to make on a recording forum describing how the tools are used, which aren't important at all from the perspective of the listener.