posted 09 May 2001 13:51              

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I am interested in purchasing a Soundfield SP250 microphone, which outputs a four channel feed - x,y,z, and ref. w . We could save ourselves quite a few dollars if a wonderfully brilliant soul (or souls) out there could write a kyma sound that could input the (4 line) b-format feed, and output a standard 5.1 surround (5 track) file recorded to disk, or better yet ASIO driven into Digital Performer. Possible?

Mic info at http://www.transaudiogroup.com/

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posted 09 May 2001 21:30            

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So what is this "B-Format" ?
couldnīt find it on the site. Please provide more info...

Frank.

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posted 10 May 2001 12:47              

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hi,
i hope this list is not absurd - it is everything i have found in the past two days on b-format and ambisonics. it is very exciting to think of this technology and its use in multi-speaker installations with kyma. it also impacts sound healing techniques, and sound design. http://www.transaudiogroup.com/soundfield/sndfield_home.html http://www.transaudiogroup.com/soundfield/b_format.html http://www.audiodim.zynet.co.uk/ http://www.stanford.edu/~mleese/Ambisonic/diy.html http://www.muse.demon.co.uk/utils/ambidec.html http://www.geocities.com/ambinutter/AMBISONIC_HOME_PAGE.html http://www.stanford.edu/~mleese/Ambisonic/faq_latest.html http://www.cantares.on.ca/decoder.htm http://www.cantares.on.ca/ssp1man.htm http://www.ambisonic.net/ http://www.york.ac.uk/inst/mustech/3d_audio/ambison.htm http://www.muse.demon.co.uk/3daudio.html http://www.muse.demon.co.uk/ref/speakers.html http://audiolab.uwaterloo.ca/~jeffb/thesis/thesis.html

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posted 11 May 2001 12:07            

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iīm dealing with the same idea. for that reason i already ordered some aes-papers. but i donīt know when i will really go into it, since i have some bigger projects in near future. if thereīs growing anything, please inform me.

best, mathis

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posted 18 May 2001 04:18            

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on aes show in amsterdam i talked with a technician of soundfield. he said it shouldnīt be too diffcult to decode the b-format.
personally i like to do this not because of costs but of possibilities. the original decoder canīt be automated. but with automation you can get incredible effects: imagine a rotating soundfield which also can get wider or narrower. we simulated it manually on the exhibition and it really works!
do you know that you can also encode b-format to a 3D soundfield? (ambisonics really records a 3D picture.) so imagine a cube with 8 speakers where you can rotate, twist and tilt the soundfield. and imagine combining all this with doppler and all the effects we love in kyma.
and a very important point for me is its complete downward compatibility: every time you make a dolby digital movie you always have to make a dolby stereo version for fallback and a stereo version for tv which also has to be mono-compatible. now imagine what happens if you use several miks like the brauner spider which do most of the spatial synthesis with a/b-technique: nine(!) not known phase relations which are unpredictable when downmixing.

[This message has been edited by mathis (edited 18 May 2001).]

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posted 05 June 2001 17:45            

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I don't think a B format decoder would be very difficult. B format is a 4 channel Soundfield format recorded from the 4 discrete outputs of their tertahedral capsule microphone array. It's a matter of remapping and mixing 4 to 5.1. I emailed Soundfield about the possiblity of a TDM implemented decoder. They said they were thinking of this. I would hazard that one of us smart kymites could do the job in short order in Kyma. B format is a very exciting format because it really isn't limited to 5.1 or quad or whatever. It's naturally phase coherent so anything from mono to extreme multi channel (10.1?) is possible from the same recorded source material.

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posted 06 July 2001 14:58            

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Please, let me also know if anything new develops. I'm highly interested in this amd also plan to get the SP250.
Carlos

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posted 09 July 2001 09:41            

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Hi
I struggled trying to read so much literature but I wonder if someone could explain a simple scenaria. If we wanted to hear the sound directly in front of one of the mics, would we just listen to the signal from that mic or would we listen to that mic plus the ref ? Similarly if we wanted to hear the sound directly behind would we listen to the ref minus that mic or something involving all four mics ?
anyone know?
I'm sure that once the rules are clear it will be a simple case of mulipying different paths by different sine and cos values, and adding them together.

regars Pete

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posted 11 July 2001 10:39            

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the b-format is basically a 3-dimensional m/s microphone. the soundfield mic renders a omnidirectional basic mic (B) and three eights (X, Y, Z). So if we define the X-axys as our front-back axys, we get a B+X for the front direction and a B-X for the back direction. If we want to steer the pattern to sidewards we have to involve the Y microphone. the same with the Z-microphone.
the problem for the multichannel decoding is we don't get good crosstalk separation this simple way. that's the reason why ambisonics uses some sort of psychoacoustic filtering. it decodes frequencies below 500 hz in another way than frequencies above 500 hz.
in the next weeks I will do some b-format recordings and make them public for collaborative experimentals.

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posted 13 July 2001 06:27            

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Edmund mentioned a contact with the Soundfield people but I contacted Transam/Soundfield USA and they weren't able to confirm if the TDM plug in is in the works or not. Any news about this anyone?
Best
Carlos

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posted 15 July 2001 14:11            

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B_FORM.kym

Attached
This is a module to listen to the sound source from any one of the directions of the three dimensional angles. I've had to invent a standard to discribe the controls . It assumes that North directly is in front of the x diaphram , East is directly in front of the y diaphram , and Up is directly in front of the z diaphram. Of cause the mic is not organized so simply but once you can pick out any direction you can adjust it. I can't test it cause I dont have one of these mics, but I suggest recording six people reciting six different poems simultaniusly, one in front of and behind each diaphram. Then seeing if this module can tune into each individualy. Then record the same people but not strieght on to the diaphrams and see if you can do the same thing.

When the UP/DOWN control is at max or min , the other control has no effect.
We would need 5 of these to make a 5.1 convertor and it doesn't deal the low frequency requirments if the b format

Please let me know if it works.

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posted 18 July 2001 21:03            

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i have to say that i feel embarrassed about your strong motivation in the kyma forum. few seconds ago i had a look on your b-format patch, which looks great for a starting point. what did i do until now? just warm words..... i promise to get that microphone very soon for some test recordings so that we really can work on it.
by the way, the microphone is in fact not a four capsule m/s microphone. it is highly more complex and the four diaphragms are also not steered in the directions we suppose (it looks like a tetraheder). it has a tricky analog computer in it which gives us this simple b-format. so there shouldnīt be a difference when rotating the mic/speakers. as a matter of fact this is the great advantage even when using this mic for mono recordings. you can place the microphone more or less wherever you want and afterwards youīre able to steer it and control the directivity like you want. you more or less only have to care about your absolut placement regarding direct/reverberant relationship.
really thanks for your commitment.

[This message has been edited by mathis (edited 18 July 2001).]

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posted 14 May 2005 16:17            

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Meanwhile, any news of the B-format to 5.1 conversion? I'm really interested in this, because of the new portable ST350 System!
http://www.soundfield.com/news/news_st350.php

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