Topic: Makers of Figure 8 mics/capsules

[F.O.Bean]

Isnt 0* supposed to be on one particular side tho? Like left or right?

Each mic maker could intend for that sign to mean something different with orientation interpretation. I'm not sure that they would, and I personally would anticipate it to be the left side (or positive lobe is a more accurate term I guess), but the easiest way is to check it out.

Thanks ALOT bro!

[John Willett]

I'm primarily interesting in capsules, especially ones that can be purchased and flown in an active style, but any info is appreciated.

Tetrahedral ambisonic mics, like our TetraMic and the mics from SoundField Ltd., can do the job well.

With no exaggeration, our TetraMic is probably one of the finest figure-8 mics in the world.  It also is one of the finest Blumlein arrays in the world.  And M/S.  And surround.

(Yes, you read that correctly: TetraMic can function as single mic, a pair of mics, or as many coincident mics as you desire.)

Just been looking at the website on this.

It seems that the capsules are cardioid - the original soundfield used hypo-cardioid (ie: wide-cardioid).

What is the reason for this?  Was it just to get around patents, or was the software written specially for the cardioid pattern?

Also, I could not see capsule frequency response curves and polar-patterns on the site.  Are they there and I just missed them?

Just curious (at the moment).

[Gutbucket]

I'm curious about the tetramic too.  I think the original soundfield patents are expired and as I understand it, the software was written specifically for the response of the particular capsule used and the physical arrangement of the four.  As for choice of pattern, cardioid capsules are easily available and inexpensive.  I'd think they'd be the natural choice, especially since the omni and figure 8 compontents of the cardioid pattern have the same relative sensitivity.

I've never used an ambisonic system and I'm by no stretch of the imagination an ambisonic expert, but I imagine any pattern that falls somewere between omni and figure-8 could work in the array, as long as the weighting of the matrix was to be changed to match.  A pattern other than cardioid would need the balance beween the omni and the figure-8 components adjusted (in the software in this case). Patterns to one extreme or the other would be less optimal as they would eat up the available headroom dynamic range if they needed large scaling factors. Using hypo-cards, you'd get more omni component, and would have to scale that down to match the level of the figure-8. Didn't the original ambisonic equations call for scaling the W component by .707? Could that have been to compensate for the extra omni content in the A format using hypo-cardioids?

I may be completely off base here and appreciate clarification by those who know.  Tell us more about your interesting mic, Len.

[Kewl]

It seems that the capsules are cardioid - the original soundfield used hypo-cardioid (ie: wide-cardioid). What is the reason for this?  Was it just to get around patents, or was the software written specially for the cardioid pattern?

The patents for the tetrahedral array have been expired for a while: this is why we saw the AGM tetrahedral array (with DPA caps) in the 90s.

If they could have used cardioids on the original SoundField, they would have: use of cardioids will provide the best S/N ratio in the B-Format channels.

- Daniel

[fotoralf.be]

Does anone here know anything about the fig-8 capsules in the various Sony MS stereo mics, i.e. ECM 909, 959 etc.?

Ralf

[darby]

Does anone here know anything about the fig-8 capsules in the various Sony MS stereo mics, i.e. ECM 909, 959 etc.?

Ralf

they are 2 cardioid caps back to back for the figure 8
plus another cardioid for the mid... if I'm not mistaken

[fotoralf.be]

they are 2 cardioid caps back to back for the figure 8

Definitely not in the 909. One capsule pointing forward and one looking sideways.

Ralf

[Len Moskowitz (Core Sound)]

Also, I could not see capsule frequency response curves and polar-patterns on the site.  Are they there and I just missed them?

You can get a sense of TetraMic's polar patterns and frequency response curves from Fons Adriaenson's data here:

http://www.kokkinizita.net/linuxaudio/tetra-pict.html

TetraMic is never used as individual capsules.  The decoded polar patterns and frequency responses have very little relationship to the individual capsule patterns and frequency responses.

Have a look at this short description of how TetraMic works.  I hope it will help.

http://taperssection.com/index.php?topic=111984.0

Here's a nice recording done with TetraMic and an unnamed mic pre/ADC:

http://www.ambisonia.com/Members/soundmanjohn/ambisonicfile.2008-04-14.9034658665

Here's a link to an excerpt of that recording decoded to Blumlein (66 MB):

http://www.core-sound.com/Orfeo-Blumlein-second-movement.wav

[Gutbucket]

Thanks for the links.

[darby]

they are 2 cardioid caps back to back for the figure 8

Definitely not in the 909. One capsule pointing forward and one looking sideways.

Ralf

http://taperssection.com/index.php/topic,116512.0.html