Core Sound TetraMic Ambisonic Microphone and RED

[Len M.]

Len, any issues with using the VSTs with something like a VST>RTAS plugin that I have for Pro Tools on a Mac?

We don't know yet if a VST to AU converter will work. If you want to try it, let me know and we'll get you copies of the two VST plugins.

 

[Robert Mott]

We don't know yet if a VST to AU converter will work. If you want to try it, let me know and we'll get you copies of the two VST plugins.

We had seriously looked at buying one last summer. Knowing that it works well with the Red we are going to re-investigate.

 

[Len M.]

Thanks to the folks on the other audio thread, we've been able to extract the four audio tracks recorded with TetraMic and a RED camera.

In post we decoded the recording to model a Blumlein array (two figure-8 microphones positioned at 90-degrees to each other) for playback in stereo.

TetraMic was positioned only a foot or so from the RED so it picked up the RED's fan and the LCD display's whine. Next time John will hopefully have the EVF that he ordered and we'll try to remember to shut down the fan.

No EQ, compression or other processing was applied to the recording other than amplifying it +18 dB . It's a 32-bit float/48 KHz stereo recording.

Please excuse the performance -- I'm not much of a guitar player!

http://www.core-sound.com/RED/RED-with-TetraMic-Decoded-To-Blumlein2.wav

If anyone wants to see the video too, let me know and I'll see if I can post it.

Many thanks to John Lizzio and Kevin Kasper for making this demonstration possible.

 

[MikeHedge]

video? can you post it on youtube?

 

[Len M.]

video? can you post it on youtube?

At the moment, I'm using an XP/PC and can't seem to extract video no matter what I try.

RED's QT plugins are Mac-only and nothing I do with RED Cine produces a QT-viewable video.

And I haven't the slightest idea how to insert a WAV audio file into a MOV video. Perhaps Final Cut Pro will do it?

If someone wants to volunteer, I'll send them the files.

 

[BASSAM MSSALATIE]

Len thanks for that clip but i couldn't hear splitted audio on different channles . i hear the same audio on my 5 spurrounded speakers.
maybe it is just becuase the file format ?

 

[Steve Sherrick]

Len, I can add the sound to the mov file for you. PM me if you still need help with it.

 

[Paul Hazlett]

Thanks for posting. can you tell me the distance and position of the mic
from the subject, thanks.

 

[Len M.]

Len thanks for that clip but i couldn't hear splitted audio on different channles . i hear the same audio on my 5 spurrounded speakers.
maybe it is just becuase the file format ?

It's a stereo file, not a 5.1.

 

[Len M.]

Thanks for posting. can you tell me the distance and position of the mic
from the subject, thanks.

If I remember correctly, TetraMic was around one foot in front of the RED and two feet to the right. (John: please correct me if I'm wrong.)

The subject was seated around five feet in front of the camera. So the mic was four to five feet from the subject.

During decode, you can bring the subject in closer using the zoom control if that's what you want. For this decode, no zoom, rotation, tilt, or tumble were inserted in post. It's a simple Blumlein model with linear amplification (no compression or limiting).

 

[Len M.]

Len, I can add the sound to the mov file for you. PM me if you still need help with it.

Done.

 

[Elizabeth Lowrey]

Len, the sample has definitely piqued my interest in your product, especially given the limitations in the testing environment. Considering that you applied an 18db boost in post and that the mic was much closer to the camera than to the subject, it sounded very good with much less noise than I would expect. Will definitely hunt up the other sound samples of the tetramic you mentioned.

 

[Len M.]

Len, the sample has definitely piqued my interest in your product, especially given the limitations in the testing environment. Considering that you applied an 18db boost in post and that the mic was much closer to the camera than to the subject, it sounded very good with much less noise than I would expect. Will definitely hunt up the other sound samples of the tetramic you mentioned.

If you're interested I can also post a version of the Blumlein stereo decode that has been zoomed, and perhaps also a mono/hypercardioid/zoom.

 

[Elizabeth Lowrey]

A zoom would be great!

Quick question for you: if I'm reading the info on your site correctly, there's a breakout cable that converts the 6-pin unbalanced mic output to 4 individual mini xlr outputs, one for each capsule. However, because the tetramic requires @ 6V phantom power instead of 48, each of the 4 breakouts must also be plugged into a phantom power adapter (couldn't find pics of these on your site) to be used with standard 48v phantom sources (like most mixers, preamps, etc.) How hard would it be to simply get the RED camera to supply 6V phantom power as an alternative to 48V? Since so much about RED is firmware controlled and since it already features mini XLR inputs, I'm just wondering if a simple solution for a RED/tetramic combo could be to make a single, short breakout cable terminated in mini XLR-male that could plug directly into the 4 mini-XLR-female ports on the RED, which would then supply the appropriate 6V phantom power directly, without any intervening connectors or hardware?

 

[Andrew Madu]

Len,

If you're interested I can also post a version of the Blumlein stereo decode that has been zoomed, and perhaps also a mono/hypercardioid/zoom.

I would be interested in hearing you Blumlein Pair decode.

 

[Len M.]

Len,

I would be interested in hearing you Blumlein Pair decode.

The original file I posted was a straight Blumlein decode. Here's the link again:

http://www.core-sound.com/RED/RED-with-TetraMic-Decoded-To-Blumlein2.wav

Here's the same recording with a fully zoomed Blumlein decode:

http://www.core-sound.com/RED/RED-with-TetraMic-Decoded-To-Zoomed-Blumlein2.wav

It has the same amount of gain added as the original decode.

Here's the same recording again -- this time it's decoded to a single cardioid with mono output:

http://www.core-sound.com/RED/RED-with-TetraMic-Decoded-To-Mono-Cardioid_2.wav

 

[David Wilson]

Len - would it be possible to post the .amb of your fine performance? (Your guitar is better than my accordion.)

 

[Len M.]

...How hard would it be to simply get the RED camera to supply 6V phantom power as an alternative to 48V?

That's really a question for the RED technical folks.

From what I can guess about the design of the RED mic pre-amps, it would be a major hardware change for its phantom power circuit to generate 6 Volts instead of 48.

The TetraMic PPAs are rather small. You can see them in the pictures that Dan Graetz posted earlier.

 

[Elizabeth Lowrey]

The TetraMic PPAs are rather small. You can see them in the pictures that Dan Graetz posted earlier.

Looking at the XLR jack I've labeled "A", I assume the PPA is within that structure, a cylindrical part roughly twice as long as a standard XLR jack on the end of a balanced mic cable? And then the small mini XLR plug coming from the 4 X breakout cable is the part labeled "B"?

Also, are the PPAs battery powered or do they somehow passively transform the voltage?

 

[Len M.]

Looking at the XLR jack I've labeled "A", I assume the PPA is within that structure, a cylindrical part roughly twice as long as a standard XLR jack on the end of a balanced mic cable? And then the small mini XLR plug coming from the 4 X breakout cable is the part labeled "B"?

That's correct.

Also, are the PPAs battery powered or do they somehow passively transform the voltage?

They operate on the 48V phantom power; no batteries are needed.