AMBISONIC ICST

Sep 6, 2013 at 2:42pm

AMBISONIC ICST

hi, I have a question. I’m recording B-format using this http://www.radio.uqam.ca/ambisonic/native_b.html but i want to know if I can use de ISCT decoder in this way??? (picture) and how can connect the subwoofer?? i’ll Really appreciate your help

Attachments:
  1. ICST_51
#264543
Sep 6, 2013 at 10:06pm

The ICST decoder (ambidecode~.mxo) is compatible with Native B-format and SoundField microphones recordings if you select the “Furse-Malham” decoding type in the Control Parameters.

#264562
Sep 9, 2013 at 6:26am

wE ARE USING THIS ARRAY, IS IT OK?? and how can connect the subwoofer??
THANKS

Attachments:
  1. ARRAY
  2. IMG_05591
  3. IMG_0559
#264701
Sep 9, 2013 at 7:56am

Looking at your array, the biggest problem is the lack of coincidence of the W channel (omni mic). Personally, I would get rid of the Z (up-down fig-8 mic) and put the W in its place. If you need to connect a sub, you can directly feed it with the W channel.

#264714
Sep 10, 2013 at 2:03pm

mmmm, but we need the Z, maybe we would put the W to the left .Right now we are measuring the polar pattern to watch the response in frecuency but we want to know, how solve the coincident problem?. we are reading some articles I hope to find something.
thanks a lot for your help Mr. Daniel

#264893
Sep 10, 2013 at 6:26pm

Short of using a tetrahedral array (SoundField, CoreSound TetraMic), one must accept to sacrifice the coincidence of one channel, but I would not sacrifice the W. Why is the Z so important for your usage?

#264917
Sep 11, 2013 at 8:02pm

The Z is important for us, because we want to use a 10.2 System. We are using the array because is cheaper and we must spend the money to buy the speakers and other stuff.
But the first thing that we are doing now is testing the array in a 5.1 system, today we were working in that, but really we didn’t have a good result. First we load an file from ambisonia.net called 8-position and was good. but we tried to load our recordings and was a mess, we couldn’t locate anything, I’m sure that something was wrong in the recording but..??

We placed the array and set all pre-amps at the same level, and W channel with -3dB. After a person talked around the array. we record this and made the Interchannel Time Alignment.
This is it.

I have some question and I really appreciate your help and knowledge about this topic.

1-The W channel must have less 3dB??
2-Is there some recommendation for signal levels?? less 6dB or something
3-The distance from the source is important??

thank for your help

Attachments:
  1. ambiencodeCOPY.maxhelp
#265065
Sep 11, 2013 at 8:44pm

Edit: Original post was about the importance of phase coherence in ambisonic reproduction of recordings (W XYZ ettc) based on that diagram, but on closer inspection realize that it is showing an example of encoding multiple discrete sources into an ambisonic field.

#265069
Sep 12, 2013 at 7:22am

First we load an file from ambisonia.net called 8-position and was good. but we tried to load our recordings and was a mess, we couldn’t locate anything, I’m sure that something was wrong in the recording but..??

Guess why. Try a Native-B, without the Z, based on the picture on my website, just to check if you can get a good recording of a walkaround. What are the mic models? We need to know the sensitivity to properly decode.

1-The W channel must have less 3dB??
2-Is there some recommendation for signal levels?? less 6dB or something
3-The distance from the source is important??

1- Yes, for equal sensitivity between the omni and the fig-8s.
2- It’s not different than any recording. Just remember to set and modify the levels as a group rather than as individual mics.
3- No, but sound objects close to the mic array will be “larger than life” when played back on a multispeaker array.

#265104
Sep 12, 2013 at 8:52am

we are using X-Y=StudioProjectB3 (http://www.studioprojectsusa.com/b3_tech.html), Z=MXL2010 (http://www.mxlmics.com/microphones/studio/2010/), and W=ECM8000 (http://www.behringerdownload.de/ECM8000/ECM8000_C_Specs.pdf). the reason for W is the small capsule.
We will record the friday and I’ll tell you what we get.

#265112
Sep 12, 2013 at 11:17am

B3: -35 dB
MXL: -36.5 dB
ECM8000: -60 dB

So either consider the most or the least sensitive of your microphones as a reference.

If I take the ECM as the reference, set it to a proper gain on the recording gear and than set the B3 at a level lower by 22 dB and the MXL at a level 20.5 dB lower.

That way, the fig-8s are like at -57 dB.

#265128
Sep 16, 2013 at 7:12am

Hi, We recorded at friday and we have a questions.
We were watching the phase in Y and we had a 180° offset compared with the other two microphones.
Must we fix the phase in Y channel or the array will work just with the time Alignment ?

Attachments:
  1. IMG_0565
#265397
Sep 17, 2013 at 2:09pm

Looking at your latest picture, the W mic diaphragm should be in the middle of the array to be more aligned with the X and Y diaphragms.

The only way to check the phase or polarity is related to the W.

To check the polarity of the XYZ channels related to the W, you have to position the sound source, like a clapper or something alike, in front of the channel that you want to test. If you’re testing the X, place the sound source at 0°, if testing the Y, at 90° on the left of the array.

Afterwards, it’s easy to see in a DAW if something is not as it should and easy to flip to polarity of the channel if it’s wrong.

#265560

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