Is Ambisonic ambient recording safe for 5.1 mix in film theaters?

[Dan Wake]

Is first order Ambisonic* ambient recording safe for 5.1 mix in film theaters? Will brings problems as phase cancellation?

 

Thanks,

 

Dan

 

*mic models as for examples: Sennheiser AMBEO VR, Rode nt-sf1

[ramallo]

No,

 

You can get some b format here https://freesound.org/people/ramagochi/ and try 

 

The first one is converted to 5.1 https://freesound.org/people/ramagochi/sounds/525033/

 

Done with Harpex-X

[Dan Wake]

15 hours ago, ramallo said:

No,

 

You can get some b format here https://freesound.org/people/ramagochi/ and try 

 

The first one is converted to 5.1 https://freesound.org/people/ramagochi/sounds/525033/

 

Done with Harpex-X

Thx for help Ramallo I’m really grateful. I’m sorry I didn’t understood. Saying “no” do you mean I will have phase issues in a film theater with 5.1 mix?

[Werner Althaus]

20 hours ago, Dan Wake said:

Is first order Ambisonic* ambient recording safe for 5.1 mix in film theaters? Will brings problems as phase cancellation?

 

Thanks,

 

Dan

 

*mic models as for examples: Sennheiser AMBEO VR, Rode nt-sf1

I think it can be "safe" but I don't think it's a particularly good choice. The spatial resolution and soundstage of FOA isn't very good except at  close range , the sweetspot is very small. Converting to channel based formats ( mono,stereo,5.1, etc) requires a matching plug-in with the appropriate correction for that particular microphone's set of capsules only being "somewhat coincident", so you'd use the Sennheiser Ambeo plug for the Sennheiser Ambeo mic but that plug-in doesn't do conversion to channelbased audio, it only converts A to B format and steers the mic's 0 axis. It's strictly for 360/ VR.

 I've used the Harpex for Ambeo and Soundfield mics. The soundfield plugin sounds better with the Soundfield mic, however, for the Ambeo mic the Harpex sounds better than the soundfield/ Rode plug-in. And while somewhat coincident you can certainly create phase issues with the plug-in decoding to channelbased formats. I can't imagine anyone mixing for theatrical release being too thrilled to be handed B-format audio but I could be wrong about that.  

[ramallo]

7 hours ago, Dan Wake said:

Thx for help Ramallo I’m really grateful. I’m sorry I didn’t understood. Saying “no” do you mean I will have phase issues in a film theater with 5.1 mix?

 

No big phase issues, mainly is a coincident technique (quasy)

[Dan Wake]

On 8/12/2020 at 4:06 PM, Werner Althaus said:

I think it can be "safe" but I don't think it's a particularly good choice. The spatial resolution and soundstage of FOA isn't very good except at  close range , the sweetspot is very small. Converting to channel based formats ( mono,stereo,5.1, etc) requires a matching plug-in with the appropriate correction for that particular microphone's set of capsules only being "somewhat coincident", so you'd use the Sennheiser Ambeo plug for the Sennheiser Ambeo mic but that plug-in doesn't do conversion to channelbased audio, it only converts A to B format and steers the mic's 0 axis. It's strictly for 360/ VR.

 I've used the Harpex for Ambeo and Soundfield mics. The soundfield plugin sounds better with the Soundfield mic, however, for the Ambeo mic the Harpex sounds better than the soundfield/ Rode plug-in. And while somewhat coincident you can certainly create phase issues with the plug-in decoding to channelbased formats. I can't imagine anyone mixing for theatrical release being too thrilled to be handed B-format audio but I could be wrong about that.  

thx for the suggestions I’m trying to figure it out this is new for me. with the objective in mind to avoid phase issues for theatrical 5.1mix maybe is it better to just record 4 separate tracks and do not use plugins? I mean raw 4 tracks straight on my DAW timelines.

If I buy an ambisonic mic it will be the Rode nt-sf1 (the others are too expansive). I tested them plugin with a bunch of sample files, the plugin offer a 5.1 conversion. Should I avoid that? I hope you have tested it maybe you can give me some feedbacks. 
If have time I would be really grateful if you could test the plugin and the samples (at the bottom of the page) here https://it.rode.com/soundfieldplugin

On 8/12/2020 at 10:35 PM, ramallo said:

 

No big phase issues, mainly is a coincident technique (quasy)

Thx Ramallo. Are little phase issues something unaboidable also using other recording technique for surround ambient recording? 
I'm new to surround recording and editing/mixing, in the past I've worked only in stereo, this is a new journey for me and I have many things to learn about it.

[Werner Althaus]

20 hours ago, Dan Wake said:

thx for the suggestions I’m trying to figure it out this is new for me. with the objective in mind to avoid phase issues for theatrical 5.1mix maybe is it better to just record 4 separate tracks and do not use plugins? I mean raw 4 tracks straight on my DAW timelines.

If I buy an ambisonic mic it will be the Rode nt-sf1 (the others are too expansive). I tested them plugin with a bunch of sample files, the plugin offer a 5.1 conversion. Should I avoid that? I hope you have tested it maybe you can give me some feedbacks. 
If have time I would be really grateful if you could test the plugin and the samples (at the bottom of the page) here https://it.rode.com/soundfieldplugin

Thx Ramallo. Are little phase issues something unaboidable also using other recording technique for surround ambient recording? 
I'm new to surround recording and editing/mixing, in the past I've worked only in stereo, this is a new journey for me and I have many things to learn about it.

It might help to first understand that Ambisonic B-Format is basically Stereo Mid-Side times 3 ( since it's along 3 axis, left to right, front to back and up to down).and just like MS Stereo it is very compatible with both up and down mixing.Hence my comment that it can be safe. But does it sound good?

I think you misunderstood my comment about plug-ins and phase. Someone will have to use either a plug-in or hardware to first convert A-Format to B-Format and then to create the desired channel based configuration for the mic. On our Calrec MK-4 the hardware controller converts A Format to B-Format and it can  generate various patterns from Omni to figure 8 in stereo ( No 5.1 with the old hardware controller) and everything in between, as well as rotate the mic along the horizontal and vertical plane. However, the analog circuitry involved creates phase issues and the digital plug ins do a much better job at this math but if pushed to extremes you can still get phase artifacts, at least to my ears. Other problems arise from the correction filters in the plug in not matching the mic's physical distances between the capsules.

If you have a specific mic in mind ( the Rode) and use the Rode plug in to generate the channel based output ( 5.1 for example) you'll be fine, if you send raw A-format and the post house uses something else to convert to B-Format and then to channel based audio you might have issues. Remember that A-format is basically useless before conversion to B-Format.