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Understanding the dry/wet slider of MIRx
Last post Tue, Aug 21 2018 by Dietz, 6 replies.
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Posted on Sun, Jul 29 2018 12:21
by Mansardian
Joined on Fri, Nov 17 2017, Posts 3
Hello dear VSL-Team,
there as a thing I would like to understand; As I took my own IRs of real rooms I know that a deconvolved file is the result of the combination of the room and the impulse source. So shouldn't the default state of the dry/wet slider be at 100% to place the instrument where it really was in the venue? The Hallradius (sorry, don't know the English word for that term) is usually pretty short and 50% by default would mean you stand right in front of the ensemble that in reality is meters away. Or did I get that wrong somehow?
Thank you for clarification!
Tags: MIR Mixing
Posted on Sun, Jul 29 2018 20:03
by Dietz
Joined on Tue, Aug 06 2002, Vienna / Europe, Posts 8105

Welcome Mansardian,

thanks for your interest in MIR and MIRx.

The question you pose is a good one!  :-)  I'll try to answer it as thoroughly as possible, as it may be interesting for others, too.

It's important to understand that the concept behind MIR is based on Ambisonics completely. Among many other benefits*) this gives us the possibility to put the original (dry) signal on exactly the same spot in the virtual room where the signal source stood during the actual IR-recording process.

This portion of the sound can now be regarded as "virtual spot microphone", which will blend perfectly time-aligned with the wet signal derived from the Main and Secondary Microphones in MIR Pro (or the combined blend of them in case of MIRx). Working with main microphone arrays and mixed-in spot mics is a very common approach for all kind of orchestral recordings, but the amount of the close spot-mics is a variable, not a fixed value (... depending on several technical factors like the Venue, position, distance from the main mic, but also on artistic ones like the composition, the arrangement, and of course personal taste, needs and preferences).

To cater this vast and quite different demands wouldn't be possible with the direct signals that come "burnt-in" with the raw impulse responses used for MIR. You wouldn't be able to change the amount of the "spot mic" mentioned above (read: the panned and pre-processed dry signal). And even worse: Due to the fact that MIR relies on Multiple IRs, the mixture of the direct signals coming from eight IRs will result in a bloody mess of phase cancellation and transient smear. ;-P

Therefore, all remnants of direct signals were removed carefully from the impulse responses used for MIR. In other words: "Full wet" is not what you would hear in the chosen Venue! Like that you will miss all the highly important location cues of that reach you ear before any reflection coming from the room will do.

*) ... more technical details are covered in a little add-on to MIR Pro's manual called "Think MIR!". It is available for download from the "MyVSL" user area.

... please let me know if there's more information needed. :-)

Kind regards,

/Dietz - Vienna Symphonic Library
Posted on Mon, Jul 30 2018 13:14
by Mansardian
Joined on Fri, Nov 17 2017, Posts 3
Hello Dietz,

Thank you, perfectly answered.

Dankeschön aus dem 10ten!
Posted on Mon, Jul 30 2018 13:18
by Dietz
Joined on Tue, Aug 06 2002, Vienna / Europe, Posts 8105

:-) *winkt vom Rosenhuegel hinueber zum Wienerberg*

/Dietz - Vienna Symphonic Library
Posted on Mon, Aug 20 2018 15:36
by Oguz Sehiralti
Joined on Mon, Dec 03 2012, Helsinki / Finland, Posts 47

Hi Dietz,

Sorry to revive this thread but I had a similar question. I'm demoing MIR Pro now after using MirX for years and I'd like to achieve a "theoretically" similar setup to a real recording situation. What I'd like to do is to route my VEP outputs to achieve these individual channels:

* Spot mic channels per instrument group,

* Stereo channel of the main microphone,

* Stereo channel of the secondary microphone.

 

How could I achieve this? I guess the "spot" mics would the the full dry sounds, so I can route them in VEP as described at the end of the  MIR Pro manual, but I can't understand how to get the "authentic" main and secondary microphone sounds - since the full wet sound has the dry element completely removed, I'd need to add some of that back to the main microphones but what would the value in your opinion?

In other words, if I'd like a mix of main mics with NO spot mics, how would I achieve this with MIR Pro?

 

Thanks!

Posted on Tue, Aug 21 2018 14:23
by Dietz
Joined on Tue, Aug 06 2002, Vienna / Europe, Posts 8105

Originally Posted by: Oguz Sehiralti Go to Quoted Post
[...] In other words, if I'd like a mix of main mics with NO spot mics, how would I achieve this with MIR Pro 

You will always have to use a certain amount of dry signal (even if it's just very low in volume, by comparison), as the recorded (original) direct signal component has been removed from all IRs used in MIR, for reasons outlined above. It was meant to be replaced by the readily Ambisoncs-positioned input signal.

BTW: You can assign dedictated outputs to MIR Pro's Secondary Mic by means of the Matrix view in the Output Format Editor window. _This_ signal will be wet-only, though. Two different Ambisoncis-decodings would mess things up completely. :-)

HTH,

/Dietz - Vienna Symphonic Library
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