MIR Microphones are not "centered" visually, are they accoustically?

[cgernaey]

When building templates in MIR I am always distracted by the fact that the microphones are never "visually in the center" of the room.  Meaning, they do not line up perfectly on the X, Y axis of the visual room.

Is there a reason for this or is it actually centered "acoustically"?  I am asking becuase when making these templates, (sure I can just sit all day long and use my ears for every instrument) but how can a perfectly centered stage placement, be truly centered, if the microphones were off axis of the room?  If people are just plopping instruments on the stage "centered" and thinking it's "center balanced" is that even actually true?

For instance, in the Mozart room, the microphones line up with the left side, of the right chairs off the main isle.  It isn't in the "center" of the dead middle isle.

Dietz, can you elaborate on this for me please (or anyone else who knows the exact true answer)?

Thanks!

Maestro2be

[FredB]

This question have already been answered here http://community.vsl.co.at/forums/p/30053/192876.aspx#192876

@atschallener said:

[...]

And btw: why the mic position in some venues is not centered?

Like explained in the MIR manual, it is not always a good idea to have a microphone positioned exactly on the symmetry axis of a room, as this is most likely the area were potential resonances and room-modes will occur.

Kind regards,

[Dietz]

The Microphone icon's center point indeed shows exactly the positions where the microphone arrays were put when capturing the impulse responses for a MIR Venue.

Most rooms exhibit certain acoustic penomena like resonances and/or frequency cancellations, or flutter echoes along their axes of symmetry. There's a reason why the best orchestral halls exempt these areas from the audiences' seating. ;-) Consequently we tried to stay outside these areas whenever it seemed necessary.

It's quite easy to overcome this real-world facts, though, by simply moving MIR's Microphone Icons towards the symmetry axis.

HTH,

[cgernaey]

Hi Dietz,

Thanks for the response and clarification.  I was never questioning if this was per say right or wrong to do (because I wouldn't know the first thing about recording a symphony live, or making impulse responses).  I will have to trust the pros for this like yourself and so far it's worked well for me :).  So hopefully you only took it as it was :).

My only concern which is now factually proven, could absolutely affect my overall "balance" and stereo image.  I am going to play with this during the weekend and make some adjustments as it seems it might (I say might) make a difference.  I just have to get over the mental "it's not centered" obsession lol.  Because I can clearly hear the separation of the the stereo field when I get to the middle of that microphone versus the middle of the isle.

I really appreciate it and always the great service from VSL staff.

Maestro2be

[cgernaey]

Thanks Fred,

I tried the link you provided but it says that page no longer exists.

Maestro2be

[cm]

@cgernaey said:

I tried the link you provided but it says that page no longer exists.

does it work now?

[Dietz]

@cgernaey said:

Hi Dietz,

Thanks for the response and clarification.  I was never questioning if this was per say right or wrong to do (because I wouldn't know the first thing about recording a symphony live, or making impulse responses).  I will have to trust the pros for this like yourself and so far it's worked well for me 😊.  So hopefully you only took it as it was 😊.

My only concern which is now factually proven, could absolutely affect my overall "balance" and stereo image.  I am going to play with this during the weekend and make some adjustments as it seems it might (I say might) make a difference.  I just have to get over the mental "it's not centered" obsession lol.  Because I can clearly hear the separation of the the stereo field when I get to the middle of that microphone versus the middle of the isle.

I really appreciate it and always the great service from VSL staff.

Maestro2be

No offense taken! I was just trying to emphasize the "What You See Is What You Get"-part of MIR. 😉

BTW: In case you own Vienna Suite, the Goniometer is the perfect tool to get visual feedback whether a stereo-signal is centered or not.

Best,

[cgernaey]

Thanks Dietz, that's a great idea!  I totally forgot about that!  Yup, I have it and will use it tonight to find out!

And additionally (I am not in front of my DAW at the moment) but I think I have it wrong.  I do believe in fact that even though the microphone image is off center, the stereo field begins to split right in the center of the stage.  It's all of this that was playing tricks on my mind lol.  I will confirm tonight and great idea about using the Goniometer to check my Stereo field balance level!

Maestro2be

[FredB]

@cgernaey said:

I tried the link you provided but it says that page no longer exists.

You don't miss anything anyway. Dietz new response is more detailed.

I realised that this link was an old post from the beta forum, that's why it doesn't work.

[Casiquire]

Thanks for the response!  Just to clarify one point, Dietz, you said "It's quite easy to overcome this real-world facts, though, by simply moving MIR's Microphone Icons towards the symmetry axis."  Would this reintroduce the distracting resonances you're referring to or was MIR sampled off-center so that these resonances never actually occur in MIR even when the microphone is virtually placed in the center?  Thanks again.

[Dietz]

 The latter. :-) Moving the microphone doesn't mean that you trigger different IRs; you "just" change their Ambisonics decoding and thus the perceived geometry.

Best,

[cgernaey]

I just wanted to update a post I made earlier "guessing" that instruments were splitting based on center isle vs microphone placement.  They do actually split in the stereo field based on the microphones position, not the center isle.  Just to clear up that little wrong guess I made earlier.

Maestro2be

[Dietz]

 Everything in MIR Pro depends on the setup chosen for the Main Microphone:

- the original microphone position

- the virtual offsets from this original position

- the rotation of the individual (virtual) capsules of the Main Microphone array and the rotation of the whole array.

As a rule-of-thumb, the central arrow shown by the Main Microphone's Icon will indicate the symmetry axis of any chosen setup. IOW: It will devide left from right.

HTH,

[cgernaey]

Thanks Dietz,

That helps greatly.  The more I learn about this application the better my results become.  I have slightly moved my instruments with the new found information and it definitely helped my stereo image.  I am quite happy with the results at the moment.

Maestro2be