Distance Dependent Volume Scaling: Some thoughts

[Pixelpoet1985]

After much more experiments I have discovered the following:

The volume scaling is CORRECT but only if you treat your instruments as "recorded WITHOUT spot microphones". In my opinion, the volume scaling has to be applied ONLY to the WET signal, not the dry. Because a spot microphone mixed in means you add volume to the mix. With the volume scaling enabled it would mean you only hear the main microphone. And this is something I never understood with MIR Pro. You always hear both signals with MIR Pro, i.e. the concept of main + spot. In a normal recording scenario you delay the spot microphone, but still has it's volume. With the volume scaling you move the spots further back and lose this volume, which is not right. Yes, the concept of MIR Pro is to have perfectly time-aligned spots, but the "real" spots are, as said, delayed and don't lose volume.

With the strings it's not a problem, because they are at the front, but with the other instruments I always switched between volume scaling on and off, only to understand that the volume scaling itself is the problem. ;)

I would like to hear what Dietz has to say about this. Would be nice to have a feature which disables the volume scaling on the spots (i.e. dry) signal. Of course, with VE Pro I can separate the dry and wet signal and compensate the volume, but it's tedious, because I don't exactly know the volume differences which are applied by the scaling. Or is there a rule of thumb (1m = XX db)?

[Dietz]

Actually things are quite straight-forward - you just confused yourself a bit, it seems. 😊

Quoting the manual -> https://www.vsl.info/en/manuals/mir-pro-3d/instrument-settings

@Another User said:

Dry/Wet determines the ratio of dry and wet signals for the channel. When MIR Pro 3D is in “Classic Mode” and “Distance Dependent Scaling” of the dry signal is On, the default value at the center position should roughly match the signal’s natural sonic impression in that Venue. [...]

Important

“100% wet” is NOT the sound you would hear in the Venue, as all impulse responses used in MIR Pro 3D had their initial direct signal removed in order to avoid ugly phasing artifacts. In other words: MIR Pro 3D expects some dry signal component mixed in to sound “natural”!

If you don't like the positioned dry signals mixed in, you can simply go "all wet", but it will sound unnatural. If you don't like the the distance dependent volume scaling of the dry signal, simply switch it off:

-> https://www.vsl.info/en/manuals/mir-pro-3d/instrument-settings#dry-signal-handling

...  you can also switch MIR 3D to "Pop Mode", if you want to de-activate the dry signal's scaling for all Icons.

-> https://www.vsl.info/en/manuals/mir-pro-3d/venue-handling

The formula MIR uses for scaling is not the scientific -6dB with each doubling of the distance. This works in the free-field only. MIR takes into account that we always are in an fully enclosed hall by definition, so it's only -3dB for each doubling (which feels more comfortable for our needs).

BTW: There is no distance scaling for the wet signal - this happens all by itself (... the natural volume relation of the IRs is preserved throughout a complete MIR Venue).

If you really think that it's necessary to implement a delay between dry and wet signal you will need the routing options MIR 3D has in VE Pro only. Here you could route the wet signal to a different bus and add some delay there: 

... my personal expectation is that the sound you'll achieve like that will be - uhm ... interesting, but most certainly not natural. 8-)

One IMPORTANT FINAL NOTE: If you use 3rd order capsule-based Ambisonics formats for the output of the MIR 3D, you will be confronted with rather strange pickup patterns when you go to the extremes (see below). This will of course have a wicked effect on the perceived behaviour of the dry signals when changing positions in relation to the main microphone!

Kind regards,

[Dietz]

PS: Before you look in the wrong places and measure unpredictable setups: For testing purposes and to rule out any other influential factors, please use a single Omni source (its Width reduced to 0), with a Main Mic set to (dual) mono (... it can be found near the bottom of the "Classic Stereo" presets). Thx!

[Pixelpoet1985]

Thanks, Dietz, for the thorough reply. Very appreciated as always! 

I don't want to use delay, it was just for comparison reasons. I think I indeed confused myself, because there are so many variables to deal with, especially the individual capsules you can edit. For example: I tested various setups with dry volume offsets on the center capsule (in my case a Blumlein with center).

I started to balance my template from the strings (dimension strings), and this was indeed the mistake. I already mentioned in another thread that the natural volume overview isn't right on certain instruments. For example, the dimension strings had -15, now -12, and I think they need -21. Maybe the numbers have been mixed up.

Of course, you are always saying that natural volume should not be used with other libraries, but that's not true. I tried with all other libraries I have (Synchron, Hollywood, Spitfire) and the volume balancing is really spot on, except some minor things which are not right in the overview (overview vs. the implementation in MIR Pro). The important thing is you always have to use a combination of main + spot when referencing.

[Pixelpoet1985]

Concerning the natural volume settings:

The natural volumes are right if all the instruments are at the same position. If distance dependent scaling is enabled (and yes it should be), the natural volumes should automatically be compensated. Do I move the instrument further back, the volume should be increased automatically. Of course, I'm talking only about the VI instruments with natural volume applied. This is a feature I want to set on the wishlist. 

I compared with really all Synchron libraries and the Synchron Stage venue. The natural volumes are really spot on (with some exception mentioned earlier).

[Dietz]

Please, read my previous message carefully: From the wet signal's POV there is absolutely no distance-dependent volume scaling. MIR's convolution engine is always fed with exactly the volume you set on the faders of the instruments.

OTOH: If you want constant volume for the dry signal (no matter where you place it on the stage of a MIR Venue), please turn off the corresponding option - either individually or globally. 

... there is nothing else that would really make sense in this respect. If you think it through, you will see that there can be no in-between solution. 

Kind regards,

[Pixelpoet1985]

Thanks and sorry for all the confusion. I still think that the natural volume are not correct. But the issue that I had were really the volume offset of the center microphones I was dealing with. :)

[ EDIT: Accidentally deleted this paragraph... :( ]

[Dietz]

:-D .... the great thing about MIR is: Nobody hinders you from using these customized values! ;-) I'm sure they sound great. You could even add more capsules if they help to achieve your goals.

Kind regards,

[Pixelpoet1985]

Yes, that's true. At the moment I hesitated to add new capsules or the ambisonics order, because I have absolutely no clues where to start. :)

[Dietz]

:-)

[Pixelpoet1985]

Awesome...! Need new glasses. :P

---

Dietz, I have another thing and didn't want to start a new thread:

I wanted to separate the dry and wet component in VE Pro. It works for one instrument, but if I add more there are cracks and other sounds. Is this normal? Actually I know how to do this and it worked in previous versions. At the moment it only works if I do it for each instrument separately, but I want this for strings, brass and woodwinds as a section.

[Dietz]

Huh! 8-0 This should work flawlessly, of course. ... if this is a reproducable issue, please get in contact with support@vsl.co.at, including all necessary details (OS, audio drivers + versions, software versions, latency settings ... you know the drill).