# Decca Tree mixing question



## Peter Emanuel Roos (Apr 7, 2013)

I feel a bit stupid that I cannot figure this out myself... :oops: 

But to be sure I want to ask you:

I have three Decca Tree mono tracks. I need to mix them with 0 dB, -3 dB, 0 dB ratios to stereo.

So I create a 3 channel file in SoundForge and drop the files in. Then I use the channel converter with settings:

Source 1: 100% - 0 %
Source 2: 70% - 70%
Source 3: 0% - 100%

SoundForge says 70% equals -3 dB.

Did I do OK? Or did I forget to apply some panning logic? And have I added too much of the Center mic?

TIA very much!


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## Peter Emanuel Roos (Apr 7, 2013)

My gut feeling tells me I made an error...

And since I am editing and combining many many IR files I am stopping now, in order not to have to redo lots of work if I got this wrong...


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## sinkd (Apr 7, 2013)

I am not familiar with the Sound Forge project way of mixing, but the 70%-70% L/R center mic is essentially summing to mono in the mix, which I think would require another -3db attenuation to balance (down to your -3dB) with the other sources which are hard panned, effectively lowering their "level". You could check this by comparing the level of the mono C source by itself to the L/R 70%-70% by itself.

I usually end up somewhere around -4.5 to -6, depending on the material. Always checking mono compatibility, etc.

DS


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## Peter Emanuel Roos (Apr 7, 2013)

Thanks, 

Just reading again about the panning law stuff and experimenting with three white noise files in Cubase. Center here is some -4 dB.

My gut feeling also told me I should not have added -3 dB to each channel, but -6 dB... Like you said.

I cannot use my ears to judge, because I am processing impulse responses from 8 mics (Decca to stereo, outriggers, ribbons and surround).

Lots of mixing decisions!


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## wst3 (Apr 7, 2013)

Hi Peter,

I think you are close... and for your specific application you might even be spot-on.

When I mix a Decca tree (which is too infrequently!) I pan the left and right channels hard left and hard right. Then I add the center channel to taste - and I listen to the mono sum as I go, it is way easy to create a mess!

In my experience the center channel is usually about 6dB down with respect to the side channels, but it can be more or less than that, depending on the material, and the space.

70% is about 3dB down, in terms of amplitude or "voltage", it is not half power. Most of the time that's a silly observation, but in this case half power is 6 dB down, or about 50%. And that's an important thing<G>!

The whole power vs level thing is a mess - I sometimes wish no one had noticed that they could use dB for other levels<G>!

Anyway, if you have the tools (and I'm sure you do) you might find it a lot easier to find the sweet spot using a three channel mixer in your DAW - SF is a fantastic tool, and I use it constantly, but mixing things is not it's forte!

Holler if you have any questions!


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## wst3 (Apr 7, 2013)

dang - meant to include links to three really good papers on Decca Tree - there are others, but they aren't readily available on the web:

http://www.wesdooley.com/pdf/DeccaTreeD2.pdf

http://www.wesdooley.com/pdf/mmpguide.pdf

http://cdn.audioimpressions.com/OrchestralRecordingTechniques_R4.pdf (http://cdn.audioimpressions.com/Orchest ... ues_R4.pdf)


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## Peter Emanuel Roos (Apr 7, 2013)

Thanks guys so very much!

I use SF because I need sample accurate editing and processing, I do not trust a DAW for creating IRs.

And thanks for those links!

Will go back and remix the Decca mono files and then continue with my mix of all microphones.


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## wst3 (Apr 7, 2013)

yeah, hadn't thought about the sample accurate part... auditioning different mixes in SF is a little clumsy, but it can be done.

One thought that might speed things up, for any given microphone collection the sample sets should be sufficiently uniform that you can use the same setting for all of them.


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## Peter Emanuel Roos (Apr 7, 2013)

Thanks again,

It's quite funny that I can calculate the distances from the emitting speaker to the mics nearly in term of centimeters by zooming in on the earliest reflections.

It's a lot work, but the first tests with very dry samples (full wet) already sounded great, before any EQ correction for the speaker's spectrum.

Too bad this cannot be a commercial IR library from Samplicity, but I really hope to do a joint venture with Hendrik Schwarzer from the Berlin Woodwinds library in the Berlin Teldex studio!

Cheers


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## sinkd (Apr 9, 2013)

Sounds very cool. If you need anyone to consult or try things out, I have Altiverb and BWWs.

And lots of Samplicity IRs already



DS


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## jaeroe (Apr 9, 2013)

have you looked into using Pyramix? are you on windows?


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## Peter Emanuel Roos (Apr 9, 2013)

On Windows yes, but I am sure I have it right now with the Decca.

Will Google for Pyramix!

Now focusing on terrible EQ matching challenges, to compensate for the speaker's spectrum and how the 9 mics recorded that.


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