FabFilter User Forum

Multi-Channel Stem Mastering with Q3


I want to set up Q3 for multi-channel (5.1) DME Stem mastering, similar to "cargo-cults StemCell".

My particular question is regarding the "processing mode":

  • Do I need "linear phase" on a DME Stem or is "zero latency" sufficient enough? Especially when different filters apply on different legs within a 5.1 Stem (e.g on L/C/R LowCut @35hz/12db - Ls/Rs LowCut @100hz/12db - LFE HighCut @120hz/12db)

Are the legs in phase to each other in "zero latency", and if not which latency mode do you recommend for filters not higher than 12db/oct on a multi-channel stem?

Thanks in advance!

jingo — May 6, 2019

Hi Jingo,

If the audio stems are related to each other in terms of phase, then you should use Linear Phase processing, otherwise, it would not be necessary. See www.fabfilter.com/video/#eq-linear-phase-vs-minimum-phase for more information

Floris (FabFilter) — May 6, 2019

Hi Floris,

yes, I know, if the Stems are related to each other (same as tracks), linear phase mode is important.

But what about the individual legs inside a Stem. With Q3, on a 5.1 track, I'm able to equalise different legs independently and differently.

E.g.: If I apply a steep filter only on the C channel, the phase respond would be pretty drastic for that channel in "zero latency" mode. How would this affect the other legs, were no equalisation is done?

Does Q3 in "zero latency" still take care for this kind of usage?

You get what I'm trying to say?

jingo — May 6, 2019

In this case, there will indeed be a phase difference between the C and other channels. This might or might not be a problem, and this is just the same as with L/R filtering. Pro-Q 3 doesn't do anything special to prevent this -- if it turns out to be a problem in practice, you should switch to Linear Phase mode.

This video tutorial is still highly relevant:


Frederik (FabFilter) — May 7, 2019

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