FabFilter User Forum

Pro-Q 2 natural phase w/multi-mic'd instruments

Something I've noticed but haven't looked into much yet is how Pro-Q 2 reacts when you use it in natural phase mode and something has been mic'd with more than one microphone.

For example, I was working on a mix and the guitar amp was recorded with a 57 and ribbon mic, the same distance from the speaker. The phasing looks perfect when I zoom in on the waveforms.

However, when EQ just one of the two mics with Pro-Q 2 in natural phase mode, things start to sound very strange.

Is this by design/nature, or a bug? Should I avoid using natural phase mode on individual mics of a multi-mic'd source like guitar amps and drums?

I don't notice the issue with other EQs, and I think it's ok in all other modes besides natural phase but I'd have to double check.

I just wanted to see if anybody else noticed this regarding natural phase mode and sources that have more than one microphone.

Justin Perkins

Hi Justin,

The situation that you describe (mixing multiple recordings of the same source), is a perfect example of when Linear Phase processing is needed!

Keep in mind that Natural Phase still affects the phase of the signal (only in a more natural/analog-like way). So if you EQ one of the signals, it will cause phase-shifts for different frequencies, which will cause strange cancellation effects when playing together with the unprocessed, other mic's audio...

So I would strongly recommend to use one of the Linear Phase modes in this case!

Of course, if you think it's really a Natural Phase mode issue, do send us a short audio example so we can reproduce the situation ourselves and investigate...


Floris (FabFilter)

Thanks for the clarification.

I will certainly avoid natural phase mode when EQ'ing something that has multiple microphones or sources, good to know.

Justin Perkins

Also, does the linear phase level (low, high, max) affect phase shifts when paired with other sources or mics?

Justin Perkins

Hi Justin,

No, in all linear-phase modes, the phase is left completely untouched. Higher linear phase modes are useful when more precision is needed (for example when EQ'ing quite steep in the lower areas.

Floris (FabFilter)
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