Master Bus - EQ = Linear Phase or Zero Phase?

[Uncle E]

I would say it doesn't matter if you can't hear the difference.

People's ability to hear the phase shift is related to their experience. I used to high pass every track and, when I listen back to those mixes now, I can hear the phase shift that I did not hear at the time.

[stillshaded]

My take:

-Avoid high passing. Try a shelf instead.

-don’t use linear phase unless you have a damn good reason too.

-if you do high pass, use a gentle slope probably. Sometimes a sharp slope will work but keep in mind you’re creating a resonant bump at the cutoff, and I hope you’re pretty confident in your monitoring down there.

[BazJacuzzi]

I would say it doesn't matter if you can't hear the difference.

People's ability to hear the phase shift is related to their experience. I used to high pass every track and, when I listen back to those mixes now, I can hear the phase shift that I did not hear at the time.

Uncle E, you're someone I respect here. I'm someone who can't hear phase shift, so I'm genuinely curious, what does it sound like?

Say I take a piece of musical audio, like a piano recording, or a drum track, and high pass it, other than the audio now obviously lacking in lower frequencies, what does the phase shift sound like? I often hear phrases like "don't high pass because phase" but this is just how filters work. I can hear ringing on high q boosts for example, but I'm presuming that's not the sound.

Please help!

[Uncle E]

It sounds like regular phase shifting, except concentrated around the frequency point. You’ll mainly hear it with high passes because the low frequency waveforms are long.

[BazJacuzzi]

Thanks, but I'm asking what phase shifting sounds like and you say it sounds like regular phase shifting, which is exactly what I'm asking the first place. I'm more clueless than you think I am!

Do you mean it sounds like a phaser? My understanding is that's an allpass filter with resonance (feedback) and EQ filters don't have feedback. But this probably isn't what you're saying.

I'm confused!

[Uncle E]

Sorry, I keep losing track of this thread. Out of phase is when a signal cancels itself out. 180 degrees out of phase is fully canceled. A phaser effect modulates the phase so you hear different degrees of cancelation. With an EQ, the EQ'd signal is mixed with the un-EQ'd signal, and if it's not a Linear Phase EQ, the frequency point where the two signals meet will sound out of phase.

In practical use, the way to avoid that phase cancelation is to only high pass when necessary or only high pass inaudible frequency ranges.

[jamcat]

That phase distortion is how analog EQ works. I wouldn't want to avoid it. It's the sound of making a record.

[BazJacuzzi]

Yeah, I really don't understand. Phase cancellation is inherent with EQ. So it sounds like an EQ.

But people keep stating that phase cancellation sounds undesirable or wrong or weird or something. I don't hear it.

When I high pass, I hear a high passed sound. But supposedly people can hear some other artifact? I don't think people are talking about ringing here (which is also just a consequence of how filters work), because ringing is mentioned separately.

[Agg]

Yeah, I really don't understand. Phase cancellation is inherent with EQ. So it sounds like an EQ.

But people keep stating that phase cancellation sounds undesirable or wrong or weird or something. I don't hear it.

When I high pass, I hear a high passed sound. But supposedly people can hear some other artifact? I don't think people are talking about ringing here (which is also just a consequence of how filters work), because ringing is mentioned separately.

I just see it as combination of multiple things that minimum-phase causes, but it gets summed up as "it affects phase" in small talk (with no explanation).

- if you eq individual tracks, you hear how the phase shift makes the interaction with other instruments different (because harmonics have different phase now).

- if you high pass busses/master, you probably high pass mid/side separately at different frequencies. You will hear the phase-shift in the stereo image because of this.

- if you high-pass / low shelf any sub-heavy tune, the fundamental of a clean sub straight out of synth stops being clean because of the phase shift.

- if you boost highs, the phase-shift often makes them sound more aggressive. Bob Katz talks about this in "Mastering Audio" (book).

Personally, I don't hear the phase-shift well in isolation, but it often becomes very obvious if you A/B test between minimum-/linear-phase modes.

[BazJacuzzi]

Thanks, that's actually really helpful. I have some things to look out for now!