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Phase relationship between bass guitar and kick drum

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Phase relationship between bass guitar and kick drum

Postby armans » Sat Dec 05, 2020 2:29 pm

I did a quick 2 bar recording today of a simple bassline over a drum groove and as an experiment I tried nudging the bass notes into phase with the kick drum by slicing the audio and then trying to align the peaks and troughs of the waveforms. I found there to be a big difference in the sound as if the bass and kick drum were more cohesive sounding. Is this just my imagination? To what extent are phase relationships between the bass guitar and kick drum taken into account?

thank you!
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Re: Phase relationship between bass guitar and kick drum

Postby Hugh Robjohns » Sat Dec 05, 2020 2:41 pm

It isn't really about phase -- that's related to frequency and clearly your kick, bass and guitar are all producing different frequencies. So it's really about transient time alignment and polarity.

And matching polarity and aligning transients will make the track sound more impactful and coherent.
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Re: Phase relationship between bass guitar and kick drum

Postby armans » Sat Dec 05, 2020 3:01 pm

Hugh Robjohns wrote:It isn't really about phase -- that's related to frequency and clearly your kick, bass and guitar are all producing different frequencies. So it's really about transient time alignment and polarity.

And matching polarity and aligning transients will make the track sound more impactful and coherent.

Ok thank you. Is there a way to do this more efficiently and perhaps more precisely? I sliced the bass notes using the "create slices" function in Cubase and then just nudged them manually so that the peaks and troughs were aligned.
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Re: Phase relationship between bass guitar and kick drum

Postby The Elf » Sat Dec 05, 2020 4:51 pm

But beware. Aligned waveforms add up - and that will sap headroom.

I'm amazed anyone would want to go to this level of minutiae!!
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Re: Phase relationship between bass guitar and kick drum

Postby Martin Walker » Sat Dec 05, 2020 7:29 pm

The Elf wrote:But beware. Aligned waveforms add up - and that will sap headroom.

I'm amazed anyone would want to go to this level of minutiae!!

Agreed - the kick and bass sounding tight together sonically is one thing, but aligning them optically is probably taking things too far.


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Re: Phase relationship between bass guitar and kick drum

Postby armans » Sat Dec 05, 2020 8:53 pm

The Elf wrote:But beware. Aligned waveforms add up - and that will sap headroom.

I'm amazed anyone would want to go to this level of minutiae!!
https://youtu.be/M_MfZqKZoGs

In that video an engineer talks about how if the bass guitar and kick drum have opposite polarities, one pulls and the other pushes the speaker creating a nullifying effect. Maybe I am confused about what he is saying but he clearly states the importance of the polarity between the kick and the bass and I am just trying to understand it so I did that little experiment and I thought that he was refering to time aligning the peaks of the waveforms so they both push the speaker at the same time. If you had a time aligned bass and drum part then wouldnt their phase be crucial if they occupied the same frequency range?
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Re: Phase relationship between bass guitar and kick drum

Postby Mike Stranks » Sat Dec 05, 2020 11:23 pm

You're confusing 'phase' and 'polarity' which is not uncommon so no need to feel in the slightest bad about it! :)

I haven't looked at the video, but what the person means is that assuming the bass guitar and bass both play a note at exactly the same time then if they're recorded out of polarity it means that the note from the guitar if played solo would cause the speaker cone to move forwards while the kick note would cause the cone to move backwards. Combine the two at the same instant and they will, at least to a degree, cancel each other out.

What you're talking about is the two notes being played almost together, but with the same polarity. Because they're not exactly together there will be some phase interaction meaning the two notes produce some artefacts. Aligning them by eye would cancel that, but actually loses, IMO, some of the dynamic of the music.

Phase and polarity aren't the same, although unfortunately the terms can be used loosely leading to confusion...

All of the above is a simplification to try and explain a point. Others may be alone with more detailed and more precise explanations... :)
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Re: Phase relationship between bass guitar and kick drum

Postby The Elf » Sun Dec 06, 2020 12:13 am

All those tiny 'phase' differences are a natural part of sound. Trying to manage it all at this micro-level will drive you crazy! And it really isn't necessary. Not once have I had a mix rejected because the kick and bass attacks weren't phase-aligned!

Of course there are people on YouTube telling you all kinds of silly stuff. It's their living.

I'd avoid YouTube for a week and just create some music! :D
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Re: Phase relationship between bass guitar and kick drum

Postby Hugh Robjohns » Sun Dec 06, 2020 1:22 am

Quite right!

Just think of all the hit records made before the popularity of the DAW in the late 80s, when the idea of precisely time aligning LF transients hadn't even been dreamt of.
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Re: Phase relationship between bass guitar and kick drum

Postby armans » Sun Dec 06, 2020 10:58 am

Mike Stranks wrote:You're confusing 'phase' and 'polarity' which is not uncommon so no need to feel in the slightest bad about it! :)

Isnt phase just a small part/increment of polarity? If I have two tracks with the same sine wave in my DAW and nudge or delay one they will be out of phase. If I keep nudging there is a point at which they will be completely out of phase. Isnt this the same as opposite polarity?
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Re: Phase relationship between bass guitar and kick drum

Postby armans » Sun Dec 06, 2020 11:03 am

Hugh Robjohns wrote:Quite right!

Just think of all the hit records made before the popularity of the DAW in the late 80s, when the idea of precisely time aligning LF transients hadn't even been dreamt of.
In the 80s engineers might have relied on different techniques. In the 80s a hit record wouldnt sound like a hit record does today. You use the tools that you have and in this age we have more tools. Perhaps these tools allow us to do different things that we couldnt do before.

I am trying to understand if having a kick and bass that are time aligned with a lot of low end in each, does that not cause phase cancellation?
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Re: Phase relationship between bass guitar and kick drum

Postby Sam Inglis » Sun Dec 06, 2020 11:18 am

Under normal circumstances I wouldn't expect the waveforms of a bass drum and a bass guitar to be similar enough that they could meaningfully be aligned, apart from the initial transient. If they are, they might end up fusing into one sound when heard together. That may not be what you want.

A good bass player will locate what's sometimes called "the pocket", which means a consistent timing relationship with the drums. Sometimes that can mean the bass notes align perfectly with the drums, but often it turns out that the sense of groove and interest in the part comes from the notes falling noticeably late or early compared with the drum hits.
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Re: Phase relationship between bass guitar and kick drum

Postby blinddrew » Sun Dec 06, 2020 12:53 pm

armans wrote:In the 80s a hit record wouldnt sound like a hit record does today. You use the tools that you have and in this age we have more tools. Perhaps these tools allow us to do different things that we couldnt do before.

I am trying to understand if having a kick and bass that are time aligned with a lot of low end in each, does that not cause phase cancellation?
You're right, of course, that the overall sonic fingerprint has changed since the 80s, especially at the low end. But fundamentally the challenge is still about balancing the kick and bass. Time aligning the initial transients will give you a hit, but unless you're going to tune each kick to each bass note you're quickly going to lose that alignment - so you're going to have a very spiky bottom end with the pitched notes lacking consistency. I think you're also going to have a very indistinct lower octave as it won't be clear what instrument is the source.
It feels like a lot of work to try and get impact that you're probably then going to have to slap a heavy compressor on to get back your headroom and to control the bass timbre.
It'd be worth looking at some of the material on Zukan's Samplecraze site as he's the jedi of the bottom octave. ;)
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Re: Phase relationship between bass guitar and kick drum

Postby Luke W » Sun Dec 06, 2020 2:53 pm

armans wrote:
Mike Stranks wrote:You're confusing 'phase' and 'polarity' which is not uncommon so no need to feel in the slightest bad about it! :)

Isnt phase just a small part/increment of polarity? If I have two tracks with the same sine wave in my DAW and nudge or delay one they will be out of phase. If I keep nudging there is a point at which they will be completely out of phase. Isnt this the same as opposite polarity?

I think that's where lots of the confusion comes from. Phase is time based, polarity is not. Imagine your two sine wave signals are equal (and fixed) in length and on two seperate tracks, and the peaks are perfectly lined up. Reversing the polarity of one track will move the peaks so that they are completely opposite to each other, but the tracks still start and finish in the same place. To achieve the same result by changing the phase, the two tracks would start and finish in a different place.
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Re: Phase relationship between bass guitar and kick drum

Postby Hugh Robjohns » Sun Dec 06, 2020 4:57 pm

armans wrote:Isnt phase just a small part/increment of polarity?

No. Polarity is basically whether the signal starts in a positive direction, or a negative one. It can apply to both cyclical and transient signals.

Phase can only relate to cyclical signals, and describes a position part way through the whole cycle in degrees (where 360 degrees is a full cycle).

If I have two tracks with the same sine wave in my DAW and nudge or delay one they will be out of phase. If I keep nudging there is a point at which they will be completely out of phase. Isnt this the same as opposite polarity?

They will appear to have opposite polarity if you view only a part of the whole signal, but it's not strictly the same thing at all!

The confusion of these terms comes from the notion that (considering a sinusoidal signal), a phase shift of 180 degrees looks exactly like a polarity inversion.... but it really isn't because a phase shift of 180 degrees inherently involves a time delay equivalent to half the wavelength whereas a polarity inversion is instantaneous and doesn't involve a (frequency-dependent) delay!

So, a polarity inversion is an inversion of the signal voltage whereas a phase shift involves a frequency-dependent delay.
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