PHASE SHIFT

Phase shifting in the mix or in the mastering can cause problems and thin out the sound or affect the ratio of mid and side signals.

UNDERSTANDING PHASES FOR THE RIGHT SOUND

At first glance, the topic of phase shifting in music is not the most popular topic and rather dry, as it has a lot to do with physics. do you want in Mixing but achieve a good sound, you don't have to deal with phase shift and the respective frequency and learn more about it. As soon as you work with similar audio signals - for example several snare sounds, synthesizers or basses - problems with the phase shift can arise. Also at record, tape with several microphones, especially the drums, you always have to pay attention to the phase. Otherwise it can happen that the instrument sounds thin in the mix and in some frequencies and does not cut through.

What is a phase?

We call this a phase vibration behavior of waves (electrical engineering) in our case sound waves (can also be electricity). If we look at the audio signal in the DAW, the waves and the waveform can be seen, which can then be rotated by 180 degrees with the Ø symbol.

First let's assume that we are duplicating an audio signal in our DAW. If we now listen to the two tracks, we notice that the signal has become louder. The two waves have added up, since they are identical signals, no new sound information is added. So the signal just gets louder. The situation is different if we rotate the phase, one of the two tracks. Now we don't hear any more signal - it comes to phase cancellation. Depending on the miking (e.g. snare top & bottom mic), it is possible that phases are in opposite directions during the recording, here it has to be be rotated so that there is no phase shift or phase cancellation.

PHASE SHIFTING IN MUSIC PRODUCTION

Another phenomenon is the phase shift. When miking a drum set, for example, it can happen that one of the microphones is not well aligned. The microphones are therefore at different distances from the sound source (with the same current and voltage), so the signal arrives at the microphones at different times, resulting in a phase shift. Here can also the so-called comb filter effect develop. If a signal that sounds identical is delayed, there may be a evenly strong level reduction and increase coming. But also when recording with only one microphone there can be phase shifts come. This happens when the microphone not only records the direct sound, but also the reflections are recorded. Depending on the angle and directional characteristics.

Other reasons for phase shifts can also be effect devices that delay the signal or plugins in a DAW without automatic latency compensation.

Other areas where it is in the mix or in the mastering phase shifts can occur are, for example, duplicating vocals. Especially if these are only provided with a slight effect such as a delay or are slightly shifted in timing, this can lead to undesired effects.

Here it is usually better to record the vocals several times instead of duplicating the vocals and trying to create an artificial width. Phase problems or phase shifts can also occur in the synthesizer area, especially if you work with detuned oscillators. Phase problems in synthesizers usually occur in the additive synthesis on, ie when mixing different sounds together. A phase difference often arises here.

However, phase shifts can also be used as an artistic effect. Sometimes the shift results in an interesting one sound of so desired is or one picks up phase modulating effects like one Phaser .

PHASE LINEAR & MINIMAL PHASE EQUALIZER

We don't work with phase-linear equalizers the applied filter can also result in a phase shift, here we are talking about one phase rotation of the two phases. This rotation depends on the strength of the filter. For example, let's use one High or low cut Phase problems can arise in the mix, here the strength of the rotation depends on the edge steepness. With EQs, a distinction is made between minimal phase and phase-linear.

How do both EQs affect the phase of the audio signal?

The minimum phase EQ causes a time delay of the signal  or the frequency, which varies depending on the frequency component - unlike the phase-linear EQ here, the phase shift is constant over the entire frequency spectrum. In terms of sound, the phase-linear EQ is therefore more neutral, while the minimal-phase EQ colors the signal more strongly. Ie we work with tonally similar Traces it is often useful to use a phase-linear EQ to avoid phase cancellations. On the other hand, if you want to color the signal, you can use a minimal-phase EQ as long as your instrument doesn't start to sound thin or other artifacts arise.

Another phenomenon of EQs is the so-called "ringing", here exist that Pre & Post Ringing. Ringing occurs when using high and low cuts. Post-ringing occurs with both types of EQ and is not usually audible. Pre-ringing, on the other hand, only occurs with phase-linear EQs and sounds like a slight fade-in. The stronger the cut, the more the signal's transients lose their punch. Often the pre-ringing does not affect the sound quality, but it can happen in the mix that a minimal-phase EQ should be used due to the pre-ringing.

If you want to take a closer look at the different EQs and their influence on the audio signal, we recommend the following video:

IDENTIFY AND CORRECT PHASE PROBLEMS

But how do I recognize phase problems?

Let's hear our mix in the stereo image most phase problems will not show up immediately, but in Mono. That's why it's important Mix regularly in mono to check. If you can hardly hear certain instruments, phase problems can be the reason. Especially in the low end you will have to pay attention to the phases because this is also in the Stereo mix in the center as a mono signal forms the foundation of your song. Before you try to "save" a signal that sounds weak in the mix with effects and EQs, it is often enough to turn or correct the phase.

A further help in recognizing phase problems can be a so-called phase correlation meter be. This shows the relationship between phase and amplitude of two stereo channels. The phase correlation meter shows you different information about your audio signal, starting from a perfect one mono signal Among other things, the stereo ratio, the phase distribution and a rough frequency distribution can be set. Possible phase problems can usually be read on a scale, which shows you whether there are cancellations or frequencies are adding up.

How can we correct a phase shift?

  1. Uses fewer microphones when recording or repositions them. Sometimes a microphone doesn't need to be moved very far to fix the shift.
  2. Try to reverse the phase. This doesn't have to be a direct 180 degrees. With plugins such as Audiocation Phase, the phase can be changed in steps from 0 to 360 degrees.
  3. If an effect causes the phase shift, you can either do without the effect or change the effect parameters so that it no longer has a negative effect on the phase.
  4. Shift the audio signal in your DAW. It is often enough to adjust the signal just a little bit to the other tracks.

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